Campbell Scientific AP200 CO2/H2O Atmospheric Profile System - Manual (Page 48)

AP200 CO
2
/H
2
O Atmospheric Profile System
LEVELS_USED: This is the number of profile levels (air sample intakes) to
be sampled. It must be an integer from four to eight. If fewer than eight inlets
are used, they should be connected to the lowest-number inlets (starting with
one). The default is eight.
The next five variables configure the automatic calibration (zero/span)
sequence. See Section 6, Infrared Gas Analyzer (IRGA) Zero and Span, for
details.
MEASURE_TANKS: This Boolean variable determines whether the AP200
will periodically switch between the profile sequence and the calibration
(zero/span) sequence. Set this variable to True to periodically switch to the
zero and CO
2
span cylinders (tanks). Set it to False to disable this feature. The
default is MEASURE_TANKS = True.
AUTO_ZEROSPAN: This Boolean variable determines whether the AP200
will command the IRGA to perform a zero and span (True) or whether it will
merely measure the zero and span cylinders (False). It is ignored if
MEASURE_TANKS is false. The default is AUTO_ZEROSPAN = True.
CAL_INTERVAL: This variable determines how often (given as time in
minutes) the calibration (zero/span) sequence will be run. It is ignored if
MEASURE_TANKS is false. The minimum time is the output interval (30
min). The maximum time is 1,440 min (once per day).
CAL_TIMEOFFSET: This variable determines when the calibration
(zero/span) sequence is started within the CAL_INTERVAL time. If
CAL_TIMEOFFSET is set to zero, the calibration (zero/span) sequence will
start at the start of the CAL_INTERVAL. Setting this variable to a non-zero
value will delay the start of the zero/span sequence by the set number of
minutes. CAL_TIMEOFFSET may be set to any value from zero to
CAL_INTERVAL.
CO2_SPAN_PPM: This is the concentration of the CO
2
span tank, in ppm. If
MEASURE_TANKS and AUTO_ZEROSPAN are both TRUE, the system
will automatically span the IRGA to this value during the zero/span sequence.
This value is also used during a manual CO
2
span operation. Any value may
be entered for CO2_SPAN_PPM, but spanning the IRGA will be disabled
unless the value is between 100 and 20,000. The factory default is –99 to
intentionally disable setting the CO
2
span until the user enters the value for the
CO
2
span tank.
The next two variables control the AP200 automatic power shutdown function.
If the supply voltage drops too low, the AP200 automatically powers down as
much of the system as possible. The AP200 requires 10.0 Vdc to 16.0 Vdc at
the input terminals. Note that the voltage measured in the datalogger,
batt_volt, will be approximately 0.3 V lower than the input voltage due to a
reverse-polarity protection diode.
BATT_LOWLIMIT: If the supply voltage batt_volt falls below this value,
the AP200 will set the batt_volt_LOW flag and shut down as much of the
system as possible until the voltage recovers. BATT_LOWLIMIT must be
9.7 V to 15 V. The default value for BATT_LOWLIMT is 9.7 V, which
corresponds to 10.0 V at the input terminal. This power-down feature is to
protect the battery from deep discharge cycles. The user should set
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