Self-regulating PTC Heating Elements for TAT Probe Accuracy
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Solution Overview
Problem
Existing TAT probes face challenges in accurately measuring total air temperature while minimizing de-icing heat error, particularly at high speeds, and require complex electronics and additional sensing elements to control heat transfer, which increases complexity and reduces robustness.
Innovation Solution
A TAT probe utilizing very high positive temperature coefficient (PTC) heating elements that are self-regulating and self-limiting, eliminating the need for electronic control, and incorporating a notched intake port and tubular heat shield to prevent ice buildup and minimize heat transfer to the airflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heaters are mounted inside the TAT probe to prevent ice buildup, then the probe remains ice-free and operational, but heat transfer into the stagnated air increases causing measurement error
Solution Approach 1:
The heating element is segmented into multiple sections along the probe body, with different sections activated based on environmental conditions. This allows selective heating of only the portions of the probe that require it, minimizing heat transfer to the air intake region while maintaining ice-free operation on the exterior surfaces.
Solution Approach 2:
The probe employs different thermal characteristics in different regions: the air sensing region uses high thermal conductivity materials to quickly equalize temperature with ambient air, while the exterior heating sections use controlled thermal properties to prevent ice buildup. This local differentiation allows the heated portions to stay ice-free while the sensing region maintains measurement accuracy.
2Measurement precision
If additional sensors and electronic control systems are added to minimize de-icing heat error, then temperature measurement accuracy improves, but device complexity increases
Solution Approach 1:
The heating system is designed to be self-regulating through the natural thermal feedback between the heated probe body and the air intake region. The high thermal conductivity of the air sensing region automatically equalizes temperature differences without requiring external sensors or control circuits. The system self-adjusts based on environmental conditions, eliminating the need for complex electronic control while maintaining measurement accuracy.
3Measurement precision
If the probe is designed to minimize the influence of the heated housing on air sensing elements, then measurement accuracy improves, but the ability to prevent ice buildup on the probe exterior is reduced
Solution Approach 1:
The heating element is divided into multiple sections along the probe body, with exterior heating sections positioned away from the air intake region. This segmentation allows independent control of de-icing function and measurement accuracy, enabling the exterior to be heated for ice prevention while the sensing region remains thermally isolated.
Solution Approach 2:
The heating strategy transitions from uniform heating to spatially differentiated heating along the length of the probe. By positioning heating sections at the exterior portions and using the natural thermal gradient along the probe axis, the system addresses ice prevention in one dimension (exterior surfaces) while protecting the sensing region in another dimension (air intake area) from excessive heat influence.
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 solution provides a robust, low-complexity, electronics-free TAT probe with high accuracy and reduced de-icing heat error, maintaining temperature measurement precision across a wide range without additional electronic components.
Implementation Method 1
A TAT probe utilizing very high positive temperature coefficient (PTC) heating elements
Implementation Method 2
very high positive temperature coefficient (PTC) heating elements that are self-regulating and self-limiting
Implementation Method 3
incorporating a notched intake port and tubular heat shield to prevent ice buildup and minimize heat transfer to the airflow
Data Source
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AI summary
A total air temperature (TAT) probe having a self-regulating heating system is provided. A TAT probe housing includes at least one heating cavity that is located proximate to a tip of the TAT probe. A heating element is received within the at least one heating cavity. The heating element is composed from a flexible material with a very high positive temperature coefficient (PTC) that provides non-linear resistance with temperature with generally relatively low electrical resistances at temperatures below freezing and relatively high electrical resistances above freezing. A power source is coupled to the heating element. The very high PTC material of the heating element causes less power to be drawn by the heating element from the power source at higher temperatures above freezing than the power drawn by the heating element from the power source at lower temperatures below freezing to maintain a desired temperature of the TAT probe.