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2 March, 2021

Probe senses current flowing in PCB tracks

19 October, 2011

Aim-TTi has launched a handheld current probe that uses a patented technology to measure the current flowing along PCB (printed circuit board) tracks, without needing to break or surround the conductor. The insulated tip of the I-prober 520 instrument is placed onto a PCB track, and the current flowing in the track can then be observed and measured via an oscilloscope.

Current measurements normally require either a shunt resistor to be inserted, or for the conductor to pass through a closed magnetic loop. Typically this is done using a split clamp device, but these cannot be used to measure currents in PCB tracks.

The new probe (shown above) operates by sensing the field close to the track. To achieve a calibrated measurement, the sensor needs to maintain a precise distance from the track. For good sensitivity, this distance must be tiny, because the field reduces approximately with the square of the distance.
The sensor incorporates a patented, miniature fluxgate magnetometer, developed in conjunction with Cambridge University in the UK. This low-noise device can measure the field at a precise point in space and has a much wider bandwidth (DC–5MHz) than a conventional magnetometer. It has a dynamic range of 10mA–20A peak-to-peak. It is safety-rated to 300V Cat II (600V Cat I) and can be used with any oscilloscope.

As well as measuring currents in PCB tracks, the probe can be used on leads or other current-carrying conductors. In ground planes, for example, it can be used to observe circulating currents, interference injection points and “hot spots”.
The Aim I-prober 520 (priced at £495 in the UK) is supplied with a control box and calibrator, a power supply, and a clip-on toroid assembly that can convert it into a conventional closed-magnetic-loop current probe.

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