Instability in the acquired voltage using 9215 module

[GiridharYadav]

Dear Friends,

I am trying to acquire signal which is 0 to 10V in range, 50 HZ frequency using NI 9215 module through cRIO. The signal acquired into the system is not at all stable. But if I measure the same thing with an multimeter, it displays a very stable signal. Infact the signal coming from the source is some what far away from cRIO system and there hgih current lines beside the line of the signal what I am trying to acquire. But I dont know whther the NI 9215 module would be able to nullify the noise or not? In this regard I request you to suggest me proper solution to resolve this problem.

I am thinking to use one instrumentstion amplifier in between the source and NI 9215 module. (Is this suggestable) 

For your information I am using State machine control program in which I am using CVT library to access I/Os. The signal what I am trying to acquire is obtained from the current trasducer in which 0 to 10V provides information about the current varying between 0 to 5000A. I need to control the current in 1%.But as the aignal is fluctuating continuosly I am unable to obtain the required accuracy. After acquiring the signal into cRIO I had calculated the RMS using RMS pt by pt as the signal is AC 50 HZ.

 In this regard I request to everyone in the community to provide me a slolution.

Still if anyone have doubts let me know.

Thanks and Regards

Giridhar

I-Design

[AdnanZ]

That's strange that you are getting a noisy signal with the 9215 module. How exactly did you wire it up? Where did you place the multimeter when measuring the same signal? Is it at the same spot as the module or near the signal source?

[GiridharYadav]

Dear sir,

I have placed the multimeter near the module where the signal connected to it. As the module is differential module, I have connected two wires to AI0+ and AI0- respectively. But still I see unstability. In this regard I request you to provide me a solution.

Thanks and Regards

Giridhar

Idesign

[AdnanZ]

The only other thing I can think of is to use bias resistors. Have a look at Table 1 in the following article:

Field Wiring and Noise Considerations for Analog Signals