To provide a sensor capable of easily conducting test and demonstration.

With the electromagnetic flow rate sensor 10 a signal processor 20 produces hypothetical signal instead of measured signal and outputs to a system body 50 based on the specific operation of a panel switch part 26 and so actual measurement of flow rate is not required in the case of conducting a test and demonstration and the test and the like can be easily performed. Also, the hypothetical information data group is produced in accordance with the actual information data group and one of the actual information data group and the hypothetical data group is selectively taken in an output operator (step S3 of a main program P4). So a test of the output operator can be conducted by giving a desired hypothetical information data group to the output operator.