Instrumentation and monitoring systems employing differential temperature sensors

An instrumentation system for monitoring fluid conditions within the interior of a pressure vessel, comprising:

• at least one duplex differential temperature sensor having a pair of first and second substantially identical probes integrally interconnected at first ends thereof and extending in parallel axial relationship and spaced by a bilateral plane and adapted to be mounted to the sidewall of a pressure vessel with the probes in communication through a penetration in the sidewall with the fluid state within the interior of the pressure vessel, each said probe incorporating a heater element and a pair of associated temperature sensing elements, the heater element and a selected temperature sensing element of said first probe and a selected temperature sensing element of said second probe comprising a first differential temperature sensor component and the heater element of the said second probe and a selected temperature sensing element thereof and a selected temperature sensing element of said first probe comprising a second differential temperature sensor component:
• heater controller means for selectively supplying electrical power to said respective heater elements of said first and second probes of said sensor, the selected heater element heating the corresponding probe and raising the temperature thereof, in the absence of a fluid in the line contacting and dissipating heat from the probe, and thereby producing a difference between the temperatures sensed by the selected temperature sensing elements associated with the respective, heated and unheated probes of the sensor, said heater controller means further comprising means for determining operability of each of the heater elements of the sensor and producing an inoperative heater element output upon determining the inoperability of a heater element;
• temperature sensing element controller means for selecting the temperature sensing elements of the first and second probes and for monitoring the sensed temperature outputs of the selected temperature sensing elements, for providing a differential temperature output indicative of the difference between the respective, sensed temperature outputs of the selected temperature sensing elements of the first and second probes, and for determining the operability of the selected temperature sensing elements of the first and second probes;
• and
• system control means for controlling said heater and temperature sensing element controller means to select the heater and sensing elements of each sensor corresponding to the first sensor component thereof in a normal monitoring mode of the instrumentation system, for defining a normal differential temperature output condition, for detecting an alarm condition in the normal monitoring mode when the differential temperature output of the selected, first sensor component differs from the normal differential temperature condition, and for producing an alarm output in response to detecting an alarm condition;
• display means responsive to an alarm output of said system control means for producing an alarm display identified with the corresponding sensor;
• and
• said system control means being responsive to an inoperative heater element output from said heater controller for the selected heater of said first probe, corresponding to the first sensor component, for automatically causing said heater controller to select the heater element of the second probe and supply electrical power thereto and thereby to switch from the first to the second sensor component of the given sensor.