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Component tester for varistors
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Traceless:
Hey everyone, does anyone know if there is a component tester that can deal with varistors? I have one of those genecric el-cheapo-ones but it detects a capacitor instead of a varistor. Obviously for a varistor a voltage/resistance plot would be interesting, similar to what the Peak Atlas DCA75 Pro can do for transistors.
Greybeard:
For I-V plots you can use a curve tracer with suitable maximum test voltage, for example Tektronix 576/577/370...

https://w140.com/tekwiki/#Curve_Tracers
https://vintagetek.org/curve-tracers/
Traceless:
Curve tracers are super interesting, ever since I saw them on Curious Marc's channel for the first time. For some reason they seem to have become "unfashionable". It seems they are no longer produced. I've looked around for used ones but they seem to be in pretty bad shape, super expensive or both. It would be nice if one could upgrade a modern DSO to operate as a curve tracer.
Ian.M:
Many DSOs make fairly lousy display devices for a curve tracer - for three terminal active components, one often needs to step one parameter to display a family of curves on the screen, which was reasonably simple to display on a CRO in XY mode, if each curve could be swept fast enough for phosphor persistence to eliminate flicker, but on a DSO the trace intensity is usually *NOT* related to the sweep speed so the fast retrace from the end of one curve to the start of the next becomes visible.  *IF* the scope has a Z (intensity) input, the curve tracer can be designed to provide a blanking pulse to eliminate this problem, but DSOs with Z inputs are fairly rare and typically expensive.

OTOH Arduinos are dirt cheap, and its fairly simple to hook a couple of DACs and >12 bit ADCs (with PGAs so they can range shift) to one.  That also brings the benefit of being able to do low duty cycle pulsed measurements e.g. turn on for one ms in a second so the effect of self-heating of the device under test can be minimised, so if I was 'rolling my own' curve tracer and I wanted something better than the classic 'Octopus' type (or variations of it), I'd almost certainly go for an Arduino based one, logging to the bench PC for display and analysis.
Whitefoot:
A power supply which develops at least the breakdown voltage of the varistor is needed. Connect the varistor to the power supply thru a resistor to limit current. Connect a voltmeter across the varistor to measure when it reaches breakdown. Raise voltage carefully to avoid excessive current.

An old capacitor tester which does leakage testing can be used. The varistor is essentially open until breakdown voltage is reached, then it begins to conduct which looks like leakage.
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