Campbell Scientific CPEC200 Closed-Path Eddy-Covariance System - Manual (Page 38)

CPEC200 Closed-Path Eddy-Covariance System
5.4 Configure the Program
A CR3000 datalogger program Cpec200_vx_x.cr3 is included with the
CPEC200 system. If the CPEC200 was ordered with the CR3000 factory
installed, the CPEC200 is shipped with the program installed. A copy of the
program is found on the CPEC200 Support CD (pn 26857) or can be
downloaded from www.campbellsci.com .
The CPEC200 program uses both constants and variables to customize the
behavior of the system for a particular installation. Constants are used for
parameters that must be determined when the program is compiled and
variables are used otherwise.
Constants are most easily modified using the CRBasic Editor, which is part of
the PC400 and LoggerNet datalogger support software packages. They may
also be edited with a simple text editor and uploaded to the datalogger using
PC200W, which may be downloaded from www.campbellsci.com . The
CPEC200 uses some constants as “compile switches” to define the state of the
system during compilation.
Variables may be edited while the program is running using either a keyboard
display or a PC connected through PC200W, PC400, or LoggerNet. Variables
that define the operational configuration of the system are defined as system
configuration variables. Any changes to these variables are automatically
saved in nonvolatile memory.
Modifications to the CPEC200 program (for example, to measure
additional sensors) are not recommended without first consulting
a Campbell Scientific applications engineer.
5.4.1 System Configuration Variables
Several special variables are used to configure the CPEC200. These variables
are included at the end of TABLE B-1 in Appendix B, Public Variables, and
are distinguished by all capital letters. They may be edited directly in the
public table or with the keypad display on the datalogger.
These variables are stored in the sys_conf_var.dat file so their values will be
saved and recalled if the program is recompiled. They are intended to be set
when a new system is installed but may be edited at any time. When a system
configuration variable is changed, the CPEC200 will write a message to the
message_log table and save the new values in sys_conf_var.dat. It will also
add a record to the config_history table. This section gives a brief description
of each of these variables and refers the reader to the appropriate section of the
user manual if a lengthy discussion is required.
BATT_LOWLIMIT:
If the supply voltage BattVolt falls below this value, the CPEC200 will set
BattVolt_OK = False and shut down as much of the system as possible until
the voltage recovers. BATT_LOWLIMIT must be 10.0 V to 15.0 V. The
default value for BATT_LOWLIMT is 10.0 V, which corresponds to 10.3 V
at the input terminal. This power-down feature is to protect the battery from
deep discharge cycles. The user should set BATT_LOWLIMIT as
appropriate to protect the battery. If AC main power and an AC/DC adapter
are used, the limit may be left at 10.0 V.
NOTE
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