A medical device system comprises a reservoir configured to store a therapeutic fluid and a medical pump configured to deliver the therapeutic fluid from the reservoir to a patient. The system also comprises a reservoir fill level detector configured to detect a fill status of the reservoir, the reservoir fill level detector including a contact pad operably attached to the reservoir whereby the contact pad moves in a predetermined path during the emptying and filling of the reservoir. A resistor strip mounted on the inside of the chamber is in continual contact with the contact pad and the resistance of an electric current passed through the resistor strip is monitored by a processor to determine the position of a selected portion of the reservoir. The position of the reservoir is directly related to the fill status.
