Hello All I need help on this matter,
I'm trying to measure a voltage variation using the NI 9221 module, my task basically consist in to energyze a motor with a 5V DC source, however besides reading that constant voltage, I need to read the current (A) generated by the motor whe it is subjected to a load. Fot that I'm using a shunt resistor that gives the next relationship (10A = 50mV), but the problem is when I got the postitive and negative lines from the shunt and try to read the voltage drop between the two terminals using the NI 9221 I have no signal, it looks like if both cables were unplugged, but when using a multimeter I can see all the voltage variations when applying the load to the motor. The question here is: Does any body has an idea on how to deal with this problem? Does the NI 9221 has the capability to read such a little values (0.2-0.5 mV). Why the multimeter shows the voltage variation increments when applying the load to the motor and the NI module is not? what am I doing wrong?
Please let me know your thoughts
I'm attaching a little diagram on how I'm plugging my setup
Thanks a lot for your help
SergeArmz