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Tester or Measurement (Instrument) Circuits

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


Last Updated: October 24, 2017 02:55 PM
Circuits Designed by Dave Johnson, P.E. :

Cheap Light Power Meter -  Some time ago I was experimenting with the use of some low leakage photovoltaic solar cells, to harvest some energy from the diffuse lighting inside a room.  The plan was to use a small array of solar cells (the type often used on solar powered calculators) . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2006

Circuit Forms Divide By 1.5 Counter -  Two inexpensive ICs  divide a TTL clock signal by 1.5.  By following the circuit with another flip/flop, you could also generate a divide by three function. . . Circuit by David Johnson P.E.-July, 2000

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:

Charge Integrator-42001.0 -  Circuit ideas for Designers App Note__ Advanced Linear Devices, Inc

Charge Monitor for 12 Volt Rechargeable Lead Acid Battery -  A battery is a vital element of any battery-backed system.  in many cases battery is more expensive than system it is backing up.  Hence we need to adopt all practical measures to conserve battery life.  As per manufacturer's data sheets, a 12V rechargeable lead-acid battery should be operated within 10.  iV and 13.8V.  When battery charges higher than 13.8V __ 

Cheap & easy inductance tester uses few components -  12-Apr-07 EDN-Design ideasThis circuit plus a frequency counter or oscilloscope measures unmarked inductors __ Circuit Design by Al Dutcher, Consulting Engineer, Paulsboro, NJ

Cheap AC Current Measurement -  The easy way to measure high AC currents is to use a clamp meter but these are generally quite expensive and cost several hundred dollars at a minimum.  Add-on clampmeter adaptors can work well but they only work with digital multimeters which have millivolt AC resolution.  This is because the output of most clamp adaptors__ 

Cheap but Sensitive Radiation Detector -  This project started out as a gag project, a "Nuclear War Detector".  The idea was to make a device that would flash a little red light if a nuclear attack were underway or if there were some sort of massive radiation spill right outside the house.  it would be like a rain detector built into an umbrella, perfectly functional but totally useless __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Cheap Light Power Meter -  Some time ago I was experimenting with the use of some low leakage photovoltaic solar cells, to harvest some energy from the diffuse lighting inside a room.  The plan was to use a small array of solar cells (the type often used on solar powered calculators) . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2006

Cheap Metal Detector -  The idea of this circuit is to hack PIC  oscillator circuit, by replacing the crystal by a coil : the frequency of the oscillator then depends on presence of metal near the coil, just like in a classic metal detector.   __ Designed by Bruno Gavand

Cheap pushbutton replaces rotary switch -  26-Oct-00 EDN Design Ideas:  The problem of setting any one of four modes of aµC-operated process has a straightforward solution  Have the µC check the states of some 4 bits of aµC.    __ Circuit Design by Abel Raynus, Armatron International Inc, Melrose, MA

Cheap Transistor 'Beta' Meter -  Measures the life of NPN and PNP transistors; Requires a digital or analog Multimeter __ Contact Flavio Dellepiane, fladello @ tin.it

Cheap Ultrasonic Range Finder based on PIC16F877A with a 8MHz crystal -  Everybody knows the speed of the sound in the dry air is around 340 m/s.  Send a short ultrasonic pulse at 40 Khz in the air, and try to listen to the echo.  Of course you won't hear anything, but with an ultrasonic sensor the back pulse can be detected.  if you know the time of the forth & back travel of the ultrasonic wave, you know the distance, divide the distance by two and you know the range from the ultrasonic sensor to the first obstacle in front of it.   __ Designed by Bruno Gavand

Cheap'n'Simple Circuit 100V Speaker/Line Checker -  This Speaker/Line Checker will be a boon to anyone setting up 100V PA systems, especially for temporary installations at sporting events, when you need to do everything quickly before the event and be sure that it is all working.  With this tester, you can immediately check each PA speaker and line as it is run.__ SiliconChip

Check Consistency of Binary Addresses -  09/28/95 EDN Design Ideas:  The validation circuit in Fig 1  allows you to check the consistency of successively recurring 3-bit address codes.  The circuit simultaneously applies the address code to the A port of IC 2, a 7485 magnitude comparator, and to IC 3, a 1-of-8 decoder.  When IC 2's B port reads the same address latched on the output of D flip-flop,  __ Circuit Design by Arthur Edang, Don Bosco Technical College, Mandaluyong, Philippines

