sampling rate

[mayasong2005]

Dear All:

             I got a NI DAQ 6221 card which  is wired to an incremental encoder. The resolution of the encoder is 500 ppr. The sampling rate is set to be 100Hz.  The item "samples to read"  is set to 5. In the block diagram, I averaged the five readings and then logged the averages to a file. What is the sampling rate of the data in my file? Comments are greatly appreciated!

zibin song

[Kevin_Price]

Here's an answer and how I arrived at it:

I'm supposing your 100 Hz sampling rate is based on a true internal hw clock making the encoder's "500 ppr" resolution irrelevant to the problem.  With 100 Hz sampling, you have an interval of 10 msec between samples.  So when your loop reads 5 samples at a time, they represent 50 msec worth of data.  When you average them down to a single value that's stored to file, you are storing a single value every 50 msec for an effective sampling rate of 20 Hz.

-Kevin P.