237 Leaf Wetness Sensor
4
Width:
7.1 cm (2.75 in)
Length:
7.6 cm (3.0 in)
Depth:
0.64 cm (0.25 in)
Weight:
91 g (3 oz) with 10 ft cable
7. Installation
If you are programming your datalogger with
Short Cut
(p. 5)
(p. 6)
.
Short Cut
does this work for you. See Section
(p. 1)
, for a
Short
Cut
tutorial.
7.1 Sensor Preparation
Water droplets that form at the onset of condensation are often too small to
bridge the electrodes and so remain undetected. Droplets can be detected
earlier in formation by application of a non-conductive spreader to the surface
of the sensing grid. The spreader most commonly employed is flat latex paint.
Campbell Scientific supplies only uncoated sensors since coating preferences
vary between applications.
Campbell Scientific has not researched, nor does it recommend,
paint formulations. The following information regarding paint
formulation is intended only to introduce the concept.
Applying a thin coat of flat latex paint on the sensor surface is a generally
accepted practice in plant disease and other applications. Besides providing
some protection for the gold-plated electrodes, this paint allows tiny water
droplets to spread and bridge the electrodes.
Gillespie and Kidd
1
found that paint colo
u
r had significant effects on
performance and found off-white worked well. Their paint was formulated
with one part black pigment to 1000 parts white paint. East
2
found that greater
precision is obtained using a high quality flat latex paint. Some researchers and
agricultural weather networks do not paint the sensor.
Before painting the sensor, clean it gently with alcohol.
However the surface is prepared, the response of the sensor is, in reality, only
an index against which actual leaf wetness can be estimated. While the absence
of a spreader will decrease sensitivity and increase the chance of scratching the
gold-plated electrodes, bare sensors may grant greater consistency and less
maintenance across a network.
7.2 Sensor Deployment
The sensor should not come in contact with leaves. The sensor is not supplied
with a mounting bracket. Gillespie and Kidd
1
found that sensor orientation
affects performance. As with surface preparation, orientation varies across
applications and users. A common practice is to mount the sensor such that it
NOTE
NOTE
