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Tester or Measurement (Instrument) Circuits

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Last Updated: November 30, 2017 10:28 AM
Circuits Designed by Dave Johnson, P.E. :

Audio Frequency Digital Noise Generator -  When you need to test an audio circuit with broadband noise, this circuit works great.  it uses just three inexpensive C-MOS ICs  that generate a series of output pulses whose widths vary randomly.  I included a level control pot. . . Circuit by David A. Johnson P.E.-July, 2000

Automatic Timeout included with this On/Off Flip/flop Circuit -  This circuit is ideal when a device needs to be turned on and off with a single pushbutton switch, but also needs to turn itself off after some period of time.  With the components shown, the output will stay on for only about 20 seconds . . . Hobby Circuit designed by David A. Johnson P.E.-May, 2012

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
6 Models Available - Call 806-368-7747




Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

Armature Current Monitor for DC Motor Applications -  The LT1999 is a high speed precision current sense amplifier, designed to monitor bidirectional currents over a wide common mode range.  The LT1999 is offered in three gain options: 10V/V, 20V/V, and 50V/V.  The LT1999 senses current via an external resistive shunt and generates an output voltage, indicating both magnitude and__ Linear Technology/Analog Devices App Note, Nov 16th 2010

AT89C2051 Digital Thermometer & Clock -  Build your own a laboratory instrument for measuring time and temperature.  The DigiThermo demonstrates the use of 'C' language, a dual-slope converter, LCD interfacing, and digital filtering as well.   __ Designed by Wichit Sirichote

Atmospheric Detector -  "Sferics"(also spelled "spherics") is short for atmospherics and refers to the crackling static in a radio produced by lightning.  This receiver is tuned to an unused portion of the LF band provides enough sensitivity to detect lightning activity for hundreds or even thousands of miles.  Best performance is achieved with an external antenna, but just a few yards of insulated wire is sufficient.  A short whip mounted on the unit will work fine for picking up local storms. __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Atmospheric Disturbance Monitor -  Schematic + info + pictures __ Designed by Lennie Zink

Audax Monitors -  This project came about when Maplin sold off their stocks of Audax drive units back in 2004.  These speakers are made from layered birch ply, and feature a John "Zaph" Krutke crossover design. __ Designed by Mark Hennessy

Audible Continuity Tester -  Here is a pretty simple, low-cost audible continuity tester that makes use of just one quad comparator IC LM339, some resistors and a piezobuzzer.  The circuit including the comparator works off...__ Electronics Projects for You

Audible continuity Tester -  A logic tester with an audible indicator can be handy when troubleshooting or testing a crowded circuit board.  it allows you to keep your eyes on the circuit, rather than on a LED on the tester.  The project described in this article is just such a tester.  it provides an audible indication of the logic level of the signal presented to its input __ Designed by Tony van Roon  VA3AVR

Audible IR Proximity Detector -  This circuit gives an audible indication when any object comes in front of the infrared reflecting sensor (containing IR LED and phototransistor).  The sound generated by the sensor will be louder...__ Electronics Projects for You

Audible Logic Probe -  Using a conventional logic probe, it is difficult to determine what is happening at a point in a circuit above 50 Hz.  The human eye isn’t able to perceive the change...__ Electronics Projects for You

Audible Logic Probe -  The probe uses 2 IC 's and a handful of components to indicate the state of the input on 3 LEDs while the piezo gives an audible indication of the state of the line.  The input is connected to two inverters in the 4049 IC .  The top one is held above mid-rail via the 1M trim pot while the bottom one is held below mid rail by the 1M/220k voltage divider __ Contact Collin Mitchell

Audio Frequency Digital Noise Generator -  When you need to test an audio circuit with broadband noise, this circuit works great.  it uses just three inexpensive C-MOS ICs  that generate a series of output pulses whose widths vary randomly.  I included a level control pot. . . Circuit by David A. Johnson P.E.-July, 2000

Audio Millivoltmeter -  For Testing Amplifiers (etc) , An analogue design, 3mV to 30V with dB scale __ Designed by Rod Elliott  ESP

Audio Notch Filter with Frequencies 100Hz-10kHz -  A variable notch filter with both high and low pass filters. __ Designed by Andy Collison

Audio output meter -  The circuit is a voltage-doubling rectifier driving a panel meter.  The input signal is AC coupled via C1.  D1 holds the signal so that the negative peaks are at ground potential.  The mean level is above ground, so the polarity of C1 is important.  The peak level is rectified by D2 and stored in reservoir capacitor C2.  The value of R1 has been selected to give the required calibration with a 250uA meter movement.  if a 100uA is used, the alternative component values should be used __ Designed by Paul Stenning

