2.5.2 Frequency Mode
The counter can be put into Frequency mode using the selection
button shown below. Note too that clicking on a new period
selection item will change to Frequency mode.
In this mode of operation, the counter will use an internally
generated gating period of 0.1s, 1s or 10s, to integrate (count) pulses
that arrive at the input during the period. Normally, the 1s period
will suffice for most readings from 50MHz
7
down, but if the input
frequency is slow (less than 1KHz), the 10s period may prove better
at the expense of a slower reading update time. The 0.1s period
offers faster reading update rates but is only useful for input
frequencies of greater than around 10KHz. Note that both of these
“limits” are simply the point at which one extra count during the
integration time has a 0.1% effect on the reading. You can of course
count lower frequencies if you don’t mind the resolution getting
worse than 0.1%.
If you have a slow input frequency, Period mode may be more
suitable.
Elan Digital Systems Ltd.
19
USBcount50 USER’S GUIDE Iss1
7
With favourable input drive (i.e. suitable amplitude to trigger the counter) the counter can reach
100MHz counting rates.
