Current Measurement: Fundamental physics problem I need to solve...

Hi Everyone,

I have a pretty difficult problem that I would really appreciate some help in solving.

I need to measure the current induced in a conductor by a strong magnetic field. I need to do this without using any conductive material in the magnetic field since this will induce current in the measurement equipment and trash the results.

Here are ideas that I've been tossing around but do not have a real grasp on.

Can I use some light emitting diode and pump the light out in a fiber optic cable and sample it away from the experimental setup?

Can I submerge the conductor in a liquid, measure heat generated by the current?

I'm at a loss on how to approach this problem, any advice?


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That is what engineering is all about. You have a problem and you are probably the world's best informed about it. Try anything. See what happens. Then make improvements.


-- Fermez le Bush

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Salmon Egg

frequency of current? predicted strength of current? impedance of circuit?

what measurement equipment? magnetometer? ocilliscope? please specify.

no. lack of linearity.

no. see calorimetric wattmeter. you can measure heat rise however how do you know perameters such as resistance reamin constant?

find a way to magnify the problem to the point that a calibrated current probe has minimal effect.

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Connect a wire to the end of the conductor. Use a good shielded cable like double-shielded RG 62 coax, for instance and maybe even put the cable in some steel or iron pipe. You will need to ground the shields (and pipe) somehow--maybe just one end, I'm not sure. Make sure the wire end of the wire is far enough away to be unaffected by the magnetic field. Then measure the current at the end of the wire. Use a high-impedance measurement setup.

Maybe that'll work, I dunno.

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Voltage is the quantity induced NOT current. The current is a function of the impedance of the circuit as well as the quantity of induced voltage . This does not help you with ur problem but at least poses the problem correctly.

Good luck.


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consider how the wire is suspended, and then optically measure the wire's deflection. The force on the wire, and its deflection, will be a function of the current in the wire. Remember, that's exactly how a moving coil meter works.

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the problem is that the voltage induced is only a function of a varying magnetic field not a constant magnetic field. what u r suggesting is correct for measuring current flowing in a conductor excited by some kind of voltage/current source....with a fixed magnetic field next to the hanging conductor....but not easy to do with the required set up when the experimenter is generating a changing magnetic field to induce the voltage in the first place.

T> consider how the wire is suspended, and then optically measure the

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I suggest a search (google, ieee, etc) for optical CTs. They are out there and they work amazingly well.

Charles Perry P.E.

Reply to
Charles Perry

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