2 reading of DC Current ; Which one is correct?
2 reading of DC Current ; Which one is correct?
(OP)
When I have measured the DC Current of DC Motor Field Coil . Two reading will be always found different on Positive and Negative Wire . The Positive wire will greater than the Negative. Which is the correct one which should be concerned to meet the rating plate.?





RE: 2 reading of DC Current ; Which one is correct?
If the ammeter is reasonably accurate, then both readings are correct and you aren't accounting for all current paths. If the ammeter isn't all that great then neither reading is correct and it is impossible to determine which might be "more correct".
RE: 2 reading of DC Current ; Which one is correct?
Thank you davidbeach for your answer; I afraid for the ripple out rectifier may be concerned this account. I think the waveform before and after in and out DC coil should be different. And they may be influence the reading. What do you think ?
RE: 2 reading of DC Current ; Which one is correct?
If you have ripple, there could be some capacitive component that returns through ground, but should be small.
If you want to check your clamp-on, maybe try wiggling it, tilting it, flipping it in reverse and see if the magnitude of the reading changes. (maybe stray magnetic field is influencing the measurement).
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(2B)+(2B)' ?
RE: 2 reading of DC Current ; Which one is correct?
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RE: 2 reading of DC Current ; Which one is correct?
RE: 2 reading of DC Current ; Which one is correct?
RE: 2 reading of DC Current ; Which one is correct?
Thank you all for value answer, No any part draw current out of negative wire . I suspect We may account in limiting of Clamp on performance , DC source come from 3 Phase Power pass through 6 ea.of Diode rectifier and inject to the DC Coil. the insulation of Coil is high reading.The wave form of Dc Voltage before and after Dc coil should be different due to filter action of DC coil . The current in negative wire may shape DC pattern better than positive wire. And that is my opinion which may be cause of 2 different reading. what something which I am misunderstand ? I always found this due to I work in repair shop.
RE: 2 reading of DC Current ; Which one is correct?
Please supply us with how much difference you see between the two sides. Then maybe we can supply a reason.
RE: 2 reading of DC Current ; Which one is correct?
Thank you OperaHouse ; Unfortunately I did not record it . But it seem that the different will vary upon the turn of rewound coil .They are different obviously especially Coil brake. After start office hours on Monday morning ; I will measure and post the result again.
RE: 2 reading of DC Current ; Which one is correct?
Best regards,
Mark.
Mark Empson
Advanced Motor Control Ltd
RE: 2 reading of DC Current ; Which one is correct?
1> The current is actually different. This would be due to leakage or a third wire. You have ruled that out.
Failing that the current WILL be the same
That leaves.-
2> Some type of metering error.
Try reversing the polarity at the source and take the readings in the same way.
Bill
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"Why not the best?"
Jimmy Carter
RE: 2 reading of DC Current ; Which one is correct?
Some clamps have automatic null. If jaws are not entirely closed when nulling, you get a zero offset.
Gunnar Englund
www.gke.org
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