Introduction; Principle Of Operation; Sensor Components; Light Source - Process Sensors MCT Series Installation And Operation Manual

1.0 Introduction

The MCT Series are near infrared photometric analyzers that use fixed infrared wavelengths to measure
one, two or three constituents in a variety of products.
The MCT is a "stand-alone" sensor with all items necessary for continuous monitoring being located in
the sensor. Optional wall-mountable or hand-held operator interfaces are available for setup, calibration
and maintenance.

2.0 Principle of Operation

The molecular bonds O-H, C-H and N-H absorb infrared radiation at several specific wavelengths. The
MCT generates these absorbance wavelengths and several other non-absorbing wavelengths using a
rotating wheel containing up to 6 infrared filters. This chopped light is reflected from the surface of the
product collected by optical components inside the sensor. The resultant electrical pulses from the
reflected light are mathematically treated in ratio-based algorithms to compute raw measurements of the
measured constituents. These raw values are then scaled by offset (zero) and sensitivity (span) factors to
provide direct readings of the constituents.
Compensation for aging of optical components and the variations in the reflectivity of different products
is provided in the algorithm treatment of the filter reflectance values.

3.0 Sensor Components

The MCT is housed in an epoxy painted cast aluminum Nema 4 housing. A rear bracket allows the
sensor to be mounted, ensuring the light beam reflects from the product at all times.

3.1 Light Source

A quartz-halogen light bulb running at reduced voltage generates infrared energy.

3.2 Filter Wheel

Up to six infrared and visible filters are held in a circular disc. A single timing notch is machined in the
edge of the disc.

3.3 Filter Wheel Motor

A precision brushless DC motor is used to accurately rotate the filter disc in front of the infrared light
beam.

3.4 Detector

A thermoelectrically cooled PbS detector is used to convert the infrared light energy into electrical
pulses.
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