Adaptive Filter; Temperature/Pressure Compensation (Tpc) - Teledyne T200 User Manual

A
DAPTIVE
The analyzer software processes sample gas concentration data through a built-in adaptive
filter. Unlike other analyzers that average the output signal over a fixed time period, these
analyzers average over a defined number of samples. This technique is known as boxcar
filtering. During operation, the software may automatically switch between two different
filter lengths based on the conditions at hand.
During constant or nearly constant concentrations, the software, by default, computes an
average sample value using the long filter. This provides smooth and stable readings and
averages out a considerable amount of random noise for an overall less noisy concentration
reading.
If the filter detects rapid changes in concentration, the filter reduces its size thus allowing
the analyzer to respond more quickly. Two conditions must be simultaneously met to
switch to the short filter. First, the instantaneous concentration must differ from the average
in the long filter by an absolute amount. Second, the instantaneous concentration must
differ from the average in the long filter by at least a set percentage of the average in the
long filter.
T
EMPERATURE
The software includes a feature that compensates for some temperature and pressure
changes that might affect measurement of NO and NO
When the TPC feature is enabled (default setting), the analyzer divides the value of the
PMT output signal (PMT Signal) by a value called TP_FACTOR, which is calculated using
the following four parameters:
Box Temp: The temperature inside the analyzer's case measured in K. This is
•
typically about 5 K higher than room temperature.
Rx Cell Temp: The temperature of the reaction cell, measured in K.
•
Rx Cell Press: The pressure of the gas in the vacuum manifold, measured in in-Hg-A.
•
Sample Press: The pressure of the sample gas before it reaches the reaction cell,
•
measured in in-Hg-A. This measurement is ~1 in-Hg-A lower than atmospheric
pressure.
As Rx Cell Temp, Box Temp, Rx Cell Press and Sample Press increase, the value of
TP_FACTOR increases and, hence, the PMT Signal value decreases. These adjustments
are meant to counter-act changes in the concentrations caused by these parameters.
The current value of each of these measurements is viewable in the editable
•
Dashboard (see Sections 2.4.2 and 2.5.3).
The preset gain parameters are set at the factory and may vary from analyzer to
•
analyzer. The TPC feature is enabled or disabled by setting the value of the variable
TPC Enable in the Setup>Vars menu. (see Section 2.5.5).
083730200A DCN7962
F
ILTER
/P C
RESSURE OMPENSATION
Teledyne API T200 NO/NO
(TPC)
concentrations.
X
/NO Analyzer with NumaView™ Software
2 x
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