Check Inductors With This Simple Q Meter -  While LCR meters are readily available at reasonable cost, they do not measure the Q of an inductor.  This circuit enables you to measure the Q of inductors with the aid of an RF signal generator.  A capacitor is connected in parallel with the inductor to form a tuned circuit.  By varying the frequency, you__ 

Check Swamp-Cooler Water Level -  10/31/02  EDN Design Ideas:  A "swamp cooler" is an easy way to obtain effective air conditioning, especially in hot and dry climates, if a water source is readily available.  Although most units are very reliable, the storage-reservoir control usually uses a single level-detector component.  Failure of this component can lead to serious water damage __ Circuit Design by Daniel Krones, Precision Design Services, Sky Forest, CA

Christmas Lights Tester -  Like every year around the same time, I hurried to get my Christmas tree all set up and the first thing we do when the tree is 'standing' we like to hang the lights in the tree.  Okay, better first test them before putting all 50 of them in the tree.  Yep!  Working beautifully.  I started a carefully planned organization of the lights so they would be evenly divided over the branches.  Now the second string of lights, tested, yep working.  in the tree with them.  Putting the plugs into the receptacle andoh no-- one series of them are on in full glory, all the others are out.  Annoyed I tried to 'fix them' by trying to push each bulb further into their sockets.  Still no go __ Designed by Jan Hamer

Christmas Tree Moisture Monitor -  Originally intended to monitor the moisture in a potted plant, this moisture monitor really shines as a Christmas tree stand water level monitor!  A fresh Christmas tree drinks water an annoying rate and bending down under the __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Christmas-Tree Lights Tester -  12/23/99 EDN Design Ideas:  Why is it that you always test 48 bulbs before you find the bad one in a 50-light string? This simple circuit allows you to divide and conquer, greatly reducing the time it takes to find the bad bulb. __ Circuit Design by William Dias, Brown & Sharpe, North Kingstown, RI

Circuit Adapts Signals for Visual Perception -  10/12/95 EDN Design Ideas:  First, the display would extend brief periods of change in logic states to a period long enough for the eye to perceive (Fig 1a).  For example, if a signal is at logic high and switches to logic low for a period of 100 nsec and then returns to a high state, the period of the low-state signal is too short for the eye to perceive.  The logic-low period should __ Circuit Design by Paul Johnson, Qualcomm Inc, Escondido, CA

Circuit Board Tester -  indicates the basic integrity of a printed board; Self-powered - 3 to 30V range __ Contact Flavio Dellepiane, fladello @ tin.it

Circuit Breaker Monitors Leakage Current -  06/21/01 EDN Design Ideas:  The residual-current circuit breaker in Figure 1 continuously monitors the supply lines for any leakage current and immediately disconnects the supply if necessary.  Load-supply wires, both live and neutral, pass through the magnetic core of the CR4311-5 __ Circuit Design by Sharath Kumar, Gemplus R&D Centre, Dubai, United Arab Emirates

Circuit Breaker Provides Overcurrent & Precise Overvoltage Protection -  7-Jun-07 EDN Design Ideas:  A simple circuit breaker delivers precision overvoltage protection and overcurrent protection __ Circuit Design by Anthony H Smith, Scitech, Bedfordshire, England

Circuit Checks Consistency Of Binary Addresses -  09/28/95 EDN Design Ideas:  The validation circuit in Fig 1  allows you to check the consistency of successively recurring 3-bit address codes.  The circuit simultaneously applies the address code to the A port of IC 2, a 7485 magnitude comparator, and to IC 3, a 1-of-8 decoder.  When IC 2's B port reads the same address latched on the output of D flip-flop,  __ Circuit Design by Arthur Edang, Don Bosco Technical College, Mandaluyong, Philippines

Circuit Checks Swamp-Cooler Water Level -  10/31/02  EDN Design Ideas:  A "swamp cooler" is an easy way to obtain effective air conditioning, especially in hot and dry climates, if a water source is readily available.  Although most units are very reliable, the storage-reservoir control usually uses a single level-detector component.  Failure of this component can lead to serious water damage __ Circuit Design by Daniel Krones, Precision Design Services, Sky Forest, CA

Circuit controls multiple thermoelectric coolers -  08/19/99 EDN Design Ideas:  Optoelectronic and other components sometimes use a thermoelectric cooler and a thermistor for temperature control.  A typical thermoelectric cooler __ Circuit Design by Frank Effenberger

