Patent ID: 6079276
Filing Date: 2000-06-27
Classification: G01L,Y10T

Abstract:
A pressure transmitter in a process control system for transmitting pressure on a process control loop, the transmitter comprising:a transmitter housing;a pressure sensor body of a brittle corrosion resistant material operably coupled to the housing and positioned in the housing, the pressure sensor body comprising a first portion bonded to a second portion by a fusion bond, the fusion bond substantially free of foreign material, the pressure sensor body including a cavity formed between the first and second portions, the cavity having at least one dimension which changes in response to applied pressure;first and second capacitive plates coupled to an interior wall of the cavity having a capacitance formed therebetween, the plates configured whereby a spacing between the plates changes as a function of the at least one dimension which changes in response to applied pressure;first and second electrical conductors extending from an exterior of the pressure sensor body and electrically coupled to respective first and second capacitive plates;a signal generator in the transmitter housing having a periodic output electrically coupled to the capacitance through at least one electrical conductor; andan analog to digital converter in the transmitter housing having a digitized output as a function of the capacitance;a loop interface in the transmitter housing configured to transmit a pressure related signal on the process control loop as a function of the digitized output, the interface further configured to completely power the transmitter with power received from the process control loop.