Transmitters are Getting Smart: What's in It for You?

摘要

Field instruments incorporating microprocessors are extending the benefits of distributed control further into the plant — enhancing instrument loop performance and reliability while augmenting the tools available to operating and maintenance personnel. Increased accuracy, reduced sensitivity to ambient and process temperature and pressure, and widened rangeability can be achieved by storing profile and calibration data at the instrument, then using the information to compensate for varying operating conditions. Greater reliability and lower maintenance costs are possible using on-board diagnostics to detect faults, with bidirectional data communication to permit remote users to perform calibrations, interrogate status and adjust operating parameters, or command specified outputs as means of verifying other loop components. The low power consumption of CMOS electronics makes it possible to drive the intelligent circuits from the 4-20 mA lines already widely used for two-wire transmitters, such that the intelligent field instruments are compatible with existing plant standards.