Resistive Heater Self-Sensing for Precise Temperature Control
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Solution Overview
Problem
Conventional resistive heating systems face challenges in accurately measuring ambient temperature without separate sensors and controlling the temperature of the resistive heating material to prevent overheating, which can degrade or destroy the material and associated insulation.
Innovation Solution
A system that uses a resistive heating material to measure ambient temperature by determining its resistance through a sense resistor and controller, allowing for precise temperature control by delivering discreet packets of electrical energy and adjusting power based on resistance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate temperature sensor (thermocouple, RTD, or thermistor) is attached to or located adjacent to the resistive heater to measure temperature, then temperature measurement capability is improved, but device complexity increases
Solution Approach 1:
The patent combines the temperature sensing function with the resistive heating element itself. The heating element's resistance is used as the sensing element to measure its own temperature, eliminating the need for separate temperature sensors. This is achieved by measuring the resistance of the heating element at different times (during heating and during sensing) and using these resistance values to determine temperature.
Solution Approach 2:
The resistive heating element serves dual functions: it acts as both the heating source and the temperature sensor. By utilizing the inherent temperature-dependent resistance property of the heating material, the system achieves multi-functionality where a single component performs both heating and temperature measurement tasks.
2Productivity
If power is continuously delivered to the resistive heating material to maintain heating, then heating effectiveness is improved, but the risk of overheating and material degradation increases
Solution Approach 1:
The patent implements periodic action by alternating between heating phases and sensing phases. During the sensing phase, power delivery is temporarily interrupted to measure the heating element's resistance and determine its temperature. Based on this temperature information, the controller adjusts subsequent heating power delivery, preventing continuous overheating and material degradation while maintaining effective heating cycles.
Solution Approach 2:
The system employs feedback control where the resistance measurement of the heating element provides real-time temperature information back to the controller. The controller uses this feedback to dynamically adjust the power delivery to the heating element, ensuring temperature remains within safe operating limits while maintaining heating effectiveness.
3Ease of operation
If the thermal transfer rate is assumed known and consistent to regulate power delivery, then power control simplicity is improved, but accuracy deteriorates when thermal transfer rate changes
Solution Approach 1:
The heating element performs self-diagnosis by using its own resistance as the sensing parameter. The system measures the resistance of the heating element directly, allowing the element to provide information about its own thermal state. This self-service approach eliminates the need for separate temperature sensors and provides accurate real-time temperature data for precise power regulation.
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
Enables accurate temperature measurement and control of the resistive heating material, preventing degradation and ensuring maximum heat delivery without damaging the material or insulation, while maintaining a target temperature.
Implementation Method 1
Electrically conductive and resistive materials can be used as heating elements. An electrically conductive material or resistive element can convert electrical energy to heat energy. That is, as a property, the electrically conductive material gets hot when electricity flows through it.
Implementation Method 2
The resistive material can be attached to an article or located such that the heat generated by the resistive material can be intentionally transferred to heat up the article.
Implementation Method 3
A resistance of the resistive heating material is a function of the temperature of the resistive heating material.
Data Source
AI summary
A heating system includes a power supply that applies a first voltage to a sense resistor in series with a resistive heating material during a first time period; and a controller that determines a temperature of the resistive heating material based on a current through the sense resistor and a second voltage across the resistive heating material during the first time period. Additionally, the controller commands the power supply to provide a third voltage to the resistive heating material during a second time period, and the third voltage is based on the temperature of the resistive heating material.