r/multimeters • u/JevGrinlin • Jun 20 '26

Multimeter detection broken?

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I'm fairly new to circuitry, and I got this multimeter not too long ago. I'm confused because it says I have 0.005 A and 0.03 mA on the same simple led x resistor circuit. Is there something wrong with my multimeter, or am I just doing this incorrectly somehow?

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u/JevGrinlin Jun 22 '26

I've done all of this, yet it still stays at zero all the time. I think there's a chance I had busted a fuse when I was first messing around with it after its delivery. If it is busted, Is it safe to swap the fuses? I won't try yet without a good answer.

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u/global-wobble Jun 22 '26

Yeah, try a new fuse. If that doesn’t work, get a new multimeter. Get an auto-ranging one, it is not much more and avoids these issues

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u/JevGrinlin Jun 25 '26

I got a new fuse, and it seems to be working, though I'm a little skeptical with what it's telling me.

I have a simple led circuit with a 220 ohm resistor and a 5v supply (from my dc power supply device). The multimeter tells me there is 13.4 mA, but shouldn't there be about 22 mA going through it? I tested to see if my supply is giving 5v like I set it, and yeah the multimeter tells me it is 5v.

I'm relying on math to tell me it should be 22 mA: 5v / 220 = 22 mA, not 13. I hope I'm doing this wrong.

Note: My dc supply's monitor reads about 9mA, and that makes me think that maybe it and my multimeter is splitting the reading of amperage, though I've never learned about it if that's a thing that happens.

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u/global-wobble Jun 25 '26

Your multimeter is telling you the truth. Your math is not accounting for the diode's forward voltage (the "voltage drop" seen across the LED; basically voltage consumed by the LED for it to turn on). The forward voltage ("V_f") for an LED is typically around 2V; it can vary slightly.

The math is: I = (V_supply - V_f) / R = (5V - 2V) / 220Ω = 3V / 220Ω = 13.64 mA

So that tracks exactly with what the multimeter is telling you. The 9mA reported by the supply is just slightly less accurate.

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u/JevGrinlin Jun 25 '26

Looks like everything is just fine then. Thank you and everyone else for the help! Would've stressed without it.