OK, trying to get a handle on accuracy...
Quite by accident I discovered that when a floppy is left in the drive and the computer complains "non-system disk", it uses a steady current. A current that varies with Vcore and multiplier, but is boot-to-boot reproducible within a 10 mA range. All the switcher noise, non of the software variability.
Using the known gain of my circuit and the nominal LSB value of my ADC, I computed the expected byte values for a series of multimeter readings. I then divided the actual value, as recorded by MBM, by the expected value.
For the statistics crowd, variance comes up as 0.3%. Not bad at all for a 2% ADC and 1% (in this range) multimeter. Unfortunately, the shunt has a 3% tolerance, so overall accuracy still sucks. I wonder how it will fair versus a fully calibrated, precision Since87 design.
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