Kin wrote:So, I think Doc said this wasn't a particularly sophisticated IR tester design. I was trying to figure out- how does it work? It is simply a resistor and voltmeter setup [I'm not sure with two leads how it would put something in both series and paralleled, but yeah). Just wondering if anyone had a quick explanation.
Kin, read this re 4-wire measurement:http://www.cirris.com/testing/resistance/fourwire.html
Thanks IBScoot. So the tester is providing a current source, which is shorted through the resistor of the battery, and then the voltage across the resistor tells you the voltage of the current source, which in turn tells you the resistors value, given a known value current source? I'm basing my understanding off of the diagram
, but to be honest I'm still not really clear what's going on even if that diagram is properly showing the situation. I'll try to read it again, and then edit this post.
Edit: The explanation seems to be discussing the importance of the fixturing resistance. I'm not totally sure what fixturing resistance is, and I can only guess it's either the contact point between your probe or the tester's own resistance. There is the section "why not just substract fixturing resistance" and it refers to fixturing resistance as something high (2ohm) so I reason that to be the resistor through which an anmeter measures current. Maybe this is part of the "current source" calculation in the previous diagram.
^Actually I wrote this a few times and changed my theory each time. The most notable lesson is just that I don't know remotely enough about electronics.
Edit, for what it's worth, I realize my understanding of the diagram is total nonsense. The current source must be the battery. That said, somehow it's describing the voltage across the internal resistance of the battery, which is not physically separable from taking the voltage across the battery terminals. meh meh.
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