Campbell Scientific CPEC200 Closed-Path Eddy-Covariance System - Manual (Page 40)

CPEC200 Closed-Path Eddy-Covariance System
PUMP_SETPT:
Variable PUMP_SETPT determines the volumetric flow rate at which the
pump will draw the air sample through the EC155 sample cell.
PUMP_SETPT must be 3 to 9. The default setting is 7.0 LPM. In tall tower
applications where decreased frequency response is acceptable, lowering the
flow rate may be desirable as it will prolong the life of the intake filter. This
may be particularly applicable if the site is dusty or if accessing instruments on
the tower is difficult. Decreasing the flow by a factor of two will generally
lead to a four-fold increase in filter lifetime.
CAL_INTERVAL:
This variable determines how often (given in minutes) the calibration
(zero/span) sequence will be run. It is ignored if CHECK_ZERO = False.
The minimum time is the output interval (30 min). The maximum time is
1,440 min, or once per day. The default is 1,440.
CAL_TIMEOFFSET:
This variable determines when the calibration (zero/span) sequence is started
within the CAL_INTERVAL time. If CAL_TIMEOFFSET = 0, the
calibration 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. The default is 59, which will start the
zero/span sequence 59 minutes past midnight. This avoids starting the
zero/span sequence at midnight, when the datalogger has the extra processing
tasks associated with closing and opening files for the ts_data table. It starts
the sequence one minute before the end of an averaging period. The sequence
is generally longer than one minute, so the EC samples that are lost to the
zero/span sequence are split between two consecutive flux output intervals.
ZERO_TIME:
Determines the time (given in seconds) for the zero gas to flow while checking
the zero. ZERO_TIME must be 20 to 300. The default is 60, which should be
adequate for low measurement heights. For taller towers, increase the time as
needed to allow the EC155 response to equilibrate after the zero air begins to
flow.
SPAN_TIME:
Determines the time (given in seconds) for the CO
2
span gas to flow. Time for
zero and CO
2
span may need to be different to allow the H
2
O to fully
equilibrate during the zero. If the scrub module is used for the zero air, the
flow rate will be different for zero and CO
2
span. This is another reason to set
the zero and span times differently. SPAN_TIME must be 20 to 300. The
default is 30, which should be adequate for low measurement heights. For
taller towers, increase the time as needed to allow the EC155 response to
equilibrate after the CO
2
span gas begins to flow.
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