DURAG D-R 290, Operating Manual

Page: 49 / 202

4 | Product description
D-R 290 49
Equation
7
Table 4.10: Equation 7
The dust concentration
c is:
Equation
8
Table 4.11: Equation 8
I
0
emitted light
k
extinction coefficient
I
received light
OD Optical density
l Measurement path length, (x 2 for
auto-collimation)
c Dust concentration
b Dust coefficient
a
Dust offset
For the reasons already mentioned, the coefficients
a and b must be determined by
gravimetric measurement. The measurements to be performed must be performed
with the occurring plant loads and the difference filtering possibilities of the respective
plant. Check measurements for different types of fuel are necessary. Only when these
comparisons figures are available can the extinction values be correctly evaluated re­
garding the dust emission. Since the dust concentration is subject to statistical fluctua­
tions, statistical methods are best for determining the calibration curve for the relation­
ship between extinction [
}
195] and dust concentration.
For further information please refer to the standards VDI 3950 (Germany), EN 14181,
EN 13284-1, EN 15259 and others.
The setting of the coefficients in the device is described in section
7.7.6 Settings
[
}
142] .