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 50MHz7 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.
7With favourable input drive (i.e. suitable amplitude to trigger the counter) the counter can reach 100MHz counting rates.
Elan Digital Systems Ltd. | 19 | USBcount50 USER’S GUIDE Iss1 |
