A counting device for distance measuring wheel includes a housing, a transmission assembly, a counter wheel assembly, and a reset control assembly. An elastic support unit of the reset control assembly is arranged at the side of each of the transmission assembly and the counter wheel assembly so that the relative positions among the transmission assembly, the counter wheel assembly, and the reset control assembly arranged inside the housing are changed and the size of the counter wheel assembly may become larger while the size of the housing is not changed.

A counting unit is provided for use in an electrical device. The counting unit is configured to count a thermal event such as an autoclave cleaning operation when the electrical device is not electrically powered. In one aspect, the counting unit includes a rotary member and an actuator, the actuator is configured to change shape from a first configuration to a second configuration when subjected to a predetermined temperature, wherein in the second configuration, the actuator engages the rotary member so as to rotate the rotary member. In another aspect, the counting unit includes a plunger, a drive and a heat resistant arm configured to release the plunger during a thermal event and retain the plunger when the electrical device is cooled down.