An extension unit provided adjacent to an amp unit comprises a measurement data accumulation memory, a measurement data acquiring part for acquiring measurement data coming through a transmission line and accumulating it in the above memory, a data analyzing part for analyzing an accumulated series of measurement data according to predetermined algorithm, a determining part for determining a data analyzed result, and an output part for outputting a control signal corresponding to a determined result to the outside. A plurality of process programs in which measurement algorithm is segmentalized are incorporated in the extension unit and a process program is selected according to a command from a personal computer and the selected process program is performed in a predetermined order.