I am measuring DC current in the range of 20 to 250mA. The acquisition unit has current ranges up to 10mA, 100mA and 1A. My circuit is slowing decreasing from 250mA and once it hits 100mA a step change occurs to ~60mA, and then behaves as expected (leveling out or continuing to decrease, depending on my experiment). The step change is not real. I've put in a handheld amp meter to measure current and a series resistor and measured voltage, to back calculate current. Both indicate the values below 100mA are not correct for the acquisition unit.
To debug, I tried another Acq Unit AND multiplexer. Same result. Any thoughts?