This system uses 3 spectrometer channels, 2 for monitoring molten plastic
thru a sapphire window and 1 channel to monitor the light source to perform lamp
drift correct for the 2 measurement channels. All 3 spectrometers have
identical optics for the VIS range of 350-750nm. There are two, twenty meter,
armored, 400um fiber optic cables that use collimating lens positioned at 2
different the sapphire ports on the plastic injection molding machines.
The instrument computer calculates the reflectance for the 2 measurement
channels and compensates their values for any lamp drift as seen by the third
channel. The 2 measurement channels are then converted to CIELAB values L* a*
and b* and Delta E*, which provide the colorimetric monitor data. These values
are continuously compared to established process monitor high and low set points
by the SpectraWiz software. If the pre-set limits are exceeded an external
event is triggered that is setup to ring an alarm bell indicating a colorization
problem. Additionally, the instrument computer transmits the CIELAB color
measurement data to the local plant computer via RS232. Additional outputs for
measurements are plotted via a 4-20ma interface controlled by the instrument
computer.
This application was able to use an instrument computer with a 66MHz 486 CPU
running MS Dos and SpectraWiz in just 1 Meg of memory! Can you imagine how many
optical channels could be monitored using a 600MHz CPU?
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