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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. :

LED Test Signal Generator-40Khz -  This 40KHz crystal controlled oscillator circuit drives an infrared LED with powerful 40ma pulses.  The circuit can be used to test optical communications circuits, designed to receive 40KHz modulated light signals . . . Hobby Circuit designed by David Johnson P.E.-February, 2002

LED/Laser Light Output Intensity Meter -  This circuit uses a large 1cm X 1cm silicon PIN photo diode and a transimpedance amplifier to measure the light power output of infrared and visible LEDs and laser diodes.  it can be modified to produce almost any milliwatts to volts scale factor.  it can b . . . Hobby Circuit designed by David Johnson P.E.-July, 2000

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Lightning Activated Camera Shutter Trigger -  This circuit is used to trigger a camera's electronic shutter circuit when a flash of lightning is present.  This circuit would also work for photographing fireworks displays or other events involving flashes of light.   __ Designed by G. Forrest Cook

Lightning Detector -  Egor!  Come quick!  A storm approaches!  Here is a VLF receiver tuned to 300 kHz designed to detect the crackle of approaching lightning.  A bright lamp flashes in sychrony with the lightning bolts indicating the proximity and intensity of the storm.  Figure 1 shows the simple receiver which consists of a tuned amplifier driving a modified flasher circuit. __ Designed by Kyriakos Kontakos

Lightning Modulator -  Schematic + info + pictures __ Designed by Lennie Zink

Lightning Simulator -  This little simulator generates short pulses at a few Hz rate and is heLPFul in designing and testing lightning detector circuits like the one at the top of the page.  The output is connected to a shielded audio cable with an RCA type connector.  The other end of the cable is connected to the antenna of the lightning detector through a 10 pF capacitor (not shown).  The shield of the audio cable is connected to the detector's ground.  The 10 pF allows the lightning detector's tuned circuit to ring and the amplitude of the ring may be observed on the collector of Q1.  The circuit is built into a Home Depot gift certificate can.  The circuit board slides into two card guides glued to the ends of the can.  Any type of construction will probably work fine, but a metal can is recommended to keep the pulses "contained.  " __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Lightwave Clear-Air Scatter Test -  After patiently waiting for the bright moon to clear the early evening skies, I was finally able to venture out for my first clear-air scatter test this past Sunday night. I had plotted the path on my Mayne island map and determined bearings as best I could, but the path was going to be very tight.  __ Designed by VE7SL - Steve

Line Output / Flyback transformer tester -  This is a 'ringer'-type tester I (Bob Barker) originally designed for in-circuit testing of Line Output (Flyback) transformers in TVs and computer monitors.  After a couple of technician-years of evaluation in actual servicing situations, it's also proved to be heLPFul in locating shorted diodes, capacitors and deflection yokes in horizontal deflection stages.  LOPT/FBT condition is shown on an 8 LED 'bargraph' display.   __ Designed by Bobarker, not the TV Host

Line receiver provides self test -  EDN Design Ideas:  07/01/2016    Use a quad differential comparator to provide adequate self-test for systems using line receivers for differential input signals. __ Circuit Design by Jay L Richman, Bendix Flight Systems, Teterboro, NJ

Linear potentiometer implements logarithmic gain control -  10/23/1997 EDN Design Ideas:  Trimmer potentiometers are ubiquitous components and are available in a variety of packages, resolutions, and temperature stabilities.  However, none of these potentiometers implements anything but the usual linear function of resistance vs shaft position.  This fact makes trouble for applications that need a wide dynamic-adjustment range.    __ Circuit Design by W Stephen Woodward, University of North Carolina - Chapel Hill

Linear potentiometer provides nonlinear light intensity control -  04/28/05  EDN Design Ideas:  Circuit matches light control to eyes intensity-response curve __ Circuit Design by Stephan Goldstein, Analog Devices, Wilmington, MA

