4-58 | Model 920 Multi-Gas Analyzer
Auto-Zero/Auto-Span
This feature allows you to initiate an automatic calibration sequence on
a component-by-component basis. However, the Calibration gas mixture
component concentrations must be entered and the calibration gas timers
and SSR outputs (span solenoids) must be assigned properly before an
Auto-Zero/Auto-Span can be initiated.
If the duration for a calibration gas timer is set to a non-zero value, and the
associated component concentration is specified as ‘
0
’, the function will be
performed and the Span Factor for that component will be reset to 1.0.
For example, there are two calibration gas mixture cylinders, one with
SO
2
and the other with a multi-component mixture of NO and NO
2
. Any
one, or all of the following functions, can be performed: the Zero, the SO
2
Span, the NO, and NO
2
Spans. Because NO and NO
2
are in the same gas
cylinder, the spans of both outputs will be performed simultaneously if
this function is performed. Further, if the calibration concentration for one
component (e.g., NO
2
) was previously entered as ‘
0
’, the Span for that
component (NO
2
) would remain at 1.0.
There is a global variable called “
Adjust Disable
” which, if set to ‘
1
’,
the Zero Offset and Span will not be corrected at the end of a calibra-
tion sequence. This allows the analyzer to control the calibration gas
flow so an external Data Acquisition System can record the actual
analyzer output signals during a calibration sequence and to monitor
for “calibration out of range” conditions.
When an Auto-Zero/Auto-Span is performed, the following events occur
automatically:
1. The Zero or Span gas solenoid valve is turned on to let the Zero or
Calibration gas mixture flow through the Measuring Cell. The User
Interface gives no indication the solenoid valve has been turned on.
2. The
Timer
duration is displayed on the top line of the User Interface
and begins counting down to ‘
0
’.
3. The analyzer Zero or Span is adjusted to the proper value based on
the average of the readings during the last 25 % of the timer dura-
tion (minutes) of the countdown (if
AdjDisable
is set to ‘
0
’). Upon
completion of the Auto-Zero/Auto-Span, CAL mode normal display
is returned. The
IntTimer
does not affect the averaging time for the
Auto-Zero/Auto-Span.
NOTE
Summary of Contents for 920
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Page 47: ...Specifications 2 19 Heater Plate ATEX and IECEx Certificates and Marking ...
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Page 53: ...Specifications 2 25 ATEX and IECEx certified Model 920 Analyzers are marked with this label ...
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Page 71: ...Installation and Start Up 3 11 Figure 3 4 Optical Bench Measuring Cell assembly ...
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Page 173: ...Controller User Interface 4 65 Figure 4 8 Customer signal connections ...
Page 187: ...Maintenance and Troubleshooting 5 11 Figure 5 1 Measuring Cell assembly ...
Page 262: ...A 2 Model 920 Multi Gas Analyzer Ribbon Cable Interconnect WX 102836 ...
Page 263: ...Appendix A Drawings A 3 GP Lower Enclosure to Electronics Wiring CE Analyzers WX 102810 ...
Page 264: ...A 4 Model 920 Multi Gas Analyzer Heater and Sensor Wiring GP Div 2 Analyzers WX 102851 ...
Page 265: ...Appendix A Drawings A 5 Heater and Sensor Wiring CE Zone 1 Analyzers WX 102852 ...
Page 266: ...A 6 Model 920 Multi Gas Analyzer Lower Cabinet Wiring CE GP Analyzers 120V 100 1341 3 ...
Page 267: ...Appendix A Drawings A 7 Lower Cabinet Wiring CE GP Analyzers 240V 100 1342 3 ...
Page 268: ...A 8 Model 920 Multi Gas Analyzer Signal Wiring PD GP Div 2 CE Zone 1 Analyzers WX 102815 ...
Page 271: ...Appendix A Drawings A 11 24V Power Supply DC Wiring CE Zone 1 Analyzers WX 102812 ...
Page 272: ...A 12 Model 920 Multi Gas Analyzer RS 232 Communications Cable Wiring 300 9480 ...
Page 273: ...Appendix A Drawings A 13 RS 232 RS 485 Module Wiring CE Zone 1 GP Div 2 Analyzers 100 2185 ...
Page 274: ...A 14 Model 920 Multi Gas Analyzer Microcontroller Board 100 0117 ...
Page 275: ...Appendix A Drawings A 15 Host Controller Board Display Interface 100 0138 ...
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