liamsul

Hello, I am using a USB-1608G to measure current using an analog differential input with the universal library for Python. I am trying to measure the the system current load by sending 4.0V across a 0.1 ohm resistor and measuring the voltage drop across it. When changing the system load's current I am unable to get accurate readings when the current is above 200 mA. However when I start to get into the lower counts, such as 20 mA, I am unable to get any accurate readings. At 4V with a 20mA load I am getting a reading of about 15mA and as the current goes lower it gets more and more inaccurate. See table below. Also during testing this I noticed that the ADC counts are higher than the expected 32,768 (2^15), with the differential input ADC count at 4.0V at 20mA being 32818 which is higher than the ADC should be able to read. I was under the impression that each the MSB was used for positive or negative with the remaining 15 being the count. With ~20ma Load: Any help on this would be greatly appreciated!

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!