Very practical current probe measurement tips, recommended to save

The oscilloscope probe is crucial to the accuracy and correctness of the measurement results. It is an electronic component that connects the circuit under test to the input of the oscilloscope. The current probe is one of the commonly used oscilloscope probes. It provides a safe, cost-effective, simple and accurate way to measure current and is an indispensable partner for the oscilloscope. So, what are the measurement tips when using the current probe? Today, PRBTEK Technology will share with you briefly:

The following are some common brands of current probes:

Improve probe sensitivity

Sometimes a current probe is needed to provide higher sensitivity for testing very small currents. You can wrap the wire a few more times as shown in the figure below.

The current probe conforms to the transformer principle, and the sensitivity increases by the same multiple as the number of turns of the coil. However, it should be noted that the insertion loss increases with the square of the number of turns. For example, with 10 turns, the sensitivity increases by 10 times, while the insertion loss increases by 100 times. Generally speaking, this is not a problem, as small currents will not generate a high enough voltage on the insertion loss.

Current Probe Measurement Tips

If you pass multiple wires through the coil of a current probe, as shown in Figure 3, the current probe will measure the total net current in those wires.

Measuring static current in a pair of conductors

If the currents in the two conductors are equal and flow in opposite directions, the net current value measured is zero. This method can be used to extend the measurement of DC or low-frequency AC current. Measure the conductor with known current and opposite flow together with the conductor under test. This not only extends the measurement range of the probe, but also eliminates the low-frequency common mode component.

When using a current probe, it should also be noted that all current probes have a certain degree of shielding in order to reduce the electric field radiation of the conductor being measured. In order to optimize the shielding effect, other parameters of the probe need to be sacrificed. For example, the ability of probes from different manufacturers to suppress fast-changing signals (dv/dt) varies. This means that the signal should be detected in the low-voltage part of the circuit as much as possible. If this cannot be avoided, it may be necessary to evaluate the size of the electric field picked up by the current probe. Connect one end of a small piece of wire to the conductor being measured, and leave the other end of the wire hanging in the air. Clamp the wire with the current probe and observe the current waveform. The waveform displayed on the oscilloscope reflects the electric field picked up by the current probe.

dV/dt sensitivity test