LI-COR LI-6400, Manual

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Light Sensor Considerations
Gallium Arsenide Phosphide (GaAsP) Sensor
8-8 Using the LI-6400
8
Temperature
Our tests have indicated that the GaAsp sensor has a temperature coefficient
of about +0.2% C
-1
.
View Angle
The GaAsp sensor, especially as mounted in the LI-6400 leaf chamber, is sub-
ject to serious errors when measuring irradiance at non-normal incidence an-
gles. There primary reason for this is reflections from the chamber walls. For
example, at angles when the sun reflects off the wall nearest the sensor, the
sensorÕs readings can be boosted by 25%. For this reason, you should not trust
this sensor very much at non-normal incidence angles.
Figure 8-4. Spectral response of GaAsP sensor and ideal quantum response.
0
10
20
30
40
50
60
70
80
90
100
300 400 500 600 700 800
Relative Response (%)
Wavelength (nm)
GaAsP Sensor
Ideal Quantum
Sensor