Gas Sampling Optical Cell

Challenge:

The client was developing a handheld Non-Dispersive Infrared (NDIR) gas analyzer for measuring the chemical composition of automobile exhaust. BD&E was approached to reduce the length of the sample tube and improve the sensitivity of the measurement.

Solution:

BD&E produced this unique folded cell design, which provides a long absorption path in a compact size. The cell increases the absorption path length by multiply folding the light through the same gas volume. The NDIR device functions by passing infrared radiation through the gas and onto two spectrally filtered detectors, one reference and one signal. The light absorbed by the gas reduces the signal relative to the reference, allowing for the determination of the gas concentration.

This folded configuration improves the instrument by increasing both the absorption path length and the efficiency of the optical coupling, while reducing the overall size of the system. Its unique design allows it to be produced by low-cost injection molding. These improvements reduced production cost, increased measurement sensitivity and decreased system size.