The Frequency Counter (like the Voltmeter and Sound Level Meter) can be positioned anywhere on the screen. The size of the display font changes when you resize the counter by dragging its borders. You can fill the screen for a really big readout that can be seen from across the room.

The counter has 3 different update rates: Fast (shown) is about 100 readings per second, Med is 10, and Slow is 1 per second. Unlike conventional counters, the update rate does not directly control resolution.

The Hertz mode shown has much higher resolution than conventional benchtop units. Those simply count the number of trigger events in the selected update interval.

Instead, Daqarta counts the total number of samples that elapse during the total number of triggers in the update interval. Since the sample rate is known and is very accurate, the signal frequency can be computed with similar accuracy after only a short time. This is analogous to setting Period mode on a conventional counter and counting the number of time-base cycles between input triggers, then computing the reciprocal. Here Daqarta takes care of all computations, and allows an aribtrary number of time-base cycles (samples) with an arbitrary number of input triggers between computations.

Daqarta also has access to more information about the signal than a benchtop counter, since it knows the amplitudes of the samples before and after the trigger event. This allows interpolation of the trigger time to give higher resolution than might be implied by the card's sample rate, compared to the clock of a conventional counter.

The msec mode displays period directly, using the same measurement as Hertz mode but without a reciprocal.

Total mode counts trigger events since the last counter Reset. If the events of interest are bursts of tone or noise, you can use Trigger Holdoff to count only one event per burst instead of every cycle.

The Total count continues to accumulate even if you switch to Hertz or msec modes, and will read correctly when you switch back.

SpecTot is a special mode for counting events based upon spectral features, rather than normal triggering. It can distinguish between events that are similar in amplitude but different in spectral content, such as bird calls of different species, or different types of calls of the same species.

An event is counted only when the spectral content between the solid and dotted Spectrum cursors exceeds the absolute value of the Trigger Level.

In Delta cursor mode this requires at least one of the included spectral lines to exceed the Trigger Level; in Sigma mode the RMS value of the total included energy must exceed this threshold, even if no individual line does.

The Places control allows selection of 0 to 5 decimal places for the reported Hertz value, currently set to 3. A separate setting is maintained for msec mode.

Questions? Comments? Contact us!