Be it ever
so high-tech, there's no place like home - ready availability of inexpensive used test
equipment makes it practical for you to configure a home laboratory, a great timesaver and
boon to your circuit-design productivity
Connect
Instruments to the Corporate Network - modern measurement instruments can be networked
using corporate lan, but before you can connect, you must work with your network
administrator
Equipping
a Startup Company - obtaining the test equipment you need to develop a product at a
startup company requires different tactics than at an established company
Old
measurements, new techniques: DSP drives speed and accuracy; coherence saves the day -
DSP techniques lead to faster, less costly frequency-response tests and enable the use of
a powerful concept, the coherence function, which acts as a watchdog to help identify and
quantify common but easy-to-miss measurement errors. Best of all, this watchdog works for
free.
Smart
conditioners rub out sensor errors - Bridge-type, piezoelectric, and other sensors are
subject to nonlinearities, as well as gain and offset errors. Smart signal conditioners
compensate for the errors and extract the true signals from the dross. Pressure
transducers, accelerometers, temperature sensors, and linear-position sensors are often
imperfect devices, prone to nonlinearities and gain and offset errors.
Using a
multimeter - A meter is a measuring instrument. An ammeter measures current, a
voltmeter measures the potential difference (voltage) between two points, and an ohmmeter
measures resistance. A multimeter combines these functions, and possibly some additional
ones as well, into a single instrument.
Using the
Multimeter to Measure Voltage and Resistance - Multimeters are commonly used to
measure voltage and resistance between two points. Current is rarely measured because you
must alter the circuit to measure the current.
Using a Volt Ohm
Meter - A very handy tool for trouble shooting problems is a VOM (Volt Ohm Meter) -
also called a Multi-Meter. It can be used to test cables, AC power levels and Batteries.
You'll often find yourself out on the road with problems that are causing you grief, but
you aren't quite sure why.
What is a decibel?
- The decibel (dB) is a logarithmic unit used to describe a ratio. The ratio may be power,
or voltage or intensity or several other things.
Every scientist, engineer, and technician involved in any form of
electronics has used an oscilloscope. Scope displays of amplitude as a function of time
provide intuitive and easily interpreted pictures of signals. Oscilloscope is one of the
most important test instruments for available engineers. It is useful for very many
electronics measurement. The main purpose of an oscilloscope is to display the level of a
signal relative to changes in time. You can use an oscilloscope to analyze signal
waveform, get some idea of signal frequency and many other details.
Oscilloscopes are intended to be operated with their chassis at
ground potential. There are good technical and safety resons for this. If you are
measuring some mains powered device, it is a very good idea to power the device through an
isolation transformer.
Traditional oscilloscopes used a CRT screen and were completely
analogue devices. Those analogue oscilloscopes are still very usable devices nowadays.
Analogue oscilloscopes work very well as general testing instrument for viewing repetitive
signals.
Digital oscilloscopes are digital versions of that analogue
instruments. Digital oscilloscopes sample signals using a fast analog-to-digital converter
(ADC). The digitized signals are sotred to the scope memory and shown on the scope screen
or at computer screen. The benefit of the digital technology is that the waveforms can be
captured to memory and then analyzed, immediatly or later, in many ways. Digital
oscilloscopes can be used to capture repetitive signals as well as transient signals.
Benefits of
Digital Oscilloscopes in Power Supply Design & Testing - This technical note
focuses on the uses of digital scopes for measuring power supply characteristics. Examples
are given of measuring power supply turn-on, hold-up time when AC power fails, in rush
current and ripple/noise.
DSO
Benefits - Communications - This technical note discusses the application of digital
oscilloscopes to a variety of problems encountered in communications. Examples are given
of how to use the benefits of a DSO in examining phase shift keying, frequency shift
keying, full duplex, etc.
Importance of X10 Probes
- A scope probe is built to minimize ringing by adding resistance. A X10 probe has the
effect of reducing capacitance by a factor of ten. The trade-off is that is also
attenuates the signal by a factor of ten. That is, 1/10 the signal applied to the tip of
the probe actually reaches the input of the oscilloscope.
Monitoring Fast
Networks with Digital Oscilloscopes - Today's high-speed digital networks use
sophisticated protocols to ensure error-free data transmission. Yet, in many cases,
monitoring the physical layer with a digital oscilloscope can pinpoint precious
information that may not be revealed by protocol analyzers.
Mysterious
ground - For single-ended measurements, don't depend on mysterious ground connections.
Always use a good, short ground connection.
Probe
Loading - how oscilloscope probles can affect the circuit being measured
Smart
scopes: Spot the secrets within waveforms - DSOs’ job keeps getting harder, but
scope makers keep finding ways to satisfy ever-tougher demands. Wider bandwidth, quicker
ADCs, and deeper memories are only part of the story. Giving designers insights and
answers when they need them now requires more intelligence.
Taking the measure of
video processors - measuring video distribution amplifiers using oscilloscope, reprint
from May, 1990 issue of BROADCAST ENGINEERING
The Oscilloscope
- most frequently taken for granted and yet often least understood by audio engineers,
article first appeared in the August 1982 issue of Recording-engineer/producer magazine
Understandign
data converters - this application note document from Texas
Instruments discusses data converter specifications as defined on a manufacturing data
sheet and considers some aspects of designing with data conversion products
Using
a Digital Phosphor Oscilloscope for Video Tape Recorder Video Tracking Adjustment -
One of the common maintenance tasks for helical-scan video tape recorders (VTRs) is the
adjustment of the timing of the heads relative to the video tracks recorded on the tape.
The main objective is to assure that any tape recorded on the VTR can be played on another
similar machine without requiring any adjustments. The video tracking adjustment,
typically done with an analog oscilloscope, requires a lively, gray-scale display.
Build an oscilloscope
BitScope - low cost mixed
signal capture engine configured as an RS-232 peripheral device, includes dual channel
wide bandwidth DSO and 8 channel Logic Analyzer, circuit diagram freely available
Calibrate
scope jitter using a transmission-line loop - Digital-clock-period jitter is the
variation in the period of a clock cycle compared with a nominal (average of many cycles)
clock period. To accurately measure period jitter using an oscilloscope, you must subtract
the oscilloscope jitter from the measured jitter. However, oscilloscopes rarely have a
jitter specification, so you must determine the oscilloscope jitter. One method of
measuring oscilloscope jitter is to use the oscilloscope to measure the jitter of a pulse
generator with known jitter. The ideal generator for measuring oscilloscope jitter would
have zero jitter. This article shows a circuit for generating a calibration signal with
near-zero timing jitter.
Coax
connectors make low-cost test pieces - you can construct low-cost small test pices
like filters, attenuators and terminators using coaxial panel jacks without pc boards or
enclosures, design idea from EDN Magazine
Counter
Circuit Improves Oscilloscope Triggering - this prescaler circuit, when plugged into
the scope's external trigger input, can provide reliable, low-jitter triggering for both
older and modern oscilloscopes
Delay
line upgrades vintage scope - Vintage triggered-sweep oscilloscopes find use in many
applications. However, they have no internal delay line, so they can't display the pulse
that triggers the sweep. Moreover, early laboratory scopes contain delay lines having
insufficient delay to display such pulses during a uniform portion of the sweep. With such
oscilloscopes, the true pulse shape remains a mystery. You can circumvent these
limitations if you add an external delay line and equalizer. The scope can then display
the exact trigger-point trace. The instrument then becomes easier to use, and the
measurements become more trustworthy.
Multiplexer
creates mixed-signal scope input - using two multiplexer ICs and some TTL logic), you
can view eight analog or digital (or some of both) signals on the oscilloscope
NTSClab - The
purpose of the lab was to create a circuit which would take an NTSC signal in and display
TV on a oscilloscope.
NTSC Synchronization
Separator For Stable Triggering of Oscilloscope Video Waveform Displays - Have you
been frustrated by video waveforms which are difficult to display on your oscilloscope? Do
you have to readjust the trigger level every time the scene changes? This article
describes a simple circuit that will allow a triggered sweep oscilloscope to provide the
most important capability of a video waveform monitor, a stable display of the video
waveform.
RF Sampler -
handly little gadget that lets you to "look" at the signal and frequency output
of radio transmitter with oscilloscope
Scope probe
measures high frequencies - measuring clocks and critical signals accurately is often
inconvenient and hard to do accurately with normal 10× probes, this article describes
100× probe that is easy to make and use, has a high bandwidth, and has a small (less than
1 pF) input capacitance
Sniffer
probe locates sources of EMI - this miniature special probe and an oscilloscope can
help to locate and identify magnetic-field sources of EMI
Taking the measure of
video processors - measuring video distribution amplifiers using oscilloscope, reprint
from May, 1990 issue of BROADCAST ENGINEERING, article describes 1:10 proble design
optimized for 75 ohm video system measurements
Trigger
circuit locks onto one horizontal line - produces an oscilloscope trigger that
synchronizes the horizontal sweep to a video signal that allows you to view any horizontal
line by adjusting a potentiometer
In those early years of computer-based measurement and automation,
the desktop computer, linked by the General Purpose Interface Bus (GPIB), played an
auxiliary role; however, the increasingly powerful PC has changed all of that. Today, the
PC can acquire, analyze, and present data at increasing frequencies, resolutions, and
sampling rates.
In the dim and distant past, engineers recorded measurements with
pencil and paper - a slow and error-prone method. Today, 20 years after the introduction
of the IBM PC, two types of instruments - inboard and outboard - take measurements and
move data into a host computer. PC technology has become the backbone of automated test
and measurement systems.
Today virtual instruments are superseding the traditional kind by
revolutionizing how measurements are made and the data shared. History of virtual
instrumentation began over 15 years ago as PCs started coming into use in test and
measurement as instrument controllers. The PC is now the most powerful and cost-effective
approach to building instruments. Virtual instrumentation leverages the power,
flexibility, and programmability of the computer and thus brings a wide variety of
benefits. Laptop computers have further encouraged this trend with a form factor ideal for
many portable applications.
Buffer
Hardware for xoscope - This circuit is a buffer between oscilloscope probes and sound
card. It provides amplification and protection against high voltage input signals.
FreeVIEW sound - This
software turns a PC or notebook into a long-time data logger, a chart recorder, a storage
oscilloscope, spectrum analyser and much more. This software works with Microsoft®
Windows® 95/98/ME.
JMM (Java
Multi Meter) - JMM is data-acquisition software for digital multimeters equipped with
a rs-232 port, such as the Metex 3850 and many others. The software is very simple to use
and the control is straight forward.
