No. These meters should be pretty accurate. I get very consistent readings everytime. I decided to check the accuracy stated on the meters spec sheet. For the 20A range of DC current it shows plus or minus 2% plus 3. This means all the UT210E meters should have less than a 4 deviation between them. I think it also means they all read 3% low. Let’s forget that 3% part because I don’t really understand it and it’s confusing.
So if I measure 9A, the real number could be from 8.82 to 9.18. If Petr measures 9.6A with the same battery model and same voltage then the difference is probably due to something else. The difference is roo large to be due to the meter (if we trust the specs).
There are many variables inside the light, battery, the test wire length and gauge, springs, etc… than can effect an amp draw test. Pushing down on the battery when doing the test saw the amperage drop from 8.7 to 8.35. That was neat to watch.
As I said earlier, as voltage drops the amperage increases. As resistance increases, amperage increases.
Even though Petr and I are measuring with the same model black Liitokala battery, there might also be small differences in its internal resistance that can effect the current draw. Certainly a battery with protection circuitry will have increased resistance and draw more amperage. Some batteries have bigger voltage sag under load and will draw more current.
His light might have a bit more resistance in the driver spring or the driver might just be drawing a bit less power. His driver might not have as good a ground path as mine, etc…
Just to see if the test wire made a difference, I measuring my light on turbo using a thin piece of speaker wire and got about 9A compared to 8.7A using a very heavy gauge wire.
I also tested it with a protected KeepPower 5200mah (protection circuit rated at 10A) since I didn’t need the tail cap to fit. At 4.1 volt I saw it draw 10.6A for a second and then step down to 4.34A.
I tested a Samsung 30Q (4.1v) and got a steady 9.3A. The smaller 30Q has a bit more voltage sag under load then the cyan and black Liitokala’s which explains why the amperage draw was a little bit higher.
I hope that helps explain that there are lots of variables.