PURPOSE: To obtain at a low cost a titled device high in accuracy and reliability by calculating the sum of a signal proportional to a dielectric constant, and a signal related to the product of the dielectric constant and measured pressure and differential pressure, and obtaining the zero point variation and span variation compensating signals.

CONSTITUTION: A signal related to electrostatic capacities C1, C2 varied in response to a differential pressure is inputted to a detecting circuit 11. The signal related to the electrostatic capacities C1, C2 from the detecting circuit 11 and a signal related to a pressure and a differential pressure are led to a compensating signal operating circuit 19, and the sum with a zero point variation compensating signal and a span variation compensating signal being proportional to a dielectric constant is calculated, added to an output signal of the operating circuit 19 at an adding point 20, and a zero point variation and a span variation due to variations of a temperature and a static pressure are compensated at the same time.