Measuring low dc current non invasive way

Hello everyone. I would like to build a parking sensor system with ultrasonic waterproof sensors. As i try to avoid cutting the wires for the reverse lights, i wonder if there is a device/sensor for Arduino that measures the currents that lits up the reverse lights? i think this would be a safe and non invasive way to realize this little project (without interfering with the electric system of a car which is quite tricky, not to mention the safety of the passengers and the car) .

A dc-capable current sensor perhaps? For example: https://uk.farnell.com/lem/lts-6-np/current-transducer-6a-pcb/dp/2146860?st=current%20sensor

I think you can get some with gates that open like a clamp meter.

Mount a LDR close to the bulb?

knut_ny:
Mount a LDR close to the bulb?

Plausible, but sunlight might be an issue.

Theoretically, if you mount a magnetometer to the outside insulation of the wire, you can measure the magnetic field strength circling around the wire due to the DC current. The magnetic field will be proportional to the current flowing through the wire.

Power_Broker:
Theoretically, if you mount a magnetometer to the outside insulation of the wire, you can measure the magnetic field strength circling around the wire due to the DC current. The magnetic field will be proportional to the current flowing through the wire.

But you have to calibrate for the precise dimensions of the wire...

No need to do that, just thread a gapped ferrite core around the conductor and stick a hall sensor in the gap,
which removes the problem of having to know the distance from the centre of the wire. This is how practical
non-invasive current sensing works, and the wire size no longer matters, so long as it fits through the core.

Thanks for the suggestions. Actually, MarkT's solution might work just fine. I really do not need to know the precise value. As long as it is anything positive higher than 0 it means that the reverse light are on, so sensors should kick in. Will do some reading and research and try the project