Products > Test Equipment
Continuity Tester
hugo:
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You'll find a simple, inexpensive and well enginnered diy continuity tester, called "In-Circuit Conduction Tester" at http://elm-chan.org/works/cch/report_e.html
Vtest: 500mV
Itest: 100μA
rhb:
I suggest you consider the likely outcome of using a 7 V (33401A) or 9 V continuity tester on a 3.3 V MCU board. And if you forward bias a transistor junction ( .3 or .7 V) you'll run the risk of spurious results.
Consider using a 0.5 V 1 kHz pulse train and an op amp to boost it to 5 V with a missing pulse detector triggering a 555 configured as a multivibrator. 0.2 V in the unlikely case you're working with germanium semis.
There are many ways to implement one. I made a crude 1.5 V tester using a small, not loud enough, piezo sounder. It works OK, but I concluded it really needs to be below the forward conduction threshold for silicon junctions.
The Cadillac is a milliohm RC oscillator which changes tone as the resistance varies. Those will let you locate shorts as well as opens. There are lots of versions of those.
Have Fun!
Reg
bdunham7:
--- Quote from: rhb on July 25, 2023, 02:04:01 am ---I suggest you consider the likely outcome of using a 7 V (33401A) or 9 V continuity tester on a 3.3 V MCU board.
--- End quote ---
Bench meters like the 34401A often have selectable continuity ranges and thresholds. You just set the threshold for a low value and then put a resistor just above that value across the test leads with one of those dual-banana adapters. So if your test current is 1mA just set the threshold for 10R, put a 20R resistor across it and your 'open circuit' voltage will be 20mV.
Fungus:
I always wanted one that has an LED in the probe. If you're going the DIY route you could try doing that.
Edit: You could also pull the PCB out of one of those Anengs and build it around that - just bring the LED out to the probe. :)
J-R:
FYI, the 34401A continuity threshold can be set from 1-1000 Ohms. Default is 10 Ohms.
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