how to measure constant voltage input through scxi-1530

[spsingh]

I find that it readfs only when the signal is varrying otherwise it shows zero.

[AVR]

The module is hard-wired for AC Coupled input - hence you will only "see" a signal when there is an AC component. If you want to measure a constant voltage (DC level), I would suggest simply using one of the SCXI-110X series. It is a much cheaper solution.

[RIO-Todd]

AVR is correct. The SCXI-1530 has a 0.2 Hz highpass filter to block the DC component of signals. Therefore, only the AC component of your signal will be passed through the module.