Bacharach RDM800 - Manual (Page 15)

5.) Auto zeroing or purging has other benefits. We discussed how it’s used to provide a zero base for
comparison to the sample measurement. This, also, allows us to monitor and compensate for
changes in I-R drive circuitry, source, bench, detector, and other electronic components. Again this
all adds to long-term reliability and accuracy.
6.) Our narrow band filters limit the I-R range from 8.1 to 9.4 uM. These optical devices cannot fluctuate
in any way. They eliminate interference from gasses with absorbencies outside this range. As it
happens, humidity, which can absorb I-R energy and create erroneous readings, does not absorb I-R
energy within this range. Our measuring bench, because of this filter, cannot measure in any other
range adding to basic stability and accuracy.
7.) All measurements are pressure and temperature compensated so that there is never a question
arising from local weather or altitude issues. We always provide the same information regardless of
the location of our equipment.
8.) Our measurements, and this is one of the most important things we do, are a function of real time,
on board calculations of Absorbance Units, based upon the Beer-Lambert Law. This provides a linear
bench output, which, when coupled with our proprietary control algorithm, gives us better full-scale
resolution. We do not simply measure a voltage and compare it to a value on a look up table. That
method provides a logarithmic output, which has good low-end but poor high-end resolution.
The bottom line is that we have taken a very simple, rugged, stable
measuring bench design and by incorporating state-of-the-art technology
we’ve enhanced it into a virtual solid state, field replaceable, low cost,
sensitive, accurate component.
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