problme with connecting two DAQ in parallel

[sabra88]

Hello everybody,

I have a problem in connecting two DAQ(which mesures voltage) in parallel, both with a resistance. when i connect the first DAQ, it gives me the right voltage which is 110 mV. but when i connect the second DAQ in parallel with the first DAQ, the second DAQ gives me 110 mV and the first DAQ gives me 819 mV which is the maximum of voltage that it can mesure.

Please help me because this is wierd to me.
You will find attached a scheme of my problem

 

[barry]

When you say "DAQ", I''m guessing you mean an analog-to-digital converter. Without knowing anything more about your system, I would guess that one of your "DAQs" is loading the input-i.e., there are two different input impedances. I would drive each "DAQ" with a separate buffer.