Proportional valves are widely used in fluid systems for controlling the volume flow rate or fluid pressure. The actuation of this valves is done by PWM-driven proportional solenoids, which enable self-sensing position determination abilities due to air gap-dependent electrical behaviour, e. g. for condition monitoring or position controlling tasks. However, the sensor properties of conventional proportional solenoids are poor due to ambiguities caused by hysteresis effects (magnetic hysteresis, eddy currents) and saturation effects. Thus, a sensor-designed actuator was developed with very low hysteresis effects and unique position determination by using electrical sheet and a particular air gap design. This paper deals with investigations of a novel self-sensing position determination approach on a demonstrator of the sensor-designed solenoid. The advantage of this method is an online consideration of transient effects such as mean current change and armature motion as well as temperature-dependent resistance. For this, a combined evaluation of the differential inductance and flux linkage during PWM periods is proposed.