DAQmx Sample Rate Coerced

[Maestro_Sanchez]

I am stuck and need help reducing my sample rate to read from 1 hz to 1000hz, When I adjust these numbers in my vi it gets coerced into 1612.90. I am using a cDAQ 9188 and a NI-9239 device to read analog voltage. How can fix my vi so that my Actual Data rate does not get coerced?

For vi Reference you can see this on the sample VI /examples/DAQmx/Analog Input/Voltage -Continuous Input.vi 

[mcduff · Accepted solution]

According to the manual the only available sample rates are

f(Sampling) = (12.8MHz/256)/ n = 50000/n

where n is an integer from 1 to 31. So the max sampling rate is 50kSa/s and the min sampling rate is 1612.9Sa/s. That is what you are stuck with.

mcduff

[Maestro_Sanchez]

Thank you!

[mcduff]

Your welcome

PS You can always low-pass filter and decimate your data after it has been collected at a higher rate.

mcduff

[rayyang]

Hi , how to use the low-pass filter if i want sample the data in 100Hz with 9239.

Only have the cDAQ Slot.

[mcduff]

Look in the Signal Processing Palette for Rational Resample. Look at the help for the function.

So in your case, collect data at higher sample rate, if you want 100 Samples/seconds as your decimated data rate, then you need to low pass filter your original data with a bandpass no greater than 50Hz, then decimate. The Rational Resample should do that for you.

mcduff