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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