January 2019
KPM KB2 Man W41100099V1.8
3
Operating principle
The KPM KB2 operates on a proven, non-contact reflection principle. The light source can be
either RGB LED (red, green, blue) or IR LED (infrared). The optical sensor is placed above or under
the web. Applications include paper or board webs, wires or felts. Thanks to the unique RGB
detection method the color of the product or the felt has no effect on the measurement
reliability. The sensor is neither affected by dirt, steam nor temperatures up to 180 °C (356 °F)
when installed according to ABB Oy, KPM specifications. There are no electronic components
located in the sensor head.
The optical sensor is connected through a fiber optic cable to the RGB/IR light source located in
the display unit. The RGB/IR LEDs emit pulsed red, green, blue, or IR light onto the web surface.
The reflected light is received and transmitted through the fiber optic cable to the detector. All
light components are analyzed fast for a reliable break detection.
A break activates a relay, which can be connected to the logic control of a paper machine. The
reflected light intensities are also available as optional 4 - 20 mA analog outputs.
Fig. 1.2. Operating principle.
The self-cleaning sensor head is a 33.7 x 1500 mm (1" x 59") stainless steel tube with two holes
serving as eyelets for the fiber optics and outlets for purge air. Continuous airflow through the
stainless steel enclosure keeps positive pressure around the sensor head's eyes and keeps the
eyelets free of steam, dust or debris. The openings should be located towards the surface being
monitored.
Fig. 1.3. Sensor eyelets and purge air operation.
Optical
sensor
RGB
transmitter
or IR
Detector
Fiber
optic cables
Paper s
heet
