A simple question about DAQ data sampling

[hanwei]

Hi all:

Now I meet a very basic question about DAQ sampling.  I am using NI PCI-6040E DAQ card, SCXI-1001 chasis, SCXI-1102, SCXI1300 terminal block, and SCXI1160 relay module.

I am not sure , is it possible if I want to test a voltage (1 volt) on a resistor. Now I am connecting the Ch0+ to resistor+ (24 volt), and connecting Ch0- to resistor-(23 volt). So the voltage between resistor+ and resistor- should be 1volt.  Actually, It is working at the first, but after I want to test 9 channels based on this connection. The Measurement & Automation can't read data from the DAQ card. (when I test it by multimeter, I can get the voltage data on the Ch0+ and Ch0- of SCXI1300 terminal block).

That's strange, does anybody know what' s wrong about it?/

Thanks a lot

[hanwei]

Besides, When I used a battery to test it, the data sampling is fine??

I am just curious what' s problem about it?  float??

[Hani R]

Hi hanwei,

According to the specifications of the PCI 6040E (page 3), the input signal and common mode voltage should never exceed 11V from ground.  I believe this is the reason you are able to measure the potential of a battery but not the 24V signal (even though the differential value is only 1V).