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8026957/AE00/V1-0/2021-08| SICKOPERATING INSTRUCTIONS | DUSTHUNTER SB30
Subject to change without notice
2 PRODUCT DESCRIPTION
2 Product description
2.1 Measuring principle, measured variables
2.1.1 Functional principle
The measuring system works according to the scattered light measurement principle
(backward dispersion). A laser diode beams the dust particles in the gas flow with
modulated light in the visual range (wavelength approx. 650 nm). A highly sensitive
detector registers the light scattered by the particles, amplifies the light electrically and
feeds it to the measuring channel of a microprocessor as central part of the measuring,
control and evaluation electronics. The measuring volume is defined by the overlap of the
sender beam and the field of view of the receiver optics.
Fig. 1: Measuring principle
In the case of small duct diameters (< 2 m or in the most unfavorable conditions for
background radiation due to brightness or reflection), a light trap and associated flange
may be necessary (see “Assembly parts”, page 70).
Determining the dust concentration
Measured scattered light intensity (SI) is proportional to dust concentration (c). Scattered
light intensity not only depends on the number and size of particles but also on the optical
characteristics of the particles and therefore the measuring system must be calibrated
using a gravimetric comparison measurement for exact dust concentration measurement.
The calibration coefficients determined can be entered directly in the measuring system as
c = cc2
· SI² + cc1 · SI + cc0
(Entry see “Calibration for dust concentration measurement”, page 46; standard factory
setting: cc2 = 0, cc1 = 1, cc0 = 0).
Sender/receiver unit
Receiver
Sender
Measuring volume length
Laser beam
Dust laden exhaust gas
Receiver field of view
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