A merchandise sensor for protecting an item of merchandise displayed on a merchandise display security device from theft includes sensor electronics and a sensor element operably coupled to the sensor electronics. The sensor element provides an output value in an initial stable state before an interaction state and in a subsequent stable state following the interaction state. The sensor electronics compares the output value of the sensor element in the subsequent stable state and the output value of the sensor element in the initial stable state to determine whether a change in the output value indicates an alarm condition. In the event that the output value of the sensor element in the subsequent stable state is not within a predetermined tolerance bandwidth of the output value of the sensor element in the initial stable state, the sensor electronics activates an alarm in response to the alarm condition.