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T400 Ozone Analyzer Operator’s Manual Theory of Operation
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13.5. SOFTWARE OPERATION
The instrument’s core module is a high performance, X86-based microcomputer running
Windows CE. Inside Windows CE, special software developed by Teledyne API
interprets user commands from the various interfaces, performs procedures and tasks,
stores data in the CPU’s various memory devices, and calculates the concentration of the
gas being sampled.
Windows CE
API FIRMWARE
Instrument Operations
Calibration Procedures
Configuration Procedures
Autonomic Systems
Diagnostic Routines
Memory Handling
DAS Records
Calibration Data
System Status Data
Interface Handling
Sensor input data
Display Messages
Touchscreen
Analog output data
RS232 & RS485
External Digital I/O
Measurement
Algorithms
INSTRUMENT
HARDWARE
PC/104 BUS
PC/104 BUS
Figure 13-21: Basic Software Operation
13.5.1. ADAPTIVE FILTER
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
technique is known as boxcar averaging. During operation, the software automatically
switches between two different length filters 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, 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,
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 customer service
for more information).
06870C DCN6332