The present invention is intended to inhibit a communication program from crashing in the case where a power source is turned off while writing or rewriting of a measurement control program from an external device is performed by a communication part, and includes: a first recording part for storing the communication program for controlling the communication part; a second recording part for storing a measurement control program for controlling the measurement control part; and a central processing unit. In this configuration, the communication program stored in the first recording part is configured to be unrewritable by the central processing unit and the measurement control program stored in the second recording part is configured to be rewritable by the central processing unit.