LASER COMPONENTS introduces five new bandpass filters for pyroelectric detectors, increasing the number of standard filters available to an outstanding seventeen versions.
The new filters include reference filters (B) and filters for the detection of CO2 (A), water vapour (M), methane (S), and alcohol (O), and are either mounted directly inside the fixed cap of the detector or available as a separate cap, which is then mounted to an existing pyroelectric detector.
A reference filter should not have any gas absorption. Filter B can be used when SO2 is part of the gas mixture
(λpeak = 3.86 μm, FWHM = 90 nm).
The CO2 filter A with a λpeak = 4.265 μm is the filter with the best possible signal and simple linearisation (FWHM = 110 nm).
Water vapour is in almost every gas mixture, which often leads to a disturbing background noise. An attempt to measure this with a 2.94 μm filter, for example, leads to problems of cross-sensitivity with CO2. The M filter has proven more reliable in such practical applications:
λpeak = 5.78 μm, FWHM = 180 nm.
Methane is primarily measured at 3.33 μm; however, this is not particularly specific. An excellent alternative is the S filter, which operates at a longer-wave band: λpeak = 7.91 μm, FWHM = 160 nm.
Breath alcohol measurement is becoming more and more popular. The new standard filter has the following specifications: λpeak = 9.50 μm, FWHM = 450 nm.
