The EVD400 driver is an evolved PID control system with driver for stepper motors, specifically designed for controlling and positioning electronic expansion valves in refrigerant circuits: its sophisticated control functions are based on dynamic comparison between the input signal and the reference value, either the superheat (complete with protection functions) or another measurement (pressure or temperature).
CAREL offers several different versions of the device, which can moreover manage valves made by other manufacturers; EVD 400 can work either in stand-alone mode, connected to a supervisor to manage the fundamental parameters, or connected in a LAN with other CAREL controllers.