Polycrystalline Silicon Cryogenic Sensor for Standard Transmitters
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Solution Overview
Problem
Existing process variable transmitters struggle to accurately measure cryogenic temperatures due to small resistance changes in typical RTD sensors, requiring modifications to circuitry and are not compatible with cryogenic applications like liquid hydrogen storage.
Innovation Solution
A cryogenic temperature sensor using polycrystalline silicon with optimized doping and dimensions, packaged with a metal probe housing and substrate, provides a resistance range compatible with standard transmitters, offering high sensitivity and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a typical RTD sensor is used to measure cryogenic temperature, then the sensor can operate at low temperatures, but the resistance change is too small to be accurately measured by existing transmitters
Solution Approach 1:
The patent changes the material parameter of the RTD sensor from traditional metals (platinum, copper, nickel) to polycrystalline silicon, which exhibits significantly different electrical resistance characteristics at cryogenic temperatures. This material substitution transforms the sensor's resistance-temperature relationship, producing measurable resistance changes that existing transmitter circuitry can accurately detect and process.
2Measurement precision
If the transmitter circuitry is modified to measure small resistance changes, then cryogenic temperature measurement becomes possible, but the device complexity and cost increase
Solution Approach 1:
By changing the sensor material to polycrystalline silicon, the electrical resistance parameters at cryogenic temperatures fall within the measurement range of existing standard transmitter circuitry. This eliminates the need for specialized low-resistance measurement circuits, maintaining device simplicity while achieving cryogenic measurement capability.
Solution Approach 2:
The polycrystalline silicon RTD sensor is designed to be compatible with existing standard transmitter devices, allowing the same transmitter hardware to serve both conventional temperature measurement applications and cryogenic temperature measurement applications without requiring different circuit designs.
3Measurement precision
If a specialized cryogenic sensor is developed, then accurate low temperature measurement is achieved, but the manufacturing cost increases
Solution Approach 1:
The patent utilizes polycrystalline silicon, a material that can be manufactured using established semiconductor fabrication processes. This approach leverages existing manufacturing infrastructure and material availability, avoiding the need for specialized cryogenic sensor fabrication techniques, thereby controlling production costs while achieving accurate cryogenic measurements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The polycrystalline silicon sensor achieves accurate cryogenic temperature measurements within the range of existing transmitters, extending from 3 K to 473 K, reducing costs and eliminating the need for circuit modifications.
Implementation Method 1
The cryogenic temperature sensor has an electrical resistance which changes in response to changes in a cryogenic temperature
Data Source
AI summary
A process variable transmitter for sensing a cryogenic temperature in an industrial process includes a cryogenic temperature sensor configured to be thermally coupled to an industrial process. The cryogenic temperature sensor has an electrical resistance which changes in response to changes in a cryogenic temperature and the industrial process is at the cryogenic temperature. Resistance measurement circuitry is electrically coupled to the cryogenic temperature sensor and measures a sensor resistance over a resistance range and responsively provides an output related to temperature based upon the measured resistance. Transmitter output circuitry coupled to the measurement circuitry to transmits information related to the cryogenic temperature to a remote location. The cryogenic temperature sensor comprises a polycrystalline silicon sensor including a dopant such that the cryogenic temperature sensor has an electrical resistance which changes over a cryogenic temperature range which is within the sensor resistance range of the measurement circuitry.