Possible autoranging with negative microamps issue (and note about imbalance)

Issues
2

Hi @NickLL,

Thanks for the detailed information! I received a similar report from one of the Joulescope beta users a while back. I was able to duplicate the issue, and it looks like you have as well. I believe that I know why this is happening, but I have not yet had time to thoroughly investigate.

Your Joulescope is intended as a single quadrant (+V, +I) device, but it does support some -V and -I for transients. Joulescope’s fast autoranging feature only works on +I overflow. -I overflow range switching is handled differently and is much slower. Here are the designed ranges (not the guaranteed specified range) for each range selection:

*** VOLTAGE ***
Select     Range    Range
             min      max
     0   -1.16 V   16.8 V
     1   -513 mV   5.04 V

*** CURRENT ***
Select     Range     Range
             min       max
     0   -1.80 A    10.4 A
     1   -470 mA    2.17 A
     2  -42.7 mA    197 mA
     3  -4.23 mA   19.5 mA
     4   -423 µA   1.95 mA
     5  -42.3 µA    195 µA
     6  -4.23 µA   19.5 µA

As an aside, one of the earlier Joulescope prototypes was fully bipolar with four quadrant operation. However, I decided to go to (mostly) single quadrant operation to save cost and double the effective performance.

That said, you should not be seeing an autoranging oscillation on the negative side. I have bumped up the priority for this investigation.

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