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Tester or Instrumentation Circuits, Page 1
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Last Updated on:
Sunday, April 15, 2012 04:16 PM

Circuits Designed by Dave Johnson, P.E. :
  • 1 AMP CURRENT INJECTOR
    When you need to measure resistance down to a few micro ohms, this circuit works great. It is powered from two "C" cell batteries and is designed to inject a well-regulated one amp of current into the unknown resistance. By measuring the voltage drop across the resistor with a digital voltmeter, the resistance value can be accurately measured. The circuit also is equipped with a low battery monitor. Published in Popular Electronics, November 1992

  • 120vac Under Voltage Tester
    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.
  • 20MHz VCSEL 3mW LASER TEST CIRCUIT
    This circuit takes advantage of some new vertical cavity surface emitting lasers (VCSEL) that don’t require light output control circuits. The circuit shows how to drive the device from a single high speed CMOS IC. The circuit can easily be modified to transmit signals from kilohertz to about 50MHz.
  • 40KHZ LED TEST SIGNAL GENERATOR
    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.

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

$5 junkbox Circuit Determines Phase Sequence  -  04/23/98 EDN-Design Ideas....Have you ever wondered which way a blower motor is going to turn when you plug it into anor socket, or have you ever inherited....File contains multiple circuits scroll to find this circuit.... [Design Idea by Hugh Adams, Fort Walton Beach, FL]
µC measures High-frequency signals  -  03/02/98 EDN-Design Ideas....To measure a high-frequency signal using an 8-bit µC, the time period of the measured frequency must be relatively close to the internal.…File contains many circuits, please scroll to find this one.... [Design Idea by Stan D'Souza, Microchip Technology Inc, Chandler, AZ]
0-50V 2A Bench power supply Circuit -  I use the lm10 IC because it has a reference voltage and that�s useful for dc power supply. With two ICs can take different output voltage and amperage.  This circuit is protected from short circuit.... [Author: hamed_iranmehr@yahoo.com]
1 Amp Current Injector -  When you need to measure resistance down to a few micro ohms, this circuit works great. It is powered from two "C" cell batteries and is designed to inject a well-regulated one amp...Published in Popular Electronics, November 1992 …. [Hobby Corner Circuit by Dave Johnson]
10 Amp 13.8 Volt Power Supply -  Just like other commercial units, this circuit uses the LM723 IC which gives us excellent voltage regulation. The circuit uses 3 pass transistors which must be heat sinked….(electronic design added 6/07) [Radio Amateur Society of Norwich]
10 Hints for Making Better Network Analyzer Measurements -  Aligent App Note  (app note added 6/07)
10 Practical Tips You Need to Know About Power Products 5965-8239E -  Learn ten simple ways to improve your testing capabilities with your power supplies and electronic loads. Aligent Application Note  (app note added 2/06)
10Hz-100kHz D.D.S. Function Generator -  (electronic circuit added 05/07)
10Hz-1300MHz Frequency Meter -  Universal VHF/ UHF frequency meter (circuit added 8/06) 
12 Volt to 120 Volt Inverter (randy Linscott) -  Ever needed a low power 120volt AC  power source for your car, van or truck? Well this circuit should do the trick for you. It will supply 15 watts of AC power to a device. It should power lamps, shavers, small stereos and small appliances. If you draw to much power …. [Randy Linscott, designer]
120 VAC Under Voltage Tester -  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.... [Designed by David A. Johnson]
121 & 240Vac LED Voltage Indicator -  Useful for power lines control.  Simple, transformerless circuitry  (added 2/07)
12v Battery Capacity Tester -  An application for the above mentioned LV Disconnect circuit that makes testing the amp-hour capacity of batteries a breeze…. [Circuit Design by Burton Lang]
13.8V 20A PSU -  This is a Regulated DC power supply with short circuit protection and with current limiter.  (electronic design added 6/07)
16-Bit ADC Simplifies Current Measurements -  DN341  Design Notes (Linear Technology) (app note added 6/06)
1A Variable Regulated Power Supply -  A 'must-have' for the experimenter.  (electronic design 05/09) [from Peter Parker's website]


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