What's the easiest way to test unmarked crystals?

[Roy J. Tellason]

On Thursday 19 October 2006 09:35 pm, Ethan Dicks wrote:
> I have a small handful of crystals and was wondering what the easiest
> way to divine their frequencies... I can say that I'm reasonably
> certain that all of them are between 32.768Khz and 50MHz, but some are
> blank, and some have non-obvious cryptic markings.  What I'm looking
> for is some simple way to get them to oscillate and measure them with
> a frequency counter (i.e. - assume one is starting with a working,
> trustable frequency counter).
>
> Is it as simple as a pair of inverters/NANDs in the classic crystal
> loop, or is that circuit massively frequency dependent (i.e. - works
> for 1Mhz-10Mhz, not faster or slower...)?

I'd go with CMOS,  myself -- any inverting gate should do it.  Put some 
high-value resistance across it to bias it (10M?),  and you may need a cap or 
two at either end to get the crystal going.  Maybe run it off a 9V battery?

I have a bunch I need to test too.  :-)

-- 
Member of the toughest, meanest, dealiest, most unrelenting -- and
ablest -- form of life in this section of spac, a critter that can
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