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Tester or Measurement (Instrument) Circuits

Test Equipment:  #'s - A        B - D        E - G
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Last Updated: December 07, 2017 02:04 PM
Circuits Designed by Dave Johnson, P.E. :

Temperature Sensor with 4 to 20ma Current Loop -  I designed a circuit similar to this one years ago to accurately measure the air temperature inside a building 1000s of feet from a control room.  The circuit uses a very robust current loop method.  it uses a highly accurate semiconductor temperature sensor. . . Circuit by Dave Johnson P.E.-July, 2000

Temperature Sensitive MOSFET   -  Recently I was asked by a company to discover why one of their products failed to operate properly in cold temperatures.  Two n-channel MOSFETs and a few resistors are wired to form a flip/flop latch circuit.  Each time the pushbutton switch is pressed, the circuit changes state and remains in that state until another activation of the switch.   . . . Dave Johnson, Lubbock TX (December 1, 2010)-DC Magazine - Issue 14 Dec 2010

Ten Turn Pot Forms Frequency Readout -  Let’s say you are designing a signal generator for a test fixture.  To adjust the frequency you would like to use a ten turn pot with a nice dial mechanism attached as a frequency display.  However, a display range of 0 to 9.99 would be impractical since . . . Hobby Circuit designed by David A. Johnson P.E.-January, 2008

Test UL Ground Resistance -  UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms.   This resistance must be tested with actual line current in excess or 10 amps.    The circuit shown uses a couple of LEDs to indicate. . . Circuit by David Johnson P.E.-April, 2001

Tester for Brown Out Voltage -  Using a cheap 24vac transformer, this circuit can test a product under low 95vac conditions.    With the components show, it has a rating of 250 watts max.. . . Circuit by Dave Johnson P.E.-July, 2006

Tester for Modulated Laser Diode -  This circuit can either be used to test laser diodes or as a general purpose modulated light source.  The circuit has an adjustable diode threshold current and an adjustable modulation frequency.  The frequency can be adjusted from below 30KHz to above 50MH . . . Hobby Circuit designed by David A. Johnson P.E.-March, 1999

Tester for Modulated Light -  This battery powered circuit will work from DC to 500KHz.  it is designed to connect to an oscilloscope to monitor the light level changes and modulated signals . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Tester for Pulsed LEDs -  This circuit is designed to test visible and infrared LEDs in pulsed mode operations.  it can drive the LED with peak currents in excess of 10 amps.  A light detector nearby can monitor the response time and intensity of the LED under test . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

Tests UL Ground Resistance -  UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms.  This resistance must be tested with actual line current in excess or 10 amps.  The circuit shown uses a couple of LEDs to indicate if in fact the resistance is less than 0.1ohms - modified on july 10, 2006 . . . Hobby Circuit designed by David Johnson P.E.-April, 2001

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:

Temperature Sensitive MOSFET   -  Recently I was asked by a company to discover why one of their products failed to operate properly in cold temperatures.  Two n-channel MOSFETs and a few resistors are wired to form a flip/flop latch circuit.  Each time the pushbutton switch is pressed, the circuit changes state and remains in that state until another activation of the switch.   . . . Dave Johnson, Lubbock TX (December 1, 2010)-DC Magazine - Issue 14 Dec 2010

Temperature Sensor Uses I2C Isolator -  6-Jun-96 EDN Design Ideas:  You can couple an LM75 digital output-temperature sensor through an isolated i2C (interintegrated circuit] interface (see Reference] as shown in Figure 1.  Electrically isolating the sensor allows operation in situations prone to high common-mode voltages; it's also useful in breaking ground loops.  IC 1 and IC 2 comprise a bidirectional isolator __ Circuit Design by Jerry Steele, National Semiconductor, Tucson, AZ

Temperature Sensor with 4 to 20ma Current Loop -  I designed a circuit similar to this one years ago to accurately measure the air temperature inside a building 1000s of feet from a control room.  The circuit uses a very robust current loop method.  it uses a highly accurate semiconductor temperature sensor. . . Circuit by Dave Johnson P.E.-July, 2000

Temperature to Frequency Converter -  3% Linearity from –20°C (Fout = 20kHz) to 75°C (Fout = 25kHz) The LTC6990 is a precision silicon oscillator with a programmable frequency range of 488Hz to 2MHz.  it can be used as a fixed-frequency or voltage-controlled oscillator (VCO).  The LTC6990 is part of the TimerBlox family of versatile silicon timing devices.  __ Linear Technology/Analog Devices App Note, Jun 16th 2010

