LI-COR LI-6400, Руководство пользователя

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Environmental Control
OpenÕs Control Manager
7-4 Using the LI-6400
7
Behind The Scenes
Once the user has specified a control and target, the control manager sets the
appropriate hardware according to the control option and target. The system
then begins a regime of periodically checking the stability status and fine tun-
ing the controls as needed.
Each control option has three software components: a fast component that ex-
ecutes every 3 seconds, a medium component that executes every 10 seconds,
and a slow component that executes every 30 seconds. These components are
called interrupt service routines, or ISRs. A particular control may not actu-
ally use all three ISRs; this depends upon how much work is being done by
the hardware, and on the response time of the quantity being controlled.
While the control manager is active, ISRs execute at regular intervals.
The LED light source, for example, responds nearly instantaneously to con-
trol changes, so fine tuning adjustments to keep it at a target value can be done
with the 3 second ISR, while the 10 and 30 second ISRs do nothing. Control-
ling leaf temperature, however, is a much slower process, so the 10 and 30
second ISRs are needed.
Active vs. Inactive Control Manger
An inactive control manager means that the fine tuning necessary for active
target tracking is not being done. The consequences of this depend on the con-
trol: Some controls are fully implemented in hardware, leaving nothing im-
portant for any of the three ISRs to do
1
. Usually, however, the ISRs are
important, and so it is important to know when the control manager is active,
and when it is not.
When is the Control Manager Active?
The control manager is active only in New Measurements mode (which in-
cludes AutoProgram activity) while either of these is going on:
¥ the display is updating with new measurements
¥ in View File ( f2 level 1) looking at the current data file
Thus, the control manager is not active while matching the IRGAs, entering
file names, editing the display format, using the Filer, etc. The practical con-
1.
A trivial example is turning off the light source; once itÕs off, thereÕs no further
adjustment necessary. A not-so-trivial example is fixed flow mode, which main-
tains itself independent of software because of the hardware circuitry controlling
it.