Eurotherm 659B Position Converter
The Eurotherm 659B is a resistance to position converter which is typically located electrically between a re-transmitting slide-wire and an electric actuator. The primary application of the 659 is in tandem operation of electric actuators.
Triac switching in the 659 drives the actuator through an angular direction corresponding to the position of the master control slide-wire. A built-in potentiometer in the actuator, with wiper arm driven by the output shaft, provides a correctional feedback signal to the 659 to provide proportional action.
The triac switching and feedback continues until balance is reached. Dead-band, which is the difference between the input signal which will drive the motor one way and the level which will drive it the other way, is adjustable from 0.1% to 8% of the master control slide-wire span.
A dead-band is recommended for less critical processes, since it will reduce mechanical wear on the actuator.