PC instrumentation
through the ages - Events beyond technology helped shape the way engineers use
computers to automate measurements. This article tells what has heppened in this field.
SweepGen
- generate sweep test tones using PC soundcard, Windows program
Test Tone Generator -
simple and easy to use free function generator for Win95/NT
Trace
voltage-current curves on your PC - Some years ago, one of the fundamental electronic
instruments was the laboratory curve tracer. A CRT display would sweep out terminal
behavior (current versus voltage) from which you could derive mathematical models. From
the displays, you could determine the bias points for optimum design performance. Today,
however, you rarely find the classic curve tracers in the lab. Instead, you find
design-simulation software, such as Spice, that's removed from hands-on, empirical
analysis. Spice models now exist for almost all electronic components. Characterization
analyzers still make the voltage-current measurements but not at the design-engineer
level. This low-cost circuit allows you to return to the hands-on approach by using your
PC as a limited curve tracer. This curve tracer sweeps out seven logarithmic-scaled
currents from 1 µA to 1 mA while measuring the voltage, 0 to 5V (3.3V on some PCs), at
each step.
Use
RS-232C port to measure pressure - simple circuit and accompanying software turn a
pressure sensor into an accurate and cheap pressure digitizer that works with any PC's
RS-232C COM port
Cables used to carry high frequency electrical signals are generally
analysed as a form of Transmission Line. The amount of capacitance/metre and
inductance/metre depends mainly upon the size and shape of the conductors. The
Characteristic Impedance depends upon the ratio of the values of the capacitance per metre
and inductance per metre. To understand its meaning, consider a very long run of cable
that stretches away towards infinity from a signal source. The result, when the signal
power vanishes, never to be seen again, is that the cable behaves like a resistive load of
an effective resistance set by the cable itself. This value is called the Characteristic
Impedance, of the cable.
Return loss (RL) is a measure of the reflected energy caused by
impedance mismatches in the cabling system. Reflections create an unwanted disturbance
signal or "noise" on the cabling link that potentially interferes with the
reliable transmission over the link. As a noise source, return loss is measured and
evaluated to assure that the reflected signal energy is sufficiently small in reference to
the transmitted signal such that the reliability of the transmission is not negatively
impacted. Return loss is an important characteristic for any transmission line because it
may be responsible for a significant noise component that hinders the ability of the
receiver when the data is extracted from the signal. It directly affects
"jitter." Return loss is especially important for applications that use
simultaneous bidirectional transmission.
A Close-Up of Return
Loss - Will You Pass the Test? - Return loss (RL) is a measure of the reflected energy
caused by impedance mismatches in the cabling system. Return loss is especially important
for applications that use simultaneous bidirectional transmission.
Defining
Shorts & Opens - dealing with CATV distribution equipment and power supplies, we
are constantly confronted with shorted and open components and circuits
Cable
Reflection Tester - a schematic for a homebrew cable reflection tester from the
December 1996 issue of Electronics Now, useful for checking coax cable runs for shorts or
even impedance mismatches
Copper Cable
Testing - Twisted pair alternatives have replaced coaxial cabling on today’s
LANs. At the Category 5 performance level or above, there are a bewildering number of
options. All standards require that installed links pass three tests: wire map (end-to-end
pin-to-pin connectivity), attenuation and near end crosstalk (NEXT).
Effects of
Multiple Crimps and Cable Length on Reflection Signatures from Long Cables - This
paper summarizes tests conducted at Northwestern University to relate deformation,
distance and reflection coefficient amplitudes after propagation along coaxial cables as
long as 530 m. TDR has been employed by geotechnical and mining engineers to measure rock
deformation since the early 1980's. In this approach, coaxial cables are grouted into a
rock mass that is expected to deform. Progressive, localized rock movement along joints
deforms the cable, which produces a change in TDR pulse reflection signatures.
Measuring Cable Parameters - application note form HP which describes testing and
characterizing cables, including characteristic impedance, capacitance per unit length,
loss, and propagation velocity
Proper testing of wiring system after installation is essential to
guarantee good operation later. The cabling system needs to be measured after installation
and the results of those measurements should be documented for later use. Measurement is
also useful during use when cabling problems are suspected. The most common cable fault is
an open circuit, usually due to problems close to or at the ends of the cables. A simple
ohm meter test generally suffices.
For multiplair cables where cable ends are many wires inside, a
simple multimeter is bothersome. For those applications multi-pair cable testes which find
showrt circuits and broken wires are a good choise.
In some application you need to measure the cable length. Depending
on the cable characteristics you know and the measuremenet instruments you have, you can
use a multimeter (resistance measurement), RLC meter (capacitance measurement). time
domain reflectometer (pulse tesing) or signal ateenuation testing (signal source and level
meter) to measure the lenght of the cable you have installes somewhere.
Copper Cable
Testing - Twisted pair alternatives have replaced coaxial cabling on today’s
LANs. At the Category 5 performance level or above, there are a bewildering number of
options. All standards require that installed links pass three tests: wire map (end-to-end
pin-to-pin connectivity), attenuation and near end crosstalk (NEXT).
Smart
Continuity Tester - offers a short-circuit test current of less than 200uA and detects
resistance values of less than 10 ohms
Multi-wire cable testers
Cable
tester is fast and cheap - simple microcontroller based cable tester verifies the
correct wiring of the cable, up to 8 conductor cables
TP
Cable Tester - circuit that consists of transmitter and receiver and can test 4 pair
(8 wire) UTP wiring as used in structures cabling systems (for example CAT-5 LAN cabling)
Cable test tone senders
Signal Tracer
and Injector - This audio signal tracer/injector will undoubtedly prove to be very
useful for many routine servicing operations. The unit consists of an audible signal
monitor for "listening" to the signals present in an electronic device (such as
an audio system, receiver, amplifier, or tape deck) at circuit points inside these
devices. It also includes an RF detector probe and signal generator.
Cable
Reflection Tester - a schematic for a homebrew cable reflection tester from the
December 1996 issue of Electronics Now, useful for checking coax cable runs for shorts or
even impedance mismatches
Ring
oscillator measures cable length - ECL exclusive-NOR gate (F100107) and a length of
cable form a simple ring oscillator, the delay from the cable and the gate determine the
ring oscillators frequency, 100m cable yields approximately a 1 MHz oscillation frequency
DMMs may not be particularly forgiving of voltages on their inputs
exceeding their specifications. You need special tools and procedures to successfuly and
safely measure high voltages. A simple high voltage probe for a DMM or VOM may be
constructed from a pair of resistors. This kind of devices are sold as ready made devices
(for example Tektronix, Agilent and Fluke sell those).
Follow safety precautions when working around high voltages. Usually
some form of equipment protection should be considered when working with high voltages.
50kV
Voltmeter - simple high voltage probe design for movin coil meter
Measuring
high voltages - simplest way to get at least a rough value of tension is to measure
the maximum distance the voltage can arc over
3 GHz Prescaler -
will take a 0.1 - 3 GHz signal and divide it by 1000 so you can measure frequencies
outside the normal range of your frequency counter
Frequency
Counter Measurement Techniques - Inexpensive frequency counters that will measure
frequency well into the microwave range are available to the hobbyist today. A frequency
counter is an excellent means of accurately determining the frequency of unknown signals,
or to see if an oscillator or a multiplier stage in a receiver or transmitter is working.
However, one must watch out as what is really being measured and exactly what the counter
is "seeing".
F/V
converter has high accuracy - high-accuracy frequency-to-voltage converter (FVC)
demonstrates how a synchronous, charge-balance, voltage-to-frequency converter (VFC) can
function as a single-supply FVC given proper biasing and level shifting
Pulse period
to voltage converter - converts a square wave input signal into a voltage proportional
to the time between edges (period) of the signal, not the frequency, the range is from
100uS to to 10mS, which produces a voltage from 100mV to 10 volts
Le
Herwood - autoradan ajanotto - A car race timer implemented with PIC16F84 and three
intelligent 7-segment displays. Text in Finnish.
Time-tag
impulses with zero-crossing circuit - A "constant-fraction discriminator"
usually performs the time-tagging of impulsive events, which have a peaking time of the
signal amplitude.
Audio volume is the most commonly measured audio signal property. VU
and dB meters both measure the audio power involved in recording and they both use
logarithmic scales to report that power.
When measuring electrical signals decibel is the difference (or
ratio) between two signal levels; used to describe the effect of system devices on signal
strength. A signal strength or power level; 0 dBm is defined as 1 mW (milliWatt) of power
into a terminating load.
When measuring electrical signals the following is true: VU is short
for "volume units" and it is a measure of average audio power. A VU meter
responds relatively slowly and considers the sound volume over a period of time. Its zero
is set to the level at which there is 1% total harmonic distortion in the recorded signal.
dB is short for "decibels" and it is a measure of instantaneous audio power. A
dB meter responds very rapidly and considers the audio power at each instant. Its zero is
set to the level at which there is 3% total harmonic distortion. Because of these
differences in zero definitions, the dB meter's zero is roughly at the VU meter's +8.
When measuring audio signal power (vibrations in air) the following
measurements are made: The decibel (abbreviated dB) is the unit used to measure the
intensity of a sound. On the decibel scale, the smallest audible sound (near total
silence) is 0 dB. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful
than near total silence is 20 dB.
What does 0 dB mean? This level occurs when the measured intensity
is equal to the reference level. i.e., it is the sound level corresponding to 0.02 mPa. In
this case we have equation:
Sometimes the amount if noise needs to be measured. Most typically
harmonic distortion needs to be measured. Harmonic distortion describes a nonlinear
property of systems where the output of the system has added energy at frequencies that
are at integer multiples of the frequencies input to the system. The traditional technique
is to input a single frequency F into the system under test, then take the output, apply a
filter that eliminates F, and measure everything that's left over. This is usually done
with a twin-T, high-G notch filter centered on F. The problem with such a technique is
that it measures EVERYTHING that's left over: not only the harmonic products of F at 2*F,
3*F, 4*F and so forth, but all noise, uncorrelated components (line frequency noise, RF
interference) and so forth. Nowadays computer techniques can be applied where a more
detailed analysis can be made (usually based on FFT methods) where harmonic and
non-harmonic components can be identified.
10-octave
audio generator speeds tests - generates a composite audio signal comprising 10 sine
waves of 10 different equal-amplitude frequencies across the audio band
3 Channel
Spectrum Analyzer - This 3 channel 15 LED spectrum analyzer can be used as an addition
to any audio amp project. It produces fantastic displays on three LED bars that can be
individually adjusted for any particular frequency range.
Building
the L-R Test Set - helps you to set up left/right channel balance on audio
broadcasting ystems
High-resolution
volume-unit meter simplifies CD recording - CD digital-recording decks typically have
peak-reading-only volume-level meters. This feature is adequate to prevent clipping but
does a poor job of reading the average volume, or loudness, level. A high-resolution,
average- (not peak-) reading volume-unit meter produces an accurate reading of loudness.
Measuring
Frequency Response - This document describes how to measure the frequency response of
any amplifier or network with a signal generator and AC RMS meter
Measuring
Input and Output Impedance - input or output impedance of any two terminal network or
electronic equipment can be determined by measuring the small signal ac currents and
voltages
Notch
Filter Extends Spectrum-Analyzer Range - you dont necessarily need specialized,
expensive equipment to measure total harmonic distortion of todays high-performance audio
devices
LED Audio VU Meter
- logarithmic scale with 3 dB steps, based in LM3915 IC
Led
Bar Audio Power Meter - This is a 10 led logarithmic (3dB steps, 30dB full scale) LED
audio power meter built using LM3915 driver IC. This page explains in detail how to build
it and how it works.
Simple
circuit forms peak/clipping indicator - This simple peak detector is the result of a
need for a single-5V-supply, level/clipping indicator for a multimedia-PC sound system.
The design is unique in that it detects both stereo channels on a single peak-hold
capacitor. All the adjustments in the circuit simultaneously apply to both left and right
stereo inputs. The output is suitable for driving a bar-graph display or for
analog-to-digital conversion and display with a microprocessor. The circuit operates as a
dual positive-peak-detector circuit.
Mixed-signal
algorithm tests transducers - simple test procedure allows you to measure damping
coefficient beta in electromechanical transducers, such as speakers, microphones, and
seismic geophones
Simple
procedure tests transducer - testing electromechanical transducers can be as simple as
measuring a dc voltage with this circuit, enables you to measure the damping coefficient
([beta]) of speakers, microphones, seismic geophones, and other transducers that exploit
electromagnetic phenomena
Understanding
Mixers - general information on RF mixers and how to measure mixer performance
Power and field strength meters
A field strength meter is perhaps the simplest piece of RF test
equipment that can be built. Used for checking transmitters, antenna experimentation, and
testing RF oscillators, field strength meters provide an indication of the presence of RF
energy. They are generally not frequency sensitive and are useful where indication of a
change in level is more important than the actual strength of the signal indicated.
The meter works by converting any RF signal present at the antenna
to a DC voltage. This voltage drives a meter movement to give an indication of relative
RF. Usually the meter includes a control to reduce its sensitivity where required.
A
Clamp-On RF Current Probe - Here's a sensor that lets you measure currents in your
LowFER, MedFER,or ham antenna and ground system without breaking the circuit. You simply
clamp the pliers-like probe around the wire you want to measure. An advantage of a current
probe over a simple relative field strength meter is that the measurements are highly
repeatable and can provide a fairly good indication of how your antenna system compares to
others.
An RF field
monitor - uses neon glow lamp as a electromagnetic field detector
Build a RF
Sniffer Probe! - This sniffer probe is miniature, only about 2 inches long and very
usable up to 1 GHz or higher if linearity isn't a problem above 1 GHz. Beloq 1 GHz this
proe has very flat response.
Clip-on
RF Current Meter - Circuit description is in Japanese, but pictures and circuit
diagram usable. This is an useful tool for RF interference troubleshooting! For EMC
investigations, you can also clip this meter on to coaxial cables, rotator cables and
other wiring in your shack, to find out where the RF currents are flowing, and how big
they are.
Clip-on
RF Current Meter - Circuit description is in Japanese, but pictures and circuit
diagram usable.
Field
Strength Meter - measures radio field strength at VHF frequencies in the range 80 -
110 MHz
Field
Strength Meter - This RF field strength meter use only few parts, a printed circuit
board is not necessary; components can simply be soldered to one another.
Field-Strength Meter I
- This circuit is a electromagnetic field meter which can be used for meaturing of
transmitters output power.
Field-Strength Meter
II - This circuit is an electromagnetic field meter which can be used for meaturing of
transmitters output power.
Field Strength Meter,
VHF Band - This circuit measures radio field strength by converting the signal to DC
and amplifying it. This field strength meter was designed for VHF frequencies in the range
80 - 110 MHz.
Funky
Fresh® LED RF Signal Meter - a high quality RF signal meter based around the Analog
Devices AD8313 0.1 GHz - 2.5 GHz logarithmic detector IC, capable of detecting signals as
low as -80 dBm
RF Probe / Signal
Strength Meter - Detecting RF signals above approx 30MHz, this may be used as a
relative signal strength meter or as an RF probe to detect sources of EMI. The unit
consists of an antenna, detector, amplifier and moving coil meter.
Simple
Field Strength Meter - simple and also quite sensitive, uses an ordinary digital
voltmeter to measure signal strength, works on VHF and FM bands
Simple RF
Measurement Probe - This probe is useful for any low level RF work, and simply
connects to your multimeter. The voltage shown will not be accurate, since this is a
rectifier probe, but the measurements are good enough for you to be able to determine
where the RF stops, or if a stage is not giving the gain you think it should.
Simple RF detectors
Cellular Phone
Helper - activates a variety of devices when your cellular phone is in use, pdf file
Homebre
RF Spectrum Analyzer . built using VCR tuner, coverage will be from around 100 MHz to
900 MHz and varies with tuner manufacturer
Signal attenuators
Attenuator
Pads - homebrew attenuation pads, descripes Pi style attenuator pads for 1 dB, 2 dB, 4
dB and 8 dB attenuation, also step attenuator circuit, also includes Pi and T Network
Resistive Attenuation Calculator
Homebrew
Attenuators - Contained herein are attenuator values for both PI and TEE types. The
need for standard values can be met by using one or the other.
Fixed
Attenuators - Fixed attenuators can be designed to have either equal or unequal
impedances and to provide any amount of attenuation (theoretically) equal to or greater
than the configuration's minimum attenuation - depending on the ratio of Z1/Z2.
Attenuators with equal terminations have a minimum attenuation of 0 dB. Unequal
terminations place a lower limit on the attenuation.
RF
Signal Generator - cheap and fairly basic circuit to generate RF signals for
realignment of radio receivers, operates from 150 KHz to 12 MHz
Other RF measuring tools
A Simple UHF
Dummy Load - A very simple and effective dummy load can be made from an old length of
coaxial cable that has an impedance of the same value as the desired dummy load.
Bias Tee - Bias
tees allow you to insert DC voltages into your signal path (coax) without disrupting the
existing signal in that path, for example for feeding active antennas
Signal Tracer
and Injector - This audio signal tracer/injector will undoubtedly prove to be very
useful for many routine servicing operations. The unit consists of an audible signal
monitor for "listening" to the signals present in an electronic device (such as
an audio system, receiver, amplifier, or tape deck) at circuit points inside these
devices. It also includes an RF detector probe for use with HF modulated signals, such as
those found on an antenna, RF amplifier, or IF section of a receiver.
There are many ways to measure temperature elecronically. A
thermocouple is a very commonly used sensor for measuring temperature. It consists of two
dissimilar metals, joined together at one end, which produce a small unique voltage at a
given temperature. This voltage is measured and interpreted by a thermocouple thermometer.
Because thermocouples measure in wide temperature ranges and can be relatively rugged,
they are very often used in industry.
Thermocouples are available in different combinations of metals or
calibrations. The four most common calibrations are J, K, T and E. Each calibration has a
different temperature range and environment. Propably the most commonly used type is
K-type thermocouple, which is a Ni-Cr-sensor very suiable for 0-200 degress celsius
temteperature measurements (can be used from -200 to 1250 celsius).
Other commonly used temperature sensors are NTC and PTC resistors,
which change their resistance according to the temperature. Also semiconductors can be
used as termperature sensors (semiconductor PN junction characteristics change when
temperature changes and this is used in some temperature measurement applications).
General information
ECEFast
Technical Papers - A selection of temperature measurement information document
platinum resistance temperature detectors, thermocouple fundamentals, noncontact
thermometers and infrared systems. Also information on water characteristics measurement
(conductivity, exygen, pH).
Temperature
Sensors - This documents is a quick introduction to thermocouples, RTDs and
thermistors.
Thermocouples
Introduction - The Thermocouple is a thermoelectric temperature sensor which consists
of two dissimilar metallic wires, e.g., one chromel and one constantan. These two wires
are connected at two different junctions, one for temperature measurement and the other
for reference.
Track
multisite temperatures on your PC - This low-cost circuit allows you to track four
remote temperatures with thermistor sensors through the parallel port on your PC. This
four-zone thermometer instrument has a temperature range of -40 to +90°C and a resolution
of better than ±1°C.
Circuit
improves on temperature measurement - When current pulses with a stable IHIGH/ILOW
ratio modulate a semiconductor junction, the ensuing voltage difference (for example, ?VBE
for a bipolar transistor) is a linear function of the absolute (Kelvin) temperature, T.
You can use this truism to make accurate temperature measurements.
Build a Temperature
Logging Serial Interface; the TEMP05 - The TEMP05 was developed by Midon Design to be
a serial logging interface between the Dallas Semiconductor One-Wire bus and a host PC. It
was originally set up for logging temperatures from the Dallas Semiconductor One Wire
Weather Station and up to 20 additional DS18S20 One-Wire Thermometers. It has since
evolved to also read one Dallas Semiconductor One Wire Rain Gauge and Dallas Semiconductor
One Wire Humidity Sensors.
Digital
Remote Thermometer - Remote sensor sends data via mains supply, temperature range 00.0
to 99.9 °C
Interfacing
A Single-Wire Temperature-Sensor IC To A PC - Maxim's MAX6577, can measure temperature
over a range of -40°C to 125°C, has single-wire interface and requires few external
components to be interfaced to PC trough parallel port
Therm4Palm
- Thermometer for Palm is a simple application and circuit made for Palm devices, that is
able to show the current temperature ( °C ) and the graphic of its evolution in the past,
by means of a simple external hardware. This application is freeware. The source code is
supplied, in order to enhance its features by other users.