Audio Power Meter -  This simple circuit indicates the amount of power that goes to a loudspeaker.  The dual-color LED shows green at an applied power level of about 1 watt.  At 1.5 watts it glows orange and above 3 watts it is bright red.  The circuit is connected in parallel with the loudspeaker connections and is powered from__ 

Audio power meter -  This VU (volume-unit) meter is capable of monitoring and displaying power levels present at the speaker terminals of an stereo audio power amplifier.  The levels are displayed in ten discrete steps.  This meter is not designed to give an accurate display of the power levelsLM3915, stereo VU meter __ Carl's Electronics

Audio Spectrum Monitor -  A digital audio signal processing experiment of real-time FFT (Fast Fourier Transform) analysis.   __ Designed by The Electronic Lives Manufacturing-presented Chan

Audio VU Meter -  A VU meter with 20 LED's.  The input source can be a line input or a microphone __ Contact P. Townshend - EduTek Ltd

Audio VU meter 9 leds -  5 LED VU Meter kit is based on LB1409 IC from SANYO, which will indicates the volume level of the audio signal it senses __ Contact IQ Technologies

Automated Plants Watering System -  During summers, most people are too lazy to water the potted plants on their rooftop gardens every day.  Explained in this section is a simple and exciting plant watering system that...__ Electronics Projects for You

Automatic Heat Detector -  This circuit uses a complementary pair comprising npn metallic transistor T1 (BC109) and pnp germanium transistor T2 (AC188) to detect heat (due to outbreak of fire, etc) in the vicinity and...__ Electronics Projects for You

Automatic Plant Irrigation System -  Here is a simple project more useful in watering plants automatically without any human interference.  We may call it as Automatic plant irrigation system.  We know that people do not pour the water on to the plants in their gardens when they go to vacation or often forget to water plants.  As a result, there is a chance to get the plants damaged.  This project is an excellent solution for such kind of problems.__ 

Automatic Power-Off Saves Battery -  12/19/96 EDN Design Ideas:  The Basic training program in Listing 1  helps visually handicapped people easily learn Braille dot code with the help of a trainer.  The trainer generates six-pin Braille code using six solenoids operating on an LPT1/2 either by directly connecting the low-power solenoids to the data bits of the parallel port or by driving solenoid pins (pull-out type] using an UN2003 power driver (Figure 1).  Push-in type solenoids require complemented (0 for 1 and 1 for 0] Braille-code data bits or an extra inverter on the LPT1 port __ Circuit Design by Jose Carlos Cossio, Santander, Spain

Automatic Rain Gauge with Digital Readout -  it collects, measures, records and empties.  Best of all, you don't have to leave the house.__ SiliconChip

Automatic Timeout included with this On/Off Flip/flop Circuit -  This circuit is ideal when a device needs to be turned on and off with a single pushbutton switch, but also needs to turn itself off after some period of time.  With the components shown, the output will stay on for only about 20 seconds . . . Hobby Circuit designed by David A. Johnson P.E.-May, 2012

Automatic water level controller -  This is simple automatic water level controller circuit.  it will make you more comfortable Because it enables open – close water pump automatically.  When full of water, was ordered off the water.  But When levels gradually reduced To the required, Then turned on fully the water.  So We do not have to worry about overflow and water out anymore.__ 

Automatically Turn Secondary Lamp On or Off -  28-May-09 EDN Design Ideas:  A transformer and a relay are all you need to automatically turn a spare lamp on or off __ Circuit Design by Vladimir Oleynik, Moscow, Russia

Automotive Thermometer -  Keep tabs on in-car temperatures__ SiliconChip

Autoranging True RMS-to-DC Converter -  A programmable gain amplifier (LTC6910-2) and a window comparator (LTC6700-1) and some control logic creates a wide dynamic range RMS to DC converter.  The comparator monitors the DC output and signals whether to increment or decrement the gain to maintain a predetermined output voltage range.  Knowing the output DC voltage and the gain setting can determine the True RMS amplitude of the signal being monitored__ Linear Technology/Analog Devices App Note, Mar 16, 2010

Autozero a position-sensing Detector -  03/18/99 EDN Design Ideas:  Autozeroing schemes can be necessary to minimize the input-offset voltages of position-sensing detectors (PSDs) , particularly when you use these detectors with high dc gain.  PSDs are useful optical transducers for accurately measuring displacement.  in practice, their typical configuration is as a differential current-to-voltage circuit (Figure 1).   __ Circuit Design by James Zannis, Renishaw S A, Champs-sur-Marne, France

Autozeroed Amplifier with halved noise needs few components -  10/25/07 EDN Design Ideas:  The unique architecture of the Analog Devices AD8553 instrumentation amplifier permits paralleling devices to lower noise __ Circuit Design by Marián Štofka, Slovak University of Technology, Bratislava, Slovakia

