Abstract: A two wire current transmitter provides a current signal representative of a parameter measured by a variable reactance sensor which may be located in a hostile environment, remote from the signal conditioning and transmitter electronics through transmission circuitry from the electronics including a separate transformer winding energized by a pair of twisted cables to reduce the capacitive, inductive and resistive effects of long wires. The transformer circuitry provides power to the sensor which provides the signal conditioning and transmitter electronics a signal, representing the parameter measured, which controls the current control, to modify the total current through the same two wires used to carry power to the signal conditioning and transmitter electronics, so that the total current is representative of the measured parameter.

Abstract: A two wire current transmitter for controlling total current in two wires in accordance with the value of a parameter to be sensed which provides for an improved voltage regulator which incorporates within the voltage regulator two separate paths for start-up current of the regulator, hence, providing improved start-up characteristics for both isolated and nonisolated two wire transmitters.

Abstract: A two wire current transmitter for controlling the total current in the two wires in accordance with a value of a parameter to be sensed, which provides for substantial linearization of the electrical characteristic representative of the value of the parameter to be sensed by adjusting the current from an adjustable current control to substantially compensate for the nonlinear relationship of the parameter to be sensed versus the electrical output of the sensor of said parameter. The circuit also provides for substantial compensation for sensor lead wire effects.