Analysis Reveals Performance Characteristics of Compact Fourier Transform Infrared Spectrometers

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A research team has utilized the Allan variance technique to analyze the performance characteristics of compact Fourier transform infrared (FT-IR) spectrometers. The study provides insights into the noise sources and instabilities of these handheld instruments, offering guidance for improving their accuracy and stability in real-time material detection and quantification applications.

Handheld Fourier transform infrared (FT-IR) spectrometers have emerged as highly promising tools for applications requiring real-time and accurate material detection and quantification. However, their compact size, limited warm-up time, and susceptibility to environmental changes can introduce short-term noise and long-term instabilities, which can impact their overall performance. In a recent study published in the journal Applied Spectroscopy, researchers investigated the impact of long-term multiplicative instabilities on the signal-to-noise ratio (S/N) of these spectrometers, employing the Allan variance technique to identify and quantify different types of noises (1). Their findings shed light on the performance characteristics of these compact FT-IR spectrometers and offer insights for improving their accuracy and stability.

The Allan variance technique is a statistical analysis method used to assess the stability and noise characteristics of a measurement system over time. It involves dividing the data into overlapping segments of varying lengths and calculating the variance between consecutive segments. By plotting the Allan variance against the averaging time, it allows for the identification and quantification of different types of noises, including short-term noise, flicker noise, and random walk noise. This technique provides valuable insights into the noise sources and instabilities present in a measurement system, helping researchers and engineers to optimize the system's performance, improve accuracy, and mitigate the effects of noise for various applications in fields such as spectroscopy, metrology, and signal processing.

The compact size and portability of handheld FT-IR spectrometers make them highly attractive for various applications, such as on-site material analysis, environmental monitoring, and biomedical diagnostics. However, the inherent constraints of their design pose challenges in maintaining stable and reliable performance. To address this, the research team focused on investigating the impact of long-term multiplicative instabilities, which can degrade the quality of spectral data and compromise the accuracy of material identification and quantification.

The study employed the 100% line-method to measure the signal-to-noise ratio (S/N) and deduced an expression for the variance in the presence of long-term multiplicative instabilities. By utilizing the Allan variance technique, the researchers were able to effectively analyze the different types of noise affecting the spectrometers. They applied their methodology to a commercial scanner module, providing a practical and real-world context for their investigation.


The results of the study revealed important insights into the performance characteristics of compact FT-IR spectrometers. By quantifying the various sources of noise and instabilities, the researchers were able to better understand the limitations and challenges associated with these portable instruments. This understanding paves the way for further advancements in instrument design, data processing algorithms, and calibration procedures, with the aim of enhancing the accuracy, stability, and reliability of handheld FT-IR spectrometers.

The findings of this research hold implications for a wide range of applications. Improved performance of compact FT-IR spectrometers will facilitate more accurate and reliable material analysis in the field, enabling rapid and informed decision-making in various industries. This study contributes to the growing body of knowledge surrounding portable spectroscopic techniques and highlights the importance of addressing performance limitations to unlock the full potential of handheld FT-IR spectrometers.

As further research and development efforts focus on refining the design and performance of these instruments, the impact of this study is expected to extend beyond the laboratory, enabling broader adoption and utilization of compact FT-IR spectrometers in real-world scenarios that demand precise and timely material analysis.


(1) Adib, G. A.; Sabry, Y. M.; Khalil, D. Allan Variance Characterization of Compact Fourier Transform Infrared Spectrometers. Appl. Spectrosc. 2023. DOI: