Bandpass filters for IR detectors: With five new products, we offer the largest range of standard products worldwide so that you may measure whatever you want! There are seventeen different filters in total.
IR detectors are polychromatic. This means that they not only detect a wavelength but a whole bandwidth, which ranges from 0.1 µm to 100 µm in pyroelectric detectors.
These bandpass filters are either directly mounted to the fixed cap of the detector or are available as a separate cap that can be attached to an existing pyroelectric detector. We will introduce our five new filters here:
Filter B: Reference Filter
A reference filter should not have gas absorption bands. The tested and proven H filter generally does not have these bands, unless there is SO2 in the gas mixture. In this case, use the B filter:
Lambdapeak = 3.86 µm, FWHM = 90 nm
Filter A: CO2 Filter
We have worked for over a year with a manufacturer of CO2 sensors to find the ideal CO2 filter with the best signal possible and a simple linearization for regulation of air-conditioning systems. The following specification has been proven to be the best:
Lambdapeak = 4.265 µm, FWHM = 110 nm
Filter M: Water Vapor Filter
Water vapor is found in almost any mixture, and it often leads to an interfering background. Attempts to measure this with a 2.94 µm filter, for example, are faced with the problem of CO2 cross-sensitivity. The M filter has been proven to be reliable in practical applications:
Lambdapeak = 5.78 µm, FWHM = 180 nm
Filter S: Methane Filter
Methane has generally always been measured at 3.33 µm; however, this is not very specific. To improve upon this, a correct spectrum can be measured or laser methods used. Alternatively, an S filter can be used that operates at a longer-wave band:
Lambdapeak = 7.91 µm, FWHM = 160 nm
Filter O: Alcohol Filter
Measuring the alcohol level is becoming more and more popular, which just screams for a standard filter:
Lambdapeak = 9.50 µm, FWHM = 450 nm
