National Instruments USB-6008 - Wrong input reading

[NI-Joe]

Hi,

I am trying to use USB-6008 to read from Kistler Type 5073A charge amplifier, which is converting the charge generated by Kistler type 9317b force sensor.

I can directly see the signal using ManuWare software, connected via COM port to the amplifier and see that the Voltage is ~0 on all inputs.

Since I need to have more control of the readings and logging data. I want to be able to use Matlab. But when reading through the NI USB-6008 there is an offset on all inputs (+2 Volts). 

When I received the equipment there were two extra wires connected to the DAQ to the Amplifier. Which I have disconnected. Is it possible that they were used to 'synchronize' the ground on the DAQ and the Amplifier?

[crossrulz]

My first thought was that you need the GND of the amplifier going to AI_GND.  If that is missing, you will get offset errors like you are stating.  You might also want to give this article a good read: Field Wiring and Noise Considerations for Analog Signals