USB-1608G Differential Analog Input

[liamsul]

I am using a USB-1608G DAQ device and had a question about how the differential analog input mode operates. I have a 10V input to the high channel, and same input that has gone through a small resistor into the low channel input. These inputs should have a difference of around 60mV, which I was hoping to current measure the current with.  I was wondering if it is necessary to program the DAQ’s analog differential input channels to have a +/- 10V Range on the inputs or if I could program it to use the +/-1V Range since the differential between the two inputs will be within that range and thus get a better analog resolution and current reading. Any help would be greatly appreciated!

[JRys]

Hello @liamsul

The default input mode is differential. The 10 volt range has a resolution of 305uV per A/D count, and a 60mV would consist of about 197 counts, so you should have gotten something close to 60mV. The measurement would consist of 1967 counts when using the 1 volt range and that would produce a measurement that is closer to 60mV. If your reading is nowhere near 60mV, then check out page 11 in the user manual. It discusses what to do if your signal is isolated,for instance, battery powered.