Anyone know why my "clip-around" AC
Anyone know why my "clip-around" AC
(OP)
Anyone know why my "clip-around" AC ammeter shows 2 slightly different readings depending on which of the 2 wires I clip-around? I've seen as much as 10% difference.






RE: Anyone know why my "clip-around" AC
Blacksmith
RE: Anyone know why my "clip-around" AC
Yes, its a single-phase system. There is no ground (yes, I know-dangerous). I didn't notice any difference when moving the meter around. BTW, this is not the first time I've observed this.
RE: Anyone know why my "clip-around" AC
RE: Anyone know why my "clip-around" AC
This is baffling.
RE: Anyone know why my "clip-around" AC
Are the two wires you are measuring very close together? Clamp on ammeters are very susceptible to stray flux causing erroneous readings. If the wires are in different locations, this could possibly account for the discrepancy. Otherwise, the return HAS to carry exactly the same current as the supply, again assuming that there is no leakage.
RE: Anyone know why my "clip-around" AC
Try making sure the iron faces on the tongs are clean and that you have each conductor in the center of the opening perpendicular to the core of the clamp-on.
RE: Anyone know why my "clip-around" AC
RE: Anyone know why my "clip-around" AC
Usually, you should only be clamping around one wire at a time. On a 2-wire circuit, the measurement at each wire should be equal, unless there's a ground current. On three-wire circuits, the reading taken on one wire should equal the reading taken by simultaneously clamping onto the other two wires, unless there's a ground fault.
Simultaneously clamping onto all wires in a circuit should read zero unless there is a ground fault. Simultaneously clamping all wires including ground conductor should equal zero unless there's some other unintentional circuit connection.
RE: Anyone know why my "clip-around" AC
Good adivce by all. The only comment I can add is to be sure the CT pole-face gap is as close to zero as possible.
RE: Anyone know why my "clip-around" AC
Thanks to all; twosockets and the blacksmith win a star.
RE: Anyone know why my "clip-around" AC
Given a typical/readily available portable CT for use with a multimeter, consider an AEMC MN210 for line-frequency measurements. http://www.aemc.com/products/html/moreinfo.asp?id=204010201&dbname=products#specifications
Published accuracies…
Output Signal 1mA/A on 1 ohm [burden]
Influence of Conductor Position 0.5% of Reading @ 50/60Hz
Influence of Load <3% of mA output 40Hz to 1kHz
Influence of Adjacent Conductor < 15mA/A @50Hz {!}
Maybe I’m misinterpreting published numbers, but it looks like adjacent-conductor influence could affect readings producing up to a 15x [15mA/A:1mA/A or 1500%] error.