Hey all,
To put first, I'm new here, so I hope I post this on the right page.
ContextI was trying to measure the current through a simple circuit connected to my arduino. The circuit basically consists out of a resistor and 28 LEDs.
First, I measured the resistance of the resistor (disconnected from the circuit, of course), and then I measured the voltage across the resistor while the circuit was running.
Then it was an easy calculation to get to the current, but I wanted to double check, with my multimeter in mA mode, which gave a different result, with the current being lower on the multimeter than the current calculated.
After some thinking what I could have done wrong, I decided I could test the current going into the arduino with a usb meter. I discovered that the current flowing through the circuit was indeed the calculated current,
unless I connected my multimeter again, then it showed the same current on the multimeter as on the usb meter.
Trying to factor out options, I tried measuring the current on A mode instead of the mA mode and put the probe in the A terminal (the mA and A have different terminals on my multimeter). Now the current shown on both the multimeter and the usb meter matched the earlier calculated current.
My multimeterMy multimeter is a UNI-T UT161E
https://www.uni-trend.com/meters/html/product/General_Meters/Digital_Multimeters/UT61%20161%20Series/UT161E.htmlI bought it from
https://www.eleshop.nl/uni-t-ut161e.htmlWhat else I triedSince I have opened my multimeter before to disconnect the buzzer, I opened it again to make sure I screwed in the terminals all the way, which they were.
I checked the resistance of both current terminals by plugging the probe into the
socket, putting the multimeter on
mode and putting the other end of the probe into the current terminals. The A terminal reads 0.00
, while the uA and mA terminal reads 0.9379 M
.
I checked the fuse, by putting the probe that's still connected to the
terminal on the upper side of the fuse and then on the lower side of the fuse. Both side give me the same 0.9379 M
resistance.
My conclusionsSomething is wrong inside my multimeters uA and mA terminal or what's behind that terminal. The part of the multimeter that actually reads the current, is good. It's just that the mA function gives a lower current because connecting the multimeter adds resistance.
My questionDoes anyone have an idea what could be wrong with my meter? I hope it will be a simply fix.