Multifunction DAQ

cancel
Showing results for 
Search instead for 
Did you mean: 

induced voltage on USB-6009

I am using a USB-6009 to gather voltage information from five voltage sensors.

A0 = 0 to +5VDC

A1 = 0 to +2VDC (temperature measurement using LM35 IC sensor, 10mV per degree C)

A2 = 0 to +2VDC (temperature measurement using LM35 IC sensor, 10mV per degree C)

A3 = 0 to +2VDC (temperature measurement using LM35 IC sensor, 10mV per degree C)

A4 = 0 to +2VDC (temperature measurement using LM35 IC sensor, 10mV per degree C)

Without the 6009 connected to my PC, my ambient temperature (A4) is about 210mV (21 degrees C). As soon as I connect the wires, I get a rise of 90-100mV on the connection, obviously skewing the readings by 9-10 degrees C.

Thoughts or suggestions on why I get this rise, and how to prevent it?

 

0 Kudos
Message 1 of 2
(2,756 Views)

I have solved the problem by using differential input.  The floating ground of my battery powered system causes the problem.  Laura in tech support sent me this reference:

"Field Wiring and Noise Considerations for Analog Signals" at http://zone.ni.com/devzone/conceptd.nsf/webmain/01f147e156a1be15862568650057df15

 

0 Kudos
Message 2 of 2
(2,745 Views)