Theory of Operation
4-15
orientation, there may be signicant variations in collar light intensity due to the
remaining structural components around the collar. Every effort has been taken to
reasonably minimize these structural shadowing effects.
Temporal variations in light intensity inside the collar area will occur due strictly to
shading effects. It is important to consider these temporal variations when
examining flux data. LI-COR has published a paper that describes the shadow
effects when using the 8100-104C Clear Chamber; request Application Note #131.
Measuring PAR with the 8100-104C
Measurements of Photosynthetically Active Radiation (PAR) for use with
the 8100-104C can be made with the LI-COR LI-190 Quantum Sensor. A Leveling
Stake (p/n 8100-604, pictured below) is available for mounting the
LI-190 and inserting into the ground near the chamber. Because the LI-190
provides a current output, a Voltage amplifier is required to convert the LI-190
current output, and amplify into a 0-5V output suitable for use with the
LI-8100A analog inputs (contact LI-COR for amplifier information). In single
chamber mode the amplified LI-190 signal can be wired directly from the amplifier
to the 8100-663 Auxiliary Sensor Interface Box. In multiplex mode the LI-190
requires a cable adapter from the amplifier to the 8100-104C Chamber. Non-
LI-COR amplifiers require the 392-08577 plug with bare wire leads (below). This
cable is terminated with a connector that plugs directly into the analog voltage
input channels on the side panel of the 8100-104/C.
Figure 4-5. The 8100-604 Leveling Stake (left) is used to mount and level the LI-190
Quantum Sensor for measuring PAR near the 8100-104C Clear Chamber. In multiplex
mode, the LI-190 requires the 392-08577 plug with bare wire leads (right) between the
amplifier and the chamber.
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