Signal processing and calibration procedures for in situ diode-laser absorption spectroscopy

Area of Science:

• Environmental Science
• Analytical Chemistry
• Spectroscopy

Background:

• Tunable diode-laser spectroscopy (TDLS) enables sensitive, specific, and rapid in situ measurements of atmospheric trace gases.
• Practical field applications face limitations due to noise, interference, and drift at low (sub-parts-per-billion) mixing ratios.

Purpose of the Study:

• To address practical challenges in TDLS field measurements at low trace gas concentrations.
• To present a signal processing strategy for trace gas monitoring.
• To describe an in situ system calibration concept for TDLS.

Main Methods:

• Review of signal processing strategies for low-level trace gas detection.
• Development of an in situ calibration concept for TDLS systems.
• Application of International Standard Organization (ISO) regulations for linearity checks.

Main Results:

• Identification of key limitations including noise, interference, drift, and background changes at low signal levels.
• Presentation of a signal processing approach tailored for trace gas monitoring.
• Demonstration of an in situ calibration method applicable to TDLS.

Conclusions:

• Effective signal processing and in situ calibration are crucial for reliable TDLS field measurements of trace gases.
• Adherence to quality assurance procedures, including linearity checks, is essential for field monitoring applications.
• The presented strategies enhance the accuracy and dependability of TDLS in environmental monitoring.