Dynamic power control for a two wire process instrument

摘要

A process instrument includes a transducer, a two wire interface, a microprocessor, a digital to analog converter, a first control circuit, and a second control circuit. A current passing through the two wire interface indicates a condition of the transducer. The microprocessor is interfaced with the transducer. The digital to analog converter receives a signal from the microprocessor indicating a current value. The first control circuit is coupled to the digital to analog converter and adapted to control the current passing through the two wire interface to the current value. The second control circuit is coupled to the digital to analog converter and supplies current to a secondary load.

主权项

1. A method for controlling power consumption of a process instrument comprising:
determining a desired total power consumption for the process instrument; calculating a value for a control signal related to the desired total power consumption; supplying the control signal to a primary power control circuit; supplying the control signal to a secondary power control circuit; adjusting a power consumption of a secondary load, using the secondary power control circuit, to a portion of the desired total power consumption; and adjusting a power dissipation in a shunt resistor, using the primary power control circuit, to cause the total power consumption for the process instrument to equal the desired total power consumption.