초록 ▼

A transmitter in a process control system transmits a pressure over a process control loop. The transmitter includes I/O circuitry, compensation circuitry and an absolute pressure sensor. The I/O circuitry transmits information over the process control loop. Compensation circuitry receives a pressur

A transmitter in a process control system transmits a pressure over a process control loop. The transmitter includes I/O circuitry, compensation circuitry and an absolute pressure sensor. The I/O circuitry transmits information over the process control loop. Compensation circuitry receives a pressure related signal and responsively controls the I/O circuitry to transmit pressure information on the loop. The absolute pressure sensor includes a cavity which deforms as the sensor deflects in response to an applied pressure. A sensor in the cavity provides the pressure related signal to the compensation circuitry in response to the deformation.

대표청구항 ▼

[ What is claimed is:] [6.] A capacitance pressure sensor, comprising:a first pressure sensor substrate of sapphire with a first flat polished surface having a first cavity etched therein and a first capacitor plate in the cavity; anda second pressure sensor substrate of sapphire with a second capac

[ What is claimed is:] [6.] A capacitance pressure sensor, comprising:a first pressure sensor substrate of sapphire with a first flat polished surface having a first cavity etched therein and a first capacitor plate in the cavity; anda second pressure sensor substrate of sapphire with a second capacitor plate and with a second flat polished surface fusion bonded to the first flat polished surface;wherein the first cavity is etched with hot POCl.sub.3 gas and the first flat polished surface is fusion bonded to the second flat polished surface by heating between 68% and 95% of the melting point absolute temperature of sapphire.