Apparatus for transmitting pressure differential signals, transmitter in a bifilar current loop circuit communication system, fixed module having a pressure transfer function, and compensation for stray capacitance in a transmitter and variation of a capacitance during manufacturing.

摘要

A two wire transmitter responsive to a pressure differential sensor includes a fixed module and a removable module. The fixed module is adapted for connection to an analog removable module having a compensation capacitance MACDA or a digital removable module having compensation capacitance CDD. Capacitance compensation circuitry is included in the fixed module which includes a compensation capacitance CDM which is selected whereby MACDA equals CDD when the analog removable module and the digital removable module are calibrated. This provides a pressure transfer function which is more linearized and less susceptible to temperature variations.