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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. :

Detector for Human Footsteps -  This circuit uses a surplus geophone to detect human footsteps from 100 feet away.  it was designed for monitoring the Mexico/USA border.  This preamp part of the system draws about 50 micro amps from a 12 volt supply . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Detects Low Voltage 120VAC Power Line  -  This hobby circuit will turn on a beeper when the line voltage drops below 100 volt AC . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

D-Flip/Flop One Shot Circuit -  Yes you can use cheap D flip/flop logic circuits as nice one-shot pulse generators.  This schematic shows how the popular CD4013 and the CD74HC74 can be used to generate pulses ranging from nanoseconds to seconds. . . Circuit by David A. Johnson P.E.-June, 2000

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 . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2000

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Detect 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

Detect Missing Pulses to Avoid Losing Data -  10-Jun-10 EDN Design Ideas:  in an SWiR (short-wave-infrared] indium-gallium-arsenide-based imaging system, the system must detect every trigger pulse; otherwise, lost data will result.  This design idea solves the problem of a data-conversion system that does not enable an acquisition in the first of 256 trigger pulses.  Figure 1 shows the SWiR sensor, IC 1.  The AD-Trig signal, Pin 24, produces one pulse for each of 256 pixels.  Figure 2 __ Circuit Design by Chien-Hung Chen and Tai-Shan Liao, National Applied Research Laboratories, Hsinchu, Taiwan

Detect Motion with a Piezo Device -  Using a piezoelectric device, this circuit will activate a beeper whenever the circuit is moved.    it could be used as an earthquake alarm. . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Detect 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

Detect 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

Detect when phone line in use & when two telephones are on the same line -  This project has two features.  it will let you know when a single phone is using the line and also when two phones are on the line!  The green LED indicates the first phone and the red LED indicates the second phone!  __ Contact Collin Mitchell

Detect wire breaks with unusual CMOS gate -  02/10/14 EDN Design Ideas:  TDR in the shop? Try this circuit to detect a wire break.  CMOS devices have large input impedance with input currents on the order of 0.01nA.  Adding feedback circuitry can result in a latch-like device that can be used to store bits, and also operate in a more analog mode as shown in this Design idea, which pinpoints the location of a break in a wire.   __ Circuit Design by Raju Baddi

Detector for Human Footsteps -  This circuit uses a surplus geophone to detect human footsteps from 100 feet away.  it was designed for monitoring the Mexico/USA border.  This preamp part of the system draws about 50 micro amps from a 12 volt supply . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Detector Lightning -  A VLF receiver tuned to 300 kHz designed to detect the crackle of approaching lightning.  A bright lamp flashes in synchrony with the lightning bolts indicating the proximity and intensity of the storm.  it has a superior RF section with a single resonance near 300kHz and plenty of sensitivity.  The antenna is a telescopic antenna that extends to two or three feet __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Detects Low Voltage 120VAC Power Line  -  This hobby circuit will turn on a beeper when the line voltage drops below 100 volt AC . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Developments in Battery Stack Voltage Measurement -  Linear Technology AN112 __ Designed by Jim Williams - Mar 2nd, 2007

Dew Sensor -  Dew (condensed moisture) adversely affects the normal performance of sensitive electronic devices.  A low-cost circuit described here can be used to switch off any gadget automatically in case of excessive humidity.  At the heart of the circuit is an inexpensive (resistor type) dew sensor element.  Although dew sensor elements are widely used in video cassette players and recorders, these may not be easily available in local market.  However, the same can be procured from__ 

Dew-Point Sensor -  Dew-point sensors are widely used in sensitive electronic equipment like cameras and copiers etc, to protect them from moisture failure by fast detection of dew.  You can easily build one yourself...__ Electronics Projects for You

DewPointer, a handheld DeW point measuring system / data logger -  This low cost Relative Humidity / Temperature meter also calculates the dew point, hence it's name the "DewPointer 9000".  This is a demonstration instrument that shows the capabilities of a PIC  microcontroller in a portable, battery powered application.  Based on a capacitive humidity sensor (Sensirion SHT 11) the design has a single operating button.  When the button is first pressed, the PIC  wakes up and displays __ Designed by Steve Hageman

D-Flip/Flop One Shot Circuit -  Yes you can use cheap D flip/flop logic circuits as nice one-shot pulse generators.  This schematic shows how the popular CD4013 and the CD74HC74 can be used to generate pulses ranging from nanoseconds to seconds. . . Circuit by David A. Johnson P.E.-June, 2000

Diagnose LEDs by Monitoring the switch-mode duty-cycle -  04/09/09  EDN Design Ideas:  Engineers often monitor the forward voltage, VF, of HB LEDs (high-brightness light-emitting diodes] to assess the LEDs’ health.  Big changes in forward voltage can indicate deterioration or even a complete failure of one or more LEDs  __ Circuit Design by Fons Janssen, Maxim Integrated Products Inc, Bilthoven, the Netherlands

