Analog signal creap/bounce on FP-AI-110/FP-1000

[Tony Kateryniuk]

I have a testing application that is using several 0-1000 PSI, .1 - 5.1 VDC signal out pressure transducers. I have noticed the signal "bounce" around -7.5 to +7.5 PSI, and recently it has been creaping up to +10, +20 and finally +30 psi; checked the voltage signal and noticed that the signal is actually rising, however when I put a voltmeter across the terminals for 5-10 seconds it seams to "drain" the signal and return it to a 'bouncy' +/-7.5 PSI, the increasing signal problem is also rectified by unpulgging the FP-AI-110 momentarly from the rack (power still on).
Any thoughs?

[JohnM]

Tony,

The problems that you are seeing can be divided into two parts. The bouncing affect is most likely caused by noise on your system. I would recommend that you use the 50 or 60 Hz filters to see if they bouncing effect goes away. Next, the increase in voltage is most likely due to line capacitance. To eliminate the problem, I recommend that you use a separate power supply for your external devices. Then, disconnect one device at a time until you no longer see the increase in voltage. Once the problem has been identified and corrected, you should no longer see the increase in voltage.

Best Regards,

John M