LI-COR LI-6400, Руководство пользователя

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Environmental Control
Temperature Control
7-16 Using the LI-6400
7
Temperature Control
Temperature control is achieved using dual Peltier devices on the sides of the
IRGA / sensor head. These devices heat or cool the air that is circulated
through the leaf chamber.
When f4 (level 2) is pressed in New Measurements Mode, the following con-
trol options are presented:
Constant Block Temperature
Block temperature is measured in the wall of the IRGA, and is primarily used
for the feedback control on the coolers. This control loop is fairly straightfor-
ward, and should be able to hold temperatures at targets that are within 7 de-
grees of ambient (larger if warming, since warming is more efficient than
cooling).
Constant Leaf Temperature
The constant leaf temperature option is not a tight control loop, for two rea-
sons: 1) the control of leaf temperature is indirect, via air temperature, and 2)
there are factors beyond the reach of the controller that affect leaf tempera-
ture, including leaf transpiration rate and incident radiation.
Table 7-3. Temperature control options
Option Description
N) None Turns off the chamber coolers.
B) Block Temp Maintains a constant block temperature. Good default
option.
L) Leaf Temp Maintains a constant leaf temperature.
N) None (Cooler Off)
B) Block temp 20 C
L) Leaf temp 20 C
Temp Control Options & Targets
Figure 7-14. The temperature control screen provides for block or leaf tem-
perature control