Technician A says that most digital and analog (needle-type) dash gauges use variable resistance sensors. Technician B says that permanent-magnet (PM) generators produce an AC signal and are used for vehicle speed and wheel speed sensors. Who is right?

Question

Quizplus · Accepted Answer

Technician A is correct because many automotive sensors, including those for temperature and fuel level, operate by varying resistance in response to changes in conditions, which in turn alters the reading on both digital and analog gauges. Technician B is correct because permanent-magnet generators, often used in speed sensors, do indeed produce an alternating current (AC) signal that varies with the speed of the object they are measuring, such as a wheel or vehicle speed.

Technician a Says That Most Digital and Analog (Needle-Type) Dash