Linear Thermometer -  T1 has a built in pair of thermistors with linearizing resistors custom scaled for a specific temperature range.  , 0C to 100C in this example.  The flying capacitor LTC1043 eliminates any dc loading on the precision network to maintain linearity over the entire temperature range.  Amplifier gain is scaled to provide an output __ Linear Technology/Analog Devices App Note, Jun 21st 2011

Linear Wind-Power Meter Compensates for Temperature -  13-Nov-08 EDN Design Ideas:  Using a free-spinning anemometer for wind speed and a diode-connected transistor for temperature sensing, this meter measures the wind power available for "green" power generation __ Circuit Design by W Stephen Woodward, Chapel Hill, NC

Linearize Optical Distance Sensors with a Voltage-To-Frequency Converter -  04/19/12  EDN Design Ideas:  Create the mathematical inverse of an analog voltage by converting it to frequency and measuring the period.   A popular series of inexpensive distance sensors integrates an infrared emitting diode, a linear charge-coupled-device array, and a signal-processing circuit in one unit.  The output is a dc voltage, VS, that depends on the distance, D, in a nonlinear manner (Figure 1). __ Circuit Design by Jordan Dimitrov, Toronto, ON, Canada

Linearize thermistors with new formula -  EDN Design Ideas:  03/03/2014     Optimize thermistor performance at any preferred temperature __ Circuit Design by Mark Biegert

Linearized NTC Thermistor -  (spice design)  __ Designed by Rick 

Linearized Platinum Resistance Thermometer with 0.025C Accuracy Over 0 to 100C -  Platinum RTD's are typically driven with a constant current so that their resistance value directly translates to a temperature dependant voltage.  Here the LT1001 and the LM129 create a constant current through the input 10K resistor which all flows through the sense resistor.  A second amplifier inverts the signal to provide __ Linear Technology/Analog Devices App Note, Jun 21st 2011

Linearizes & Convert Thermistor Data -  12/07/95 EDN Design Ideas:  Although the response of thermistors is inherently nonlinear, you can make the devices' resistance over a selected range of temperatures linear.  You can convert the thermistor value to a voltage for display on either a DMM or a panel meter.  The circuit in Figure 1 performs linearization and provide as gain and offset for a YSI 44031 thermistor, whose nominal resistance is 10 k[ohm] at 25C.    __ Circuit Design by Matthew Beckner, Ball Corp Boulder, CO

Link Neatly Measures Temperature -  10/26/00 EDN Design Ideas:  Figure 1 shows a convenient and neat way to measure temperature using the USB of a PC.  An ADM1023 IC senses the temperature, and an Anchor Chips EZ-USB AN2131SCC provide as control.  The ADM1023 is a low-cost device with an accuracy of 1C and a resolution of 0.125C.  The IC is a two-channel device that can measure its own local temperature and the temperature of a remote location __ Circuit Design by Mary Burke, Analog Devices, Limerick, Ireland

Liquid Barometer -  Have you ever noticed how those technical-looking aneroid barometers in the stores all indicate a different pressure? And when you __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Liquid Level Alarm -  Here is a simple circuit for liquid level alarm.  it is built around two BC547 transistors (T1 and T2) and two timer 555 ICs  (IC 1 and IC 2).  Both IC 1 and IC 2...__ Electronics Projects for You

Liquid-Level Indicator -  The LTC2990 is used to monitor system temperatures, voltages and currents.  Through the i2C serial interface, the device can be configured to measure many combinations of internal temperature, remote temperature, remote voltage, remote current and internal VCC.  The internal 10ppm/C reference minimizes the number of supporting __ Linear Technology/Analog Devices App Notes, Mar 16th 2011

Lithium Battery Tester -  I bought some lithium ion rechargeable batteries a while back.  I was planning on using them to modify some solar powered LED spot lights.  What I like about these new batteries is that they are the same size as a standard 1.5v alkaline AA cell . . . Hobby Circuit designed by David A. Johnson P.E.-February, 2012