Temperature/ Light Brightness Meter with LCD -  Circuit measures the temperature and ambient brightness of the surrounding environment at the location it is placed.  The data from the ADC is the calculated and displayed on the LCD.  The main CPU unit on board the device is the PIC 16F873.  __ 

Temperature-controlled 12V DC Fan -  Suitable for computer cooling fans.  LED motor speed indicator.   __ Contact Flavio Dellepiane, fladello @ tin.it

Temperature-Measurement Scheme Uses IR Sensor & Sigma-Delta ADC -  3-Apr-03 EDN Design Ideas:  Many noncontact temperature-measurement systems use infrared sensors, such as thermopiles, which can detect small amounts of heat radiation.  Biomedical thermometers that measure the temperature of an ear or a temple use noncontact temperature measurement, as do automotive-HVAC systems that adjust temperature zones based on the body temperature of passengers __ Circuit Design by Albert O'Grady and Mary McCarthy, Analog Devices, Limerick, Ireland

Temperature-Sensing Diodes Selector -  Low-cost semiconductor diodes such as 1N914, 1N4148 and 1N400X can be used as temperature sensors in applications where high accuracy is not required.  They can be mounted on transistors, power diodes, ...__ Electronics Projects for You

Temperature-to-Frequency Converter -  Precision oscillator structure uses SCR effect to discharge integration capacitor.  A temperature dependent device (LM134) effects the integrator trip point to form a variable interval.  An output transistor detects the reset action and forms a logic pulse.  __ Linear Technology/Analog Devices App Note, Jun 21, 2011

Temperature-to-period provides linearization of thermistor response -  11/10/05 EDN Design Ideas:  Highly accurate pulsewidth varies with temperature __ Circuit Design by S Kaliyugavaradan, Anna University, Madras Institute of Technology, Chennai, India

Tempmaster Electronic Thermostat Mk.2 -  Want to convert an old chest-type freezer into an energy-efficient fridge? Or convert a spare standard fridge into an excellent wine cooler? These are just two of the jobs this low-cost and easy-to-build electronic thermostat has been designed to do.  it can also be used to control 12V fridges or freezers, as well as heaters in hatcheries and fish tanks.  it controls the fridge/freezer or heater directly via their power cables, so there's no need to modify their internal wiring.__ SiliconChip

Ten Turn Pot Forms Frequency Readout -  Let’s say you are designing a signal generator for a test fixture.  To adjust the frequency you would like to use a ten turn pot with a nice dial mechanism attached as a frequency display.  However, a display range of 0 to 9.99 would be impractical since . . . Hobby Circuit designed by David A. Johnson P.E.-January, 2008

TENS for muscle stimulation -  Medical and health related electronic circuit diagrams / circuit schematics.  These circuit are to be used at your own risk And I "DO NOT" imply any medical benefit can be obtained from their use. __ Designed by G.L. Chemelec

Test batteries without a voltmeter -  11/09/00 EDN Design Ideas:  The circuit in Figure 1 is an easy approach to testing batteries without exiting the voltmeter.  The battery holders in sizes AAA, AA, C, and D make this tester so much faster than a voltmeterPDF contains multiple circuits, scroll to find the one of interest __ Circuit Design by Nam Phan, Pasadena, CA

Test batteries without a voltmeter, part 2 -  03/03/01   EDN Design Ideas:  From a high-volume-production point of view of the Design ideas - "Test batteries without a voltmeter " (EDN , Nov 9, 2000, pg 167) , it is a time-consuming and laborious task to tweak the large number of potentiometers on each of the comparator input refere __ Circuit Design by Harry Gibbens Jr

Test Capacitors with this -  EDN-Design ideas -- 02/17/11    Check capacitors for leakage.  Electrolytic capacitors tend to leak with time.  The circuit in Figure 1 lets you test capacitors and decide whether they’re worth using.  You can set the constraint on the leakiness through the values of CREF/RREF.  The values in the figure are typical for general testing of all capacitors, from 1-nF ceramic versions to 1000-μF electrolytic types.  The value of CREF in the circuit is near the value of the test capacitor, CX.  You can also choose RREF, by a rotary-switching arrangement, to be greater than or less than 22 MΩ.   __ Circuit Design by Raju R Baddi, Tata Institute of Fundamental Research, Maharashtra, India

Test Continuity -  This circuit will detect low resistances and high resistances to produce a tone from the speaker.  it will detect up to 200k and the circuit automatically turns off when the probes are not used.  __ 555-Timer

Test Continuity -  This circuit senses only dead shorts on a populated board.  it will not ring through or damage components.  it shuts off when not in use.  it was first published in Electronics magazine, June 21, 1979, page 145 __ Designed by Andrew R. Morris

