Teledyne GFC-7000T - Trace CO2 Analyzer - manual - Manual (Page 231)

Theory of Operation Model GFC7000TA Carbon Dioxide Analyzer
Teledyne Analytical Instruments 213
9.5. Software Operation
The Model GFC 7000TA Gas Filter Correlation Carbon Dioxide Analyzer has a high performance,
VortexX86-based microcomputer running Windows CE. Inside Windows CE, special software developed
by Teledyne Instruments interprets user commands via the various interfaces, performs procedures and
tasks, stores data in the CPU’s various memory devices and calculates the concentration of the sample
gas.
Windows CE
API FIRMWARE
Analyzer Operations
Calibration Procedures
Configuration Procedures
Autonomic Systems
Diagnostic Routines
Memory Handling
DAS Records
Calibration Data
System Status Data
Interface Handling
Sensor input Data
Touchscreen/Display
Analog Output Data
RS232 & RS485
External Digital I/O
Measurement
Algorithm
ANALYZER
HARDWARE
PC/104 BUS
PC/104 BUS
Linearization Table
Figure 9-18: Basic Software Operation
9.5.1. Adaptive Filter
The GFC 7000TA software processes the CO2 MEAS and CO2 REF signals, after they are digitized by
the motherboard, through an adaptive filter built into the software. Unlike other analyzers that average
the output signal over a fixed time period, the GFC 7000TA averages over a set number of samples,
where each sample is 0.2 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.
Once triggered, the short filter remains engaged for a fixed time period to prevent chattering.
During conditions of constant or nearly constant concentration the software, by default, computes an
average of the last 750 samples, or approximately 150 seconds. This provides the calculation portion of
the software with smooth stable readings. If a rapid change in concentration is detected the filter