You’re saying the induced current won’t charge/discharge the capactive portion of the circuit enough to disrupt at least a few sensing cycles? That should (briefly) have considerably more effect. Now of course if the sensor circuit is doing some kind of Kalman filter approximation over several seconds then yes, of course, you’d be completely right, but I’m not aware of any road sensors that are that complicated. They’re very simple, and there isn’t even any subsequent reading confirmation on the part of the management system. In short, you’re not wrong about the circuit overall, but at the same time I suspect it is considerably more sensitive to moving magnetic fields than you’re giving it credit for.
