What about all of the other modes? No mention of them.
Do I want to even ask why you were trying to log the AC line.. Nah. Many people believe the meters don't need to survive a transient, just keep the operator safe. Sounds like you are still fine.
I had tried it as well towards the end of that last video. I asked them about trying it with a battery/resistor to at least eliminate their current source. No word if they did anything more with it. You don't by chance have one of those meter calibrator things do you?
Looking at their pictures, I thought I could pick up the same source but they are out of stock.
http://shop.voltagestandard.com/product.sc;jsessionid=DAEB70EDBC48F53DD528284FB53FCF35.p3plqscsfapp003?productId=5&categoryId=1
If you have a 121, it may be worth it. They claim 500mV compliance but that would be with a good battery. Looks like it has a microcontroller for some reason. Maybe try it with the source running off your bench supply and dial it down. Maybe it goes unstable before it drops out.
When in mA range without any probes connected the meter shows about 80 uA. When Inserting the probes goes to 800 nA and with the probes shorted it goes to 1.5 uA.
Something similar happens when in uA range. It is present only in DC mode. In AC everything is 0.000
Is it normal? Is it an effect of the opamp used for the low burden voltage?
Alexander.
Originally they were testing w/ 1.22 but I have no idea after that what was loaded. I installed 1.22 in the prototype and it seems just as stable. So I setup the Brymen BM869s next to the 121GW prototype and had some fun with the tape eraser.
It would seem that there are a few things that the OP could have going on.
*****
Combined it all into one video and added another test
If you have a 121, it may be worth it. They claim 500mV compliance but that would be with a good battery. Looks like it has a microcontroller for some reason. Maybe try it with the source running off your bench supply and dial it down. Maybe it goes unstable before it drops out.
Looking at the manual for the AM270, looks like in the 5000uA range its spec'ed at 150uV per uA. Maybe just stick a 150 ohm resistor in series with the 121 to simulate it.
Thanks you for the reply. I could understand it for 50 uA range and I mentioned it in my original post. But in 500 mA range also? And why only DC mode?
This offset current is always there. Regadless If I connect probes or not. I tested with many probes. With golden ones, even with a thick wire soldered directly in banana plugs.
And the most important is that the meter measures high in relation the the other meters I own. How much higher? 100 uA. Exactly the offset I see. If I rel the offset, it measures exactly like the others.
What the rest of you see if you sort COM and 500 mA input?
I am just trying to figure it out. To understand it.
Alexander.
Did you play with the calibration function of the 121GW?
Well, probably yes.
I already re- calibrated 3 of the Ohm ranges, because it was done improperly (not optimal) @ UEI...
It might depend on the environmental temperature, if this offset can be persistently be calibrated, may be it vanishes, when summer temperatures go back to normal.
I'm not sure, if a zero calibration only is possible, because both cal constants for a particular range are stored after gain adjustment only.
Therefore you might need a calibrated constant current source.
Frank
Well, probably yes.
I already re- calibrated 3 of the Ohm ranges, because it was done improperly (not optimal) @ UEI...
It might depend on the environmental temperature, if this offset can be persistently be calibrated, may be it vanishes, when summer temperatures go back to normal.
I'm not sure, if a zero calibration only is possible, because both cal constants for a particular range are stored after gain adjustment only.
Therefore you might need a calibrated constant current source.
Frank
If I read the manual correctly it is possible to make only a zero calibration.
Since I have backed up the calibration data, is it safe to play around with calibration?
Alexander.
Well, probably yes.
I already re- calibrated 3 of the Ohm ranges, because it was done improperly (not optimal) @ UEI...
It might depend on the environmental temperature, if this offset can be persistently be calibrated, may be it vanishes, when summer temperatures go back to normal.
I'm not sure, if a zero calibration only is possible, because both cal constants for a particular range are stored after gain adjustment only.
Therefore you might need a calibrated constant current source.
Frank
If I read the manual correctly it is possible to make only a zero calibration.
Since I have backed up the calibration data, is it safe to play around with calibration?
Alexander.
It is not safe to play around with calibration data.
hi Dr Frank, what did you use to calibrate the ohms ranges? e.g. Vishay 0.01% low ppm resistors?