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How do I eliminate noise with two inputs into SCC-AI05?

How do I eliminate noise with two inputs into SCC-AI05?

‎04-23-2003 03:25 PM

I am using an SCC-2345 with an SCC-AI05 1V signal conditioning module. I have two sensors that I want to take readings from: a pressure sensor powered by a 12 VDC regulated power supply and a force sensor powered by a battery. When I have only the pressure sensor plugged in, the Test Panel shows approximately +/- 0.0008 V of noise. When I have both the pressure sensor and the force sensor plugged in, the pressure sensor has approximately +/- 0.006 V of noise. I tried grounding the negative lead of the force sensor to AISENSE with a 14K ohm resistor. That ended up giving me the +/- 0.006 V of noise even when the force sensor was not plugged in. I also tried grounding it to the digital ground instead of AISENSE
but got the same results. The force sensor has +/- 0.00075 V of noise in all of the above configurations.
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Re: How do I eliminate noise with two inputs into SCC-AI05?

‎04-25-2003 10:10 AM

Greetings,

We are talking about an extremely small amount of noise in the microvolt range. It is hard for me to provide a suggestion without the following information. Which DAQ board are you using? How long has it been since you calibrated your board? What are the gain settings for DAQ board and SCC module? What is your input signal range?

You may want to calibrate your board and perform an accuracy calculation to see just how accurate of a measurement you will be able to take with your current settings for gain, range, etc.

The Calibration Solutions page has an accuracy calculator and information on accuracy and calibration. You may also check out the Specifications Appendix in the User Manual for your DAQ board. Accuracy information will be
provided there. Refer to http://www.ni.com/manuals.

Calibration Solutions from National Instruments
http://www.ni.com/support/calibrat/

Also, check out the following Knowledge Base ...

Data Acquisition: How Should I Troubleshoot Noisy Readings?
http://digital.ni.com/public.nsf/websearch/76376E484424B93286256A3700764E33?OpenDocument

Regards,
Justin Britten

Applications Engineer
National Instruments
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