Temperature
sensor doesn't discharge battery - active temperature sensor in the rechargeable
battery pack does not drain the battery, and it needs only one terminal for its
power-supply input and temperature output, output suitable to be connected to a
microcontroller
Web Thermometer -
WebThermometer + NetThermometer are a couple of utilities to measure the temperature
remotely on the browser via HTTP (the former) or TCP/IP (the latter). It works with a PC
with Windows 9x/ME/NT/2K or Linux installed and a simple hardware connected to the COM
port.
Circuit
protects system from overheating - This two-chip circuit in provides fan control and
overtemperature warning and shutdown signals to protect systems from excessive heat. The
circuit monitors the temperature of the pc board and the die temperature of a CPU, an
FPGA, or another IC with an on-chip temperature-sensing transistor.
Micro
power temperature alarm - sounds an alarm when the temperature exceeds a certain point
(around 65 degrees celsius), can be powered for years by a single 3 volt lithium battery,
pdf file
Program
converts temperature from RTD sensor - platinum resistance-temperature-detector (RTD)
sensor provides an accurate means of obtaining temperature readings but has nonlinear
resistance-vs-temperature characteristic; therefore, for accurate measurements, you must
calibrate the sensor and use a table of resistance vs temperature to get the right results
out
Temperature
Sensor ICs Simplify Designs - When you set out to select a temperature sensor, you are
no longer limited to either an analog-output or a digital-output device. There is now a
broad selection of sensor types, one of which should match your system's needs.
Tradeoffs in
Selecting IC Temperature Sensors - A discussion of IC temperature sensors has become
timely and important because electronic systems are increasingly dense, power-hungry, and
hot. Temperature sensors also have a lot of gadget appeal. Many ICs perform highly
abstract functions.
Basic Multimeter -
A number of shunts and multipliers selected by a switch can be used in association with a
single basic meter to form a multirange instrument, known as a multimeter. this is capable
of measuring volts, current and resistance. A multirange meter can be constructed in two
units, the first containing the 0-1mA meter movement with switches to select various shunt
and series resistors to give six d.c. current ranges up to 1 amp and eight d.c. voltage
ranges up to 1000 volts. An internal battery provides an ohms range readable up to 200,000
ohms which corresponds with the first division of the meter (0.02mA)
Extending
Voltmeter Ranges - The value of series resistance is determined by the current
required for full-scale deflection and by the range of the voltages to be measured.
Digital Voltmeter
- The ICL7107 is a 3 1/2 digit LED A/D convertor. It contains an internal voltage
reference, high isolation analog switches, sequential control logic, and the display
drivers. The auto-zero adjust ensures zero reading for 0 volts input. This how this
circuit uses that IC to make a voltage meter.
Circuit
yields accurate absolute values - This circuit delivers the absolute value of the
input signal with an accuracy better than 10 ppm of the full-scale range.
Op-amp
rectifier signals input state - op-amp rectifier operates from a single supply and
provides a logic output and an LED that indicate the state of the input voltage
Precision
rectifier is glitch-free to 1 MHz - manufacturers circuit for a precision,
current-mode, full-wave rectifier converts a voltage signal to a current, eliminating
errors arising from voltage drops across the rectifying diodes
RMS-to-dc
converter is accurate and stable - combining the well-known true rms-to-dc circuit
with a simple S/H circuit eliminates offset errors, which increases accuracy and
temperature stability
RMS Values and
Measurement - document tries to help alleviate confusion about measurement of RMS
(Root Mean Square) values of AC voltage
Voltage monitoring
Capacitor
Discharge Indicator Circuit - circuit which will discharge the high voltage power
supply filter capacitors and main energy storage capacitors and show when they are safely
discharged
Live Wire
Detector - The short antenna held near any mains-carrying cable will detect a current
flow. This will be indicated by a flashing light-emitting diode (LED).
Simple
circuit detects voltage overranges - a visual indication of whether a sensed voltage
is above or below its nominal value, provides different-color indications if the sensed
voltage is above or below the preset value
Simple
circuit monitors battery voltage - monitors four NiCd rechargeable batteries and
causes the LED to flash if the voltage of the batteries goes lower than 4V
Polarity testers
Simple
Polarity Tester - can be used to check the polarity of any power source up to 12V DC
or AC
Measuring electrical current can be done using many methods. The
most commonly used method for measuring current is to run the current through a know
resistor. The voltage drop over this resistor is determined by the current and the
resistor value. If you select a small resistence, you do not cause much voltage drop over
it, so measung does not considerably affect the measured circuit.
When measuring high currents on mains cables devices called
"current transformers" are used. Their main purpose is to produce, from the
primary current, a proportional secondary current that can easily be measured or used to
control various circuits. The primary winding is connected in series with the source
current to be measured, while the secondary winding is normally connected to a meter,
relay, or a burden resistor to develop a low level voltage that is amplified for control
purposes. In many high current applications the primary coil is just wire going through
the toroidal core of the current transformer (=equivalent to one turn primary coil). Many
clamp-on multimeters and clamp-on current measuring adapters that can measure AC current
are built in this way.
Some clamp-on multimeters can also measure DC currents. Those
application use torid cares, where the Hall generator/sensor is placed within air gap of a
magnetic core to measure the current. The hall sensor in the air gap measures the magnetic
field cause by the wire runnign through the toroidal core.
In some SMPS designs current transformer (usually made using a
ferrite toroid) helps to track the current in the control circuit's feedback loop. This
current is then used to determine how the future behavior of the SMPS will be modified.
Generally clamp-on multimeters need the toroidal type core to be
closed to get measurements. Lately there has become available "open jaw" style
Electrical Tester for measuring current using measurement device which does not need the
fully closed core.
With traditional clamp-on current meters, measurements can only be
made on single conductors. If you need to measure current in multipair cables (for example
mains cables), this usually needs covers to be moved to gain access to individual wires.
Some new special multimeters can measures current in multi-core cables and power cords
without the need to split them. This kind of multimeter use techologies which are called
(dending on manufacturer) with names like Flexiclamp, multi-core digital clampmeter and
SMF Technology.
When measuring current on mains wires please note that most AC
current meters are designed to give right current ratings only when they are connected to
pure sinusoidal mains current. Pulse-width motor control systems, SCR and triac
controllers and switchmode power supplies, for example, add high frequency (HF) components
to the 50Hz mains that can cause false readings on traditional multimeters. Instruments
with True RMS employ circuitry that rejects the HF signals and correctly calculate and
display the RMS value.
AC Line
Current Detector - This circuit will detect AC line currents of about 250 mA or more
without making any electrical connections to the line. Current is detected by passing one
of the AC lines through an inductive pickup
AC Line Current
Detector - This circuit will detect AC line currents of about 250 mA or more without
making any electrical connections to the line. Current is detected by passing one of the
AC lines
Construction of
low resistance shunts - This page has instruction how to make very low resistance
resistors for measuring purposes from normal wire. This kind of measuring resistor can
convert a high current running throug it to low voltage which can be measured with voltage
measuring devices.
Picoammeter
circuit with 4 ranges - This circuit uses a CA3420 BiMOS op amp to form a picoammeter
with 4 ranges and exceptionally low input current (typically 0.2pA)
Selection
Guide to Clamp-On Current Probes - Clamp-on curren tprobes are designed to extend the
current measuring capabilities of DMMs, power instruments, oscilloscopes, hand-held scopes
recorders or loggers and other diverse instruments. The probe is "clamped"
around the current carrying conductor to perform non contact current measurement.
Simple
circuit detects current pulses - provides a visible indication of positive and
negative current pulses whose amplitudes can vary from 20 to 150 mA
SMF Tecnology -
SMF Technology (Suparule Magnetic Field Technology) are based on the measurement of the
magnetic field generated from a current carrying conductor. This technology allows
"open jaw" and "multi-core digital clampmeter". The key to the
performance of this new sensor is a series of planer magnetic coils placed in a specified
layout around the conductor. The magnetic field created by the current in the conductor
induces a voltage in the magnetic coils, which is proportional to the magnetic field of
the conductor.
Measuring power is useful when you want to know how many watts
certain electronic device takes power. If the device is powered from DC voltage,
determinign the power is easy: measure the voltage going to the device and the current
going to the device (just connect two multimeters to the powering circuit). Then calculate
the power using formula power = voltage * current.
Measuring AC power is harder. The equation power = voltage * current
does still hold, but you can't necessarily do the measurement easily with two multimeters.
If you just measure the current and voltage with two multimeters, you will get the current
and voltage values. You can calculate the power wil formula power = voltage * current
(power in VA unit), but remeber that this power is not a real power taken by the device.
Depending the phase angel of the current and voltage, the real power taken by the device
can be anythign between zero and the power calulated with formula power = voltage *
current when current and voltage are measured with multimeter. Power meters which measure
real power, need to measure the instantaneous voltage and current many times in a AC power
phase, and with every measurement need to do the calculation of voltage * current. The
real power is the sum of those calculations. This more complex power measurement method
works also for non-sine waveforms.
Power meters provide an early warning of thermal overload by
monitoring power consumption in high-reliability systems. Power monitoring is especially
suitable for motor controllers, industrial heating systems, and other systems in which the
load voltage and current are both variable.
Make a
low-cost benchtop power meter - with a few inexpensive ICs and passive components, you
can easily make a multirange power meter suitable for use on your benchtop
Power
meter is ±1% accurate - Power meters can provide an early warning of thermal overload
by monitoring power consumption in high-reliability systems. Power monitoring is
especially suitable for motor controllers, industrial heating systems, and other systems
in which the load voltage and current are both variable.
The two instruments most commonly used to check the continuity (a
complete circuit), or to measure the resistance of a circuit or circuit element, are the
OHMMETER and the MEGGER (megohm meter). The ohmmeter is widely used to measure resistance
and check the continuity of electrical circuits and devices. Typical ohmmeter range
usually extends to only a few megohms.
There are two basic methods of measuring resistance. One is to apply
a known voltage to the unknown and measure the current. The other is to apply a known
current and measure the voltage. A basic analogue ohmmeter typically consists of a dc
ammeter, a dc source of potential (usually a 3-volt battery) and few resistors. Digital
multimeters generally measure resistance by applying a known current to the resistor and
measuring the voltage drop over it (directly proportional to the resistance value).
Megger is less often needed instrument. The megger is widely used
for measuring insulation resistance, such as between a wire and the outer surface of the
insulation, and insulation resistance of cables and insulators. The range of a megger may
extend to more than 1,000 megohms. Megger has the same operation principle, but it
generally uses a much higher measurement voltage, typically 250, 500 or 1000 volts DC.
