An extension unit configured to be applied to a multiple displacement sensor system comprising: an amp unit row in which amp units are adjacently provided and are electrically connected to a sensor head unit for a displacement sensor such that the amp units constitute an amp isolated type of displacement sensor, and a transmission line connected to each amp unit constituting the amp unit row and transmitting measurement data generated in each amp unit downstream in direction of the extension unit, wherein the extension unit is configured to be connected to and provided adjacent to the amp unit positioned at an end of the amp unit row on the downstream of the transmission line in the amp unit row, the extension unit comprising: a measurement data accumulation memory in which the measurement data is accumulated; a measurement data acquiring part adapted to acquire measurement data coming through the transmission line and accumulating it in the measurement data accumulation memory; the extension unit being characterized by further comprising: a data analyzing part adapted to analyze the series of measurement data accumulated in the measurement data accumulation memory according to a predetermined algorithm; a determining part adapted to determine a result analyzed by the data analyzing part; and an output part adapted to output a control signal corresponding to a result determined by the determining part, to the outside. an amp unit row in which amp units are adjacently provided and are electrically connected to a sensor head unit for a displacement sensor such that the amp units constitute an amp isolated type of displacement sensor, and a transmission line connected to each amp unit constituting the amp unit row and transmitting measurement data generated in each amp unit downstream in direction of the extension unit, wherein the extension unit is configured to be connected to and provided adjacent to the amp unit positioned at an end of the amp unit row on the downstream of the transmission line in the amp unit row, the extension unit comprising: a measurement data accumulation memory in which the measurement data is accumulated; a measurement data acquiring part adapted to acquire measurement data coming through the transmission line and accumulating it in the measurement data accumulation memory; a measurement data accumulation memory in which the measurement data is accumulated; a measurement data acquiring part adapted to acquire measurement data coming through the transmission line and accumulating it in the measurement data accumulation memory; the extension unit being characterized by further comprising: a data analyzing part adapted to analyze the series of measurement data accumulated in the measurement data accumulation memory according to a predetermined algorithm; a determining part adapted to determine a result analyzed by the data analyzing part; and an output part adapted to output a control signal corresponding to a result determined by the determining part, to the outside. a data analyzing part adapted to analyze the series of measurement data accumulated in the measurement data accumulation memory according to a predetermined algorithm; a determining part adapted to determine a result analyzed by the data analyzing part; and an output part adapted to output a control signal corresponding to a result determined by the determining part, to the outside.