A sensor apparatus is disclosed. A sense circuit is provided to convert inputted physical quantity to electrical signal. An amplifier amplifies an analog signal outputted from the sense circuit. An A/D converter converts the output signal of the amplifier to digital data. A sensing interval setup unit sets a sensing interval for the sense circuit. A power supply unit supplies electric power to the sense circuit, the amplifier and the A/D converter. The amplifier and the A/D converter constitute an analog signal processing unit. A power supply control unit is provided to control the power supply unit. A storage unit stores the digital data outputted from the A/D converter every sensing interval of the sensing interval. A data value change judgment unit changes the setup of the sensing interval by the sensing interval setup unit. The data value change judgment unit also changes the control mode of the power supply control unit in response to judgment of value change between a plural number of digital data which are designated from the digital data being stored in the storage unit.