Sensor and method of measuring mass flow non-intrusively

A method of non-intrusively measuring mass flow of a medium flowing through a tube, said method comprising the steps of:

• disposing a probe having a predetermined length along an external wall of said tube;
• heating said first probe at a first point along the length of said probe;
• measuring a temperature Th of said probe at said first point;
• measuring another temperature Tt of said probe at a second point along the length of said probe;
• measuring an ambient temperature Ta along the external wall of said tube a distance away from said probe;
• and
• measuring said mass flow based on a ratio of temperature differential measurements (Th−Ta)/(Tt−Ta).

A non-intrusive sensor for measuring mass flow of a medium flowing through a tube, said sensor comprising:

• a thermocouple housing having a predetermined length wrapped about a circumference of an external wall of said tube and in thermal contact therewith;
• a heating element disposed at one end of said housing for applying heat to said housing;
• a first thermocouple disposed at said one end for measuring a temperature Th of said housing at said one end;
• a second thermocouple disposed at a point along the length of said housing for measuring a temperature Tt of said housing at said point;
• a third thermocouple disposed along the external wall of said tube a distance away from said housing for measuring an ambient temperature Ta;
• wherein the first, second and third thermocouples being interconnected to effect temperature differential measurement signals (Th−Ta) and (Tt−Ta);
• and
• analog circuitry coupled to said temperature differential measurement signals for generating a mass flow signal based on a ratio of temperature differential signals (Th−Ta)/(Tt
• −Ta).