Campbell Scientific AP200 CO2/H2O Atmospheric Profile System - Manual (Page 98)

Appendix F. Valve Sequence Timing
time). For example, if there are eight levels used, the profile cycle time is 120
s. This means 40 s must be added to the zero/span sequence. This has been
allocated as 10 s extra (each) for the span and zero, and 20 s extra for
equilibration on level 1 at the end of the sequence.
The zero/span sequence takes the place of one profile cycle for five, six, seven,
or eight levels. However, if there are four levels used, the profile cycle time is
only 60 s. This is less than the 80 s required for a zero/span check, so two
profile cycles must be replaced. This gives a total of 120 s, the same as the
scenario with eight levels.
TABLE F-3. Timing for Zero/Span Sequence (check only)
Number
of Levels
Profile Cycle
Time (s)
Span
Time (s)
Zero
Time (s)
Equilibration
Time (s)
Total Zero/Span
Time (s)
Minimum 30 40 10 80
4 60 40 50 30 120
5 90 30 40 20 90
6 90 30 40 20 90
7 120 40 50 30 120
8 120 40 50 30 120
Similar to the profile sequence, the zero/span sequence timing parameters are
implemented as a set of three arrays: CalSequence(), CalOnCounts(), and
CalOmitCounts(). These arrays are not accessible in the Public table, but they
are output to the TimeInfo table as a record of the system configuration. See
Appendix D, Output Tables, for details on this table.
Each zero/span sequence adds two records to the SiteAvg and CalAvg output
tables: one for CO
2
Span and one for Zero.
With Zero and Span
If the AP200 is configured with MEASURE_TANKS = True and
AUTO_ZEROSPAN = True, it will check the zero and CO
2
span, command
the IRGA to set them, and then verify the new readings. This section gives
timing details for this case. The AP200 zero/span sequence will:
• Select inlet 10 (CO
2
Span), omit at least 20 s for equilibration, and
include 10 s in the average
• Select inlet 9 (Zero), omit at least 30 s for equilibration, and include
10 s in the average
• Stay on inlet 9 (Zero) and set the CO
2
zero (~10 s)
• Stay on inlet 9 (Zero) and set the H
2
O zero (~10 s)
• Stay on inlet 9 (Zero) and average for ~10 s
• Select inlet 10 (CO
2
Span), equilibrate for 30 s, and average 10 s
• Stay on inlet 10 (CO
2
Span) and set the CO
2
span (~10 s)
• Stay on inlet 10 (CO
2
Span) and average for ~10 s
F-4