LI-COR LI-6400, Руководство пользователя

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OPENÕs System Variables
Background Information
Using the LI-6400 14-3
4 A short description.
This is what you see in the list generated by the ÒWhatÕs WhatÓ function key
in New Measurements mode.
5 A variable name
The variableÕs name is how you refer to it in a program. For example, if you
are writing an AutoProgram (Chapter 25) or defining a user variable (Chapter
15) and need to refer to the sample cell CO
2
concentration, the variable name
is co2_2_um .
Table 14-8 on page 14-19 lists the System Variables defined by OPEN, in-
cluding their labels, variable names, descriptions, and references to where
they are defined or discussed.
When Are They Computed?
In New Measurements mode, system and user variables are computed as fol-
lows:
1 Measured Quantities
The instrumentÕs A/D converter has a set of new readings available every
0.75 seconds. These readings are the raw signals from each sensor (including,
for example, the battery (V), the temperature sensors (mV), the CO
2
reference
IRGA (mV), etc.). Each time these new A/D readings are available, OPEN
computes the sensorÕs readings in meaningful units, and some ancillary val-
ues, such as relative humidity, which are based on multiple sensors.
Thus, system variables that are associated directly or indirectly with sensors
are computed and available with updated values every 0.75 seconds. These
variables are documented under the headings
Measured Variables and
Computed Variables , below.
2 User variables (photosynthesis rate, conductance, etc.)
Every 2.25 seconds, user variables are computed. These typically include
photosynthesis, conductance, etc. There are a couple of system variables that
are computed at this frequency as well, and these are described in
Boundary
Layer Variables on page 14-17.
3 Status variables
ThereÕs a group of system variables that convey some system status informa-
tion. These are updated every 10 seconds, and are described in
Status Vari-
ables on page 14-12.