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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. :

Divide a TTL Clock Signal by 1.5 -  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 . . . Hobby Circuit designed by David Johnson P.E.-July, 2000

Does Power Line have 120 VAC or 240 VAC? -  Two LEDs indicate if a power line has 120vac or 240vac voltage on it. . . Circuit by Dave Johnson P.E.-July, 2006

DVD Recorder + TV Camera Make Cheap Data Logger -  Sometimes recording the results of a test requires as much ingenuity as designing the product.  Consider a situation which requires the collection of many different variables over a long period of time . . . Hobby Circuit designed by David Johnson P.E.-April, 2005

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:

Digital RF Field Strength Indicator -  Useful as a transmitter tune-up meter or an RF sniffer, this is an RF field strength indicator that is loosely based on the Broad Band RF Field Strength Probe, described elsewhere.  it detects RF via a square law detector, basically its a crystal set with gain.  The bias circuit for the detector is significantly modified from the probe to reduce the effects of battery voltage droop during use.   __ Designed by Dick Cappels

Digital Soil Moisture Meter -  A soil moisture meter is used for indicating the water content of a given soil sample.  As crop production requires water at different stages and in different amounts, it is important...__ Electronics Projects for You

Digital Soil Moisture Tester -  Here is a simple and compact digital soil moisture tester to check whether the soil is dry or wet.  it can also be used to check the dryness or wetness of...__ Electronics Projects for You

Digital Step-Km Counter-Max. Range: 9,950 meters -  This circuit measures the distance covered during a walk.  Hardware is located in a small box slipped in pants' pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km.  and its dot is always on to separate Km.  from hm.  The rightmost display D1 (the least significant digit) shows hundreds meters and its dot illuminates after every 50 meters of walking.__ Learning Electronics

Digital Stereo Potentiometer -  in PDF format, text in Finnish__ 

Digital Storage Logic Probe -  it interfaces to a Win98 PC to give you more flexibility than you ever thought possible.__ SiliconChip

Digital Thermometer -  This digital thermometer can measure temperatures up to 150C with an accuracy of +_1C.  The temperature is read on a 1V full scale-deflection (FSD) moving-coil voltmeter or digital voltmeter.  Operational amplifier IC ...__ Electronics Projects for You

Digital Thermometer Sends Data over AC Power Line -  This circuit is intended for precision centigrade temperature measurement, with a transmitter section converting to frequency the sensor's output voltage, which is proportional to the measured temperature.  The output frequency bursts are conveyed into the mains supply cables.  The receiver section counts the bursts coming from mains supply and shows the counting on three 7-segment LED displays.  The least significant digit displays tenths of degree and then a 00.0 to 99.9 °C range is obtained.  Transmitter-receiver distance can reach hundred meters, provided both units are connected to the mains supply within the control of the same light-meter.   __ Contact Flavio Dellepiane, fladello @ tin.it

Digital Thermometer/Thermostat -  it covers the range from -55 °C to 1200°C and has an over or under temperature alarm and switched outputs for thermostatic control.__ SiliconChip

Digital Thermometer-Cum-Controller -  This standalone digital thermometer controls the temperature of a device according to its requirement.  it also displays the temperature on four 7-segment displays in the range of –55°C to +125°C.  At...__ Electronics Projects for You

Digital Thermostat with LED Temperature Display -  I needed to replace two old, unreliable thermostats for controlling the heating and cooling for a large garden shed.  Commercial basic digital thermostats are available quite cheaply, but some lack the ability to control heavy loads or have the extra features that I require for saving energy when the door is often left open or to indicate temperature being out of range etc.  I like the PIC 18F1320 microcontroller used in my previous project, so decided to use it again in a very similar design to drive three multiplexed LED displays and read the temperature from a Dallas/DS18x20 "1-Wire" digital sensor.   __ Designed by D. Thorpe, 2006

Digital Volt & Amp Meter with Temperature Control -  This project was designed and constructed as enhancement to the 0-30V Stabilized Power Supply Project with the DiY electronics hobbyist in mind.  The circuit uses a single PIC  Microchip to perform the Voltage, Current and Temperature conversions and display functions.  The PCB Board uses large  __ Designed by RSABear © 2008

Digital Voltmeter -  The IC L7107 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.   __ Contact IQ Technologies

