A valve assembly comprising: a valve housing; a regulating member mounted within a bore of a valve housing , the regulating member being moveable between a plurality of open positions where fluid flow is permitted through a port (310a-310d) of the valve housing and a closed position where fluid flow is blocked through the port (310a-310d); a solenoid linear actuator comprising a solenoid including a coil and an armature positioned within the coil , adapted to linearly drive the regulating member between the closed position and the plurality of open positions; a magnetometer , the magnetometer being adapted to measure a magnetic flux through at least a portion of the solenoid linear actuator, wherein a magnetic flux value measured by the magnetometer corresponds to a linear position of the regulating member relative to the port (310a-310d); a current meter that measures electrical current in the solenoid linear actuator, wherein measured electrical current values measured by the current meter in the solenoid linear actuator are mapped to expected magnetic flux values measured by the magnetometer ; an electronic control unit which electrically connects to the solenoid coil and is adapted to direct current to the coil to control operation of the valve , characterised in that the electronic control unit includes a module housing that houses the magnetometer and the current meter operatively coupled thereto, the electronic control unit being mechanically and electrically connected to the solenoid coil of the solenoid linear actuator by an electrical connector that is received within a socket corresponding to the solenoid coil , wherein due to a fixed mechanical coupling of the solenoid to the module housing , there is a fixed or substantially fixed distance between the magnetometer and the coil of the solenoid . a valve housing; a regulating member mounted within a bore of a valve housing , the regulating member being moveable between a plurality of open positions where fluid flow is permitted through a port (310a-310d) of the valve housing and a closed position where fluid flow is blocked through the port (310a-310d); a solenoid linear actuator comprising a solenoid including a coil and an armature positioned within the coil , adapted to linearly drive the regulating member between the closed position and the plurality of open positions; a magnetometer , the magnetometer being adapted to measure a magnetic flux through at least a portion of the solenoid linear actuator, wherein a magnetic flux value measured by the magnetometer corresponds to a linear position of the regulating member relative to the port (310a-310d); a current meter that measures electrical current in the solenoid linear actuator, wherein measured electrical current values measured by the current meter in the solenoid linear actuator are mapped to expected magnetic flux values measured by the magnetometer ; an electronic control unit which electrically connects to the solenoid coil and is adapted to direct current to the coil to control operation of the valve , characterised in that the electronic control unit includes a module housing that houses the magnetometer and the current meter operatively coupled thereto, the electronic control unit being mechanically and electrically connected to the solenoid coil of the solenoid linear actuator by an electrical connector that is received within a socket corresponding to the solenoid coil , wherein due to a fixed mechanical coupling of the solenoid to the module housing , there is a fixed or substantially fixed distance between the magnetometer and the coil of the solenoid . <EOS>