Set up Your Detector for Different Gas Measurements - Five New Bandpass Filters for Pyroelectric Detectors

15 Mar 2017

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 (peak = 3.86um, FWHM = 90nm).

The CO₂ filter A with a peak = 4.265um is the filter with the best possible signal and

simple linearisation (FWHM = 110nm).

Water vapour is in almost every gas mixture, which often leads to a disturbing

background noise. An attempt to measure this with a 2.94um filter, for example, leads

to problems of cross-sensitivity with CO₂. The M filter has proven more reliable in

such practical applications: peak = 5.78um, FWHM = 180nm.

Methane is primarily measured at 3.33um; however, this is not particularly specific.

An excellent alternative is the S filter, which operates at a longer-wave band: peak =

7.91um, FWHM = 160nm.

Breath alcohol measurement is becoming more and more popular. The new standard

filter has the following specifications: peak = 9.50um, FWHM = 450nm.