Jules Richardson wrote:

I've had various multimeters over the years; the last two have a
frequency counter setting, which might sometimes come in useful - if I
knew how to use it :-)

The manual for the current one is no help. Is there some kind of standard
for what signal they're expecting?

cheers

Jules

Any signal within the meter's base capabilities, typically 1,000V. Give
it DC and read 0 Hz, connect to wall outlet and read 60 Hz, connect to
aircraft generator and read 400 Hz, etc.