Lithium Ion Battery Stack Monitor with Both Signal & Power Isolation  -  Software to communicate with the EVAL-CED1Z and AD7280A is provided with the AD7280A evaluation board package.  Connection between the EVAL-CED1Z and the USB port of a PC is via a standard USB 2.0 connection cable that is provided as part of the EVAL-CED1Z package.  , Getting Started Complete details of setting up the hardware and installing the software are contained in UG-252__ Analog Devices from the Lab

Little More Serious Frequency Meter/CounterATtiny2313, AT90S2313 -  Maximum input frequency is specified to be 30 MHz in the multi-chip configuration, and in single-chip configuration, there are both 5 MHz and 10 Mhz versions operating with 10 and 20 MHz crystals, respectively.  All versions have 9 1/2 digit resolution.  I have used __ Designed by Dick Cappels

Live-line Detector -  Detects the presence of a live mains conductor; Minimum parts counting __ Contact Flavio Dellepiane, fladello @ tin.it

LM35 termometer -  an adjustment termometer by LM35 this file simulated by Proteus 7.2 and micro program is on Bascom __ Designed by rajbai.somee.com

LM3914 Battery Monitor -  This circuit should be powered by its own battery, otherwise you might get an innacurate reading.  hook the to-be-monitored battery to pin 5 of the chip.   __ Designed by Andy Wilson

Load Assembly Code In 8052-Basic System -  10/26/95 EDN Design Ideas:  The 8052-Basic chip, a member of the popular 8051 family, is a useful C that permits rapid prototyping and software development.  The C has an on-chip Basic interpreter.  However, the interpreted Basic may be slow for certain applications.  You can speed things up by coding time-critical sections of a program in assembler.  Fig 1 shows a simple system that connects to a host PC running a terminal-emulation program like Vterm or Procomm.  The Basic-52 Listing allows you to load assembly routines into the system's RAM. __ Circuit Design by Dhananjay Gadre, Inter-University Centre for Astronomy and Astrophysics, Instrumentation Lab, Pune, India

Load Monitor Alarms Above 60W -  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

Load Pulser Tests Supply's Transient Response -  04/11/96 EDN Design Ideas:   Modern Ps place severe demands on the transient response of the power source.  For example, intel's P6 specification stipulates an output-current capability of at least 30A/sec while maintaining output-voltage regulation within specified limits __ Circuit Design by Chester Simpson, National SemiConductor, Santa Clara, CA

Load Simulator Maintains Constant Power -  04/11/96 EDN Design Ideas:  The circuits in Figures 1 and 2 show how you can emulate a constant-power load for cases when a simple load resistor is unacceptable.  For example, using a simple resistor as a load is unacceptable for applications that require you to accurately monitor generated or consumed power.  One such application is in battery-energy measurement.  You measure battery energy density (watts/hour) by measuring the total output power (W=Vxi) over time.  This task is relatively simple if you use an automated system to take frequent and periodic measurements of the discharge current and battery voltage while keeping track of time.   __ Circuit Design by Khy Vijeh, Analog Devices, Santa Clara, CA

Load Transient Response Testing for Voltage Regulators -  Linear Technology AN104 __ Designed by Jim Williams - Oct 1st, 2006

Load-transient-response testing for voltage regulators -  09/28/06  EDN Technical Article: Variations occur in voltage regulators' transient loads; thus, the devices require careful evaluation and testing.   __ Circuit Design by Jim Williams, EDN's most revered contributor, passed away in June 2011 after a stroke.  He was 63.