Avago Tech Note: Isolated current sensing with ∑-∆ optoisolators -  EDN Design Ideas:  06/12/2014    Sigma-delta optocouplers make for accurate isolated sensing, and can trade off speed for ENOB.    __ Circuit Design

Avago Tech Note: Strain sensing using optical phase interrogation technique with polymer optical fiber -  EDN Design Ideas:  07/16/2015   Optical phase interrogation with polymer fiber offers an easy to handle and integrate strain sensing solution __ Circuit Design by Avago Tech Note

AVR Digital Voltmeter -  We build a simple and inexpensive three digit display.  it's a voltmeter module but it has also general purpose digital iO pins.  You could use it as well to read a digital sensor and display the value.  it can be freely programmed, calibrated and even be programmed with a non linear formula.  it's a display where you can define the relation between the measured value and the displayed number.   __ Designed by Guido Socher

AVR Thermometer -  Build a simple digital thermometer using 20-pin uC, AVR 90S2313 and DS1820.  The thermometer is capable of measuring temperature from -55C to +125C!  with 1 degreeC resolution.   __ Designed by Wichit Sirichote

AVR thermometer / thermostat based on an Atmel ATtiny2313 -  This is a simple thermostat that I designed to use with my central heating system.  When is not in use acts like a thermometer.  The prototype uses the AT90S2313 but it’s obsolete now, so I changed it with the pin to pin compatible ATtiny2313 (the photo shows my first prototype).  __ AVR Projects Dim

B&K 747 tube Tester schematic -  Vintage schematic__ 

Back EMF PM Motor Speed Control -  Back-EMF refers to using the voltage generated by a spinning motor (EMF) to conclude the speed of the motor's rotation.   This can be used in motion control algorithms to modulate the velocity or to compute the angular distance the motor has traveled over __ Contact Acroname Inc.

Bad Light Bulb Indicator -  This request came from a Discover Circuits visitor.  He wanted to turn on a LED indicator light whenever a circuit detected a burned out tail/brake light on a car or truck.  The circuit shown below uses a transistor switch, to detect current flowing through a low value resistor. . . Circuit by David A. Johnson P.E.-December, 2006

Bad-bulb finder fixes Christmas lights -  EDN Design Ideas:  12/01/2014     15 years later, here’s a new take on one of our most popular Design ideas - ever!  A long, long time ago there was a great Design idea for a simple gadget to find a bad bulb in a series-connected string of Christmas lights:  This is really simple and works great, but it exposes the user to potentially lethal line voltages.  The PROBE in the figure above is inserted into the light bulb bases, so there is  a good chance that you could be touching a part of the probe, while the probe is touching line voltage.   This Design idea is a modernized LED version of that one.  The light string is still plugged into an outlet, but that outlet is connected to a 9V battery, not the AC line.  Otherwise, the operation is the same as the neon bulb version: you use the probe to search for the open bulb in the string.  On one side of a dead bulb, the red LED will glow, and on the other side, the green LED will glow.  By probing your way back and forth, you can quickly get to the bad bulb. __ Circuit Design by Dan Meeks

Ball Lightning Detector -  Schematic + info + pictures __ Designed by Lennie Zink

Ballantine 300 AC Voltmeter manual w/schematic -  Vintage schematic__ 

Bang-bang thermostat is Simple Circuit & efficient -  11/06/97 EDN Design Ideas:  Perhaps  simplest and oldest feedback loop is  nonproportional, all-or-nothing, "bang-bang" rmostat.  Fully turning on a heater when  temperature is below setpoint and off when it's above setpoint is a straightforward example of a servomechanism.  Yet, elementary and crude as servomechanisms are, examples surround __ Circuit Design by W Stephen Woodward, University of North Carolina--Chapel Hill

Barometer That Measures Your Height -  July 31, 2009   Here's a weather instrument - the Dodecahedral Barometer - that can actually determine how tall you are by reading the barometric pressure between your head and your feet.  Mark Thoren notes that his gadget was inspired by the release of some new electronic  products.   __  Gadget Freak-Case 145

Barometer WiFi ESP8266-Lua -  Glass & Brass barometer is precise digital wifI barometer with pressure sensor BMP085 or BMP180 and wifI module ESP8266.  it's a miniature web server.
By mapping ports of your router, you can connect to it from anywhere on the world.  The barometer uses Lua software and
trendy vector graphics format SVG.  The barometer is particularly interesting for its graphic design.  in terms of program, this is simple.
Thanks to this, barometer is quite fast and stable, which was my goal. __ Designed by © Pavel Janko

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Test Equipment:  #'s - A        B - D        E - G
H - L        M - O        P - S        T - Z


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