9207

[CLynnChidester]

The 9207 mentions built-in 50/60Hz rejection.  I'm running this module on a 400Hz system.  What is the 400Hz rejection specification?

[Wild_man]

Could you explain your application in more detail? Are you looking to measure a signal with a 400hz frequency or are you using this in a system that is around/powered by 400hz high-voltage wiring?

[CLynnChidester]

The system mains frequency is 400Hz.  The cRIO & 9207 are powered by DC voltages, from DC power supplies which are in turn powered by the 400Hz AC mains.  Hence, I expect some 400Hz noise on the signals to be measured, just as there is 50/60Hz noise on signals powered by these mains frequencies.

[Wild_man]

Thanks for the clarification. From what I can find there are no specs listed for 400hz rejection. 400hz is above the nyquist frequency as the maximum sample rate on this card is 500S/s so any 400Hz noise will manifest itself as harmonic frequency peaks lower in the spectrum if you take an FFT of the data.

My recommendation would be to do the following:

1. Verify that the DC power supply is low-ripple so noise from it is not a primary concern.

2. Be sure to shield the signal wiring as well as possible.

3. Try out the system and if you see more noise than is acceptable implement a physical low-pass/anti-aliasing filter.

Thanks,

[CLynnChidester]

Thanks for the information.  I appreciate the recommendations.

C. Lynn Chidester