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Tester or Measurement (Instrument) Circuits

Test Equipment:  #'s - A        B - D        E - G
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Last Updated: October 24, 2017 02:55 PM
Circuits Designed by Dave Johnson, P.E. :

A Current Transformer used to Harvest Energy -  Energy harvesting is all the rage these days.  With some modern electronics, information from low power sensors can be sent to a distant data collection point using a low power RF transmitter.  To power these remote sensors, various energy sources can be . . . Hobby Circuit designed by David A. Johnson P.E.-January, 2010

AC Current Controls Hour Meter -  Many systems require routine maintenance based on machine operation time.  The circuit below is a simple way to turn on a hour meter whenever AC power is supplied to the machine.  An inexpensive snap-on current transformer from Magnetics inc, is used to. . . Circuit by David A. Johnson P.E.-February, 2010

AC Current Indicator Light -  This circuit could be wired into a 120vac power line, which feeds power to any load, ranging from 40 watts to 250 watts.  it will turn on a LED light whenever current is being drawn by a load.  it is especially useful for remote lights, where you may not . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2005

AC Current Monitor -  This circuit uses a small AC current transformer from Magnetek to produce an isolated voltage proportional to the AC current in the primary winding.  The transformer contains a single turn primary with a low 0.001-ohm resistance.  it can easily handle 30 . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

AC Indicator-Self Powered -  Often there is a need to monitor when AC current flows into a load.  The circuit below works well for this application.  it uses an off-the-shelf torrid type AC-1020 current transformer from Triad, available from Mouser.  A wire carrying the AC current is . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2007

AC Isolated Current Monitor -  The hobby circuit below shows how a small current transformer from Magnetek can be used to monitor AC current to a load.  The AC voltage developed at the secondary of the transformer can be scaled so it can be read by any digital multimeter.  The transformer . . . Hobby Circuit designed by Dave Johnson P.E.-January, 2001

AC Line Under/Over Voltage Alarm -  Power lines, which deviate much beyond normal voltages can damage expensive electronic equipment.  The circuit below sounds an alarm whenever the line voltage is higher or lower than normal.  I set the alarm limits at about +-15% from standard levels . . . Hobby Circuit designed by David Johnson P.E.-March, 2009

AC Peak Detector that is Precise -  This unique circuit uses a very inexpensive voltage comparator to form a peak detector.  The DC voltage produced tracks the positive peak of the input signal.  it works from about ten millivolts to about 10 volts peak to peak.  The maximum frequency is about . . . Hobby Circuit designed by Dave Johnson P.E.-February, 2002

AC Power Line High/Low Voltage Tester -  if you wish to test a line-powered device under both a 15% high and a 15% low voltage condition, you can use the circuit below.  The circuit uses an 18v transformer with a 3 amp rating.  A double pole, double throw toggle switch then switches in the. . . Circuit by David A. Johnson P.E.-March, 2010

Acceptable Voltage Indictor -  I have used this circuit many times in custom test fixtures where a simple go-no go indication was needed.  The circuit can also be used to adjust a particular voltage be within specific high or low limits.  The three LEDs will indicate if the voltage is. . . Circuit by Dave Johnson P.E.-February, 2002

Accurate Low Capacitance Meter -  The circuit measures the unknown capacitance by applying a clean 20KHz 5v peak to peak triangle signal to the capacitor.  The current routed through the capacitance is sent to a current to voltage converter.  The voltage that emerges is therefore a 20KHz square wave signal, whose amplitude is proportional to the capacitance.  The signalís peak amplitude is rectified and filtered to produce a DC voltage. . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2004

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

A Simple Circuit RF Probe for your DVM -  This probe is configured to work with a DVM with the industry standard input impedance of 10 Megohm. __ Designed by VK5JST / VK5TR

A Simple Circuit Thermistor Interface to an ADC -  App Note/ 1753 / Oct-03__ Maxim Integrated

A Simple Circuit Thermocouple Amplifier -  Continuing with the thermocouple interface concept, the next step is to amplify the TC's millivolt signal into a more readable analog voltage, on the order of 0 to 5VDC.  This simple circuit fits the bill.  The LM358N is a dual op-amp IC .  i'm quite sure any op-amp IC would do fine, just be sure it can accept a Vcc which is compatible with your battery pack.  The IC draws ~ 1.0 mA.  __ 

A Speed Alarm for Cars; Pt 1 -  is your license looking a bit a bit dodgey? This compact speed alarm will help you stick to the speed limits.__ SiliconChip

