Why do mA and A settings on multimeter give different result?

[Marvo]

Yeah, trying to measure a current of less than 0.1 Amps with a multimeter using the 10 Amp scale will not give an accurate result. I would use the tester on its miliamp scale but I would probably do a quick calibration check using a known value resistor with the battery to make sure the tester is accurate and functioning correctly. For example a 1 kiloohm resistor in series with your car battery should give you about 12-13 miliamps, this would be a good value to test the meter accuracy.

 

[johntheo]

Should't the red lead be in the 10A socket whatever reading is been taken, no?. the 69ma on the 10A scale is certainly more accurate IMO, all my cars bar 1 read 40 to 60ma, the exception, a 2005 Polo reads 95ma even after the ECU goes to sleep.

 

[Lucien Nunes]

No, the right-hand socket serves for the lower current ranges and includes the markings μA and mA. In most meters the 10A shunt is connected to a separate socket to avoid having to switch this current with the function selector, while allowing the use of a higher-value shunt for the lower ranges.

 

[johntheo]

I use my one in the 10A socket which has 3 different scales 10, 200m and 20m.
Connected it between a 12.46V battery and a 14.3ohm resistor = 0.871amps and got 0.86on the 10 scale and 08.6 and 0.86 on the other two scales. (not bad on the 10A scale?)

 

[johntheo]

With apologies in advance for the newbie question...
I'm using a multimeter to figure out the source of my battery drain, so attempting to measure the leakage current between my battery terminal and its lead. When taking the readings shown below, they are quite steady, but as you can see, on the 10A setting I get a measurement of (-)69 mA, while on the mA setting I get 1.5 mA. Is this just because of the lower resolution (and higher error) in the 10A mode? I ask because online how-to information for doing this say to do the check in the 10A mode, and to be concerned if the current is more than about 50 mA. Based on the mA settign reading, I see no problem, but is there reason for concern based on the 10A reading?
I'd appreciate any pointers - thanks!
Rob

View attachment 90599View attachment 90600

I didn't realize how accurate these M.meters are even on very low measurements. I have a a 6200ohm resistance that I use to test/trip my RCDs (30ma) and when i connected this across the ma scale I got 2.1milliamps, theoretically 2.026 milliamps with the battery at 12.56V.

 

[Mikegh]

I didn't realize how accurate these M.meters are even on very low measurements. I have a a 6200ohm resistance that I use to test/trip my RCDs (30ma) and when i connected this across the ma scale I got 2.1milliamps, theoretically 2.026 milliamps with the battery at 12.56V.

Wouldn't surprise I've a little 10 euro dmm and when I checked it was bang on over a range of resistance measurements

Fluke T5 I have I wouldn't trust any reading off it

 

[pc1966]

I didn't realize how accurate these M.meters are even on very low measurements.

Even fairly cheap DMM are pretty good on DC volts, many are specified as 1% but often a bit better than that when new. DC current is usually poorer than DC volts even on expensive meters as it is much harder to get very high accuracy low-resistance shunts.

But what you normally have to pay more for is high accuracy true RMS for AC, accuracy that lasts over time & temperature range, and to have a meter that is measurement category CAT-III / CAT-IV rated. This last point is essential for safe use on systems like mains power where fault currents can be well over kA and voltage spikes can go to several kV due to far-away lightning or the switching of large motors, etc.

Measurement category - Wikipedia

en.wikipedia.org

If you only ever use if for traditional automotive circuits that is not much of an issue, but I expect EV / hybrid cars also have quite a nasty surprise waiting if you make a mistake with a DMM (e.g. on amps when you go to measure volts, etc)