Circuit Detects & Disconnects Overvoltage -  04/25/96 EDN Design Ideas:  The circuit in Fig.1 protects circuits and systems with power supplies that may exceed safe limits.  One example is small consumer products that use external ac adapters; it's easy to mistakenly plug in the wrong adapter.  Another example is a portable system that uses a rechargeable battery pack.  if the battery pack is absent or fails to open during recharging, a high-compliance charger can deliver excessive voltages to the system __ Circuit Design by Kerry Lacanette, National Semiconductor Corp, Santa Clara, CA

Circuit Detects DC Ringing -  08/17/00 EDN Design Ideas:   Ring detection is a common task in telephony-related digital design.  The goal is to sense an ac ringing voltage applied to the telephone line by a central office or PBX (private branch exchange) and then pass an appropriate signal to the µC or µP __ Circuit Design by Jerzy Chrzaszcz, Warsaw Institute of Technology, Poland

Circuit Detects first event -  05/03/01  EDN Design Ideas:  The circuit in Figure 1 is a "first-event" indicator, like a game show's "who's first to answer" detector.  it indicates which of the two momentary switches, S 1 or S 2 , closes first by latching the corresponding channel, IC A or IC B , to a high state.  A __ Circuit Design by Kelly Flaherty, National Semiconductor, San Mateo, CA

Circuit Detects Rapidly Falling Signals & Rejects Noise -  EDN-Design ideas -- 11/03/11    Combine an op-amp and a logic IC to determine signal peaks beyond a set threshold. __ Circuit Design by Vladimir Rentyuk, Zaporozhye, Ukraine

Circuit Detects reset source -  04/27/00 EDN Design Ideas:  Embedded single-board computers do not rely only on power-on resets; they often use multiple sources to reset CPUs to prevent CPUs from being locked into endless loops.  However, in most cases, CPUs start from the starting points of memories to fetch their first code, because they have no way of knowing what generated the reset.  The circuit in Figure 1 allows a CPU to know the source of a reset.   __ Circuit Design by Shyam Tiwari

Circuit Detects total on-time -  02/04/99 EDN Design Ideas:  NOTE:    Page includes several designs.  Scroll to find this one.  The circuit in Figure 1 provide as a voltage that is directly proportional to the sum of the total on-times for a number of positive pulses that occur during the interval between sample signals.  When a positive pulse arrives at the control input to switch IC 1A, a constant-current source charges capacitor C1  through IC 1A for the duration __ Circuit Design by Richard Nachazel, Vista Electronics Co, Ramona, CA

Circuit Detects voltage overrange -  10/10/96 EDN Design Ideas:  Sometimes, a visual indication of whether a sensed voltage is above or below its nominal value can be useful.  Most approaches to overvoltage or undervoltage sensing use two voltage comparators and a resistor divider to form a win __ Circuit Design by Mark Stitt, Burr-Brown, Tucson, AZ

Circuit disconnects load -  02/17/00  EDN Design Ideas:  Placing a load-disconnect circuit on the output of a bootstrapped step-up regulator allows the regulator to start with load currents much higher than would otherwise be possible (Figure 1).  During shutdown, the disconnect completely isolates the battery __ Circuit Design by Larry Suppan

Circuit Disconnects Load From Battery -  03/14/96 EDN Design Ideas:  To prevent battery damage, the circuit in Figure 1 disconnects the load at a predetermined level of load voltage.  This load voltage, VTRiP, is closely proportional to the battery voltage.  R1 and R2 determine the level of VTRiP  that corresponds to voltage of 1.15V at pin 3 of IC 1.  A voltage of 1.15V at pin 3 of IC 1 causes the internal comparator to trip.  Thus, VTRiP=1.15 (R1+R2) /R1 __ Circuit Design by Michael Keagy, Maxim Integrated Products, Sunnyvale, CA

Circuit Disconnects Load From Low-Voltage Supply -  04/24/03  EDN Design Ideas:  Circuit ensures safety in power-on operation.  Power supplies often include a circuit that disconnects the load when the supply voltage drops too low, such as when a battery is nearly discharged.  A p-channel MOSFET connected between supply and load is the typical approach.  However, a 1.5V single-cell battery or other low-voltage supply is insufficient to fully turn on the MOSFET.  For such low-voltage systems, consider the circuit of Figure 1.   __ Circuit Design by Steve Caldwell

Circuit distorts duty cycle for CML inputs -  5-Aug-04 EDN Design Ideas:  To test a gigabit-speed data-recovery chip, you need a clock with a controllable duty cycle.  Because most pattern and clock generators have a fixed duty-cycle output of 50%, the design may require a small circuit to distort the duty cycle.  The signal with controllable duty cycle drives a standard CML (current-mode-logic] input with on-chip termination resistors __ Circuit Design by Dieter Verhulst and Xin Yin, Ghent University, Belgium