Test Continuity -  This is another invaluable piece of test equipment for digital work.  it has been designed by us to cater for a particular application servicing digital projects sent in for repair.   __ Designed by Collin Mitchell

Test Continuity -  Several simple circuits were tried -a lamp, battery and probes still demanded the attention of the eyes; replacing the lamp with a buzzer was more successful but needed some three to four volts and gave no indication of a series semiconductor.   __ Designed by Tony van Roon  VA3AVR

Test Continuity with an LED -  01/06/11 EDN Design Ideas:  Test circuits for resistance against a preset limit.   [Design ideas by Raju R Baddi, Raman Research institute, Bangalore, india __ Circuit Design by Raju R Baddi, Raman Research Institute, Bangalore, India

Test High-Speed Drivers with Bursts & Pseudorandom Bit Pattern -  05/12/94 EDN Design Ideas:  Combine a high-performance, dual-channel pulse generator having burst and pseudorandom bit-stream capabilities with a high-bandwidth sampling oscilloscope for an effective and reliable way to characterize high-speed drivers.  Both manufacturers and users of high-speed drivers need to verify the performance of these devices because performance from part to part varies and depends on the environment in which the driver must work.   __ Circuit Design  Andreas Pfaff, Hewlett-Packard GmbH  05/12/94

Test Human Reaction Time with the 555 IC -  With this simple circuit that is built with the 555 IC you can test human reaction time.  You can find out how fast do you react by trying to catch a flashing LED.  How does the human reaction tester works? When S1 is ON the circuit acts as a astable multivibrator and the LED is lit for about 0.1second and is flashing every 1.5 __ Designed by Popescu Marian

Test Power-Outage Susceptibility -  03/03/97 EDN Design Ideas:  Brief (1 sec or shorter) power outages are common in developing countries and seem to be increasing in the United States.  They are generally nondestructive, so power-protection equipment should not trip and disconnect the load.  Electric motors do not appreciably slow, and electronic equipment can usually ride through the outages on the energy stored in filter capacitors.  As a point of reference, a 10-msec outage makes an incandescent light bulb flicker.  At 100 msec, you can see the bulb go completely dark.  Figure 1 shows a simple circuit for generating brief outages for equipment-susceptibility testing.    __ Circuit Design by Ron Tipton, TDL Electronics, Las Cruces, NM

Test Sample-And-Hold Amplifiers -  4-Mar-10 EDN Design Ideas:  Measure voltage drop with a digital voltmeter __ Circuit Design by Marián Štofka, Slovak University of Technology, Bratislava, Slovakia

Test Setup Performs Functional Testing of Linear, Single-Cell Lithium Chargers -  10-May-07 EDN Design Ideas:  A handful of off-the-shelf components makes a test setup that allows you to test the operation of a linear single-cell lithium charger __ Circuit Design by Marián Štofka, Slovak University of Technology, Bratislava, Slovakia

Test timer -  The output goes high for a fixed period of time when power to a unit under test (UUT) is turned on, and again when it is turned off.  it was used with a magnetic sensor to test the spin-up and spin-down time of a gyroscope.   __ Designed by Andrew R. Morris

Test Twisted-Pair Cables -  01/19/12 EDN Design Ideas:  Quickly test a cable containing twisted-wire pairs and detect open or reversed pairs, shorted pairs, and shorts between unrelated pairs.  Using the system shown in Fig 1, you can quickly test a cable containing twisted-wire pairs and detect open or reversed pairs, shorted pairs, and shorts between unrelated pairs.  The tester consists of an active test set that plugs into one end of the cable, and a passive terminator that plugs into the other end. (An RS-449 cable is used as an example.)  __ Circuit Design by Mark D Braunstein, Contel Information Systems, Fairfax, VA

Test UL Ground Resistance -  UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms.   This resistance must be tested with actual line current in excess or 10 amps.    The circuit shown uses a couple of LEDs to indicate. . . Circuit by David Johnson P.E.-April, 2001

Test VCOM Drivers -  11-Nov-04 EDN Design Ideas:  Flat-panel LCD monitors offer excellent image quality andcompact form factor than CRTs—hence, their steadily increasing popularity.  Unfortunately, the complexity of their manufacturing process makes LCD monitors considerablyexpensive than CRTs.  The amplifier that drives VCOM, the voltage on the backplane of the LCD panel, must be able to drive large capacitive loads, deliver h __ Circuit Design by Soufiane Bendaoud, Analog Devices, San Jose, CA

Tester Checks Christmas-Tree Lights -  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

Tester checks LCDs -  10/03/02 EDN Design Ideas:  RF oscillator uses current-feedback op amp - Manufacturers of electronic equipment use LCDs for calculators, watches, mini-videogames, and pagers, for example.  in comparison with LED-based displays, which consume power on the order of tens of milliwatts, an LCD consumes only a few microwatts.    __ Circuit Design by D Prabakaran, NL Polytechnic College, Tamil Nadu, India

