Teledyne t320u Manual Do Utilizador

Página de 426
Theory of Operation 
Teledyne API – Model T300/T300M CO Analyzer 
324 
13.5.2. CALIBRATION - SLOPE AND OFFSET 
Calibration of the analyzer is performed exclusively in software.   
During instrument calibration (see Section 9) the user enters expected values for zero 
and span via the front panel control buttonand commands the instrument to make 
readings of calibrated sample gases for both levels.  The readings taken are adjusted, 
linearized, and compared to the expected values. With this information the software 
computes values for instrument slope and offset and stores these values in memory for 
use in calculating the CO concentration of the sample gas.   
The instrument slope and offset values recorded during the last calibration are available 
for viewing from the from the front panel (see Section 3.4.3). 
13.5.3. MEASUREMENT ALGORITHM  
Once the IR photo-detector signal is demodulated into CO MEAS and CO REF by the 
sync/demod board and converted to digital data by the motherboard, the T300/T300M 
analytical software calculates the ratio between CO MEAS and CO REF.  This value is 
compared to a look-up table that is used, with interpolation, to linearize the response of 
the instrument.  The linearized concentration value is combined with calibration slope 
and offset values, then normalized for changes in sample gas pressure to produce the 
final CO concentration.  This is the value that is displayed on the instrument front panel 
display and is stored in memory by the analyzer’s DAS system. 
13.5.4. TEMPERATURE AND PRESSURE COMPENSATION 
Changes in pressure can have a noticeable, effect on the CO concentration calculation.  
To account for this, the T300/T300M software includes a feature which allows the 
instrument to compensate for the CO calculations based on changes in ambient pressure.   
The TPC feature multiplies the analyzer’s CO concentration by a factor which is based 
on the difference between the ambient pressure of the sample gas normalized to standard 
atmospheric pressure.  As ambient pressure increases, the compensated CO 
concentration is decreased.   
13.5.5. INTERNAL DATA ACQUISITION SYSTEM (DAS) 
The DAS is designed to implement predictive diagnostics that stores trending data for 
users to anticipate when an instrument will require service.  Large amounts of data can 
be stored in non-volatile memory and retrieved in plain text format for further 
processing with common data analysis programs.  The DAS has a consistent user 
interface in all Teledyne API analyzers.  New data parameters and triggering events can 
be added to the instrument as needed.   
Depending on the sampling frequency and the number of data parameters the DAS can 
store several months of data, which are retained even when the instrument is powered 
off or a new firmware is installed.  The DAS permits users to access the data through the 
instrument’s front panel or the remote interface.  The latter can automatically download 
stored data for further processing.  For information on using the DAS, refer to Section 7. 
06864B DCN6314