DAQ Noise with Laptop

I'm directly measuring the voltage from a 1.5V battery for example
using differential input with unshielded 1m cable from the terminator
board to card. Even using the Test Panels with my DAQCard 6024-E
PCMCIA card in my laptop I see lots of noise, +/- 1 volt or more. When
I remove the AC power and just run on the laptop batteries, the noise
is reduced, but still evident. In my vi's I get around it by
averaging, but is there any other way to reduce the noise?
Jeff

A battery is a floating signal source, it has an isolated ground-reference point. If you want to use differential (diff) analog input mode you must tie the ground reference of the battery to your DAQCard analog input ground to establish a local or onboard reference for the signal. E.g. if you have +ve and -ve battery terminals connected into ch0 and ch8 input respectively, place a wire from ch8 to aignd.
Alternatively, you could just use single-ended ground referenced (rse) mode, where you just connect +ve and -ve battery terminals into an analog channel input and analog input ground (aignd) respectively.
I have attached a jpg of summary of available analog input configuration for DAQCards, it was taken from an NI user manual for E series DAQCards.
Not su
re if you know how to change the input configuration, but it is done through MAX. When you go to Devices and Interfaces branch and right click your device and select Properties, then go to the AI tab and it is under Mode menu item.
Gluck!
Attachments:
Analog_Input_Connections.jpg ‏70 KB

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Large analogue input noise with laptop and 6024

Acquiring an analogue signal leads to large noise of +-100mV !
I'm using a NI 6024 card with shielded cable and a selfbuild connector box on a Dell D800 Laptop. The analogue inputs are used as differential inputs and connected to external amplifiers. In the box additionally the frequency output (GPCTR0_OUT and DGND) is connected to a small electronic circuit with an octal buffer (74HCT250) and 5V voltage regulator (An external 12V power supply is additionally used).
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