Adaptive Filter; Temperature/Pressure Compensation (Tpc); Figure 6-18. Basic Software Operation - Teledyne T400 User Manual

Windows CE
API FIRMWARE
6.2.1 A
DAPTIVE
The Model T400 software processes sample gas measurement and reference data through
an adaptive filter built into the software. Unlike other analyzers that average the output
signal over a fixed time period, the Model T400 averages over a set number of samples,
where a new sample is calculated approximately every 3 seconds - this is a technique is
known as boxcar averaging. During operation, the software automatically switches
between two different length filters, short and long, based on the conditions at hand.
During conditions of constant or nearly constant concentration, the software, by default,
computes an average of the last 32 samples (long), or approximately 96 seconds. This
provides the calculation portion of the software with smooth, stable readings. If a rapid
change in concentration is detected, the filter length is changed to average the last 6
samples (short), approximately 18 seconds of data, to allow the analyzer to respond more
quickly. If necessary, these boxcar lengths can be changed between 1 and 1000 samples
but with corresponding tradeoffs in rise time and signal-to-noise ratio (contact Technical
Support for more information).
Two conditions must be simultaneously met to switch to the short filter. First, the
instantaneous concentration must exceed the average in the long filter by a fixed amount.
Second, the instantaneous concentration must exceed the average in the long filter by a
portion, or percentage, of the average in the long filter.
6.2.2 T
EMPERATURE
The software includes a feature that compensates for some temperature and pressure
changes that might affect measurement of the gas concentrations.
When the TPC feature is enabled (default setting; can be enabled/disabled in the
Setup>Vars menu), the analyzer divides the value of the PMT output signal (PMT
162
Memory Handling
DAS Records
•
Calibration Data
•
System Status Data
•
Measurement
Algorithms

Figure 6-18. Basic Software Operation

F
ILTER
/P C
RESSURE
Teledyne API – Model T400 O
Instrument Operations
Calibration Procedures
•
Configuration Procedures
•
Autonomic Systems
•
Diagnostic Routines
•
Interface Handling
Sensor input data
•
Display Messages
Touchscreen
•
Analog output data
•
RS232 & RS485
•
External Digital I/O
•
(TPC)
OMPENSATION
Analyzer
3
PC/104 BUS
INSTRUMENT
HARDWARE
PC/104 BUS
083730400A DCN8130