Digital voltmeter (DVM) -  This multimeter was designed to measure output voltage and current in a PSU, where the current sense shunt resistor is connected in series with load at the negative voltage rail.  it needs only one supply voltage that can be acquired from main PSU.  An additional function of the multimeter is that it can control (switch on and off) an electric fan used to cool the main heatsink.  The power threshold at which the fan switches on can be adjusted using One Touch Button Setup.__ 

Digital Voltmeter for Your Car -  A PIC  microcontroller makes it a snack to build.__ SiliconChip

Digital Voltmeter with LED Display -  This is an easy to build, but nevertheless very accurate and useful digital voltmeter.  it has been designed as a panel meter and can be used in DC power supplies or anywhere else it is necessary to have an accurate indication of the voltage present.  The circuit employs the ADC (Analogue to Digital Converter) i.  C.  CL7107 made by iNTERSiL __ Designed by © of this circuit belongs to smart kit electronics

Digital volume control -  The Tiny Audio Amplifier kit is a good choice for battery operation.  it is based on LM386 IC .__ 

Digital Volume Control -  The heart of this digital volume controller DVC circuit is IC 2 4067, 16-channel analog multiplexer.  Because the 1kΩ has been connected between every input and output, the multiplexer can act like a potentiometer.  The total resistance is 15kΩ.  You can use different values for the resistor to obtain a different characteristic.   __ Designed by Popescu Marian

Digital Volume Control -  This circuit could be used for replacing your manual volume control in a stereo amplifier.  in this circuit, push-to-on switch S1 controls the forward (volume increase) operation of both channels while a similar switch S2 controls __ Contact IQ Technologies

Digital volume control has log taper -  04/11/02 EDN Design Ideas:  Digital potentiometers provide a compact and convenient way to attenuate audio-amplifier signals.  However, most such potentiometers suffer from at least one flaw  a nonlogarithmic step increment.  To avoid this problem, a user must usually step the potentiometer in a nonlinear sequence to simulate a logarithmic taper __ Circuit Design by Doug Farrar, Los Altos, CA

Digital Volume Control using DS1669 Digital Pot IC -  This digital volume control has no pot to wear out and introduces almost no noise in the circuit.  instead, the volume is controlled by pressing UP and DOWN buttons.  This simple circuit would be a great touch to any home audio project.   __ Designed by Aaron Cake

Digital Wattmeter, measures from nanowatts to kilowatts using AD8307, PIC16F876, LCD Display -  The extra input B is for a later SWR brigde project, also the TX serial output will be in use later.  The uncalibrated signal response is: +1/-1 dB from 1MHz to 450MHz.  input SWR vill varry from 1.00 to 1.30, depending on input frequency.  To make the SWR this good, you need to assemble the input circuit correct and adjust the capasitor.  input power range: -60 to +30dBm that is 1 nW to 1 Watt.  __ Thomas Scherrer OZ2CPU

Digitally controlled potentiometer sets cutoff frequency -  06/10/99 EDN Design Ideas:  The traditional method of controlling the upper cutoff frequency in the basic inverting-amplifier circuit of Figure 1 is to add capacitor C in parallel with R2.  The value of C controls the cutoff frequency.  R1  and R2 independently establish the magnitude of the circuit gain, which __ Circuit Design by Chuck Wojslaw, Xicor Inc, Milpitas, CA

Digitally Programmable Instrumentation Amplifier Offers Autozeroing -  10/30/08 EDN Design Ideas:  The current trend in advanced instrumentation amps is to use no external resistors.  in these amplifiers, a gain-control word, comprising a binary-coded one, sets the voltage gain.  Several integer gains within one to 1000 are currently available; however, this range does not __ Circuit Design by Marián Štofka, Slovak University of Technology, Bratislava, Slovakia

Digitally programmable resistor serves as test load -  03/03/05  EDN Design Ideas:  Figure 1 illustrates a digitally programmable precision resistance that can serve as a microprocessor-driven power-supply load in custom-designed ATE (automatic-test equipment].  An 8-bit current-output DAC, IC 1, a DAC08, drives curre __ Circuit Design by Francesc Casanellas, Aiguafreda, Spain

Digitally Programmable-Gain Amplifier Uses Divergent-Exponential Curve -  01/08/09  EDN Design Ideas:  The divergent-exponential and negative time constants are the core concepts of the DENT (differential-divergent-exponential-negative-time-constant] digitally programmable-gain-amplifier topology __ Circuit Design by W Stephen Woodward, Chapel Hill, NC

