The thermal mass meter measures Gas/Air flow based upon the concept of convective Heat Transfer. Either in-line flow bodies or insertion-style probes of the meter support two sensors that interface with the gas being measured. The sensors are RTD's, consisting of extremely durable reference-grade platinum Windings clad in a protective 316 SS or Hastelloy C enclosure. One of the RTD is heated by an integrated circuit and functions as the flow sensor, while a Second RTD acts as the reference sensor, and determines the Gas/Air temp. As media flows by the heated sensor, flowing gas molecules transport heat Away from the sensor and as a result, the sensor cools and the energy is lost. The circuit balance is disrupted, and the temperature difference AT between the heated RTD and the reference sensor has been altered. Within a second, the circuit restores the lost energy by heating the flow sensor, to adjust the overheat temperature. The electrical power required to sustain this overheat denotes the flow signal.
