Sierra Instruments’ Innova-Switch represents state-of-the-art in liquid flow switching or liquid level control and continues Sierra tradition of providing highest quality mass flow meters and controllers in the industry. Flow and level detection is accomplished by using high-resolution thermal differential technique. The sensor consists of a pair of matched Resistance Temperature Detectors (RTD’s). One RTD is self-heated using a constant DC current. The other RTD is unheated and provides an accurate process temperature reference. The thermal differential created between the reference and the heated RTD pair is a function of the density and/or velocity of the media with which the sensor is in contact.