ECN Forum Forums General Topics of the Trade General Discussion Area AC Current Clamp

The line splitter is very convenient, and most types also include a x10 clamp section for measuring smaller currents.

I have the Simpson version of the Amp-Clamp and line splitter.

Remember that the meter must be set on the appropriate AC-milliamp scale, and with a 1000:1 ratio in the probe, 1 mA on the meter corresponds to 1 AMP trough the probe ‘loop’.

Is this a dedicated receptacle? If not, and you check current at the panel, you will also be measuring other loads. If you have zero current when the strip is unplugged, then you can probably assume that nothing else on the circuit is drawing current.


I agree with resqcapt19. If you don't even know how to use an amp meter, you should not be opening a breaker panel up. However, you can safely use a line splitter and some versions are quite inexpensive. Check Sears, as that is where I purchased mine a number of years ago.

I think I *may* have coonfused some people, but first let me say Thank you so much for all your replies... I really appeciate this...

I just think that I am being misunderstood. First of all, this is in a data center (if that makes it easier). The customer has a plug stip going to a 20amp twist-lock plug dedicated outlet above their cabinets. This outlet runs to a breaker inside of a PDU. Each outlet on this power strip populated an we are thinking that they are close to the 20amp max on this ckt but we can not unplug all the equipment on the strip so we need something that can monitor the amperage draw on the ckt. Does that make it easier? From the info I have been given by all of you, I am finding it difficult to decipher how I am to accommplish this task...

nykevins,
I don't think that you can accomplish this task. You do not appear qualified to work on or near energized electrcial equipment.
Don

It sure sounds to most posters here that you don't understand how a clamp on ammeter works, which suggests that you do not have the experience to safely accomplish the test that you probably need to do.

A clamp on ammeter works by detecting the magnetic field around a conductor produced by the current flowing through that conductor. There are many different types of clamp on ammeter (current transformer, open loop hall effect, closed loop hall effect, etc.) but they all work on this basic concept.

The current reported by a clamp on ammeter is the _net_ total current of _all_ the conductors in the clamp. If you run the clamp around a supply cord to an appliance, the current that you read _should_ be zero; if you get anything other than zero than you have a fault somewhere and current is flowing where it shouldn't. In a properly functioning circuit, the current flowing in one conductor in the supply cord should be _exactly_ balanced by the current returning in the other lead, so that the _net_ current is zero.

If you want to measure the current being used, you need to somehow separate the two conductors of the circuit and run the clamp around just _one_ of those conductors.

If you can power down the device and unplug it, then the 'line splitters' described above work perfectly. You plug the line splitter into your receptacle. You plug your appliance into your line splitter, and then you clamp around one side of the line splitter. The line splitter carries the various conductors on its two sides, with a hole in the middle, so that you can easily clamp around a single conductor.

If you cannot power down the system, then you need to gain access to a single conductor _somewhere_ in the circuit. An electrician with proper protective equipment could probably gain access to a single conductor at the circuit breaker panel that feeds the receptacle in question...if you are certain from your records which circuit breaker supplies the load in question.

If this equipment really _must_ be on all the time, then it may have a UPS built into the equipment rack, in which case you could probably unplug the rack momentarily in order to install the line splitter. Using the plug to disconnect a running load is not ideal, but the plug _should_ be rated to interrupt the full load current.

Finally, if this is a 20A receptacle on a 20A circuit breaker, remember that you are only supposed to supply 16A on a continuous basis, continuous being defined as any period greater than 3 hours. If you make your measurement and determine that your load is 17A, don't take this to mean that you could add 3A of equipment...instead take this to mean that it is time to get a new circuit added.

Regards,

Jonathan Edelson

Nykevins, the line splitter "plugs-in" in series with the power strip. In other words, you can plug the line splitter into the wall outlet and then plug the power strip into the other side of the line splitter. You then use the power strip as usual with everything plugged in.

Like I said in my previous post, you can also clamp the amp meter around the wire where it emerges in the panel and terminates at a breaker. However, if anything else is on the same circuit (other than the power strip) you will also be measuring that current.

I suggest you purchase the line splitter since they are cheap, easy to use, and (most importantly) safe. It may not seem feasible for this one use but once you have it, countless future readings can more easily and readily be made.

If the equipment can NEVER (24/7) be unplugged even for a few seconds, then the amperage readings will have to be made at the panel. Since you are not even familiar with the simple use of an amp meter then your "boss?" should not be asking you to make this measurement. On the other hand, assuming you are injured and survive the experience, you will most definitely be a VERY rich man. Having an employee perform a potentially dangerous task that he/she knows they are not qualified to do will be very solid grounds for a lawsuit!

Wow!

In the few minutes it took me to wright my response to nykevins last statement, two more people already replied and stated the same thing!

Thanks to winnie and triple for answering this question for me. This is exactly what I figured was the answer. We do have a UPS (A & B) but we can not take the ckt down w/o an act of congress. My original thought of placing this clamp around a single lead going into the breaker should accomplish this but I will seek our in house electrician to perform the work.

Until then, I will stick to using a Flexiclamp to get approxiimate readings.

nobody has mentioned the new amprobes that go around both conductors, or the ideal circuit testers here that would suffice?