Re: Opto Coupler Help?

Harvey White

On Thu, 22 Feb 2018 12:29:51 -0500, you wrote:

Thanks Harvey. While they're in-circuit with no current going through
them? Why would measuring reisistance in-circuit work for photocells but
not for resistors?
It works equally well or equally poorly. From what you said, the
photocells are all in series, so the parallel combination is of one
photocell (the one you test) with the rest of them in series (and
hopefully very high resistance). You assume that the top of the
photocell string is shorted to the bottom for a worst case reading.

It's no different from measuring any resistance in circuit, you
account for the parallel resistances when you measure.


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