Multispectral Readout System for Detecting Tiny Color Changes of Gas Sensitive Colorimetric Dyes

We present a simple sensor setup for detecting very small color changes of gasochromic materials. The sensor includes up to ten LEDs for capturing different spectral channels, ranging from ultraviolet to the near infrared. In order to detect diminutive color changes of dyes at gas concentrations in the sub ppm range, the system includes a differential photodiode circuit, as well as two additional photodiodes to determine the absolute reflectance of the dyes.