Patent ID: 6504489
Filing Date: 2003-01-07
Classification: G08C

Abstract:
A process control transmitter having an externally accessible DC common, comprising:first, second and third externally accessible feedthrough terminals, wherein the first and second terminals are couplable to a process control loop and adapted to conduct a loop current IT through the transmitter; a series-shunt regulator having an input terminal coupled to the first terminal and a shunt current output terminal coupled to the second terminal, the series-shunt regulator conducting a load current IL and controlling the loop current IT by regulating a shunt current IS out the shunt current output terminal; and circuitry energized by the load current IL and adapted to control the loop current IT in response to a sensor signal and provide a digital signal to the third terminal that has a voltage that is regulated relative to a DC common of the circuitry that is coupled to the second terminal, whereby the digital signal is externally accessible between the second and third terminals.