Campbell LWS, Инструкция по эксплуатации

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LWS Dielectric Leaf Wetness Sensor
heat capacity of the leaf is ≈1425 J m –2 K –1 . This heat capacity is closely
approximated by the thin (0.65 mm) fiberglass construction of the LWS, which
has a heat capacity of 1480 J m –2 K –1 . By mimicking the thermodynamic
properties of a real leaf, the LWS closely matches the wetness state of the
canopy.
The sensor closely matches the radiative properties of real leaves. Healthy
leaves generally absorb solar radiation in much of the visible portion of the
spectrum, but selectively reject much of the energy in the near-infrared. The
surface coating of the LWS absorbs well in the near-infrared region, but the
white color reflects most of the visible radiation. Spectroradiometer
measurements indicate that the overall radiation balance of the sensor closely
matches that of a healthy leaf. During normal use, prolonged exposure to
sunlight can cause some yellowing of the coating, which does not affect the
probe’s function. The surface coating is hydrophobic — similar to a leaf with
a hydrophobic cuticle. The sensor should match the wetness state of these
types of leaves well, but may not match the wetness duration of pubescent
leaves or leaves with less waxy cuticles.
6. Specifications
Features:
• Imitates characteristics of a leaf
•
Does not require painting or calibration of individual sensors
•
Detects trace amounts of water or ice on the leaf surface
• Compatible with Campbell Scientific CRBasic dataloggers: CR6,
CR200(X) series, CR800, CR850, CR1000, CR3000, CR5000, and
CR9000(X)
Measurement Time: 10 ms
Excitation: 2.5 Vdc (2 mA) to 5.0 Vdc (7 mA)
Minimum Excitation Time: 10 mS
Output: 10% to 50% of excitation
Operating Temperature: –20 to 60 °C
Probe Dimensions: 11.2 cm x 5.8 cm x .075 cm
Maximum Lead Length: 250 ft
Interchangeability: Interchangeable without painting or individual
calibration
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