Pyrometer Dark Current Measurement via Segmented Target
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Solution Overview
Problem
Conventional pyrometers face challenges in accurately measuring low target temperatures due to low photon emission, which results in a low signal-to-noise ratio, and at higher temperatures, excessive dark current generation increases noise, making it difficult to subtract dark current accurately.
Innovation Solution
A pyrometer is oriented to alternately sense target elements and null elements, generating output signals with alternating pulse widths and null widths, allowing direct measurement of dark current and enabling accurate temperature determination without modeling, using high bandwidth electronics and Fast Fourier Transform for data processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional pyrometers are used to measure low target temperatures, then temperature measurement is possible, but the signal-to-noise ratio deteriorates due to low photon emission and dark current interference
Solution Approach 1:
The target is segmented into alternating target elements and baseline elements, allowing the pyrometer to separately measure target signal and dark current signal during different time intervals, thereby improving signal-to-noise ratio and measurement accuracy
Solution Approach 2:
The dark current signal is extracted from the total signal by measuring during null intervals when the pyrometer views only baseline elements, enabling accurate subtraction of dark current from target signal measurements
2Temperature
If conventional pyrometers operate at higher temperatures, then measurement range is extended, but noise increases due to excessive dark current generation
Solution Approach 1:
The measurement cycle is segmented into target viewing intervals and null intervals, allowing separate acquisition of target signal and dark current signal even at high temperatures where dark current is significant
Solution Approach 2:
The measured dark current signal from null intervals is fed back as a real-time correction term to compensate for dark current effects in target signal measurements, maintaining accuracy across a wide temperature range
3Measurement precision
If dark current is modeled and subtracted from target signal, then temperature measurement is possible, but measurement precision deteriorates due to difficulty in accurately modeling dark current
Solution Approach 1:
The pyrometer performs self-calibration by automatically measuring its own dark current signal during null intervals and using this measured value to correct target signal measurements, eliminating the need for external dark current modeling
Solution Approach 2:
The pyrometer dynamically changes its operating state between target viewing mode and null viewing mode, allowing direct measurement of dark current parameters under actual operating conditions rather than relying on theoretical models
4Measurement precision
If cooling systems are added to reduce dark current, then measurement accuracy improves, but device complexity and weight increase
Solution Approach 1:
The patent converts the harmful effect of dark current into a useful measurement by directly measuring the dark current signal during null intervals and using it to correct target signal measurements, eliminating the need for cooling systems
Solution Approach 2:
The dark current component is extracted from the total signal through temporal separation, allowing the pyrometer to operate without active cooling while maintaining measurement accuracy through software-based dark current subtraction
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 approach enhances sensing accuracy at both low and high temperatures, reduces the need for cooling systems, and allows for the measurement of rotational speed, leading to weight savings and increased packaging space, as well as enabling operation in higher ambient temperatures.
Implementation Method 1
the number of photons received by the pyrometer drops steeply at lower target temperatures
Implementation Method 2
dark current, or current generated in a detector of a pyrometer even when no photons enter the detector
Data Source
AI summary
Techniques for using a pyrometer to measure one or more operating characteristics of a target are provided. In one example aspect, a pyrometer is oriented relative to a target having target elements spaced from one another such that, as the target is rotated, the pyrometer alternately i) senses a target element for a period of time; and ii) then does not sense any of the target elements for a period of time as no appreciable signal is received. The pyrometer generates an output signal having alternating target pulse widths and null widths. The target and null widths have different amplitudes. The amplitude of the null signal provides an amplitude baseline for which the amplitudes of the target widths or signals may be compared to so that a temperature or other operating characteristic associated with the target can be determined.