Tester Continuity -  Among the essentials for circuit design and prototyping is the continuity tester, a simple device which provides an audible indication when a sufficiently low resistance is applied between its input probes.  This version has a feature which automatically turns off the tester after about two minutes, thereby saving the 9 volt battery from inadvertent discharge.  The tester produces a high-pitch tone when less than 10 ohms is placed between the input probes.  The 10 ohm threshold is a convenient value that indicates hard-wired paths, but excludes indications for circuit paths through most components.  in addition, the amount of current presented to the circuit by this __ Designed by Arthur Harrison

Tester for Brown Out Voltage -  Using a cheap 24vac transformer, this circuit can test a product under low 95vac conditions.    With the components show, it has a rating of 250 watts max.. . . Circuit by Dave Johnson P.E.-July, 2006

Tester for Modulated Laser Diode -  This circuit can either be used to test laser diodes or as a general purpose modulated light source.  The circuit has an adjustable diode threshold current and an adjustable modulation frequency.  The frequency can be adjusted from below 30KHz to above 50MH . . . Hobby Circuit designed by David A. Johnson P.E.-March, 1999

Tester for Modulated Light -  This battery powered circuit will work from DC to 500KHz.  it is designed to connect to an oscilloscope to monitor the light level changes and modulated signals . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Tester for Pulsed LEDs -  This circuit is designed to test visible and infrared LEDs in pulsed mode operations.  it can drive the LED with peak currents in excess of 10 amps.  A light detector nearby can monitor the response time and intensity of the LED under test . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

Tester for Remote Control -  Here is a simple tester for checking the basic operations of an infrared remote control unit.  it is low-cost and easy to construct.  The tester is built around infrared receiver module TSOP1738....__ Electronics Projects for You

Testing & Troubleshooting Digital RF Communications Receiver Designs -  Application Note__ Aligent

Testing CDMA Base Station Amplifiers -  Application Note__ Aligent

Testing inductors at application frequencies -  Coilcraft RF Magnetics App Note- __ Designed by Coilcraft Power Magnetics Application Note

Testing Linearity of the LTC2400 24-Bit No Latency Delta SigmaTM A/D Converter Help from the Nineteenth Century -  Design Solutions 11 Design Notes__ Linear Technology/Analog Devices

Testing Metal Detector Coils -  I Decided to Check my coils for inter-wire and Total Capacitance.  it is a Well Known fact that internal Capacitance in a coil reduces its frequency response.  in the Tests Below, The coil Lead Lengths on all coils was about 5 inches.  No Coax cable used __ Designed by G.L. Chemelec

Testing-Functional Module Tester  -  No description, just schematic - OpAmps Lab inc is the manufactor ofAmplifiers (Video / Audio / Distribution / Microphone / Equalization / Line / VCA / Power) , Switchers (Routing / Assign / Matrix) , Mult (Press) (Network-Feed) Boxes, Audio Transformers, Oscillators, Power-Supplies, Custom Sub-Systems.  __ Application OpAmps Lab Inc.

Testing-Simple Circuit Log-Frequency Response Chart  -  No description, just schematic - OpAmps Lab inc is the manufactor ofAmplifiers (Video / Audio / Distribution / Microphone / Equalization / Line / VCA / Power) , Switchers (Routing / Assign / Matrix) , Mult (Press) (Network-Feed) Boxes, Audio Transformers, Oscillators, Power-Supplies, Custom Sub-Systems.  __ Application OpAmps Lab Inc.

Tests UL Ground Resistance -  UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms.  This resistance must be tested with actual line current in excess or 10 amps.  The circuit shown uses a couple of LEDs to indicate if in fact the resistance is less than 0.1ohms - modified on july 10, 2006 . . . Hobby Circuit designed by David Johnson P.E.-April, 2001

TGS 813 Detection of Combustible Gas -  Figaro Production information TGS 813 Rev: 9/02__ 

Thank you, Bill Hewlett -  02/01/01  EDN Design Ideas:  Jim Williams remembers Bill Hewlett—co-founder of Hewlett-Packard.  it was a simple deal.  if my next report card had a B average, my parents would give me a trip or two weeks at summer camp.  My grandfather suggested New York City where I could see Mickey Mantle (his hero) play at Yankee Stadium.  My mother liked Yellowstone National Park, and my dad came up with Washington, DC, or sailing around Mackinac island.   __ Circuit Design by Jim Williams, EDN's most revered contributor, passed away in June 2011 after a stroke.  He was 63.

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


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