Fraunhofer Institute for Physical Measurement Techniques IPM
Basic Raman sensor for hydrogen and the analysis of complex gas matrices
Raman spectroscopy is a comparatively complex method that typically requires high-quality components such as powerful lasers and cooled high-end cameras. As part of the publicly funded TransHyDE project, we have now developed a simple and low-cost Raman sensor for hydrogen. The sensor can detect hydrogen very selectively and reliably, making it suitable also for analyzing complex gas matrices. The measurement principle, outlined in figure 1, uses filter-based detection: Light emitted by a 532 nm laser passes through a gas cell, the scattered light is laterally projected onto a large-scale camera, and a specific bandpass filter permits only Raman light of hydrogen to pass through.
Effective detection without spectrographs
Figure 2 shows the Raman spectra of N₂, H₂, and CH₄, as well as the spectral range detected in this way. This filter-based configuration enables effective detection of Raman light with very high optical throughput and therefore requires only low-cost components (low laser requirements, standard camera) and operates without a spectrograph.
Figure 3 illustrates a test run of the Raman sensor: A gas mixer is used to produce a hydrogen-nitrogen mixture in 20 percent increments, which is then measured using the Raman sensor. The sensor's good linearity across the wide measuring range and good signal-to-noise ratio are evident.
