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Tester or Instrumentation Circuits, Page
2 Testers: #'sA-BCDEF-GH-KLM-OPQ-RSTV-Z
Last Updated on:
Friday, August 29, 2008 02:34 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:
4 to 20 mloop needs no external power source: 09/13/01 EDN Design Ideas / (added 11/05) simple circuit in Figure 1 uses a
low-current-drain MAX407)3H amplifier to sense current flowing through a 4to 20-mA loop. circuit senses current through a 1Ω resistor with a fixed gain of 100 and uses no
battery or dc power supply. low current drain of amplifier (0.
6 Digit 40MHz Frequency Counter Module: Here is design for a very low cost 6-digit frequency counter module using of shelf components
(and not that expensive 74C926!). The standard circuit will display directly in Hz (1MHz max), and re is a separate on board divider that will allow you to display directly in KHz (approx
40MHz max). Because display reads directly in Hz or KHz re is no need for decimal point switching and associated complexity. There are no switches or controls, simply feed
signal into one of two inputs and you have a direct readout in Hz or KHz. This circuit is ideal for adding a low cost frequency display to a function generator or or design. I doubt if it is
possible to get a cheaper design using off shelf components!. In fact, I challenge anyone to make a cheaper design using garden variety components!.... (add 11/05)
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