Those high voltage ranges are often used to test the quality of the insulation in
electrical cables and equipments (safety checks).
Continuity
Tester - audible output if resistance is less than 300 ohms
High-Voltage
Insulation Tester - This is the circuit for a high-voltage insulation tester. The
circuit is very straightforward and seems to be east to built. This circuit was originally
designed for testing high-voltage capacitors used in transmitter tank circuits , it is
very useful for checking the flash-over voltage for air-spaced variable capacitors used in
high-power aerial tuning units.
Johtavuusilmaisin
- A simple resistance measurement circuit which shows if resistance is smaller or higher
than the threshold set to circuit. The output is using two LEDs. Test in this circuit is
in Finnish.
Johtavuusilmaisin
- A simple resistance measurement circuit which shows if resistance is smaller or higher
than the threshold set to circuit. The output is using two LEDs. Test in this circuit is
in Finnish. This document is in pdf format.
Low-Ohm
Meter - article which describes few different low resistance measuring circuits
Low Resistance
Adapter For DMMs - When the resistances to be measured a very low, say 0.1 ohms,
analog meters are useless because the reading becomes indistinguishable from zero. A four
and a half digit DMM may have 1/100 ohm resolution but the resistance of the connecting
leads, the contact resistance where the leads plug into the meter and where the leads clip
to the unknown is significant compared to the unknown. This circuit uses four-wire
measurement technique to make more accurate measurements.
Megger - The
megger is a portable instrument used to measure insulation resistance. The megger consists
of a hand-driven DC generator and a direct reading ohm meter. A simplified circuit diagram
of the instrument is shown in this document.
Testing
Solid Insulation of Electrical Equipment - The megger test method for determining the
condition of electrical insulation has been widely used for many years as a general
nondestructive test method.
The importance of sound electrical insulation systems has been
acknowledged from the early days of electricity. Insulation failure can cause electrical
shocks, creating a real hazard to personnel and machinery. A regular program of testing
insulation resistance is strongly recommended to prevent this danger, as well as to allow
timely maintenance and repair work to take place before catastrophic failure. All new
equipment, motors, transformers, switch gears, and wiring should be tested before being
put into service. This test record will be useful for future comparisons in regular
maintenance testing.
High potential insulation tests are "go no-go" tests. The
cable or equipment is required to withstand the specified voltage for the specified time
duration. These tests will normally reveal gross imperfections due to improper handling or
construction.
The megger is widely used for measuring insulation resistance, such
as between a wire and the outer surface of the insulation, and insulation resistance of
cables and insulators. The range of a megger may extend to more than 1,000 megohms. Megger
has the same operation principle, but it generally uses a much higher measurement voltage,
typically 250, 500 and 1000 volts DC. Those voltage ranges are often used to test the
quality of the insulation in electrical cables and equipments (safety checks). For high
voltage testing typically votages 2500 and 5000 volts DC are used. Those high voltage
ranges are often used to test the quality of the insulation in electrical cables.
All old wiring and equipment should be carefully checked (for
safety), both visually and with an insulation tester. In particular the insulation
resistance between live connections and any exposed metal parts should be checked with a
high voltage tester ("Megger"- is this just a UK term?) at 500V for 230V
equipment and 250V for 110V. If there is any leakage worse than about 50 megohms then
track it down.
HiPot testing is a special insulation testing. Some people refer to
this as Insulation Testing but this can lead to the mistake of making a resistance
measurement using 500Vdc. While this is good practice and useful (to identify potential
failures in filters) it does not test insulation strenghnesss. For production, voltages
between 1,500 and 2,500 Volts are necessary to verify that insulation is in place.
Anything less may “Pass” faulty insulation. Some standards allow AC or DC HiPot
testers. DC testing should always be the preference because measurements are not affected
by filter capacitance. But do make sure there is an indication that the external load is
discharged after testing.
Basic insulation
testing - What does the measurement tell me? Fundamentally, how "good" the
insulation is.
Cable/Harness
Testing Easy - The table in this doocument shows the guidelines for using voltage to
detect insulation defects. These tips can assist you in training people for cable and wire
harness quality assurance.
Insulation
Resistance Testing For Maintenance & Safety - Insulation failure can cause
electrical shocks, creating a real hazard to personnel and machinery. A regular program of
testing insulation resistance is strongly recommended to prevent this danger, as well as
to allow timely maintenance and repair work to take place before catastrophic failure.
Portable Appliance
Tester - Portable Appliance Tester is a test instrument which performs basic
electrical safety tests required for portable appliances and equipment.
Principles of
Insulation Testing - Probably 80% of all testing performed in electrical power systems
is related to the verification of insulation quality. This Technical Bulletin briefly
describes the fundamental concepts of insulation testing including: insulation behavior,
types of tests, and some test procedures.
Testing
Solid Insulation of Electrical Equipment - The megger test method for determining the
condition of electrical insulation has been widely used for many years as a general
nondestructive test method.
What
impulse testing of transformers tells - Impulse testing simulates a transient surge
coming into the transformer terminal from lightning strikes at various distances on the
line. The test surge is created by the impulse testing equipment, which includes a group
of capacitors that is charged and discharged during the test. The purpose of the impulse
test is to show that the insulation of the device being tested can withstand expected
transient voltages. And, it is an excellent measure of quality control.
A meter is a measuring instrument that combines functions of
ammeter, voltmeter and ohmmeter , and possibly some additional ones as well, into a single
instrument. Multimeters are designed and mass produced for electronics engineers.
Multimeters are commonly used to measure voltage and resistance between two points.
Current is more rarely measured because you must alter the circuit to measure the current
(except if you use a clamp type meter which is available for high current measurements).
An analogue meter moves a needle along a scale. Digital meters give
an output in numbers, usually on a liquid crystal display. Most modern multimeters are
digital and traditional analogue types are destined to become obsolete.
Here is how a typical measurement are made in typical digital
multimeter nowadays:
DC voltage: The A/D circuitry in the multimeter is designed to
directly show DC voltage values typically in few volts range. For higher voltages the
input voltage is divided by a voltage divider network. For lower voltages the voltage is
amplified with amplifier.
AC voltage: Basically same idea as the DC measurement, except that
the input voltage is rectified somewhere in the process.
DC current: Input current is run through a known low ohm resistance,
which converts the input current to a small voltage drop. This voltage is fed to the DC
voltage measurement circuitry.
AC current: This is measures in the same way as DC current, except
that the voltage is fed to the AC voltage measurement electronics.
Diode test: A low current (typically less than 1 mA) is fed to the
measurement leads (output voltage limited to few volts). The voltage between measurement
leads is measurement with DC voltage measurement electronics.
Resistance measurement: An accurately known low current (varied
dependign on ohms range) is fed to the measurement leads. The voltage (directly
proprortional to the resistance conencted) between measurement leads is measured.
Some multimeters can have some of the following functionalities in
addition to the basic ones described above:
Continuity tester: Works like the resistance measurement measurement,
If the voltage between measurement leads is lower than specified value (usually 50 to 300
ohms) would give, make the beeper to signal.
Frequency: Input signal is converted to square wave first. The
multimeter has either pulse counter (count pulses for one second gifes ouput in Hz) or
frequency to voltage converter (output od converter measured with DC voltage measurement
circuitry)
Capacitance: Feed known frequency low amplitude signal through the
capacitance. Measure the AC current which go through the capacitor. Other option is to
measure the capacitor charge and discharge times.
Temperature: Voltage from thermocouple sensor is amplified and
processed. Then the result is fed to DC voltage measurement electronics.
Please note that the information give above are just general
statements. The implementation may vary between multimeter brands and models.
If you measure low voltage circuits and do not need very accurate
results, some cheap multimeter could be a good choise. You do need to worry much on the
meter and measurement wires. If you are going to measure mains voltage circuits, then I
recommend to get a good reliable multimeter (IEC 1010 and CE compliant) with safe test
leads (1000V rated PVC or silicone insulation, safety banana plug connectors, IEC 1010 and
CE compliant). If you are going to measure high current circuit (something with high
short-circuit current) be sure that you have a properly fused multimeter (all scales
fused) and prefereably fused test probes also.
Almost multimeters owadays have safety banana connecors in then
which can accpet both normal banana plugs and safety banana plugs (bananas with plastic
"tube" insulation surrounding the plug tip). Please note that there are several
different versions of safety banana connectors in use. The banana plug metal tip part
inside insulator is similar, but there can be differences in the mechaical construction of
the insulation (inner and outer diameter, length of the insulating part etc.). Those
differences cause that you might not be able to interchange measuring leads between
different multimeter brands and you can't use all available multimeter measuring leads
with your multimeter because of this compatibility issue.
General information
Check
The Specs For Safety - When working with test equipment, it’s important to
understand category ratings. The most important single concept to understand about safety
standards is the Overvoltage Installation Category, defined as Categories (CAT) I through
IV.
Playing
it safe with your DMM - Taking safe measurements starts with choosing the right meter
for the application and the environment in which it will be used. There are a lot of
safety issues to think about, from clothing to tools to procedures. Here’s a sampling
of just some of the things you should consider on your DMM safety checklist.
Selecting
the clamp for your job - Choosing the right type of clamp meter is critical when you
want to ensure proper power supply to all electrical equipment on a circuit. Current
clamps are a simple and reliable means to verify if current is flowing, and if there is
continuity between contacts or points of connection. The current clamp has been a mainstay
of the electrical technician's toolbox for decades, because it is a cost-effective, simple
and accurate means to measure current.
The Effect of Meter
Resistance - All meters have resistance. The value of this resistance depends upon the
voltage range selected. A typical moving coil meter has a SENSITIVITY of 20,000 ohms per
volt. Digital multimeter have typically higher resistance (input impedance typically
around 10 megaohms on many ranges on good digital multimeters).When the meter is connected
to a circuit to measure voltage, this resistance will affect the circuit and therefore the
accuracy of the measurement obtained.
Using the
Multimeter to Measure Voltage and Resistance - Multimeters are commonly used to
measure voltage and resistance between two points. Current is rarely measured because you
must alter the circuit to measure the current.
Using the
Multimeter to Measure Voltage and Resistance - Multimeters are commonly used to
measure voltage and resistance between two points. Current is rarely measured because you
must alter the circuit to measure the current.
