Non-invasive process fluid temperature indication

A process fluid temperature estimation system comprising:

• a mounting assembly configured to mount the process fluid temperature estimation system to an external surface of a process fluid conduit having a known thermal conductivity;
• a sensor capsule having at least one temperature sensitive element disposed therein, the sensor capsule being disposed to position the at least one temperature sensitive element proximate the external surface of the process fluid conduit;
• a terminal temperature sensor;
• measurement circuitry coupled to the sensor capsule and the terminal temperature sensor, the measurement circuitry being configured to detect an electrical characteristic of the at least one temperature sensitive element and the terminal temperature sensor that varies with temperature;
• a controller coupled to the measurement circuitry, the controller being configured to obtain at least one external surface temperature measurement from the measurement circuitry and to obtain a reference temperature from the terminal temperature sensor and to employ a heat flow calculation with the reference temperature, the external surface temperature measurement, and the known thermal conductivity of the process fluid conduit to generate an estimated process fluid temperature output;
• and
• backup logic configured to monitor status of the terminal temperature sensor and selectively provide a second reference temperature measurement from an electronics temperature sensor to the controller.