Hi, I am trying to measure power using 'NI DAQ USB-6211' in arm streamline.
Arm Streamline User Guide Version 7.5
According to the page above, when energy probe is used, the maximum shunt voltage is 165mV and the appropriate resistor must be selected according to the formula written on the page.
Then what is the maximum shunt voltage when using USB-6211 above, and what formula should I use to select the appropriate resistor?
(USB-6211 Specifications - National Instruments (ni.com) USB-6211 spec)
Hi
You should refer to the documentation from NI to be sure, but I believe caiman assumes the voltage drop is given as +/-200mV and Vsupply is 5V. (https://github.com/ARM-software/caiman/blob/84194e50ba051e711c38f58a20c57bce3645fc8e/caiman/NiDaq.cpp#L231).
One follow up.
It is also worth noting that the acceptable voltage drop depends on your target circuit. If you drop too much over the shunt resistor, you may under-volt the rest of the circuit and it may stop working correctly. 0.2V is quite a large drop for the main circuit to absorb.
One of the advantages of using the NI DAQ is that it's a more sensitive/accurate probe, so in general you can use smaller resistors and accurately measure a smaller voltage drop.
Cheers, Pete
Thanks everyone!
It really helped a lot.