A Speed Controller for Film Projectors -  Do you have old family movies on film? Have you watched them lately? You may be shocked by how much they have deteriorated over the years.  They need to be transferred to DVD before the film deteriorates to the point where it is unwatchable.  Video conversion is not as straightforward as you might think but this simple project enables you to do it.__ SiliconChip

A svelte beast cuts high voltage down to size -  11/24/99  EDN Technical Article: Piezoceramic transformers have many features, including small form factor, that make them inherently well-suited to CCFL-backlight inverters.   __ Circuit Design by Jim Williams and J Phillips and G Vaughn, im Williams, EDN's most revered contributor-At 63 years of age, Williams passed away in June 2011 after a stroke.

A Switchable RF Probe/Watt Meter for the FM Transmitters -  This unique project is one of the most trusted homemade test instruments to have, once you get your FM transmitter up and running !  !  ! This simple little device is capable of finding your FM transmitters' __ Designed by braincambre500 @ yahoo.com

A Temperature Sensor Control -  A basic circuit using Diodes to detect temperature differences __ Designed by G.L. Chemelec

A Thermoelectric Cooler Temperature Controller for Fiber Optic Lasers: Climatic Pampering for Temperamental Lasers -  Linear Technology AN89 __ Designed by Jim Williams - Apr 1st, 2001

A Thermostat Control for Electric Heaters -  One Advantage of these two units is the Sensor can be placed Away from the heater, therefore sensing the Actual Room temperature, not the direct heat from the heater.  These can also be used in a confined space with a Heat Lamp, to create a Drying Oven  __ Designed by G.L. Chemelec

A Transformerless Power Supply -  Power Supply Circuits:  This circuit will supply up to about 20mA at 12 volts.  it uses capacitive reactance instead of resistance - so it doesn't generate very much heat.  The circuit was designed to provide a cheap, compact power supply for CMOS logic circuits that require only a few milliamps.  The logic circuits were then used to control mains equipment, using an optically-isolated TRIAC. __ Designed by Ron J.

A Very Accurate Thermometer/Thermostat -  Based on the very accurate Dallas DS18B20 digital temperature sensor, this thermometer/thermostat provides accurate readings to one decimal point.  The LCD shows current, minimum and maximum temperature readings.  An internal buzzer will sound when temperature limits are exceeded.  it is intended for controlling air conditioners, heaters, cool rooms, wine cellars, etc.  The software is user-customisable.__ SiliconChip

A very stable freerunning beacon oscillator for 50 MHz -  Just a picture to demonstrate that a circuit does not have to be pretty to work well.   __ Designed by Herbert Dingfelder

A VHF/HF Aerial Analyser -  This project was published in the December 2015 issue of the Australian magazine "Amateur Radio", and you can obtain an excellent and complete kit of parts (including the printed circuit boards and pre-programmed Picaxe processor) from the Adelaide Hills Amateur Radio Society (AHARS).  This kit is brilliant value, and actually sells for less than the price you would pay for the individual parts __ Designed by VK5JST / VK5TR

A Wide Dynamic Range Field Strength Meter -  This unit is an updated version of the Wide Dynamic Range Field Strength Meter.  While the basic function is the same, it has several critical differences: it uses a specialized integrated circuit, the Analog Devices AD8307.  This chip is designed specifically as a logarithmic amplifier for use through 500 MHz.  Using the AD8307, it has a wider dynamic range (85 dB versus 55 dB) and it has built-in temperature compensation.  Because of the different nature of this type of detector - and the fact that it has temperature compensation - means that there is no need for a "zeroing" control.  One disadvantage of this approach as compared to the diode approach is that the AD8307 has a lower frequency response than the diode.  The frequency limit of the meter is dictated pretty much by the diodes themselves along with their physical layout and related components: There is no reason why the earlier version could not be constructed to work through 10 GHz or so - but the AD8307 is falling flat by the time you get to 1 GHz, making it unsuitable for detecting wireless LANs or PCS-type cell phones.__ 

A worked Stepping Motor Example -  Perhaps some of the most commonly available stepping motors, for the experimenter, are the head positioning motors from old diskette drives.  These can be found at electronics swap meets, in computer surplus outlets, and even in trash dumpsters.  in addition to a stepper, a typical full-height 5.25 inch disk drive includes a 12 volt DC motor with tachometer and motor control circuit board, two microswitches, and a matched LED-photosensor pair (schematic design 6/06)  __ Designed by Douglas W. Jones