Using a Volt Ohm
Meter - A very handy tool for trouble shooting problems is a VOM (Volt Ohm Meter) -
also called a Multi-Meter. It can be used to test cables, AC power levels and Batteries.
You'll often find yourself out on the road with problems that are causing you grief, but
you aren't quite sure why.
Why
"True-RMS"? - Many modern loads - including solid state motor drives and
heating controls - often conduct non-sinusoidal (distorted current). Since the current
wave shape can have a drastic effect on a current clamp reading, troubleshooting with an
average responding meter will be wrong. In these cases, a True-rms reading is the only
option to get accurate measurement results.
Multimeter circuits
Basic Multimeter -
A number of shunts and multipliers selected by a switch can be used in association with a
single basic meter to form a multirange instrument, known as a multimeter. this is capable
of measuring volts, current and resistance. A multirange meter can be constructed in two
units, the first containing the 0-1mA meter movement with switches to select various shunt
and series resistors to give six d.c. current ranges up to 1 amp and eight d.c. voltage
ranges up to 1000 volts. An internal battery provides an ohms range readable up to 200,000
ohms which corresponds with the first division of the meter (0.02mA)
Build your own
Gaussmeter - Have you ever wanted to find out how strong a magnet really was, or how
the strength of the magnetic field varied as you changed the distance from the magnet or
the temperature of the magnet, or how well a shield placed in front of the magnet worked?
This circuit is a hand-held Gaussmeter for measuring the polarity and strength of a
magnetic field. This circuit is a very simple, inexpensive Hall effect device Gaussmeter
you can build for as little as $6. This circuit uses a normal multimeter as the display
device.
Inductance
Meter Adapter - a circuit that, when connected to a digital multimeter, lets you
measure low-value inductances
Power
Meter/Dummy Load - adapter to measure small transmitter power with normal multimeter
Computer software for multimeters
JMM (Java
Multi Meter) - JMM is data-acquisition software for digital multimeters equipped with
a rs-232 port, such as the Metex 3850 and many others. The software is very simple to use
and the control is straight forward.
Electronic
Altimeter - This design uses a PIC16F877 to measure the output of a temperature sensor
and an absolute pressure transducer to measure altitude.
Pressure
gauge responds linearly to altitude - you can use a common pressure transducer as an
altimeter if you employ a special technique to make the transducer respond linearly
Programmable
Pressure Transducer - micromachined monolithic silicon piezoresistive-bridge pressure
transducer (SPPT) is a dominant technology in automotive, industrial, medical, and
environmental pressure-sensing applications
Use
RS-232C port to measure pressure - simple circuit and accompanying software turn a
pressure sensor into an accurate and cheap pressure digitizer that works with any PC's
RS-232C COM port
Impedance is and AC equivalent to what resistance is for DC. To
measure inductance you generally need some signal measuring instruments and a signla
source which gives out measurement at the frequency you want to do the impedance
measurement at. Usually the impedance more or less varies dependign on the frequency.
Build
A Vector Network Analyzer - vector network analyzer (VNA) is an essential tool for
measuring the complex impedance of a circuit at a given frequency
Measuring
Input and Output Impedance - input or output impedance of any two terminal network or
electronic equipment can be determined by measuring the small signal ac currents and
voltages
General measurement for testing all kind of semicondictors is to
measure the PN-junctions in the component. You can perform this measurement with a
multimerter, but please note that analog and digital meters behave quite differently when
testing nonlinear devices like diodes and transistors. On a (digital) DMM, there will
usually be a diode test mode. Using this, a silicon diode should read between .5 to .8 V
in the forward direction and open in reverse. This test can show catastrophic failures
like shorts and opens on diodes, bipolar transistors, SCRs and MOSFETs.
Curve tracers are pieces of electronic test equipment similar to an
oscilloscope. They can not only test transistors and other devices but evaluate the
functional specifications as well.
Genral transistor tests are checking semiconductor junctions and
measuring gain of a transistor. Typical basic in-circuit transistor testers measure the
collector-base or base-emitter junctions. This kind of tester can determine the polarity
(npn or pnp) and function of a transistor (a very useful feature in measuring unknown
transistors). Transistor gain can be easily measured with many modern multimeters or
specialized circuits (like a curve tracer).
Transistor
tester fits into your pocket - It can be helpful to rapidly and easily determine the
polarity (npn or pnp) and function of a transistor. This pocket transistor tester is
claimed to be ideal for quickly testing without regard to such parameters as gain and
frequency response.
There are many techniques for measuring capacitance. Some of these
techniques require a function generator to provide either a sinusoidal, or step-function
voltage source. The current going through capacitor is generally measured in a way or
another. Some measurement techniques measure the time for the capacitor to charge to a
known voltage when it is charged with a known current.
99 Cent ESR Test
Adapter - ESR meters tend to use test signals of around 100 kHz and 100 mVAC. This
simple circuit does this test. The results can be viewed with oscilloscope.
Build
your own bypass-capacitor tester - Most circuits use bypass capacitors and can deliver
substandard performance if the capacitors have poor pulse characteristics. Few if any
articles cover how to test bypass capacitors for pulse characteristics. This circuit tests
these characteristics. It charges the capacitor under test through 100 kohm for
approximately 1 msec and then discharges it through 10 ohm for approximately 40 nsec.
Build
your own bypass-capacitor tester - Most circuits use bypass capacitors and can deliver
substandard performance if the capacitors have poor pulse characteristics. Few if any
articles cover how to test bypass capacitors for pulse characteristics and describes a
simple circuit that tests these characteristics.
Capacitance Meter
- This project is an instrument capable of measuring all but the largest capacitors used
in radio circuits. The common 555 timer IC forms the heart of the circuit and deflection
on the meter is directly proportional to the value of the unknown capacitor.
Digital Capacitance
Meter - this meter will measure capacitance from a low 10 picofarad to 10,000 uF in
five ranges
ESR Meter Stuff -
The document has ESR meter schematic, theory of operation and some sales literature.
High
Voltsge Electrolytic Capacitor Reformer - use of this unit for testing electrolytic
capacitors in old valve equipment, this device can also fix some problems in old
electrolytic capacitors
Measure
Device Capacitance: Easy Circuit Measures Voltage Dependent Capacitance - There are
many techniques for measuring capacitance. Some of these techniques require a function
generator to provide either a sinusoidal, or step-function voltage source. The following
design idea has the advantage of requiring no special excitation source, but rather relies
on a simple test circuit, and the single-shot capture, and measurement capabilities
inherent in digital oscilloscopes (DSO’s).
Inductance
Meter Adapter - a circuit that, when connected to a digital multimeter, lets you
measure low-value inductances
Inductance
Meter Adapter - a circuit that, when connected to a digital multimeter, lets you
measure low-value inductances
Inductor
self-resonance tester - with aid of an oscilloscope and a signal generator this
circuit will allow you to measure resonant frequencies from kilohertz to over 10
megahertz, adds only few picofarads of parallel capacitance to inductor, pdf file
Method
simplifies testing high-Q devices - The design of low-phase-noise oscillators requires
careful attention to resonator unloaded Q. In the construction of a low-phase-noise,
high-frequency oscillator, the goal is to achieve an unloaded-Q figure greater than 400 in
a reasonable package. This simple test set uses nothing more than the voltage-divider
relation with the device under test embedded as a series trap network to test inductor.
Measuring
connectors - would like to replace one connector type with a different, less expensive
model. How do I prove the two connectors have the same electrical characteristics? Also,
how will the power and ground-pin assignments within the connector affect its performance?
Optoelectronics component testing
Diode and LED
Tester - simple and cheap unit for testing diodes and LED's for forward conduction and
reverse blocking
IC testing
IC Tester -
IC Tester is electronic device for testing ics (integrated circuits) and may test some
others electronic elements with appropriate addon. Device is connecting to parallel
(printer) port at computer, currently you can connect it to PC and amiga computers.
Logic ChipTester
- ChipTester presented here is used with an IBM compatible PC, and will test nearly all
logic devices, providing they operate from a single 5V supply and have no more than 24
pins, Originally published in the 1995 Cirkit Catalogue
Continuity
Tester - This tester will "buzz" within two ranges - LO up to 3 ohms and HI
up to 185 ohms, pdf file
Fleapower
circuit detects short circuits - short-circuit tester that supplies a low current to
the device under test (DUT) and also uses voltages lower than 100 mV to prevent conduction
of semiconductors
Logic Probe -
uses a single CMOS IC and shows three logic conditions, High, Low and Pulsing
Oscilloscope
or Logic Analyzer? - When given the choice between using an oscilloscope and using a
logic analyzer, many people will choose an oscilloscope. Why? because a scope is more
familiar to most users.
PC Based 32
Channel Logic Analyser - It is a 32 Channel, 40Mhz, fully PC controlled TTL/CMOS logic
analyser with internal/external triggering and trigger delay.
Simple
logic analyzer pushes microcontroller to its limit - A simple logic-analyzer design is
compatible with all versions of Windows and pushes the PIC 18C252 chip to its speed limit
to achieve a 1-MHz sampling rate (Figure 1). The circuit can examine three channels of
relatively low-speed logic signals that have infrequent, or sparse, transitions.
Simple
logic probe uses bicolor LED - probe can measure high, low, and high-impedance logic
states, in addition to indicating switching logic states
Broadaband
50 Mhz optical fiber receiver - circuit attaches a plastic fiber optic PIN photodiode
assembly to a small box containing a small 3v battery and a standard standard BNC plug
designed to be plugged into to the input of an oscilloscope with a 50 ohm termination
resistor, can detect light pulse frequencies beyond 100MHz, not very sensitive, pdf file
Diode and LED
Tester - simple and cheap unit for testing diodes and LED's for forward conduction and
reverse blocking
DMM measures
light level - this circuit allows you to measure light levels using a regular digital
voltmeter
IR Remote Control
Tester - measures the relative intensities of different Infra red light sources
Light
Measurement Instrumentation - It is helpful to understand the different types of
information you can get from different light measurement devices. Here is a quick
taxonomy.
Simple ESD
gun tests IC - you can use this simple ESD-test gun to test the effects of ESD through
sensitive ICs, based in piezo-electric type kitchen gas lighter
AC-power
monitor uses remote sensing - This circuit senses the main power loss through the
radiated power-line signal. The battery-operated circuit has a quiescent-current drain of
approximately 2 µA.
A Simple
Fluxgate Sensor - The fluxgate is one kind of magnetic field sensor which combines
good sensitivity with relative ease of construction. The basic principle is to compare the
drive-coil current needed to saturate the core in one direction as opposed to the opposite
direction. The difference is due to the external field.
