at least one of a circuit and a processor receiving an output value from a sensor and outputting a measured value of a physical quantity associated with an action of an external force applied to the sensor, the at least one of a circuit and the processor being configured to:

calibrate the output value from the sensor to output the measured value by specifying and using a relational expression that associates the output value with the physical quantity, the relational expression including a formula that has a predetermined parameter, the relational expression being used to calculate, according to an offset value, the physical quantity from the output value, the offset value being an average of a plurality of the output values acquired at fixed time intervals when the sensor is free of contact;

derive a function for calculating a parameter value for the predetermined parameter from the offset value, the function being generated from the output value obtained when a known external force of predetermined magnitude is applied to the sensor and the offset value having been acquired in a preceding step; and

determining the parameter value using the function to calculate the parameter value from another offset value acquired in a state in which the sensor is disposed on a predetermined site where the external force is to be measured.