What is AL SENSE in the pinout of the NI 6034E?

[JessCornejo]

Hi,

Am using the NI 6034E to sample a few signals should I ground the AL SENSE and all the anagloue inputs that am not using to ensure that they don't produce unwante noise?

Many thanks,

Jess

[nathand]

I don't see anything in the 6034E manual that suggests it's necessary to ground unused inputs.  You should not ground AI SENSE unless you insert resistors as shown in "Field Wiring and Noise Considerations for Analog Signals."

[NIquist]

The AI Sense is the negative input through the MUX and into the ADC.  Whether you ground it or not depends on the signals you're measuring.  If they're differential then, no.  If single-ended it depends on your grounding scheme.  Look in the DAQ manual in the analog input section and you will see the methods you can use. 

[NIquist]

Actually, nathand's link is a better version of what you find inthe DAQ manuals.  It should answer your questions better.

There is one reason to ground unused channels: Ghosting.  Sometimes you will see a large signal from an adjacent channel bleed into a channel where you are measuring a small signal.  The standard fix is to scan an extra channel that is between the two, but first ground the inputs to that "guard channel".  This will slow down your scan a bit since you're measuring extra grounded input channels but it can reduce noise and interference if you must measure both large and small signals in the same scan.  In this case you're not just grounding AI Sense of course, you ground both + and - inputs.  This issue is specific to multiplexed DAQ cards, you don't need this trick for simultaneous sampling cards.