A sensor module comprising: a sensor; a notification unit configured to notify a measurement value obtained by the sensor and a value based on the measurement value; a battery configured to supply a voltage to an electric circuit including the sensor and the notification unit; a voltage measurement unit configured to measure an end-to-end voltage of the battery at a predetermined measurement interval; and a measurement interval change unit configured to change the measurement interval of the voltage measurement unit, wherein the measurement interval change unit is configured to set, in a case where the end-to-end voltage of the battery measured by the voltage measurement unit is equal to or higher than a first specified voltage value which is previously set, the measurement interval to a first time interval, and wherein the measurement interval change unit is configured to set, in a case where the end-to-end voltage of the battery measured by the voltage measurement unit is lower than the first specified voltage value, the measurement interval to a second time interval which is shorter than the first time interval; and wherein the sensor module further comprises: a load connected to the battery in parallel, a resistor value of the load being already known; a switch connected to the load in series; and a residual battery capacity estimation unit configured to estimate, in a case where the end-to-end voltage of the battery measured by the voltage measurement unit is lower than the first specified voltage value, estimates the residual battery capacity, characterized in that the residual battery capacity estimation unit is configured to calculate an internal resistance using the end-to-end voltage of the battery measured by the voltage measurement unit and Z configured to estimate the residual battery capacity using the internal resistance of the battery; and wherein the voltage measurement unit is configured to measure the end-to-end voltage of the battery when the switch is opened and closed; the sensor module further comprising a current measurement unit for measuring an electric current flowing through the load when the switch is in the closed state; wherein the residual battery capacity estimation unit is configured to calculate the internal resistance using the electric current using the end-to-end voltage of the battery when the switch is in the opened state and the electric current flowing through the load when the switch is in the closed state. a sensor; a notification unit configured to notify a measurement value obtained by the sensor and a value based on the measurement value; a battery configured to supply a voltage to an electric circuit including the sensor and the notification unit; a voltage measurement unit configured to measure an end-to-end voltage of the battery at a predetermined measurement interval; and a measurement interval change unit configured to change the measurement interval of the voltage measurement unit, wherein the measurement interval change unit is configured to set, in a case where the end-to-end voltage of the battery measured by the voltage measurement unit is equal to or higher than a first specified voltage value which is previously set, the measurement interval to a first time interval, and wherein the measurement interval change unit is configured to set, in a case where the end-to-end voltage of the battery measured by the voltage measurement unit is lower than the first specified voltage value, the measurement interval to a second time interval which is shorter than the first time interval; and wherein the sensor module further comprises: a load connected to the battery in parallel, a resistor value of the load being already known; a switch connected to the load in series; and a residual battery capacity estimation unit configured to estimate, in a case where the end-to-end voltage of the battery measured by the voltage measurement unit is lower than the first specified voltage value, estimates the residual battery capacity, characterized in that the residual battery capacity estimation unit is configured to calculate an internal resistance using the end-to-end voltage of the battery measured by the voltage measurement unit and Z configured to estimate the residual battery capacity using the internal resistance of the battery; and wherein the voltage measurement unit is configured to measure the end-to-end voltage of the battery when the switch is opened and closed; the sensor module further comprising a current measurement unit for measuring an electric current flowing through the load when the switch is in the closed state; wherein the residual battery capacity estimation unit is configured to calculate the internal resistance using the electric current using the end-to-end voltage of the battery when the switch is in the opened state and the electric current flowing through the load when the switch is in the closed state.