SICK DUSTHUNTER T, Operating Instructions Manual, Page: 14 / 142

14 DUSTHUNTER T · Operating Instructions · 8012428 V2.2 · © SICK AG
Product Description
Su
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2.1
Measuring principle, measured variables
2.1.1
Functional principle
A high performance LED sends light in the visible range (white light, wavelength approx.
450 to 700 nm) through the active measuring path containing particles to the reflector
where it is bounced back to the receiver (

Fig. 1 ). A highly sensitive measurement receiver
accepts the signal weakened by particles, amplifies the signal electrically and feeds it to
the measuring channel of a microprocessor as central part of the measuring, control and
evaluation electronics.
Continuous monitoring of the sender output (partial beam to monitor receiver) registers the
smallest changes in brightness of the light beam sent which then serves to determine the
measurement signal.
Figure 1 Measuring principle
Measured variables
The measuring system uses transmission (T) as primary optical measured variable. The
other measured variables opacity (O), relative opacity (ROPA), absorption (E) and dust
concentration (c) are derived from this variable.
Transmission, opacity, relative opacity:
Transmission, opacity and relative opacity are usually specified in percent.
Extinction:
LED
Reflector
Measurement Monitor
receiver receiver
Active measuring path
(gas flowing through, free path)
Concave mirror
T N
I
meas
I
mon
------------ 
=
O 1 T – =
ROPA 1 e
E
D
Do
2 D
meas

-----------------------

– =
N = scaling constant
I
meas
= light received
I
mon
= monitor signal
D
Do
= stack diameter at the top end
D
meas
= active measuring path
E
1
T
---
 
 
log =