[time-nuts] Very slow freq. counter / event counter

[Hal Murray]

erm1eaae7 at ermione.com said:
> In the lab, I would like to have an event counter that can double as
> frequency/period counter, with maximum clock rate in the order of the tens
> of Hz or so, better with TIC function (aka "chronometer"). Resolution need
> not be better than 1/100s, counts to 9999, but the input should be simple
> and permissive, something like 0-5V or 0-12V, or short-to-activate. 
...
> Someone has a suggestion? 

Are you willing/happy to write some software?

Most *nix OSes support a PPS input.  The original idea was to use it for 
timekeeping, but it works fine for other hacks.  The typical hardware is a 
modem control signal.   They are rugged, but not very sensitive.  (I don't 
know anything about Windows.)

It works fine at 60 Hz.

The general idea is that the interrupt routine grabs a timestamp when the 
appropriate signal changes.  There are separate slots for rising/falling edge.


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