Sensor

The utility model is provides a sensor which comprises a sensor body and a magnet, wherein the sensor body comprises an insulating support body, a signal receiving device and a signal line, wherein the signal receiving device is arranged inside the insulating support body, and a first end of the signal line is connected with the signal receiving device; and a second end of the signal line penetrates through the insulating support body, and the magnet is arranged on the insulating support body. According to the sensor, the sensor body is adsorbed on a switching device with a ferrous housing through the magnet arranged on the sensor body, so that the error generated in measurement by human reasons is prevented, the effective and accurate measurement of internal partial discharge of the switching device is realized, and simultaneously the safety of related devices and testers is ensured.