writing data to measurement file

[98mazdaman]

Hello all,

I am trying to record rpm's of a quadrature encoder (200 ppm) to a LVM file along with a timestamp for each value recorded. It seems to be working, except that it records more values in the LVM file than I want. I have set the DAQ Assistant to record read 1 sample at a rate of 1 Hz. However, when I open the LVM file generated by the Write to Measurement File Express VI, sometimes I get 42 values recorded per second, sometimes I get 13, and so on. So I am not getting a consistent number of measurements per second. How can I specifiy to just record 1 measurement per second, or 5 measurements, and so on?

I am using LabVIEW 2011. The values from the encoder are being read as a frequency and then converted to rpm's. Thanks! Files and images attached.

[James.M · Accepted solution]

Your Express VI isn't set to read at 1Hz. The timing method is set to Implicit, which is used for Frequency readings like you're doing. It basically means that you're sampling on the rising edge of your input signal, so you're really sampling your Frequency at the same rate as your Frequency.

To do what you want, you can change to 1 Sample (On Demand) mode and add a 1000ms Wait to your loop.

[98mazdaman]

Aye, it worked! Thanks!