Patent ID: 9182256
Filing Date: 2015-11-10
Classification: G01D,G05B

Abstract:
1. A two-wire process variable transmitter for use in an industrial process, comprising: terminals configured to couple to a two-wire process control loop; a process variable sensor configured to sense a process variable of a process fluid of the industrial process; output circuitry coupled to the terminals configured to provide an output on the two-wire process control loop which is related to the sensed process variable; current measurement circuitry coupled to the terminals configured to measure a loop readback current flowing through the two-wire process control loop and a shunt current; terminal voltage measurement circuitry coupled to the terminals configured to measure a voltage related to a terminal voltage of the process variable transmitter, the terminal voltage comprising a voltage measured across the terminals of the two-wire process variable transmitter; a microprocessor configured to perform loop diagnostics on the two-wire process control loop based upon the measured loop readback current, the measured shunt current and terminal voltage and calculate a loop resistance based upon a difference in the measured terminal voltage measured with two different current levels flowing through the two-wire process control loop and a difference in the measured loop readback current with the two different current levels flowing through the two-wire process control loop.