An electronic component has an element, a pair of terminal portions which are disposed on the element, and an external covering material which covers a part of the terminal portions and the element. A simple planetary gearset as a front planetary gearset and a double-pinion planetary gearset as a rear planetary gearset are mounted in a rear section of a transmission housing. However, when the voltage of the first node exceeds the first threshold voltage, and the voltage of the second node exceeds the second threshold voltage, the bi-directional buffer is disabled, which disconnects the first and second nodes. The updated firmware code is installed in second firmware component. This thickness is related to a substance to be detected.