To provide a transmitter of a simple and an inexpensive configuration for providing a high precision signal which covers the entire displacement range with a single secondary conversion element even when the displacement range to be detected is large with a constant-value control range changing significantly.

The transmitter 10 comprises a detector 20 and a converter 30. Here, a pressure change in an object, which is to be detected, detected with the detector 20 is amplified/converted to the electric signal of 4-20 mA for output, based on a transfer function of polygonal line so set that linear functions of different factor are coupled, with the factor large in the range which is to be an object for constant-value control while it is small in the region before and after that, and the entire range which is to be detected is accommodated in the output range of 4-20 mA.