Infrared
Reading a signature in the spectrum
We provide a comprehensive design service for laser, nondispersive infrared (NDIR), CIPS, photoacoustic and other IR chemical measurement systems. We will help bring your application to market using our bespoke modelling tools.
Working demonstration
What sets the detection limit
Choose a gas, set the concentration and the optical path, then set how quiet the receiver is. The absorbance, the transmission and the smallest concentration the instrument could honestly report all follow from Beer Lambert.
Peak absorbance
0.250
Transmission at band centre
56.2 %
Detection limit
2 ppm
Signal to noise
2.5k
Comfortably above the noise floor
Absorbance, transmission and detection limit are computed directly from the relations above using an effective band absorptivity for each gas. The band shape is an indicative rovibrational model, P and R branches spaced by twice the rotational constant with a Boltzmann envelope at 296 K, drawn to show structure and overlap rather than to stand in for line by line data. Past an absorbance of 8, the beam is fully absorbed and the panel reports that state directly rather than an escalating signal to noise figure that no longer describes anything a real detector would see.
What the modelling gives you
Modelling comes before the hardware
Most instrument proposals turn on the same question: can this measurement be made at the concentration that matters, over the path length the application allows, with a detector anyone can afford. Predictive modelling of the spectroscopic response answers that on paper, which is considerably cheaper than answering it on a bench.
The same models set the specification once a build is agreed. Band selection, source and detector pairing, path length, modulation scheme and the processing that recovers a concentration from a noisy signal all follow from the same numbers.
Mixed gases and confusion signals
Atmospheres are rarely one gas. Water vapour absorbs broadly across the mid infrared and overlaps almost every band worth using, and hydrocarbons overlap each other too. Modelling that interference is how a design avoids reporting a confident number when something else in the sample actually produced it.
Techniques
Laser, NDIR, CIPS and photoacoustic, chosen on the merits of the measurement.
Each technique buys a different combination of sensitivity, selectivity, cost and robustness. The design work is deciding which trade the application can live with, then building to it.