Digithermo 0-100.0 °C -  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

Diode Serves as a Sensor for a Thermal Probe -  02/16/12  EDN Design Ideas:  A two-transistor thermal probe can be used to diagnose circuit problems, such as hot components and thermal runaway.   __ Circuit Design by Raju Baddi, Tata Institute of Fundamental Research, Pune, India

Diode tester limits reverse voltage & forward current to protect sensitive junctions -  Some diode manufacturers caution against using the diode tester function in ohmmeters because it could exceed the reverse-voltage and forward-current ratings of sensitive diodes.  This is especially true in optical devices such __ Designed by Michael J. Gambuzza

Dip Oscillator for HF -  amateur radio construction projects.   __ Designed by Peter Parker VK3YE

Direction sensing Motion Detector -  Detects motion and indicates the direction that a human or animal is moving (left or right).12 pages.  This project is not available as a kit of parts.  __ Golab.com

Disconnect 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

Disconnect 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

Distance Counter -  Presented here is a simple pedometer circuit.  it measures the distance covered by you while walking.  it may not work very well for running!  Circuit and working Fig.1 shows circuit diagram of...__ Electronics Projects for You

Distort Duty Cycle for CML Inputs -  08/05/04  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 __ Circuit Design by Dieter Verhulst and Xin Yin, Ghent University, Belgium

Divide a TTL Clock Signal by 1.5 -  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 . . . Hobby Circuit designed by David Johnson P.E.-July, 2000

DIY 4-Digit LED Digital Voltmeter Module based on ATmega8 -  Three Voltage Ranges (DC: 1000V, 100V, 10V, AC: 700V, 70V, 7V) as well as an onboard Shunt (1Ω) allows to measure Voltages and Currents.  A DC/DC Converter offers galvanic isolation from the Supply.  An Atmega8 with a 10 bit A/D Converter as well as an onboard Precision Voltage References make this an useful and educational utility. __ Designed by Alexander C. Frank, aka Ajarn Changpuak

DIY BFO metal Detector -  BFO (beat frequency oscillator) metal detectors use two oscillators, each of which produces a radio frequency.  One of these oscillators uses a coil of wire that we call the search loop.  The second oscillator uses a much smaller coil of wire, and is usually inside the control box and is called the reference oscillator.  By adjusting the oscillators so their frequencies are very nearly the same, the difference between them is made audible as a beat note __ Designed by Essex Metal Detectors

DIY Digital AC Watt Meter -  Have you ever been curious about the power consumption of an appliance? For example did you wonder how much it will cost you to leave your television in standby mode whole night? Or did you want to learn how much change your refrigerator settings will make on your electric bill? if your answer is yes, you can use a wattmeter to measure the power consumption of a device.  in this project we are building one.__ 

DIY ECG Patient Simulator / ECG Tester -  One of the most important test equipment in the biomedical workshop is the ECG Tester or Patient Simulator.  The Patient Simulator is connected to the ECG monitor and delivers the typical ECG signal.  Only with such a tester an ECG monitor can be repaired, the functions and alarm settings checked and loose connections of the patient cables be located.  A Patient Simulators usually costs several hundred dollars and is unaffordable for small hospital workshop specially in developing countries. __ Designed by Frank Weithöner

DIY LAN Cable Tester -  in our hospital we often have problems with computer network cables.  Cables tear because of poor material quality or bad installation or were gnawed by animals.  The new installed cable then does not work because the crimped plugs do not have contact or the sequence of the wires are wrong.  __ Frank Weithöner

DIY Lie Detectors -  Makezine recently posted a diy lie detector kit that uses your skin resistance (aka sweat) to detect a lie.  The kit is well explained and consists of two probes you place on your palm with a red/green LED readout.  __ 

DMM Measures Frequency -  07/07/94 EDN Design Ideas:  The circuit in Fig 1 uses two IC s, a few passive components, and a standard DMM to measure frequency.  in the circuit, a switched-capacitor network, analog switch IC 2and capacitor C1, simulates a frequency-dependent resistor __ Circuit Design by Walter P Sjursen, Base Ten Systems Inc, Trenton, NJ

DMM Measures Light Level -  08/15/96 EDN Design Ideas:  The circuit in Figure 1 allows you to measure light using a regular digital voltmeter.  The TSL230B (IC 1] is a programmable light-to-frequency converter whose output frequency is proportional to the light level.  inputs S0 and S1 se __ Circuit Design by Yongping Xia, EBT Inc, Torrance, CA

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


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