Locate a Plastic Pipe -  I used this circuit once to track down the location of a plastic pipe, buried underground.  it transmits a weak RF signal, which can be picked up by a portable AM radio from about 6 feet away . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2004

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

Logic analyzer pushes microcontroller to its limit -  12/07/00  EDN Design Ideas:  A simple logic-analyzer design is compatible with all versions of Windows and pushes the PIC  18C252 chip to its speed limit to achieve a 1-MHz sampling rate (Figure 1).  The circuit can examine three channels of relatively low-speed logic signals that have infrequent, or sparse, transitions.  The analyzer can record only 510 transitions per run, but a run can last as long as several minutes, if necessary.  Applications include monitoring the i/O of an iBM keyboard or printer port, Ti-calculator intercommunication, and serial (RS-232) signals __ Circuit Design by Tom Lyons Fisher, Inexpensive Systems, Huntingdon, PA, and Michael Deskevich, Juniata College, Huntingdon, PA

Logic Designer & breadboarding system for Digitals -  if you have never built a digital circuit before, this is where you start.  Our LOGIC  DESiGNER is the beginning to digital designing and can be used in 2 ways.  Firstly it can be used by itself to perform counting operations in either binary or decimal or it can be combined with any of the "bread-boarding" systems currently available in all major electronics shops. __ Designed by Collin Mitchell

Logic Gates Form High-Impedance Voltmeter -  05/26/11  EDN Design Ideas:  Estimate voltages across high-value resistances.  You can use the circuit described in this Design idea to estimate voltages across 10- to 100-MΩ resistances.  it also works for reverse-biased diodes.  The common CMOS gates in Figure 1 have an input threshold voltage in which the output swings from logic zero to logic one, and vice versa.  The threshold voltage depends on the supply voltage (Figure 2).   __ Circuit Design by Raju R Baddi, Tata Institute of Fundamental Research, Maharashtra, India

Logic offers Complementary Switch Control -  12/06/01 EDN Design Ideas:  The complementary-switch controller in Figure 1 uses a few inverter gates to provide drive signals for the complementary switches.  Complementary-switch configurations find wideaspread use in synchronous-rectification circuits, charge pumps, full-bridge control circuits, and other circuits.  The circuit in Figure 1 provide as not only a complementary drive signal but also a deadtime delay __ Circuit Design by Yen-Hsu Chen, Analog Integrations Corp, Hsinchu, Taiwan

Logic Probe -  An useful and easy to build Logic Probe with Pulse injector.  An schematic of a "digital version" is included.   __ Designed by Jose Pino

Logic probe -  This logic probe uses a single CMOS IC and shows three logic conditions, High, Low and Pulsing.  in addition if the probe input is neither hI or low (the high impedance state of tri-output logic IC 's) then no LEDs will light.    Power from the logic probe is taken from the logic circui __ Designed by Andy Collison

Logic Probe MkIIB -  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

Logic Probe uses Bicolor LED -  03/13/98 EDN ideas - (FILE
has several circuits, scroll to this one) A project posed the challenge of replacing existing analog potentiometers (used to set brightness and contrast levels]in video monitors with digitally controlled potentiometers.  The different brands and models of monitors presented widely varying voltages across the potentiometers.  The design.    __ Circuit Design by Mark Shill, Burr-Brown Corp, Tucson, AZ

Logic Probe Uses Six Transistors -  12/15/10 EDN Design Ideas:  Build a logic probe from discrete components.   [Design ideas by Raju R Baddi, Raman Research institute, Bangalore, india __ Circuit Design by Raju R Baddi, Raman Research Institute, Bangalore, India

Logic Probe Uses Two Comparators -  EDN-Design ideas -- 08/25/11    Build a logic probe whose voltage thresholds vary with your circuit's power supply voltage.  Measurement instruments must not affect the circuits theyre measuring.  A logic probe, for example, must correctly detect logic levels, and it must place no undue loads on the test circuit.  The logic probe must set thresholds on automatically checking logic levels, depending on the supply voltages of the ICs  it is checking.  it should also not cause the checking circuit to function incorrectly. __ Circuit Design by Vladimir Rentyuk, Zaporozhye, Ukraine

Logic probe with 7-segment display -  Logic probe with 7-segment display based on 74LS00 and 74LS47__ 

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

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