I don't have one here to easily check, but it seems to me that a resistance
reading would just read the coil in either direction, since that's the path
of least resistance.
Does this actually work? If so, why?
Jeff/KD4RBG
On Wed, Mar 10, 2010 at 2:13 PM, Paul Christensen <w9ac@arrl.net> wrote:
> Bill,
>
> DC coil polarity is an issue because polarized relays generally contain a
> reverse-biased snubbing diode across the relay coil to: (1) protect a
> solid-state driving circuit from damage resulting from the rapid coil flux
> collapse; and (2) to decrease the relay . Measure the coil resistance with
> a DVM or VOM, then reverse the test leads and measure again. This may give
> you an indication if the snubbing diode is already part of the relay.
> Equal
> readings generally signifies a non-polarized relay coil.
>
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