Radiation Thermometer Water Vapor Absorption Filter
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Solution Overview
Problem
Conventional radiation thermometers are affected by water vapor absorption in the atmosphere, particularly at high temperatures, which compromises measurement accuracy, especially in environments like furnaces where air's capacity to hold water vapor increases rapidly.
Innovation Solution
Incorporating radiation filtering means that block wavelengths between approximately 0.92 and 0.98 microns in the optical input path of the radiation thermometer, while maintaining sensitivity to radiation within the 0.85 to 1.1 micron range, reduces the impact of water vapor absorption and provides improved measurement capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a silicon detector is used to measure radiation in the 0.85 to 1.1 micron waveband, then the thermometer is sensitive to temperature and insensitive to emissivity, but water vapor absorption bands in this waveband compromise measurement accuracy at high temperatures
Solution Approach 1:
The patent extracts and removes the harmful water vapor absorption band (0.92-0.98 microns) from the detected radiation spectrum by inserting a band-rejection filter in the optical path. This filter specifically blocks the problematic wavelengths while allowing other wavelengths in the 0.85-1.1 micron range to pass through to the silicon detector, thereby eliminating the interference without sacrificing the detector's temperature sensitivity.
Solution Approach 2:
The patent modifies the spectral transmission parameters of the optical path by introducing a filter with specific wavelength-selective properties. The filter is designed to reject radiation in the 0.92-0.98 micron range while maintaining transmission in adjacent bands, effectively changing which wavelengths reach the detector and thus eliminating water vapor absorption effects on the measurement.
2Object-affected harmful factors
If a daylight blocking filter is used to remove radiation up to 0.85 microns, then interference from Sun and visible lamps is eliminated, but the working waveband is reduced to approximately 0.85 to 1.1 microns
Solution Approach 1:
The patent segments the filtering function into two distinct stages: first, a daylight blocking filter removes radiation below 0.85 microns to eliminate interference from the Sun and visible lamps; second, a band-rejection filter removes only the specific problematic water vapor absorption band (0.92-0.98 microns) while preserving other wavelengths. This segmented approach maintains adaptability by preserving as much of the useful waveband as possible while addressing specific interference issues.
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 effectively eliminates the effect of water vapor absorption, maintaining the thermometer's temperature measurement capability and performance similar to conventional instruments, while reducing interference from other radiation sources.
Implementation Method 1
IR incident on a photonic detector causes electrons to be excited into higher energy states. This manifests itself typically as either a change in resistivity of the detector element or, if the detector contains a pn junction, as a photoelectric current.
Implementation Method 2
filtering means are provided in the optical input path and which are arranged to block radiation having a wavelength between approximately 0.92 and 0.98 microns
Implementation Method 3
Infrared radiation (IR) is emitted by all materials at temperatures above absolute zero. This energy travels in the form of electromagnetic waves with wavelengths typically in the range 0.7 to 20 microns.
Data Source
AI summary
A radiation thermometer comprising a radiation detector and an optical input path arranged to direct radiation from an object of interest to the radiation detector is disclosed. The radiation detector is adapted to output a signal related to the radiation received from the object of interest, and a processor is adapted to generate temperature measurements from the signal. Filtering means are provided in the optical input path which are arranged to block radiation having a wavelength between approximately 0.92 and 0.98 microns.