Stray Induced Current

[smokey73]

When my Generator is running and I measure the current on the Green Wire shows 0.33 A with the reading taken very near the generator electrical end. When I measure on the exact same green wire a foot or so away from the generator it reads 0.0A See the pictures below.

I am guessing that the 0.33 A is simply some sort of induced current because the instrument is so close to the generator. Otherwise, how could there be 0.33 A at one point on the wire and then 0 A just a couple feet down the same green wire? Both measurements on the picture are on the same wire.

Any thoughts?

 

[Davidasailor26]

If there are no other connections or junctions between the two measurement points I agree with you. One other way you could probably check is to put a multimeter on the 10A setting in series with the green wire. Since you’re only seeing less than an amp even with the suspect reading that approach *should* be safe for testing purposes. The in-line multimeter should not be affected by whatever magnetic disturbances are causing the .33A reading.

 

[smokey73]

Like the idea @Davidasailor26. Take the induction current out of the equation. There are no other connections or junctions between the two points measured which is what is the conundrurm. Hard to explain why on the same wire there are two different readings other than an induced current from the magnetic field around the generator.

I may also re-route the wire (it goes under a board for about 2 feet) to where I can measure along the entire length. If the reading drops the further I get away from the generator then it is most likely induced current.

 

[dLj]

Did you try just putting your meter right next to the green wire near the generator to see if it gave you the same reading? Or take a strand of wire not connected to anything, hold it in the same location and measure that. Interesting science project.

dj

 

[smokey73]

Did you try just putting your meter right next to the green wire near the generator to see if it gave you the same reading? Or take a strand of wire not connected to anything, hold it in the same location and measure that. Interesting science project.

dj

Interesting idea. Just brainstorming here but I would imagine that without a wire it might not show anything. With a wire I would think it might have to be connected to something. Guess I'll have to dust off my EE book from 50 years ago and study?
Worth a try though. Just perplexed at different readings from the same wire at different points along its length. That and the fact that it is a green AC electrical wire and its supposed to have no current on it if everything is hooked up right.

 

[kloudie1]

That reading is a result of the magnetic field from the generator affecting the measuring sensor of the meter. Non contact current measuring meters use magnetic field measurement so what the meter is telling you is that there is a weak, unshielded magnetic field close to the generator in that location.

 

[dLj]

That reading is a result of the magnetic field from the generator affecting the measuring sensor of the meter. Non contact current measuring meters use magnetic field measurement so what the meter is telling you is that there is a weak, unshielded magnetic field close to the generator in that location.

@kloudie1 - of course, but my question to you is, which of the above two scenarios that I proposed would give a reading? And, would that reading be the same? What if you changed the geometry of the unconnected wire? So you think you could "tune" it to the correct frequency and maximize your reading? All just random thoughts on a Saturday morning....

dj

 

[smokey73]

Interesting theoretical discussions. When I first measured the current at the location near the generator where I could each the wire easily, I was checking to see if I had some fault in my wiring since the green wire should be 0 A and only carry current if there is a fault somewhere. When I saw the .33 A I was worried that I had a fault. That is my concern and it looks like I don't need to worry about it. I may still try the direct reading ammeter suggested by @Davidasailor26 just to give my self piece of mind.

 

[dLj]

Interesting theoretical discussions. When I first measured the current at the location near the generator where I could each the wire easily, I was checking to see if I had some fault in my wiring since the green wire should be 0 A and only carry current if there is a fault somewhere. When I saw the .33 A I was worried that I had a fault. That is my concern and it looks like I don't need to worry about it. I may still try the direct reading ammeter suggested by @Davidasailor26 just to give my self piece of mind.

These theoretical discussions actually have a very practical aspect. If you would perform some of these measurements, and see what the outcome is, it could be useful for someone else who has the same question. So if you put the meter in the same position but not around the wire, do you still get that measurement? If you don't, what about with a small unconnected wire held there? Play around with it. It could be very interesting = or not, what do I know?

dj

 

[smokey73]

@dLj Agree. I intend to try a few of those things since they are easy and an interesting experiment. It make sense that a generator would put out some small magnetic fields nearby but I was really concerned with the possibility of stray AC currents.

 

[sailme88]

The QED to determine proximity stray field energy is to remove the testing equipment from the area. Remotely sample the fields with extended wires.

 

[kloudie1]

@dLj Yup The reading will vary with position around the generator housing as more or less of the shielding gets between the meter and the generator.. Air cooling openings in the generator housing probably have some effect, but that is a guess on my part.. .. The green may be acting as a "flux guide" and intensifying the field in that spot.. As you say, it would be interesting to take readings all around the housing and at the ends of the housing too.

 

[JoeWhite]

Place an LED in series in the green wire. If it lights up there is current in the wire.

 

[smokey73]

Update - I measured the apparent current at different locations in the vicinity of the AC generator end and the reading varies by a considerable amount by location and the angle the hand held instrument is held. This was done with no wire at all inside the enclosed loop so its clearly the effect of the magnetic field from the generator and not any actual current in a wire. You don't have to get very far away from the actual electrical end of the generator before it drops off to 0. Something to keep in mind if you are trying to use one of these types of instrument. Not surprising but I am now comfortable that there is no actual fault in my wiring.

 

[dLj]

Update - I measured the apparent current at different locations in the vicinity of the AC generator end and the reading varies by a considerable amount by location and the angle the hand held instrument is held. This was done with no wire at all inside the enclosed loop so its clearly the effect of the magnetic field from the generator and not any actual current in a wire. You don't have to get very far away from the actual electrical end of the generator before it drops off to 0. Something to keep in mind if you are trying to use one of these types of instrument. Not surprising but I am now comfortable that there is no actual fault in my wiring.

Good to know. How far away should you be? Like a foot, or two feet? Ballpark number...

dj

 

[smokey73]

@dLj Probably a foot or so should be fine. It dropped off pretty quickly as you moved away but I did not take it to 0 to check that. I was about 18 inches away (ballpark) when read I read 0 in the picture in post #1. I attached pictures. The best thing to do would be to take a reading adjacent to where you ae trying to measure with nothing in the loop and make sure its 0 there and then measure with the wire enclosed in the instrument loop.

 

[JamesG161]

Guess how a DC clamp ampmeter works?

The Hall Effect semiconductor.

That uses Electro-Magnetism...

Guess what interfers with a DC Clamp ampmeter reading?

Ans: My beer drinking...
Jim...

 

[smokey73]

Yea, should have known that from the get-go. To be honest, I did have a Yuengling Black and Tan in my hand when I was taking the initial readings. Just goes to show you that influences electrical readings (or at least their interpretation). I think they call it the "Yuengling Effect". It has applications in a broad range of endeavors.

 

[JamesG161]

"Yuengling Effect"

Some DC ampmeters do show you the direction of current flow.

I have always wondered if you could use a DC ampmeter to detect if

Induced DC Current Corrosion

was coming from a nearby boat.

Jim....

 

[JamesG161]

Please note that @kloudie1 gave the correct reason first.

To answer @dLj question about distance from the Generator's magnetic field, to get a good meter reading..

Simple answer is make sure no motor driven devices are near by then Let your meter show you. Just like Smokey did.
Jim...

PS:Sometimes I only use "Likes" to show what I agree with, instead of being redundant on a thread answer.