AC continuity tester finds single ended faults in cables -  02/21/08 EDN Design Ideas:  A continuity tester injects an AC signal into the conductors of a cable to find circuit faults __ Circuit Design by Kevin Bilke, Maxim Integrated Products, Fleet, Hants, UK

AC Current Controls Hour Meter -  Many systems require routine maintenance based on machine operation time.  The circuit below is a simple way to turn on a hour meter whenever AC power is supplied to the machine.  An inexpensive snap-on current transformer from Magnetics inc, is used to. . . Circuit by David A. Johnson P.E.-February, 2010

AC Current Indicator Light -  This circuit could be wired into a 120vac power line, which feeds power to any load, ranging from 40 watts to 250 watts.  it will turn on a LED light whenever current is being drawn by a load.  it is especially useful for remote lights, where you may not . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2005

AC Current Measurement -  The LTC1966 is a true RMS-to-DC converter that utilizes an innovative patented DS computational technique.  The internal delta-sigma circuitry of the LTC1966 makes it simpler to use, more accurate, lower power and dramatically more flexible than conventional log-antilog RMS-to-DC converters.  __ Linear Technology/Analog Devices App Note, Mar 31, 2010

AC Current Monitor -  This circuit uses a small AC current transformer from Magnetek to produce an isolated voltage proportional to the AC current in the primary winding.  The transformer contains a single turn primary with a low 0.001-ohm resistance.  it can easily handle 30 . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

AC Current Monitor -  Senses high current-flow into power cables; No wire-cutting, three versions available __ Contact Flavio Dellepiane, fladello @ tin.it

AC Current Probe for Oscilloscope Use -  I needed several current probes when designing the deflection circuits and high voltage supply for a computer display monitor, and the lab in which I was consulting only had one current probe, which I shared with the other four engineers on the project.  We did not really have a budget for test equipment on that project.  Designing the deflection circuit included designing several inductors, a current transformer among them.  it was merely a small diversion to design and put together a couple of simple current probes so I could, for example.  simultaneously watch the base current and the collector current of switching transistors.  The probe described here was designed to be used over the range of several tens of Hz to a couple MHz with currents from a few tens of milliamps to about 10 amps peak-to-peak.  Formulae are give which will allow you to create a design suitable for your own applications.   __ Designed by Dick Cappels

AC Indicator-Self Powered -  Often there is a need to monitor when AC current flows into a load.  The circuit below works well for this application.  it uses an off-the-shelf torrid type AC-1020 current transformer from Triad, available from Mouser.  A wire carrying the AC current is . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2007

AC Isolated Current Monitor -  The hobby circuit below shows how a small current transformer from Magnetek can be used to monitor AC current to a load.  The AC voltage developed at the secondary of the transformer can be scaled so it can be read by any digital multimeter.  The transformer . . . Hobby Circuit designed by Dave Johnson P.E.-January, 2001

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 (L1) made with a 1 inch diameter U-bolt wound with 800 turns of #30, #35 magnet wire.  The pickup could be made from other iron type rings or __ Designed by Bill Bowden

AC Line Under/Over Voltage Alarm -  Power lines, which deviate much beyond normal voltages can damage expensive electronic equipment.  The circuit below sounds an alarm whenever the line voltage is higher or lower than normal.  I set the alarm limits at about +-15% from standard levels . . . Hobby Circuit designed by David Johnson P.E.-March, 2009

AC Peak Detector that is Precise -  This unique circuit uses a very inexpensive voltage comparator to form a peak detector.  The DC voltage produced tracks the positive peak of the input signal.  it works from about ten millivolts to about 10 volts peak to peak.  The maximum frequency is about . . . Hobby Circuit designed by Dave Johnson P.E.-February, 2002

AC Power & Current Monitor -  The LT2940 measures a high side current and a differential voltage, multiplies them and outputs a current proportional to instantaneous power.  Bidirectional high side currents and bipolar voltage differences are correctly handled by the four-quadrant multiplier and push-pull output stage, which allows the LT2940 to indicate__ Linear Technology/Analog Devices App Note, Apr 26th 2010

AC Power Current Detector with LM1458 -  This circuit will detect power line currents of 250 mA or more without making electrical connections to the line.  Current is detected by passing a line of alternating current through an inductive pickup (L1) as a screen diameter of 1 inch U-bolt__ 

