Process transmitter isolation compensation

An industrial process temperature transmitter for measuring a temperature of a process medium contained in a process vessel through an isolation wall, the transmitter comprising:

• a temperature sensing unit comprising:
• a process temperature sensor separated from the process medium by the isolation wall and in contact with the exterior surface of the isolation wall, the process temperature sensor configured to produce a process temperature signal based on the temperature of the process medium;
• a secondary temperature sensor configured to produce a secondary temperature signal based on a temperature at a location spaced from the process medium and the isolation wall;
• and
• processing electronics configured to produce a temperature signal that is indicative of the temperature of the process medium based on the process temperature signal and the secondary temperature signal;
• a compensation circuit configured to compensate the temperature signal for a response time of the temperature measurement, and output a compensated temperature signal;
• an output circuit configured to produce a transmitter output as a function of the compensated temperature signal;
• a stem portion having a first end attached to the process vessel and a second end that is displaced from the process vessel and the isolation wall;
• and
• a housing attached to the second end of the stem portion and containing the secondary temperature sensor.

A method for measuring a temperature of a process medium using an industrial process temperature transmitter, the method comprising:

• performing a temperature measurement of the temperature of a process medium using a temperature sensing unit including:
• sensing the temperature of the process medium through an isolation wall using a process temperature sensor comprising a thermistor;
• and
• sensing a temperature of a terminal block of the transmitter using a secondary temperature sensor;
• producing a temperature signal in response to the temperature measurement comprising processing a process temperature signal from the process temperature sensor and a secondary temperature signal from the secondary temperature sensor;
• compensating the temperature signal for a response time of the temperature measurement using a compensation circuit;
• generating a compensated temperature signal, in which the response time of the temperature measurement is reduced or eliminated, using the compensation circuit;
• and
• producing a temperature output as a function of the compensated temperature signal using an output circuit.