I have two wires that have current going in the same direction. Can I put them both between the clamps of a current meter and read the sum?
Edit: I should mention that both wires carry DC current, and I have a clamp meter that also measures DC.
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\$\begingroup\$ In theory: yes. In practice: probably yes but I'll wait for someone who's actually tried it to answer. \$\endgroup\$– Criticizing Israel not allowedCommented Jul 28, 2022 at 17:27
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1\$\begingroup\$ A clamp meter will read the algebraic sum of all the currents passing through the clamp. \$\endgroup\$– Neil_UKCommented Jul 28, 2022 at 19:14
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2 Answers
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Yes, assuming your clamp meter is an AC type, and both conductors are carrying AC current you will read the sum of the 2 currents assuming both have the same phase. If it's an AC meter and one/both of the conductors is carrying DC, you won't get the correct current.
If your clamp meter is capable of reading DC, and your conductors are carrying DC then you should read the sum of the 2 DC currents.
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\$\begingroup\$ I have both wires with DC. see my latest edit of the op. should work right? @John D \$\endgroup\$– FlakRCommented Jul 28, 2022 at 17:42
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\$\begingroup\$ If your clamp meter works for DC, then you're good, you should read the sum of the 2 currents. \$\endgroup\$– John DCommented Jul 28, 2022 at 17:45
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\$\begingroup\$ I guess the two ACs should have the same phase? \$\endgroup\$ Commented Jul 28, 2022 at 18:45
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According to this website from clamp meter manufacturer Hioki (https://www.hioki.com/us-en/learning/how-to/u-clamp-meters.html), you should not measure multiple wires together. Moreover, the wire should be positioned in the center. That's for measuring load current.
You can and should, however, clamp over all of the wires if you're measuring leakage current.
To those who answered that it's OK to clamp over multiple wires, I'd be curious to know whether this manufacturer's instructions are being overly cautious, or whether they don't apply generally. Thanks.
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\$\begingroup\$ From the Hioki web site: "Clamp meters designed to measure load currents can only be clamped around one wire. Be careful not to clamp the instrument around multiple wires at the same time as doing so will prevent proper measurement." What does proper measurement mean? I believe it's a guide for neophytes and the surest way to make a measurement for neophytes is one wire at a time. \$\endgroup\$– qrkCommented Jan 23 at 4:24
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4\$\begingroup\$ In my opinion, they're just trying to avoid complaints that it "doesn't read correctly" when someone clamps it over a pair of red and black wires carrying the same current in opposite directions and it reads close to zero. The DC equivalent of clamping it over a line cord and expecting a reading of the AC current. In general, the reading will vary a bit from the position of the wire(s) in the window, so putting it (or them) near the centre will result in better accuracy. \$\endgroup\$ Commented Jan 23 at 4:53
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1\$\begingroup\$ I think you can clamp it in any way you want, but you are responsible understanding what you are measuring and why and how to make that desicion. So unless you understand what you are doing, the takeaway is that if you want to measure current in one wire, you clamp it over that one wire, and in most cases that is likely what someone wants to do. You will be measuring different things if you clamp it over 2 wires or 3 wires or 4 or 5. Also depends what goes in those wires, but I assume mains AC, multiple phases, neutral, and PE. \$\endgroup\$– JustmeCommented Jan 23 at 6:15
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1\$\begingroup\$ It is generally true that the most accurate reading is obtained when the wires are centered in the clamp, since the clamp meter is not ideal. We're talking about minimizing an already small error, not about getting grossly wrong readings. But even if you get a couple % error in the reading, in many cases it doesn't matter. I think Hioki was tired of customer complaints from people who had no idea what they were doing, and decided to cut the nonsense. \$\endgroup\$ Commented Sep 17 at 10:34