TRANSMITTER WITH MAGNETIC ZERO/SPAN ACTUATOR

摘要

A transmitter for use in a process control system has externally accessible actuators for permitting external adjustment of the zero and span (or full scale) settings of the transmitter . the transmitter has an explosion-proof housing which includes an interior chamber in which transmitter circuitry is located. Each of the actuators includes a movable magnet which operates a magnetic reed switch located within the interior chamber of the housing through a wall of the housing . Each of the magnets is mounted on a movable actuator which extends into a blind hole in a wall of the housing . By moving the magnet within its hole , the corresponding reed switch can be changed from a non-actuated to an actuated state. When the zero reed switch is actuated, the transmitter circuitry adjusts its output so that the present value of the parameter represents a process zero. When the span (or full scale) reed switch is actuated, the transmitter circuitry adjusts its output so that the present value of the sensed parameter represents a process maximum.