Difference Amplifier uses digital potentiometers -  05/30/02 EDN Design Ideas:  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.  The circuit in Figure 1 presents an alternative approach that is useful when low cost and low drift are important, but when you don't need high precision __ Circuit Design by Reza Moghimi, Analog Devices, San Jose, CA

Differential Bridge Amplifier -  The LTC2050HV are zero-drift operational amplifiersavailable in the 5- or 6-lead SOT-23 and SO-8 packages.  The LTC2050 operates from a single 2.7V to 6V supply.  The LTC2050HV operates on supplies from 2.7V to ±5.5V.  The current consumption is 800μA and the versions in the 6-lead SOT-23 and SO-8 packages offer power shutdown __ Linear Technology/Analog Devices App Note, Apr 29th 2010

Differential Bridge Amplifier with Gain Programmed through the Serial Interface & Analog to Digital Conversion (Standby Current Less than 100μA) -  The LTC6915 is a precision programmable gain instrumentation amplifier.  The gain can be programmed to 0, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, or 4096 through a parallel or serial interface.  The CMRR is typically 125dB with a single 5V supply with any programmed gain.  The offset is below 10μV with a temperature __ Linear Technology/Analog Devices App Note, Apr 29th 2010

Differential Integrator with Frequency Controlled Gain -  Circuit ideas for Designers App Note__ Advanced Linear Devices, Inc

Differential scope probe Delivers 6-GHz bandwidth to the screen -  02/20/03 EDN Design Ideas:  With digital scopes that offer 6-GHz bandwidth suddenly almost commonplace and with industry participants now recognizing differential signaling as all but essential for sending multigigahertz signals across pc boards and backpla __ Circuit Design by Dan Strassberg

Digital & Binary clock with thermometer & hygrometer -  Here we have a clock.  it's not another clock.  it has digital and binary output.  it also has a thermometer and a hygrometer.  it's not another thermo-hygrometer.  it display's absolutely humidity (gr/m 3) also.  Schematic __ Designed by Konstantinos Bellosstyle

Digital Capacitance Meter -  This is a simple capacitance meter which can measure capacitance value easy.  There are some measurement methods for capacitance, at one time the capacitance was measured with a impedance bridge or a dip meter.   __ Designed by The Electronic Lives Manufacturing-presented Chan

Digital Engine/Race Computer Board -  The objective of this project is to design a high speed digital engine tachometer.  This requires the design and development of a hardware and software solution to monitor the status of an engine in real time.  in addition, information relating to the overall health and systems of the vehicle can be displayed.   __ Designed by Stephen Manley-smanley @ nyx.net

Digital IC Testers -  This manual tester uses a combination of four-pole switches and patch leads in order for it's tests to be configured.  A discrete design is used for the oscillator circuit, perhaps in ignorance of the ability of the 7400 IC used to form an oscillator on its own - instead it simply buffers the output as well and handling the "pulse" input which in fact changes the state of a flip-flop, rather than providing the momentary pulse characteristic of other designs.  Unlike most, this design sports a panel meter to report either the current consumed by the test IC (in case the user might determine it excessive) , or the regulated output voltage provided to the test IC , with the different functions selected using a switch __ Designed by Kevin Koster

Digital LED AM meter -  Measures current up to 10A with selected 100mA, 10mA and 1mA resolutions.  __ 

Digital LED Voltmeter -  Measures voltages up to 199.9V with 0.1V resolution.  __ 

Digital Lock-In Milliohmmeter -  A milliohmmeter is just the tool for checking trace resistance on a printed circuit board, tracking down shorted traces, and measuring the contact resistance of a switch or connector.  its the kind of tool that would come in real handy occasionally, but not often enough to justify shelling out hundreds of dollars.  Wanting one anyway, I set out to make my own.  it turned out to be not only an exciting project, but a true adventure of discovery as it provided a window into the workings of lock-in amplifiers __ Designed by Dick Cappels

Digital Mains Voltage Indicator -  This is a circuit for a digital mains voltage indicator that displays main voltage in the form of a LED bar graph with 16 LEDs.  The first LED indicates voltage level at 50 V and the 16th LED shows voltage level for 280 V__ Electronics Projects for You

Digital Mains Voltage Indicator -  Continuous monitoring of the mains voltage is required in many ap- plications such as manual voltage stabilisers and motor pumps.  An analogue voltmeter, though cheap, has many disadvantages as it has moving parts and is sensitive to vibrations.  The __ Designed by Radio LocMan

Digital Megohm & Leakage Current Meter -  Looking for an electronic megohm and leakage current meter, for quick and easy testing of insulation in wiring and equipment? Here's a new design which allows testing at either 500V or 1000V.  it can measure insulation resistances up to 999MΩ and leakage currents to below 1μA.  it uses a PIC  microcontroller and displays the results on a 2-line LCD panel.__ SiliconChip

