Principles of Operation
Teledyne API - Model T200H/T200M Operation Manual
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8.8. 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 8-25:
Basic Software Operation
8.8.1. ADAPTIVE FILTER
The T200H/M NO
X
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, the T200H/M averages over a defined number of samples, with samples
being about 8 seconds apart (reflecting the switching time of 4 seconds each for NO and
NO
X
). 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 of the last 42 samples, or approximately 5.6 minutes. 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 the averaging to
fewer samples or shorter time to allow 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 at least 50
ppb. Second, the instantaneous concentration must differ from the average in the long
filter by at least 10% of the average in the long filter.
07270D DCN7141