I am attempting to measure motor shaft rpm using a proximity sensor and a cDAQ-9174 with an NI 9401 module in slot 4. The output from the proximity sensor switches from 0V to approx 4.25V. The measurment frequency is expected to range from close to 1 Hz up to approximately 500 Hz. I hooked the signal to pin 16 and the COM to pin 1. When I choose ctr0, the measured value changes drastically, as shown in the attachd counter chart image. I checked my signal by hooking it to a NI 9205 and using an oscilloscope VI, as shown in the attached image. This shows exactly what I would expect for frequency and amplitude. What could be the problem when trying to use the counter? I have also tried this in MAX and get the same strange results.
Thanks,
Matt