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Brymen, difference in reading between mA and uA scale
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J-R:
Oh boy, BM869s vs. BM789...

Brymen claims better accuracy from the BM789, 0.075% + 20d from lower ranges, vs. the BM869s at 0.15% + 20d.  In my testing, I found them to be virtually identical.  For example, a quick test at 50mA, the BM789 was 6 counts high, while the BM869s was 4 counts low.

The higher number of nominal counts with the BM789 (approx. 66,000) vs. the BM869s (approx. 53,000) seems like an interesting difference, and the calibration point for the BM789 is mid-scale (so 3V for the 6V range, for example) vs. top of the scale for the BM869s (5V for the 5V range).

In my testing of voltage, I found that the BM869s had some error mid-scale, mostly with 500,000 count mode (for example, around 2.5V), and the BM789 had some error at the top end of the scale (5V).  This is somewhat to be expected as each DMM has to extrapolate perhaps the proper values from a single calibration point (plus zero).  So there is not a clear winner unless you pick a specific calibration point, such as 5V.  In that case, you could adjust the BM869s to be spot-on at 5V, while the BM789 would have a hard time keeping up since the nearest calibration point is 3V.

If you are looking for high accuracy, the solution is probably a bench DMM...
J-R:
Shunt measurements on my BM789:
A - 0.0212 Ohms
mA - 2.474 Ohms
uA - 102.5 Ohms

And for easy comparisons, my BM869s:
A - 0.0276 Ohms
mA - 1.758 Ohms
uA - 101.543 Ohms

Would be nice if some other forum users could measure their BM789/BM869s and post their results.  I wonder if they changed the specs or if the manual is truly just completely wrong...
Fungus:

--- Quote from: J-R on August 14, 2023, 10:20:00 am ---Oh boy, BM869s vs. BM789...

Brymen claims better accuracy from the BM789, 0.075% + 20d from lower ranges, vs. the BM869s at 0.15% + 20d.

--- End quote ---

The 789 has higher burden voltage so it can give more accurate readings (there's a bigger voltage to measure).  :)
EEVblog:

--- Quote from: MarioBros69 on August 14, 2023, 08:46:50 am ---
--- Quote from: TimFox on August 13, 2023, 10:18:35 pm ---What do you mean by "real current"?
Your meter is reading the actual current through its terminals, which is lower than that which would flow into a short circuit, since your meter is not a short circuit.

--- End quote ---
Maybe I expressed myself wrong, by real current I meant the current that flows through the circuit when I am not measuring

--- End quote ---

If it's a large current mA to A then you can use a clamp meter to measure current without disturbing your circuit. But they aren't very accurate like what you can get with a proper current meter.

As I said, adding a resistor (shunt resistor it's called in a current meter) in series with the circuit you are measuring may change the current in that circuit. It's up to the user to not only be aware of that, but also know if it will impact your circuit or not and by how much.
My Silicon Chip article:
https://alternatezone.com/electronics/ucurrent/uCurrentArticle.pdf
J-R:
I don't see enough of a difference between the shunts used in the BM869s and the BM789 to outright state the BM789 is more accurate, and as I mentioned in my testing I did not see a visible indication that the BM789 was any better than the BM869s.  If the uA shunt was truly 200 Ohms like the manual states, then that would be a bigger difference compared to 100 Ohms.
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