I have read the manual for my new multimeter but unsure which (red) terminal to use for what. The meter has one VΩmA fused 500 mA max terminal and one Unfused 10A Max terminal. I just want to measure the voltage of a wall outlet. Which terminal do I use? It would be great with some examples of what the 10A terminal is used for as opposed to the VΩmA terminal. I'm not an electrician by any means so the manual is not covering this.
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11RTFM (again). The "10A" terminal should ONLY be used when measuring amps, and only when the 10 amp range is intended. All other measurements should be made using the VΩmA terminal.– Hot LicksFeb 29, 2020 at 23:53
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3@HotLicks arguably an Unfused 10A multimeter terminal should not be used for anything– Pete KirkhamMar 1, 2020 at 15:35
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1I'm not well versed in electric terms so "only used to measure amps" doesn't really tell me what I can use the terminal for. Thank you for pointing out that the manual should be sufficient for those who knows these things. I used it on my troubled outlet and got the reading I needed.– ChristianMar 1, 2020 at 18:03
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1@Christian: When you measure voltage (in volts), the meter acts as a resistor -- some electricity passes through it, but it's (ideally) not a lot. By contrast, when you measure current (in amps), the meter is essentially a wire (rather than a resistor), allowing the current to flow through it at full force. Their point was that the higher-current terminal shouldn't be used unless you need the higher-current tolerance specific to that terminal.– NatMar 1, 2020 at 21:45
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1Adding to what @Nat said: when used as a voltmeter (to measure volts), the meter is in parallel to the load. When used as an ammeter (to measure amps), the meter is in series with the load.– Z4-tierMar 2, 2020 at 12:49
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3 Answers
Stay away from the 10A terminal. That is for amp measurements ONLY, and creates a dead short between the 10A terminal and the common. This will blow your fuse, burn up your probes, and/or destroy the meter. Never use that unless/until you know exactly what you are doing.
answered Feb 29, 2020 at 14:41
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2I did that when I was a kid and bored. I knew better, but I wasn't thinking. It made impressive fireworks, blew a chunk out of a probe, and the 10A scale didn't work anymore.– AaronDFeb 29, 2020 at 22:27
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1@AaronD - Yep, blew out a resistor in my newly-constructed Heathkit VOM when I was about 14, from switching between volts and ohms at the wrong moment. Feb 29, 2020 at 23:51
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1Stay away from using a multimeter to check for a 'trouble outlet', full stop. They're for checking that the incoming power is what it's supposed to be, and (not that I've ever had to, but if I did) I'd RTFM again. - I use solenoid voltage detectors; no reading required, and as long as you don't keep it lit for more than ten seconds, and don't try to check voltages higher than 440 (which you literally shouldn't even go near) it will not blow up in your face.– MazuraMar 1, 2020 at 22:34
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@AaronD Let be honest, we've all done this. When I was a bored kid though, I thought it would be fun to wrap a coil of enamelled wire around the three pins of a UK plug, and plug it in. (My dad was an electronics engineer, and had been showing me stuff about electromagnets). Made a big flash, and parents came running :) I guess I'd wrapped it tight enough to break through the enamel on a few turns.– SiHaMar 2, 2020 at 12:52
Keep in mind that using a meter that's not rated for the task can be dangerous! Even with relatively low risk things like residential receptacles.
Right off the bat - if you got this meter for free with a purchase of a blue tarp at Horrible Freight, just throw it out.
Next, make sure the meter is properly rated for the task. Meters have CAT ratings roman numeral I through IV, and are designed for safe use depending on the application. For residential receptacles, it should be marked CAT II, and should be from a maker you trust to properly rate their products. (Hint - reputable makers don't give away meters free with a blue tarp.)
Technically, for CAT II the receptacle should be at least 30 feet away from the electrical panel supplying the receptacle; if it's right close to the panel that feeds the receptacle, you are supposed to use a CAT III rated meter.
In the comments, the original poster links their meter's web site and looking at the picture below, you see that it is rated CAT II so it's suitable for the purpose. (It also shows that the left jack, for 10A current measurements, is actually fused, not unfused as stated in the original post - which makes sense, and is a relief.)
So to measure voltage, yes you want the red lead plugged into the jack labelled "VΩmA" and the black lead plugged in the common jack, the configuration shown in the photo from the web site.
To address an issue that's mentioned in the comments - since safety is a factor, you don't want to skimp on a meter, and a good meter is not cheap. Plus there's a little learning curve involved using a meter correctly and safely. As an alternative, for checking voltage at receptacles, consider a Kill A Watt or similar plug in device:
This measures voltage as well as power utilization and it's dead simple to use, safer than a toaster.
answered Feb 29, 2020 at 13:21
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1Thank you for a educational lesson! I did buy the meter. It's a cheap one ($12). You can see it here: is.gd/AvPjBz The manual is available online also. I do not use a meter often so I didn't spend much on it thinking it would be able to do some basic tasks like this one in addition to battery checking etc. Feb 29, 2020 at 14:40
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1Only buy good quality meters, one of mine is by Fluke, the other by Avometer... and they were a factor of 10 more than what you paid - good tools are not cheap @Christian Mar 1, 2020 at 6:32
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2@Tim We don't know what the OP was doing but since the question is on Home Improvement not Electronics, it's a fair bet that the mains supply was involved. As for doing things "regularly", you don't learn from your mistakes if the first one kills you. Mar 1, 2020 at 15:16
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4@Christian a cheap screwdriver won't electrocute you, a cheap hammer will still put a nail in but a cheap meter may fail or the probe insulation is poor (guess why cheap is cheap...) and you get the shock... Mar 1, 2020 at 18:14
Memory key: Because you want to measure voltage (V), use the VΩmA terminal.
(Also use that terminal for measuring resistance (Ω) and small currents (mA).)
The 10A terminal is special purpose, only for measuring very high current (up to 10 amps).
