Capacitive Temperature Sensing in Planar Heating Devices
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Solution Overview
Problem
Existing heating devices for liquid media face challenges in improving insulation properties for accurate temperature measurement, particularly in using temperature-dependent capacitive and resistive properties of dielectric layers.
Innovation Solution
A heating device with a flat carrier, a temperature-dependent dielectric layer, and electrodes forming capacitances, along with a base insulation layer to secure heating conductors and isolate them from the carrier and medium, allowing for capacitive and resistive property changes to be detected for temperature measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dielectric layer with temperature-dependent capacitive properties is used for temperature measurement, then temperature measurement capability is improved, but insulation properties deteriorate
Solution Approach 1:
The patent divides the measurement system into two separate capacitor structures: a first capacitor with electrodes extending beyond the heating conductor for temperature measurement, and a second capacitor formed by the heating conductor itself. This segmentation allows the measurement function to be separated from the heating function, enabling temperature measurement while maintaining insulation integrity through the dielectric layer.
Solution Approach 2:
The dielectric layer serves as an intermediary between the electrodes and the heating conductor, providing both the temperature-dependent capacitive properties needed for measurement and the insulation required for safety. The layer's dielectric properties enable capacitance changes to be detected while preventing direct electrical contact between measurement and heating circuits.
2Measurement precision
If electrodes are placed close to heating conductors for temperature measurement, then measurement sensitivity is improved, but electrical interference increases
Solution Approach 1:
The dielectric layer acts as an intermediary that allows the electrodes to be positioned close to the heating conductor for sensitive measurement while preventing electrical interference. The layer's insulating properties block harmful electrical fields while its dielectric properties enable capacitance-based temperature detection.
Solution Approach 2:
The patent extracts the measurement function from the heating conductor itself by providing separate dedicated electrodes that extend beyond the heating conductor. This allows the measurement system to operate independently from the heating circuit, reducing electrical interference while maintaining measurement sensitivity through close proximity positioning.
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
This configuration enables precise temperature measurement by evaluating changes in capacitance and resistive properties, enhancing insulation and safety while minimizing interference and parasitic effects, allowing for effective temperature monitoring and control.
Implementation Method 1
a dielectric layer (17), in particular a glass layer or a glass-based layer, having capacitive properties that change as a function of temperature
Implementation Method 2
The dielectric layer is advantageously a glass layer or a glass-based layer with εr that changes as a function of temperature
Implementation Method 3
The measuring device is connected to the two electrodes and is designed to detect a change in capacitance at the electrodes, this change in capacitance being temperature-dependent
Implementation Method 4
a heating conductor (27) that is applied to the base insulation layer (25)
Data Source
Figure 1~3
Figure 4~5
AI summary
A heating device comprises a planar support, at least one heating conductor, a measuring device, a dielectric layer over or on the support, two adjacent electrodes over or on the dielectric layer, and a base insulating layer over the two electrodes, with the at least one heating conductor being applied over the base insulating layer. The dielectric layer exhibits temperature-dependent capacitive properties. The measuring device is connected to the two electrodes and is configured to detect a temperature-dependent change in capacitance at the electrodes and to evaluate this as a measure of a temperature change at the heating device.