Device which can be plugged into household socket to show current in circuit?

The electricity in your house is wired into separate zones, and there’s a circuit breaker for each zone which flips if the current is too high. Is there anything which I can plug into the wall socket which will tell me how much current is currently being used in that circuit?

There are devices like the Kill-a-Watt which can show how much current a specific device is using. The device in question (TV, stereo, etc) is plugged into the Kill-a-Watt and it will tell you how much it is using. However, that’s not really practical for knowing how much electricity a certain household circuit is using.

Sometimes our kitchen breaker flips when we have several appliances going at the same time. That’s not necessarily surprising based on how much electricity they all use. However, I’d like to have a device which I could check to see how much was currently being used in the kitchen circuit to know if I could run another appliance at the same time.

Yes and no.

No, in that’s just not how it works., Current flows through something. The current has to flow though the device, so you have to plug the device into the outlet, then plug the load into the device to measure the amps of the load.

Yes, in that there are ways to measure the current on a circuit at any given time, but they’re going to involve going into your breaker box. You can either get a multi-meter with a clamp and clamp it on to the wire in question OR Kill-A-Watt* makes a devices (basically a clamp on meter) that you put around the wire next to the breaker that will send a signal to a computer or wireless meter that will tell you what you want to know.

But, no, there’s nothing you can just plug into a random outlet to know how much current that circuit is using.

*I think it’s Kill A Watt.

There isn’t anything that can tell you how much current is being used by a particular circuit just by plugging into an outlet on that circuit simply because all of the current in that circuit probably won’t be going through that outlet. There are things like clamp-on ammeters which can tell you how much current is going through the wire, and you could use that at the breaker box to determine how much current that circuit is using, but that’s not going to be practical if all you want to do is monitor the current usage from the kitchen.

(ETA - or what Joey P said… dang ninjas)

You might want to contact an electrician about adding some new circuits for your appliances so that you can turn them all on simultaneously without blowing any breakers.

Here it is, not Kill-A-Watt,
The Energy Detective.
http://www.theenergydetective.com/spyder

Just to clarify, I think the OP is thinking in terms of a voltmeter, which can be used to show voltage anywhere in a circuit. An ammeter has to have all the current pass through it to provide a reading, so it has to be at the head of the power loop, which is often right at the breaker box for household AC.

(It might be possible to find a “head” fixture from which all others in that room or area are chained, and install an ammeter there, but without a wiring plan or physically checking, there’s often no way to know.)

The technical term for amateurs who try to wire an ammeter into their breaker box is Kild-A-Dude. Verb. sap.

Amp meter go **around **the wire. Not into the circuit. They have a clamp attachment.

this guy explains what not to do first. never insert the meter into the circuit. use the clamp feature instead.
http://www.youtube.com/watch?v=OwuImfhP0Zg

you can measure current through something using an inline shunt (resistor of low but known value) and measuring the voltage drop across it. After that it’s just Ohm’s Law. The complication with that is you have to physically tap into the circuit, and in the case of AC with a complex load the best you can do is estimate V*A instead of watts.

Clamp-style ammeters go around the wire. They are only one kind and although they have a number of limitations (not the least of which is loose accuracy) they are good for quick circuit checks.

The far more accurate version is inserted in line with the load, but there are even more drawbacks to that kind in household wiring checks (especially by amateurs).

This is called “an ammeter.” :slight_smile: All ammeters read low differential voltages across a shunt resistor, which for household use needs to be on the order of 0.005 ohm and be able to carry 20-50 amps. A very specialized thing often created at the hobbyist level by etching a specific width of circuit board copper. At least, all the DIY plans I’ve seen do it that way, as well as the semi-commercial kit I redesigned a few years back. The resistor in that was about one inch by three inches of double-weight copper cladding, and was adjusted by nicking away at its width.

I noticed in the video the two clamp meters the guy used gave different readings. Clamp on aren’t precise. They are very useful in checking the load on a motor. Like the fan motor in a central AC unit. If the motor is shutting down its often drawing too much power. The thermal switch kicks it off.

Also, they have to go around only one wire at a time. You can’t just clamp it around the Romex cable. You have to get it around the individual black or white wire.