Hello,
I have a problem with a frequency measurement accuracy of an 8MHz signal, using internal base clock, measurement is made using the counter section of a NI-PCIe6351 card. Frequency measurement acceptance limits are 8MHz +/-25ppm.
I am suspecting a problem with measurement accuracy due to internal base clock accuracy which device specifications indicates that is 50ppm.
I am looking for a formula to calculate absolute accuracy for frequency measurement, something similar with analog output accuracy equation described on device specification document. Considering how well is documented accuracy calculation for the analog measurement / generation section, I was surprised to see how little official information is available in the same document regarding accuracy calculation for frequency measurement / generation using counters, in respect.
Any information on this topic would be appreciated. Thank you !