Build
a Magnetic Field Immunity Tester - a precompliance test system can help you determine
whether your products comply with standards such as the CE Marking
Build your own
Gaussmeter - Have you ever wanted to find out how strong a magnet really was, or how
the strength of the magnetic field varied as you changed the distance from the magnet or
the temperature of the magnet, or how well a shield placed in front of the magnet worked?
This circuit is a hand-held Gaussmeter for measuring the polarity and strength of a
magnetic field. This circuit is a very simple, inexpensive Hall effect device Gaussmeter
you can build for as little as $6. This circuit uses a normal multimeter as the display
device.
Electric
Field Detector - this circuit will come handy when you have to follow the mains wires
buried in the wall or even water pipes provided they are not too far away (2-4cm max)
Electromagnetic
Field Detector - This circuit uses a radial type inductor as a probe and responds well
to low frequency changing magnetic and electric fields. Ordinary headphones are used to
for detection.
Electromagnetic
Field Probe with Meter Output - designed to locate stray electromagnetic (EM) fields,
response from 50Hz to about 100kHz, will easily detect both audio and RF signals
Induction
Receivers - This induction receiver is very sensitive and can serve a variety of
purposes. It is excellent for tracing wiring behind walls, receiving audio from an
induction transmitter, hearing lightning and other electric discharges, and monitoring a
telephone or other device that produces an audio magnetic field ("telephone pickup
coil").
Live Wire
Detector - The short antenna held near any mains-carrying cable will detect a current
flow. This will be indicated by a flashing light-emitting diode (LED).
RC network
eliminates precision reference - this circuit uses a magneto-resistive sensor to
detect small magnet displacements without resorting to a precision voltage reference
Sensitive
Geomagnetic Field - a rather sensitive circuit which will detect minute variations of
a magnetic field, particularly the Earth magnetic field
Capacitance
type liquid level monitor - originally designed to monitor the level of liquid natural
gas in a tank but it can be used to also measure almost any liquid, uses two custom
insulated metal tubes form a capacitor plate, capacitance between the two tubes increases
as the level of the liquid rises, circuit converts an increase of capacitance into a
positive voltage change, pdf file
Capacitance
type liquid level monitor - This circuit was originally designed to monitor the level
of liquid natural gas in a tank but it can be used to also measure almost any liquid. This
document is in pdf format.
Fluid Level
Sensor - uses an ac-sensing signal to eliminate electrolytic corrosion on the probe
Low-cost
relative-humidity transmitter uses single logic IC - This low-cost
percentage-relative-humidity radio transmitter operates in a cold-storage warehouse for
vegetable storage at temperatures of 1 to 5°C. The transmitter design is simple: It uses
a readily available, capacitor-type percentage-relative-humidity sensor for which the
capacitor value increases with humidity. The circuit can be tuned to operate at 10- to
50-MHz RF band.
One-wire
bus powers water-level sensor - You can use the simple sensor circuit to remotely
monitor the level of liquid water in a vessel such as a swimming pool. A host PC or µC
reads the output of the pulse counter via the Dallas Semiconductor one-wire bus.
RF/Capacitance
Level Instrumentation - Capacitance level detectors are also referred to as radio
frequency (RF) or admittance level sensors. They operate in the low MHz radio frequency
range, measuring admittance of an alternating current (ac) circuit that varies with level.
Admittance is a measured.
Ethernet
10BaseT simulator jig yields zero emissions - tool to evaluate emissions from Ethernet
unshielded-twisted-pair (UTP) 10BaseT LAN-interface devices without contaminating the
measured results with its own RF emissions, this cirucit generates 10BaseT equipment link
test pulses without RF emissions so that 10BaseT equipment will keep sending data
Fleapower
circuit detects short circuits - a short-circuit tester that supplies a low current to
the device under test (DUT) and also uses voltages lower than 100 mV to prevent conduction
of semiconductors
Multicore Cable
Tracer - unit is designed to help when establishing the connections in multicore
cables or when identifying a large number of cables contained in a trunking or conduit,
supports up to 63 channels up to 100 meters or more, Originally published in ETI, August
1995
Test Plug -
circuit which indicates whether your mains socket is wired correctly, for 220-240V
systems, Originally published in Electronics in Action, March 1994
A
System Designer's Guide to Isolation Devices - Isolation amplifiers provide galvanic
isolation of the incoming signal to safeguard equipment and personnel, but the world of
isolation, with its own terminology, technologies, and standards, is unfamiliar to many
designers. This article reviews the basic concepts and technology of isolation devices and
discusses the various options available to the system designer.
Beware of
under- or overspecifying your next sensor - to choose the best photoelectric sensor
for your application, you need to consider a number of criteria, including sensor
configuration; environment; and the placement, nature, and speed of the target
Circuit
makes simple FSK modulator - The need for a compact telemetry system poses a challenge
for designing a small, light, low-component-count system. Commercial FSK
(frequency-shift-keying) modulators are bulky and need many passive components. This
circuit uses a single NOT gate (inverter), an On Semiconductor NL27WZ14 in a surface-mount
package, to generate continuous FSK data from TTL-level signals. This circuit is designed
to provide 2400 Hz / 1200 Hz FSK, but can be adapted for other frequencies up to an
operating frequency of approximately 80 kHz.
ECEFast
Technical Papers - A selection of temperature measurement information document
platinum resistance temperature detectors, thermocouple fundamentals, noncontact
thermometers and infrared systems. Also information on water characteristics measurement
(conductivity, exygen, pH).
Ground Loops and
Their Cures - DC power systems used for instrument and loop power are subject to a
number of possible ground loops. The method to solving ground loop problems is generally
twofold. Remove any extra grounds so that there is one ground in the system. If there must
be more than one ground, make sure to isolate each from other(s).
Improved
amplifier drives differential-input ADCs - ADCs with differential inputs are becoming
increasingly popular. This popularity isn't surprising, because differential inputs in the
ADC offer several advantages: good common-mode noise rejection, a doubling of the
available dynamic range without doubling the supply voltage, and cancellation of
even-order harmonics that accrue with a single-ended input. This document shows shows two
easy ways to create a differential-input differential-output instrumentation amplifier.
Inductive
Proximity Switches Introduction - Inductive proximity switches are no-touch,
non-interactive devices and sensitive to all metals. They consist of an oscillator,
demodulator, level and switching amplifier.
Testing
MEMS: Don't reinvent the wheel - but take little on faith - MEMS, which not only
condition signals but also move, require consummate care in handling. But the
manufacturers have figured out much of what you must know to successfully apply the
devices. So be highly selective in choosing where to independently build up your private
body of knowledge.
Understanding pH
measurement - In the process world, pH is an important parameter to be measured and
controlled. The pH of a solution indicates how acidic or basic (alkaline) it is. The
formal mathematical definition of pH is the negative logarithm of hydrogen ion activity. A
pH measurement loop is made up of three components, the pH sensor, which includes a
measuring electrode, a reference electrode, and a temperature sensor; a preamplifier; and
an analyzer or transmitter. A pH measurement loop is essentially a battery where the
positive terminal is the measuring electrode and the negative terminal is the reference
electrode. The measuring electrode, which is sensitive to the hydrogen ion, develops a
potential (voltage) directly related to the hydrogen ion concentration of the solution.
The reference electrode provides a stable potential against which the measuring electrode
can be compared.
Understanding pH
measurement - In the process world, pH is an important parameter to be measured and
controlled. The pH of a solution indicates how acidic or basic (alkaline) it is. A pH
measurement loop is essentially a battery where the positive terminal is the measuring
electrode and the negative terminal is the reference electrode. The measuring electrode,
which is sensitive to the hydrogen ion, develops a potential (voltage) directly related to
the hydrogen ion concentration of the solution. The reference electrode provides a stable
potential against which the measuring electrode can be compared.
Wiring For Trouble
Free Signal Conditioning - Signal conditioning equipment for process signals has kept
pace with modern technology, but many users never realize the full potential of the
equipment because of poor installation and wiring practices. Such practices can degrade
equipment performance from a small percentage of error to the point where the equipment is
unusable.
The symbol for an instrumentation amplifier may look similar to that
of an opamp and may have a broadly similar function: differential amplification of its
inputs, but it is an entirely different creature. An opamp is designed to be used in a
negative feedback topology, both to achieve a uniform gain and to compensate for amplifier
imperfections. An instrumentation amplifier, on the other hand, is used for open loop
differential amplification, and has been designed with this in mind. It provides a smaller
gain that is typically set by one external resistor. It is often used as a
"pre-amp" for signals that are too low-level for an ordinary opamp buffer.
Instrumentation amplifiers can be built out of individual opamps or you can use a
single-chip implementation.
Typical Instrumentation Amplifier monitors voltages from a few
millivolts (DC or AC). It has several switch settings to allow you to select the best
gain. It can be used with may measurement devices like A/D converter cards, programmable
logic etc.
Circuit
adds programmability to sensor amplifier - This pressure-sensor amplifier circuit
offers a number of advantages over the traditional approach using the classic three-op-amp
instrumentation amplifier. The circuit can operate from a single supply and uses only two
op amps and 1% resistors.
Differential
amp needs no power source - A true-differential, power-source-free,
high-input-impedance amplifier with bipolar output would present distinct advantages in
remote devices. Such an amplifier, with its bipolar output, would be a better choice than
a unipolar, 4- to 20-mA device. This circuit is a differential amplifier which requires
not local power (it is powered through same 2 wire interface as the amplifier signal
goes).
Difference
amplifier uses digital potentiometers - You sometimes need to measure a small signal
in the presence of a large common-mode signal. Traditional instrumentation amplifiers that
use two or three op amps in their internal structure find common use in these
applications. This circuit presents an alternative approach that is useful when low cost
and low drift are important, but when you don't need high precision. The circuit uses IC1,
a dual 1024-position AD5235 digital potentiometer with nonvolatile memory. The programming
capability of the AD5235 allows you to perform gain setting and trimming in a single step.
0.02% V/F
converter consumes only 26 µA - voltage-to-frequency (V/F) converter that produces a
0- to 10-kHz output for an input range of 0 to 5V with linearity of 0.02% and gain drift
of 60 ppm/8C
60-Hz
modulator records process variables - allows you to record process variables (4 to 20
mA, 0 to 10V dc) on a three- phase power monitor designed to record only ac waveforms
Other signal format converters
Circuit
converts pulse width to voltage - This circuit converts pulse information to a clean
dc voltage by the end of a single incoming pulse. In another technique, an RC filter can
convert a PWM signal to an averaged dc voltage, but this method is slow in responding.