AC power line box heat Monitor -  This simple circuit monitors the mains distribution box constantly and sounds an alarm when it senses a high temperature due to overheating, helping to prevent disasters caused by any sparking in the mains box due to short circuits.  it also automatically switches on a bright white LED when the power fails.  The LED gives ample light to check the mains box wiring or fuses in darkness.  The circuit beeps once when power fails and again when power resumes.   __ Designed by D. Mohan Kumar

AC Power Line High/Low Voltage Tester -  if you wish to test a line-powered device under both a 15% high and a 15% low voltage condition, you can use the circuit below.  The circuit uses an 18v transformer with a 3 amp rating.  A double pole, double throw toggle switch then switches in the. . . Circuit by David A. Johnson P.E.-March, 2010

AC Power Line Voltage Indicator -  The solidstate voltmeter circuit described here indicates the mains voltage with a resolution that is comparable to that of a general-purpose analogue voltmeter.  The status of the mains voltage is available in the form of an LED bar graph__ Electronics Projects for You

AC Power Meter -  if you would like to save electric energy, you first of all need to measure the AC current flowing through your appliances.  AC line voltage times the measured current value gives the power.  Build an AC power meter with a current transformer as shown in the schematic given above.   __ Designed by MINOWA, Makoto  7N3WVM

AC power Monitor uses remote sensing -  04/26/01 EDN Design Ideas:  The detection circuit in the Design ideas - "Circuit monitors ac-power loss" (EDN , Nov 24, 1999, pg 172) requires a physical connection with the mains to sense the power loss.  The circuit in Figure 1 senses the power loss through the radiated power-line signal __ Circuit Design by Sanjay R Chendvankar, Tata Institute of Fundamental Research, Colaba, Mumbai, India

AC Voltage Measurement Errors in Digital Multimeters 5988-5513EN -  Application Note__ Aligent

Acceleration meter for cars -    NOTE:  This page is available in Greek and English language.  This circuit it is count the acceleration from -1000mg up to +1000mg.  Can be used in lot of applications like cars, elevators, ramps and more.   __ Designed by Michael Karaoglanidis

Accelerometer -  A handheld vibration meter, to measure how much those poorly balanced machines are shaking!  __ Designed by Manfred Mornhinweg

Accelerometer output gives temperature info -  11/19/98 EDN Design Ideas:  NOTE:  File contain several designs.  Scroll to find this one.  The ADXL202 dual-axis micro-machined accelerometer from Analog Devices (Norwood, MA) is appropriate for high-resolution applications.  in these applications, you sometimes need to know the ambient temperature for control purposes or for circuit-drift compensation.  The scheme in Figure 1 offers a novel way to convey temperature information to the system ĶC without the need for an A/D converter or any additional i/O pins. __ Circuit Design by Harvey Weinberg, Analog Devices Inc, Cambridge, MA

Acceptable Voltage Indictor -  I have used this circuit many times in custom test fixtures where a simple go-no go indication was needed.  The circuit can also be used to adjust a particular voltage be within specific high or low limits.  The three LEDs will indicate if the voltage is. . . Circuit by Dave Johnson P.E.-February, 2002

AC-Continuity Tester Finds Single-Ended Faults In Cables -  02/21/08  EDN Design Ideas:  A continuity tester injects an AC signal into the conductors of a cable to find circuit faults __ Circuit Design by Kevin Bilke, Maxim Integrated Products, Fleet, Hants, UK; Edited by Charles H Small and Fran Granville

Accurate Digital LC Meter -  Based on PIC 16F84A microcontroller, 16x1 LCD and LM311 IC  __ Designed by Radio LocMan

Accurate Digital LC Meter based on a PIC16F84 -  Several years ago, I built a "one transistor oscillator", which I used to measure small inductance values (by measuring the frequency of oscillation and applying the formula for resonant frequency of an LC circuit)  __ Designed by Phil Rice's Home Page‎

Accurate Low Capacitance Meter -  The circuit measures the unknown capacitance by applying a clean 20KHz 5v peak to peak triangle signal to the capacitor.  The current routed through the capacitance is sent to a current to voltage converter.  The voltage that emerges is therefore a 20KHz square wave signal, whose amplitude is proportional to the capacitance.  The signalís peak amplitude is rectified and filtered to produce a DC voltage. . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2004

Got Designs?
Please eMail
if you want me to link to and/or post your original design.  Thanks.

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

 


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