offset

[Pedro Sousa]

Hi! I'm very happy with the CurrentRanger performance. I using it in a research lab. As I was playing with the board and upgrading the firmware I think I messed up the meter. The current with no load (open circuit) on the nA scale is now showing ~260 nA (previously was ~0 nA) . Can I offset this value on the firmware or did I damaged some hardware?. Thanks!

[Felix]

You can revert it to original firmware (if you have the UF2 bootloader CR version (since march 2020) and backed it up by following the guide). You can then recalibrate with the old values and should be good.
Anyway the scales should show 0 even without calibration. In the nA scale it can show a little offset if the inputs are open, but if you short them it should definitely read 0.
Does this happen only in nA?

[Pedro Sousa]

Hi Felix. Thanks for the reply.
In microA and mA scales I get -0.4 to -0.8 (with the Bias on) and 0 with bias off. Something is really messed up: I get the same number on the microA and mA (1016) (2.79 mA on a multimeter) and thus the auto range does not work.  I will try to revert it to the original firmware and hope it solves the problem.

[Pedro Sousa]

Hi,
I reverted the firmware to R1. The microA and mA scales are working (and measuring) perfectly but the nA scale reads ~280 nA with the open circuit (56 nA with Bias on).   If I short the inputs it reads 0.

[Felix]

Then i think it's OK, may need recalibration but that wont really make the 260 noise go away. When you apply a real load, say 100nA, I think it should display the real reading.
Technically the reading is only when there is a load, or a short it should read 0, which it does.
Make sure to power it from a LiPo battery with not too long leads.