This circuit works better and faster.
Current loop interfacing
4-20mA is an analog current loop protocol which has become the
defacto U.S. standard for supplying DC power to a field transducer, and receiving a scaled
return signal. DC power is typically supplied via an unregulated +10 to +30Vdc supply.
Many industrial current-loop data acquisition systems operate on a 24V or 28V single
supply. The field transducer controls the current flow, and is often referred to as a
2-wire "transmitter". You can easily receive 4-20 mA signals by passing the
current through 100 ohm resistor, so you get 0.4-2V voltage over the resistor (if you
select 250 ohm resistor, you will get 1V to 5V reading).
Single
Supply 4-20mA Current Loop Receiver - Many industrial current-loop data acquisition
systems operate on a 24V or 28V single supply. You can make a single-supply current loop
receiver with the RCV420 by using its 10V reference as a pseudo ground. The RCV420 will
convert a 4-20mA loop current into a 0 to 5V output voltage with no external components
required. The current loop can be sourcing or sinking and can be referenced to either the
power-supply V+ or ground.
Sensor and measuring circuit ideas
Autoreferencing
circuit nulls out sensor errors - This autoreferencing circuit nulls out the error of
a sensor, such as a pressure transducer, at its reference level, for example, at ambient
pressure. The circuit is an analog-digital-feedback control system that uses a digitally
programmable potentiometer to provide the variability.
Design
approach simplifies signal conditioning - low cost and wide availability of 8-bit
microcontrollers, such as Motorola's MC68HC11, allow you to easily incorporate
intelligence in pressure-measurement systems, your main challenge is to signal-condition
the sensor's small, differential bridge signal into a single-ended output voltage that the
µC's A/D converter
Method
offers fail-safe variable-reluctance sensors - Variable-reluctance sensors are
preferred for industrial and automotive environments, because they sustain mechanical
vibration and operation to 300°C. In most applications, they sense a steel target that is
part of a rotating assembly. Because the unprocessed signal amplitude is proportional to
target speed, a sensor whose signal-processing circuitry is designed for high speed ceases
to function at some lower rate of rotation. Hall-effect sensors are preferable for speeds
of several pulses per second, but they require the attachment of a magnet to the rotating
assembly. Neither variable-reluctance nor Hall-effect sensors offers fail-safe detection
of the processed signal in the event of failure in the cable or sensor. This circuit is a
fail-safe variable-reluctance sensor for low- to medium-speed operation.
Network
imitates thermocouples - Thermocouples find widespread use for temperature measurement
in systems. During system design or testing, you must observe the system's response at
different temperatures. However, it's inconvenient to heat a thermocouple every time you
need to check a system's performance. This simple circuit allows you to set a number of
voltages equal to the thermocouples' outputs at given temperatures.
Bringing
Bit-Error-Rate Testing Up to Speed - Testing today's communication devices with a
parallel bit-error rate tester can give comprehensive testing in less time, reducing
bottlenecks in high-throughput operations. You also get to reliably identify bad devices.
Nonvoice
Calls and Line Testing Tutorial - This tutorial examines the history of line testing
and the various challenges brought about by recent technological change, all within a
service provider's business context
Test
high-speed drivers with bursts and pseudorandom bit patterns - combine a
high-performance, dual-channel pulse generator having burst and pseudorandom bit-stream
capabilities with a high-bandwidth sampling oscilloscope for an effective and reliable way
to characterize high-speed drivers
Testing the
telephony interface - when you are interfacing to a standard telephone line with
voice, data, or fax signals, you need to support signaling protocols and provide
acceptable connected performance so you need suitable test instruments for it
Lightning
Detector - a VLF receiver tuned to 300 kHz designed to detect the crackle of
approaching lightning
Lightning
Detector - VLF receiver tuned to 300 kHz designed to detect the crackle of approaching
lightning
PC
hardware monitor reports the weather - You usually use PC hardware monitors to keep a
close eye on power-supply voltage levels, the speed of system cooling fans, and even the
temperature of the CPU. However, now that low-cost hardware monitoring ASICs are
available, advanced hardware monitoring has become a standard feature in most new PCs. And
hardware monitors are now finding their way into diverse applications, such as weather
stations. This weather station measures wind speed, humidity and temperature. Circuit
connextgs to PC parallel port.
220V Mains
Monitor - With this circuit you will be able to monitor the quality of the mains.
There are 4 distinct sections, each supervising a parameter pertinent to the quality of
the supply line. There are sections for noise, spikes, voltage and flutter.
AC-power
monitor uses remote sensing - This circuit senses the main power loss through the
radiated power-line signal. The battery-operated circuit has a quiescent-current drain of
approximately 2 µA.
Mains Frequency
Meter - Mains frequency is pretty stable and it is unlikely that you have to measure
it but if you have an emergency generator you might find this circuit useful as it will
give an indication whether the generator is running too fast or too slow.
Optocoupler
simplifies power-line monitoring - The use of a linear optocoupler and a
capacitor-based power supply yields a simple, yet precise power-line-monitoring system.
This circuit converts the 110V-ac power-line voltage to an ac output voltage centered at
2.5V, covering 0 to 5V. The circuit isolates the output signal from the power line. This
circuit can be modified for power-line voltage of 220V ac by changing the value of one
resistor.
Vaihejärjestysindikaattori
- Simple indicator to test the rotation direction of 3-phase network power. The text of
this document is in Finnish.
Airflow
monitor protects components - circuit combines a temperature transducer with a heater
resistor to derect if cooling does not work correctly
Low-cost
anemometer fights dust - You can detect poor filter maintenance by determining the
actual airflow with a "hot-wire" anemometer, but most electronic anemometers are
costly and bulky. As an alternative, you can create an SMBus/I2C anemometer using an I/O
expander, a few inexpensive switches, and a low-cost remote-temperature sensor.
Idea for a car
tachometer - A tachometer is simply a means of counting the engine revolutions of an
automobile engine. In this suggested idea a NE555 timer is configured as a monostable or
one shot. The 555 timer receives trigger pulses from the distributor points. Integration
of the variable duty cycle by the meter movement produces a visible indication of the
automobiles engine speed.
Tacho generator motor
speed feedback - This page is a bit different from most in that it covers the use of
tacho generators as feedback elements in motor control systems. This page covers tacho
generator rectifier circuit for 4QD Pro-120 electric motor controllers.
ADC
enables temperature-compensated weigh-scale measurements - You can provide temperature
compensation in weigh-scale applications by simultaneously measuring both the temperature
of the bridge and the primary output of the bridge transducer.
Adjustable
filter provides lowpass response - You can configure simple lowpass filters as pi
sections with nominal three-pole, 0.1-dB Chebyshev response to provide a moderate amount
of stopband selectivity. This example is for frequency settings of 3.083, 6.586, 14.491,
and 21.310 MHz.
Audio
Perimeter Monitor - using a single cable such as speaker wire or doorbell cable, this
circuit can be remotely positioned to detect all sound in that area
Build
a Magnetic Field Immunity Tester - A precompliance test system can help you determine
whether your products comply with standards such as the CE Marking.
Circuit
forms low-frequency circulator - This circuit provides four-port ciculator operation
at low frequencies, using the readily available 941 (equivalent to the ubiquitous 741) and
LM318 op amps. This four-port circulator is designed for 50 ohm impedance levels. The
circuit can readily accommodate other impedance levels, such as 75 and 600 ohms. You can
use the electronic four-port circulators in various applications with the fourth port
terminated. Possible applications are for example baseband-amplitude equalizer,
group-delay equalizer, low-frequency return-loss bridge and an electronic isolator.
Circuit
forms adjustable bipolar clamp - The easy way to clamp a signal to a given value is to
use two zener diodes, connected back-to-back. This method has several disadvantages. The
accuracy of the clamping depends on the tolerance of the zener diodes, and the clamping is
not adjustable, except by changing diodes. This circuit is a bipolar clamper with a range
of ±1 to ±10V, with the clamping level a function of the input voltage.
Electric meter reader -
This contraption uses a laser and photo resistor to non-intrusively measure the rotational
speed of that ominous disk inside the electric meter. With this information, we can
calculate how many Watts we're pulling.
Fuse Monitor / Alarm
- simple circuit way to see if a fuse has blown without removing it from its holder, LED
provides visual indication of when a fuse has blown
Improved
frequency modulator uses "negatron" - You can improve a capacitive-sensor
circuit with a modulator and an RF transmitter by modifying the modulator portion to
obtain better accuracy. More improvements result from adding a "negatron"
circuit, a configuration that uses equivalent negative capacitance.
RF Lap
Scoring System - This article describes the hardware and software implementation of an
RF lap scoring system to be used in motorcycle racing and other sporting events. The
project essentially involves acquiring vehicle identification and timing information to
update a central database as the vehicles pass the start/finish line.
Seismic
detector - piezoelectric element of a kitchen gas lighter is used in this simple, yet
effective seismic detector
Series
Lamp Limiter - connect a 100W lamp bulb in series with the supply to the equipment
being repaired to avoid very nasty high short circuit current is something goes seriously
wrong, useful for power supply testing and repairing
Simple
method measures duty cycle - interesting alternative approach to traditional method is
to take random samples of the digital input signal
Soft
Power On Tester for Amplifiers - The worst thing that can happen is that when you turn
an electronics device you are fixing on, it immediately pops a fuse - or worse yet a
valuable part you've just installed! If you don't have a variac with a current meter so
that you can make power on gradual, the next best thing is this widget. It can be whipped
up from parts in your local home supplies store.
Specifying
Electrostatic Measurement Tools - There are many instruments available for making
electrostatic measurements. What types of equipment do I need to audit and evaluate my
program?
Versatile
power-supply load uses light bulbs - Improvising loads for bench-testing and designing
power supplies is often a frustrating and sometimes hazardous experience. Many electronic
loads are on the market but are usually expensive and of laboratory-type precision and
often represent overkill for the average designer. Incandescent light bulbs make excellent
loads, able to handle large amounts of power. Moreover, they come in small packages and
require no heat sinks. The drawback is that the resistance of an incandescent lamp changes
dramatically with the power input. A simple approach to this control problem is to
pulse-width-modulate a power MOSFET in series with the load.