Circuit eases three-phase Monitoring -  12/17/98 EDN Design Ideas:  Measuring line-to-line voltages in a delta-connected three-phase system can present special problems.  Because all three lines may be floating several hundred volts above ground, you can not use nonisolated, grounded oscilloscopes or other single-ended instruments.  Special isolation amplifiers are available for oscilloscopes, but they can cost several thousand dollars.  You still need to make three measurements even with proper instrumentation   Page includes several designs.  Scroll to find this one __ Circuit Design by Henno Normet, Tavares, FL

Circuit Extends Battery Life -  07/29/10  EDN Design Ideas:  Using a relay, the circuit completely disconnects the batter during to eliminate power consumption - two previous Design ideas - describe simple ways to automatically disconnect a battery from its load after a preset on period, which extends battery life (r __ Circuit Design by José M Espí, Rafael García-Gil, and Jaime Castelló, University of Valencia, Valencia, Spain

Circuit Fault Protection with Latching Load Disconnect & Early Warning Indication -  The LT6109 is a complete high side current sense device that incorporates a precision current sense amplifier, an integrated voltage reference and two comparators.  Two versions of the LT6109 are available.  The LT6109-1 has the comparators connected in opposing polarity and the LT6109-2 has the comparators connected in the same__ Linear Technology/Analog Devices App Note, Sep 7th 2011

Circuit Fault Protection with Very Fast Latching Load Disconnect -  The LT6108 is a complete high side current sense device that incorporates a precision current sense amplifier, an integrated voltage reference and a comparator.  Two versions of the LT6108 are available.  The LT6108-1 has a latching comparator and the LT6108-2 has a non-latching comparator.  in addition, the current sense amplifier__ Linear Technology/Analog Devices App Note, Sep 7th 2011

Circuit for Measuring Motor Speed Uses Low-Cost Components -  11/08/07  EDN Design Ideas:  A microcontroller-based circuit provide as both an LCD readout and an analog motor-speed output __ Circuit Design by R García-Gil, J Castelló, and JM Espí, Escola Tčcnica Superior d’Enginyeria, University of Valencia, Spain

Circuit Forms Divide By 1.5 Counter -  Two inexpensive ICs  divide a TTL clock signal by 1.5.  By following the circuit with another flip/flop, you could also generate a divide by three function. . . Circuit by David Johnson P.E.-July, 2000

Circuit forms gamma-photon Detector -  04/24/03  EDN Design Ideas:  LED driver delivers constant luminosity - The circuit of Figure 1 includes a PIN photodiode that detects individual photons of gamma radiation.  The reverse bias on the photodiode sometimes creates a depletion region.  When such a ph __ Circuit Design by Bruce Denmark, Maxim Integrated Products, Sunnyvale, CA

Circuit forms industrial-grade digital potentiometer -  09/20/01 EDN Design Ideas:  Both ac and dc motors in modern industrial systems often receive their control from PLCs (programmable-logic controllers] in a control room safely away from the process.  if an operator must manually set the motor speed while observing the process, the component of choice is usually an industrial-grade potentiometer __ Circuit Design by Phill Leyva, Maxim Integrated Products, Sunnyvale, CA

Circuit Forms Multichannel Temperature Monitor -  03/04/04 EDN Design Ideas:  You can use an ADT7461 single-channel temperature monitor, an ADG708 low-voltage, low-leakage CMOS 8-to-1 multiplexer, and three standard 2N3906 PNP transistors to measure the temperatures of three separate remote thermal zones (F __ Circuit Design by Susan Pratt, Analog Devices, Limerick, Ireland

Circuit Implements Photovoltaic-Module Simulator -  04/07/11  EDN Design Ideas:  Use combinations of diodes to simulate photovoltaic cells.  Electronics engineers often use photovoltaic-module simulators to test dc/dc-power converters, inverters, or MPPT (maximum-power-point-tracking) -control techniques.  The use of these simulators lets you work in the laboratory with predefined photovoltaic conditions, thus avoiding the drawbacks of real photovoltaic modules.  Various commercial simulators are available, but they are often expensive.   __ Circuit Design by José M Blanes and Ausiŕs Garrigós, University Miguel Hernández, Elche, Spain

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Test Equipment:  #'s - A        B - D        E - G
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