The Kinetrol EL is one of the valve automation industries performing electro-pneumatic positioners available. It combines the precision and adaptability of a digital electronic control circuit with the smoothness and efficiency of Kinetrol’s proven proportional servo valve, to give the best available 4-20mA positioning performance from rotary pneumatic actuators.
The EL positioner is designed to smoothly and precisely drive a rotary or linear actuator to a position set by the 4-20 mA input signal, and then accurately hold it there until the signal changes.
Inside the EL, a microprocessor in the loop powered 4-20 mA positioner circuit reads signal via one channel of a 12-bit A-D convertor, reads the position voltage from tie pot via the second channel of the A-D convertor, and compares the two. If an error between the desired position and actual position exists, the EL changes it’s output to the servo valve in order to drive the actuator in the direction required to eliminate the error.
In sync with the movement of the actuator, the feedback pot voltage changes, and the microprocessor continually calculates how to adjust the servo valve in order to guide the actuator accurately into position. Because the servo valve is a fully-proportional device, it can be adjusted precisely and smoothly to slow the actuator to a stop exactly at the required position. Programmed in the microprocessor is an advanced algorithm that allows this critical dynamic valve adjustment to be made correctly, giving optimal results with any actuator/load combination. Slow or fast responding, high friction or low friction, high inertia or low inertia, all can be optimized by PGAIN and DAMP parameters via the positioner circuit pushbuttons. The 12-bit A-D conversion gives an amazing resolution of approximately 1/40 of a degree angular.