How a passive current probe passes a signal to an oscilloscope

What is a passive current probe?

A passive current probe is a 1 type of current measurement device that does not require an external power supply. It measures current by the principle of induction, usually consisting of a clip and a connecting wire. The clamp contains one or more windings of the coil, when the measured current through the wire, will produce an induced voltage in the coil, the induced voltage is proportional to the measured current.

The working principle of passive current probe

The core of the passive current probe is a Hall effect sensor or other type of magnetoelectric sensor. The following is its basic working principle:

Induced magnetic field: When current passes through a wire, a magnetic field is generated around the wire. The clip of the passive current probe partially surrounds this wire, and the coil inside will sense this magnetic field.

Induced voltage: According to Faraday's law of electromagnetic induction, a changing magnetic field will generate an induced voltage in the coil. The magnitude of this induced voltage is proportional to the rate of change of the magnetic flux passing through the coil, which in turn is proportional to the magnitude of the measured current.

Signal transmission: The induced voltage is transmitted to the input of the oscilloscope through the connection line. The oscilloscope will amplify and process the voltage signal, and finally show the current waveform.

Advantages of passive current probes

No external power supply: Passive current probes do not require an external power supply and are easy to use.

Simple and easy to use: Just clamp the clip on the wire under test to start measuring, easy to operate.

Portable: Because there are no complicated circuits and power modules, passive current probes are usually small and easy to carry.

Low cost: Compared to active current probes, passive current probes are more affordable.