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Tester or Instrumentation Circuits, Page 14
Testers:  #'s    A-B    C    D    E    F-G    H-K    L    M-O    P    Q-R    S    T     U    V-Z
Last Updated on: Friday, March 12, 2010 12:07 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:
UJT Test - This testing procedure is for use with a digital multimeter in the OHM's test-range.  The UJT is a solid-state 3-terminal (TO-18 case) emiconductor.  UJT's are used in pulse/timing, oscillator, sensing, and thyristor triggering circuits. The most common one being probably the 2N2646 from Motorola. (Tony van Roon's design added 2/06)
UL Ground Resistance Tester - UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1 ohms.  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 0.1 ohms.  It uses a modified transformer to produce a 2.5vac output with at least 10 amps of supply current. ….(designed by David A. Johnson)
Ultrasonic Range Meter - This circuit is measuring the range to an object by using ultrasonic transmitter and ultrasonic receiver. The distance is calculated by PIC microprocessor and is displayed on the three digit 7-segment LED display. ….(electronic design added 10/06)
Unusual clock with AT89C2051 - ….(electronic schematic added 08/08)
Use a PC's printer port to measure frequency - 10/26/95 EDN-Design Ideas:  (design idea added 11/05)
Use a switching regulator controller to generate fast pulses - 04/13/06 EDN-Design Ideas:  Switching-regulator-controller ICs can deliver gate-drive pulses with rise and fall times of less than 2 nsec, making them ideal candidates for laboratory pulse-generators.....(design idea added 9/08)
Use OpAmp injection for Bode analysis - 09/16/04 EDN-Design Ideas:  Bode analysis is an excellent way to measure small-signal stability and loop response in power-supply designs. Bode analysis monitors gain and phase of a control loop. It performs this monitoring by breaking the feedback loop and injecting a signal into the feedback node and then comparing the injected signal with the output signal of the control loop.....(design idea added 1/05)
Use RS232C Port to Measure Pressure - 08/01/97 EDN-Design Ideas:  A simple circuit and accompanying software turn a pressure sensor into an accurate and cheap pressure digitizer that works with any PC's RS-232C COM port. Many manufacturers make micromachined silicon piezoresistive pressure sensors.....(design idea added 6/06)
Use Your Printer Port as a High Current Ammeter - 07/06/00 EDN-Design Ideas:  -With a few inexpensive components and INT1Ch, you can turn the printer port of your PC into a high-current ammeter.....(design idea added 6/06)
Using Vector Modulation Analysis in the Integration, troubleshooting and Design of Digital RF Communications Systems - Aligent Application Note  (app note added 6/07)
UTP Cable tested - (schematic added 8/03)

           
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