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 . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2000

Digital pedometer -  Medical and health related electronic circuit diagrams / circuit schematics__ 

Digital pedometer -  Pedometer has a range of 9.950 meters with2-digits.  Slip it in pants pocket for walking and jogging __ Contact Flavio Dellepiane, fladello @ tin.it

Digital position encoder does away with ADC -  05/08/97 EDN Design Ideas:  The position encoder in Figure 1 is a simple yet powerful circuit that converts the change in resistance of a potentiometer into a digital value without using an expensive A/D converter.  The working principle is a resistance-to-PWM converter built around the common 555 timer IC .  A change in the potentiometer's __ Circuit Design by Jose Carlos Cossio, Santander, Spain

Digital pot adjusts LCD's contrast -  02/04/99 EDN Design Ideas:  NOTE:    Page includes several designs.  Scroll to find this one.  You can use a digitally controlled potentiometer for many purposes.  in this example, you can use the device to regulate the contrast of a standard (such as two lines by 40 characters] LCD.  You can use the circuit in Figure 1 in a portable test system, in which you need to change the contrast of the LCD as a function of the viewing angle.  You choose the contrast setup __ Circuit Design by Jef Collin, CSE Systems, Turnhout, Belgium

Digital Pot Corrects for System Drift -  EDN Design Ideas:  11/10/94    The circuit in Fig 1 looks simple but usually comes as a revelation to designers.  Under control of the system's µP, the digital potentiometer, IC 1, becomes a variable set-point reference that can adapt to the long-term drift of the variable measured.  The digital potentiometer replaces schemes involving A/D and D/A converters (see "Autocalibrator nulls dc offsets, " EDN, June 9, 1994, pg 139, and "infinite-hold circuit zeros out long-term drift, " EDN, March 3, 1994, pg 90).    __ Circuit Design by Mark Rutledge, Xicor Inc, Milpitas, CA

Digital potentiometer autonulls op Amp -  10/22/98 EDN Design Ideas:  Op-amp applications that need the highest possible dc accuracy are generally best served by CMOS chopper-stabilized amplifiers, such as the LTC1050.  But high-speed, low-noise applications may require high-performance rockets, such as the 700-MHz LT1226.  So what to do for applications __ Circuit Design by Stephen Woodward, University Of North Carolina, Chapel Hill, NC

Digital Potentiometer Controls LCD Bias -  03/17/94 EDN Design Ideas:  Designers of pen-based computers can easily relegate some controls that were previously mechanical, such as switches and potentiometers, to on-screen icons.  For example, the circuit in Fig 1 shows one way that digital logic can control the -24V-dc LCD bias using two general-purpose i/O command lines.  The DS-1669 from Dallas Semiconductor __ Circuit Design by Michael Cortopassi, Dauphin Technology, Lombard, IL

Digital Potentiometer Controls Phase Shift -  02/15/96 EDN Design Ideas:  You can use dual, quad, or hex potentiometers to put all phase-shift sections under control of a microprocessor, as in Figure 2.  The DS1806 hex digital .    __ Circuit Design by Rick Downs, Dallas Semiconductor Dallas, TX

Digital potentiometer programs & stabilizes voltage reference -  05/30/02 EDN Design Ideas:  The potentiometer portion of a mixed-signal, digitally programmable potentiometer adds variability to an analog circuit, and its digital controls provide programmability.  You can use a digital potentiometer in two ways in an analog circuit.  You can use it as a two-terminal variable resistance, or rheostat, or as a three-terminal resistive divider __ Circuit Design by Chuck Wojslaw, Catalyst Semiconductor, Sunnyvale, CA

Digital potentiometers enable programmable biquadratic filter -  07/22/04 EDN Design Ideas:  Of the many types of analog filters available to designers, few allow easy adjustments of the filter parameters.  The biquadratic, or biquad, filter is an exception, however.  You can change that filter's corner frequency (ω0], Q, and gain (H] by adjusting the values of three resistors.  For that purpose, the lowpass biquad circuit of Figure 1 includes three digital potentiometers configure __ Circuit Design by Deborah Mancuso and Donald Schelle, Maxim Integrated Products, Sunnyvale, CA

Digital Potentiometers: Frequently Asked Questions -  App Note/ 593 / Nov-05__ Maxim Integrated

Digital Radar Speedometer -  This circuit is a Digital Radar Speedometer.  it allows us to evaluate the speed of any object moving, especially cars and other vehicles.  The speed is calculated in kilometers per hour (KPH).  its display has three digits.  This radar works with the laser reflexion.  it sends laser radiation to the object and this object reflects the laser radiation.   __ Contact IQ Technologies

Digital Remote Thermometer -  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

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