Large Range of Frequencies using Two Counters Measurement Method on PXI 6229

[jshehata]

Hi All,

I was reviewing the documentation on NI's site regarding on setting up a task for taking a measurement:

http://zone.ni.com/reference/en-XX/help/370471AE-01/daqmxcfunc/daqmxcreatecifreqchan/

I had a question regarding the divisor parameter of this fuction. It mentions a rollover count error, however it doesn't mention much else. Can anyone provide me some more details on the nature of the error and how to know if it occurred?

Thanks

[DiegoH214]

Hello jshehata

divisor is the value by which to divide the input signal when measurement method is Large Range with 2 Counters. Leave this input unwired if measurement method is not Large Range with 2 Counters. The larger the divisor, the more accurate the measurement. However, too large a value could cause the count register to roll over, which results in an incorrect measurement.

The roll over error is if the divisor is greater that the counter pulse, so it will not capture it correctly, resulting in a measurement that does not makes sense. That is when you will know you got a rollover error.

Diego Hidalgo

Applications Engineer

National Instruments

http://www.ni.com/support