Set 6602 counter0 Freq. to 1. Period shows 1.003 sec. Howto make it accurate?

[Bobbie]

I used GeneratePulseTrain.vi to set PCI6602 counter0 Frequency to 1. But the real pulses are 1.003 sec apart instead of 1 sec. It is 3ms too long. Is the error too big ? How to make the period more accurate ?

[rgharrison]

Hi Bobbie,

The counter's on the 6602 make use of a 80MHz oscillator. The frequency on the output should not be off by more than +/- 1 clock cycle. At 80MHz, this is a very small error (less than 6 ns). So I don't believe the error is with the generation. How are you measuring the period?

One approach would be to use the example program measuring frequency using 2 counters. Using 2 counters greatly increases the accuracy of the measurement. Simply measuring the period using 1 counter will not be as accurate. The shipping example "Measure Frequency (NI-TIO).vi" is a good example to try in terms of getting accurate measurments.

Hope that helps. Have a good day.

Ron