Laser Gas Analysis Apparatus Delay Compensation
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Solution Overview
Problem
Laser gas analysis apparatuses using TDLAS face signal transmission delays that vary with installation environment, leading to reduced measurement accuracy due to unpredictable delays caused by factors like sync cable length and installation state.
Innovation Solution
Incorporating a delay measuring circuit and edge detection circuit to measure and cancel total system delays, allowing for precise timing adjustments and improved data processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser beam is transmitted through process gas to perform non-contact measurement, then measurement speed and component selectivity are improved, but signal transmission delay varies with installation environment reducing measurement accuracy
Solution Approach 1:
The delay measuring circuit performs preliminary measurement of the signal transmission delay through the process gas before the actual gas concentration measurement. By measuring the delay time of a test signal transmitted through the same optical path, the system预先 determines the delay amount that will affect subsequent measurements, allowing for accurate timing compensation.
Solution Approach 2:
The system uses the measured delay time as feedback to adjust the timing of data acquisition. The delay time measured by the delay measuring circuit is fed back to synchronize the data acquisition timing, ensuring that the measurement system compensates for the actual signal transmission delay through the process gas.
2Measurement precision
If the oscillation wavelength of the diode laser is changed to measure specific absorption peaks, then wavelength selectivity is improved, but the measurement system becomes more sensitive to environmental fluctuations
Solution Approach 1:
The system continuously monitors the delay time and uses this feedback to adjust the timing of data acquisition. This closed-loop approach compensates for environmental fluctuations that affect signal transmission, maintaining measurement reliability despite changes in temperature, pressure, or gas composition.
Solution Approach 2:
The system changes the oscillation wavelength of the diode laser to match specific absorption peaks of target gases, achieving high wavelength selectivity. By using the spectrum area method rather than peak height, the system reduces sensitivity to environmental parameter changes while maintaining the benefits of wavelength-specific measurement.
3Reliability
If the spectrum area method is used to reduce sensitivity to coexisting gas components, then measurement robustness is improved, but the system still requires precise timing synchronization
Solution Approach 1:
The delay measuring circuit performs preliminary measurement of the signal transmission delay through the process gas before actual measurements. This preliminary timing characterization allows the system to establish the correct synchronization offset for subsequent spectrum area measurements, ensuring accurate timing without requiring complex real-time adjustments.
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 accurate measurement and analysis by compensating for environmental delays, enhancing the overall accuracy of laser gas analysis.
Implementation Method 1
A laser gas analyzer using a TDLAS (Tunable Diode Laser Absorption Spectroscopy) method has an advantage in that the laser gas analyzer can measure high-temperature or the concentration of a target component to be measured such as corrosive gas or the like in a non-contact manner
Implementation Method 2
a detection unit including a light receiving element for detecting the laser beam transmitted through a measurement space in the process gas atmosphere
Data Source
AI summary
A timing generating circuit outputs, to a laser controller, a change pulse signal for changing an oscillation wavelength of the laser beam, and outputs, to a data acquisition circuit, a timing pulse signal for outputting data to a processor. An edge detection circuit detects an edge of a measurement signal outputted from a detector circuit. A delay measuring circuit receives a change pulse signal outputted from the timing generating circuit, receives an edge detection signal outputted from the edge detection circuit, and measures a delay of a time for which the laser beam with an oscillation wavelength changed based on the change pulse signal reaches the detector circuit after the change pulse signal is outputted from the timing generating circuit. The timing generating circuit delays a time for outputting data from the data acquisition circuit to the processor based on the delay of time outputted from the delay measuring circuit.