Hi bdunham7,
thanks for the reply and tips. I think I have some more information that at least starts to shed a little more light, at least for my understanding.
I have measured the current output in both ohms ranges you mentioned. I've done it using the 500ohm and 5kohm resistors that I made for the calibration purposes.
With the good 189, I put the unit in ohms mode, with the load resistor on a dual banana plugged into the input jacks, and then make a mV voltage measurement with another meter, a Fluke 45 in this case. And using that 500, I end up with almost exactly 50mV, which checks out with the 1mA at the low ohms range. Doing this measurement with the other 189, I get about the same. So, I've tried some lower resistor values, 10, 4, and 2. And what I get with the original and 2nd 189, is about the same, 10mV, 4mV and 2mV respectively. So, this leads me to believe the current source is Ok. Because, during that measurement, the original 189, showed the corresponding ohms values on the display correctly, but the 2nd 189 showed the values a little higher, 12, 6 and 4 ohms respectively.
With my original message above, my error was roughly 1ohm off, now for whatever reason today, it's a little more than 2ohms off.
Being it's different today, might be a sign pointing to the fault. But at least I feel the current sourcing from the meter is solid in the ohms function.
As well aside from the displayed measurement being a little more off today than my earlier post, the conclusions of this is telling me the calibration points for the lower range don't get updated correct when I do the calibration procedure.
And, at least with what you said about the 15% error... this might mean that because of the degree of the error I'm seeing, the calibration table isn't being updated. I get what you said about the gain function, and it makes sure sense now as to why you can't use a shorting bar.
With that in mind then, is this silly of me to think, but could I perhaps brute force that lower range little by little to get it within range to write the value I want? In other words, I could insert say 15% lower than what I see when a near short is there, for that low point, perform the calibration, see if it updates. Then, insert again 15% lower, see again if it writes, and so on until I get below 15% error for the 0 measurement, and theoretically, it would then update properly? Without a proper calibrator, would this actually work or is it silly? I realize this might be some crazy series of iterations into an asymptotic path of lunacy, never to be reached, but if I could get close enough to zero, maybe 10mOhms, I'd be happy.
I could use a pot with static divider on to fine tune it to within 15% by reading it with the other meter.
Thanks again for taking the time,
Have a nice remainder of your weekend,