CALIBRATING METHOD OF STATIC-PRESSURE ERROR OF CAPACITANCE TYPE DIFFERENTIAL PRESSURE TRANSMITTER

摘要

PURPOSE:To enable zero-point calibration by static pressure at low cost by a method wherein one capacitor made of an electrostrictive material is connected to a region whereto a static pressure is applied and the other to a region whereto no static pressure is applied while two capacitors for adjusting a calibration amount are connected outside. CONSTITUTION:Electrostatic capacities CA and CB of capacitors 11 and 12 are varied by differential pressure. The capacitors 11 and 12 are connected in parallel with capacitors 13 and 15, and 14 and 16, respectively as shown in the figure. The capacitors 13 and 14 are provided with electrodes on the opposite surfaces of a thin plate of an electrostrictive material. the capacitor 13 is set in a region receiving a static-pressure sustaining region, and the dielectric constant thereof is varied by a static pressure. The capacitors 14-16 are set in a region receiving no static pressure. Composite electrostatic capacities CH and CL between C and (a) and C and (b) are expressed by formulas I and II respectively, and a differential pressure is detected by detecting CH and CL. Capacities CSA and CSB are selected appropriately so that the difference between the electrostatic capacities may not be varied by a change in the static pressure. By this method, zero-point calibration is facilitated.