Thermal Diffusivity Measurement Using Pulsed and Modulated Laser Heating
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Solution Overview
Problem
Existing thermal diffusivity measuring devices face challenges in achieving low measurement uncertainty over the full temperature range, particularly for samples with changing thermal diffusivity during measurement.
Innovation Solution
A thermal diffusivity measuring device using a continuous wave laser with intensity-modulated laser beam and a pulsed laser or flash lamp, combined with an evaluation unit to calculate thermal diffusivity from time-dependent infrared radiation intensity, allowing for measurements with reduced uncertainty by employing both the light pulse and Angstrom methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light source uses a pulsed laser or flash lamp for the light pulse method, then thermal diffusivity can be measured, but measurement uncertainty increases for samples with changing thermal diffusivity during heating
Solution Approach 1:
The patent combines both the light pulse method and the Angström method in a single measuring device, allowing the system to switch between or combine results from both methods. This merger enables reliable thermal diffusivity measurement across the full temperature range by compensating for the limitations of each individual method when used alone.
Solution Approach 2:
The patent changes the measurement parameter by using two different excitation approaches (pulsed light for light pulse method vs. modulated continuous light for Angström method) and selects or combines results based on the thermal diffusivity characteristics of the sample, thereby adapting to samples with changing thermal diffusivity during heating.
2Measurement precision
If the Angström method is used with modulated laser beam, then thermal diffusivity measurement is possible, but measurement uncertainty remains high for temperature-dependent measurements
Solution Approach 1:
The patent integrates both the light pulse method and the Angström method into one device, combining their respective strengths. This allows the system to achieve high measurement precision across the full temperature range while managing device complexity through unified control and evaluation of both measurement approaches.
3Reliability
If samples irreversibly change during heating, then thermal diffusivity varies during measurement, but measurement uncertainty increases
Solution Approach 1:
The patent adapts the measurement approach by switching between or combining results from the light pulse method and the Angström method based on the sample's thermal diffusivity characteristics. This parameter change strategy maintains measurement reliability and accuracy even when samples irreversibly change during heating.
Solution Approach 2:
The evaluation unit automatically calculates thermal diffusivity and can determine which measurement method (light pulse or Angström) provides more reliable results for the current sample conditions, effectively using feedback to select or combine the most appropriate measurement data.
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 thermal diffusivity measurement with low uncertainty, even for samples that irreversibly change during heating, by minimizing systematic deviations and ensuring reliable results through automated calculation and method selection.
Implementation Method 1
a continuous wave laser (46), designed to emit an intensity-modulated laser beam (48), the intensity of which is modulated with an intensity modulation frequency fI
Implementation Method 2
automatically calculates the thermal diffusivity of the sample on the basis of the time-dependent infrared radiation intensity
Implementation Method 3
an infrared sensor (24) for time-dependent detection of an infrared radiation intensity I22 emitted due to the irradiation of the sample with the pulse of light
Data Source
AI summary
A thermal diffusivity measuring device includes a sample holder, a light source, e.g., pulsed laser or flash lamp, designed to emit a pulse of light of a predetermined impulse energy, an optical system for directing the pulse of light in a light path onto the sample in the sample holder, an infrared sensor for time-dependent detection of an infrared radiation intensity emitted by the sample, and an evaluation unit designed to automatically calculate the thermal diffusivity of the sample on the basis of the time-dependent infrared radiation intensity. In addition, the light source may have a continuous wave laser that is designed to emit an intensity-modulated laser beam, the intensity of which is modulated with an intensity modulation frequency. The light source is arranged to emit the laser beam along a light path. The evaluation unit is designed to automatically calculate the thermal diffusivity of the sample on the basis of the time-dependent infrared radiation intensity and the intensity-modulation frequency.