A thermal mass dispersion flow rate sensing transducer and transducer assembly or instrument for improved functional life of the transducer without degradation in sensing accuracy. Several aspects of the transducer components and structure reduce thermal leakage within the transducer so the sensor (RTD) output signal is accurately transmitted to the signal processor, resulting in precise ΔT determinations and consequent precise determinations of mass flow rate of the fluid flowing in the conduit. Additionally, the same components and structure also have long life without appreciable degradation, thereby delaying any basis for the need for recalibration of the instrument.