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Feature:
- ‧ Fully
automatic.
- ‧
Bichromatic optics. Standard model includes four filters, six filters
are available for a nominal charge.
- ‧ On
board data reduction calculations include regressions, curve fitting
and cutoff absorbance calculations with step-by-step user prompting.
- ‧ Large,
non-volatile memory stores at least 50 user tests.
- ‧
Includes parallel and serial outputs.
- ‧
Operates with or without a computer. A bi-directional accessory is
available for linking to IBM compatible computer.
IAD
vs. Multi-Cavity Interference Filters
Awareness
Technology uses Ion Assisted Deposition (IAD) filters which are more
expensive, but will give superior performance far longer than multi-cavity
filters, resulting in reduced service costs and down-time for filter
replacement.
Awareness
Technology specializes in optical design, and has always considered filter
quality to be of major importance in achieving photometric accuracy and,
therefore, reliable test results. That is why Awareness Technology chooses
only Ion Assisted Deposition (IAD) filters when manufacturing Stat Fax and
ChemWell instruments. IAD filters are more expensive, but will give
superior performance far longer than multi-cavity filters, resulting in
reduced service costs and down-time for filter replacement. Before IAD
technology was commercially available, Awareness Technology used the best
quality 3-cavity sealed interference filters on the market. In 1993, after
extensive testing of regular production lots of both types of filters,
Awareness Technology confidently made the change to superior filters; ones
produced using IAD technology.
What
is IAD?
Prior
to the 1990's, narrow-band interference filters were subject to
instability and deterioration due to humidity, aging, and temperature
changes, resulting in low peak transmittance and out-of-band transmittance
("leakage").
Filters
manufactured using IAD technology and processes are vastly superior to
sealed soft-coated interference filters especially in terms of stability
and longevity.
IAD
is an advanced coating process that yields significant reduction in film
porosity in an effort to solve the stability problems inherent to soft
coated filters. The principal function of IAD is to bombard the coating
material with accelerated ions to densify the coating. An ion gun is
directed at the substrate, and when energized, establishes a plasma stream
of high energy particles flowing toward the substrate. As the accelerated
ions collide with the coating material at the substrate, the coating
material is compacted creating a dense film structure. Filters produced
using IAD have demonstrated spectral shift characteristics
approaching
and often achieving zero, comparing very favorably with the 10 to 20 nm
shift typical of conventionally deposited coatings.
Testing
Both
types of filters were tested in an environmental test chamber (temperature
and humidity) that was designed to simulate MIL-STD-810C for the purpose
of testing the environmental integrity of the filters. Each day in the
test chamber corresponds to approximately 1 year of operation in extreme
(high) temperature and humidity. Filters were tested for 7 days and
checked for delamination, visible deterioration and %T changes
periodically, with a final inspection and assessment on day 7.
The
multi-cavity filters exhibited incipient delamination sometimes as early
as the third day in the test chamber, and most failed at the end of 7
days, either by delamination or >10% increase in %T.
Over
the course of 3 years, we continued environmental testing of filters from
every production lot. A sample filter was randomly selected and placed in
the test chamber. With very few exceptions, the IAD filters passed the
tests of their physical integrity, %T and exhibited no significant peak
shift.
In
another test, a set of filters (340, 405, 450, 492, 545, 600 - IAD type)
were placed outdoors and exposed to direct sunlight, rain and temperature
extremes typical of South Florida. After 2 years, the filters had no
significant change in physical integrity, %T or peak shift.
Because
we use these higher quality, longer lasting, more expensive filters, we
may not always compete on price alone with companies selling cheap
instruments with low quality filters. When a competitor's instruments are
brand new, their filters may give adequate results, but as the filters
deteriorate, results can become unsatisfactory. It is important that
customers realize the long-term value and the advantages of IAD filters
over the multi-cavity type. The small additional cost of IAD technology
filters is negligible when compared to the advantages in added
dependability and overall performance of the instrument over many years
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