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Can a non-invasive AC current sensor measure DC current? What is the theory behind it?

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    \$\begingroup\$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. \$\endgroup\$
    – Community Bot
    Aug 10 at 8:56

2 Answers 2

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What is the theory behind it?

The theory behind non-invasive current measurements is measuring the magnetic field on a closed path around the conductor. According to Ampère's law the integral of the magnetic field along this path is defined completely by the current through the surface enclosed by the path.

This can be done in several ways:
E.g.

  • using a Hall effect sensor (inserted in slit ferrite core around the conductor),
  • using a toroidal flux-gate sensor (surrounding the conductor) or
  • in case of AC with a known waveform and frequency (e.g. sinusoidal, 50Hz) also using a current transformer.

Can a non-invasive AC current sensor measure DC current?

If the sensor is called explicitly AC current sensor I'd assume that it uses a current transformer to convert the alternating magnetic field into a current in the secondary winding.
If this is actually the case it doesn't work with DC.

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Can a non-invasive AC current sensor measure DC current?

And

What is the theory behind?

In short, the theory is The Hall effect; it can measure DC currents non-invasively but is subject to quite strict placement of the sensing head to get accurate results. Another source of information: HyperPhysics: -

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    \$\begingroup\$ Induction based AC magnetic field (or current) sensors are insensitive to DC fields. Think of your e-guitar 😉 \$\endgroup\$
    – tobalt
    Aug 10 at 9:10
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    \$\begingroup\$ The question is about "an AC sensor". I am saying that not all AC sensors are Hall elements, and that therefore your answer is situationally wrong . \$\endgroup\$
    – tobalt
    Aug 10 at 9:15
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    \$\begingroup\$ I'd say the theory is measuring the magnetic field strength on a closed path around a conductor. Using Hall effect is just one way of measuring the magnetic field but there are also others. Also a toroidal flux-gate sensor could be used, see e.g. here: danisense.com/flux-gate \$\endgroup\$
    – Curd
    Aug 10 at 9:26

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