"John S"
Read more complete specs:
www.pira.cz/pdf/vc3165.pdf
I have one and I feel that the input and trigger sensitivity is low.
** The specs look OK to me - too much sensitivity leads to unstable
readings.
The mediocre frequency accuracy of such counters results from a crystal that
sits open on the PCB and so drifts with the local ambient temperature.
If there is a trimmer cap next to it, one can set the accuracy to better
than 1ppm using a broadcast frequency standard - assuming you are near
one - or using a known frequency reference. But the drift issue remains.
The biggest part of the temperature drift is mostly due to internal heat
sources in the unit, workshop room temps being comparatively stable. So all
you have to do is mount a small (ie 30mm) fan above the crystal, blowing
room temp air onto it.
Hey presto, no warm up drift.
..... Phil