What is the correct voltage type used when checking a Vehicle Speed Sensor during testing?

When testing a Vehicle Speed Sensor (VSS), the correct voltage type used is AC voltage. Most VSS units, particularly those configured as inductive sensors, generate an alternating current (AC) signal as the vehicle moves. This occurs because the sensor produces a voltage that is proportional to the speed of the vehicle, caused by the motion of a magnetic field around the sensor.

The operation of these sensors usually relies on the principle of electromagnetic induction. As the vehicle's wheel or driveshaft turns, it alters the magnetic field seen by the sensor, leading to the generation of an AC voltage signal. The frequency of this AC signal correlates to the speed of the vehicle; thus, it is essential for the function of vehicle systems that rely on speed data.

In contrast, while some other types of sensors might utilize DC voltage, VSS focuses specifically on the characteristics of AC voltage due to its design and operational mechanics. Therefore, recognizing the nature of the voltage signal generated by a Vehicle Speed Sensor is crucial for effective testing and diagnostics.