Ecotech Serinus 40 - Kalman Filter Theory; Figure 1 - Simple Pneumatic Diagram; Equation 2 - no

Serinus 40 User Manual 2.2
Page 24
 The concentration of NO
2
is then calculated by subtracting the NO measurement from the NO
x
measurement
Figure 1 – Simple pneumatic diagram
 This reaction releases energy in the form of chemiluminescent radiation, which is filtered by the
optical bandpass filter and detected by the photomultiplier tube (PMT)
 The level of chemiluminescence detected is directly proportionally to the NO in sample
 The concentration of NO
2
is calculated by subtracting the NO measurement from NO
X
measurement
NO
X
= NO + NO
2
Or
NO
2
= NO
X
– NO
Equation 2 – NO
2
calculation
1.4.2 Kalman Filter Theory
The digital Kalman filter provides an ideal compromise between response time and noise reduction
for the type of signal and noise present in ambient air analysers.
The Kalman filter enhances measurements by modifying the filter time base variable, depending on
the change rate of the measured value. If the signal is changing rapidly, the instrument is allowed to
respond quickly. When the signal is steady, a long integration time is used to reduce noise. The
system continuously analyses the signal and uses the appropriate filtering time.