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LWS Dielectric Leaf Wetness Sensor
The CR200(X) uses the
ExDelSE()
CRBasic instruction to measure the probe’s
output. The
ExDelSE()
instruction and parameters are as follows:
ExDelSE
( Dest, Reps, SEChan, ExChan, ExmV, Delay, Mult, Offset )
7.3.2 Interpreting Data
Many leaf wetness applications, such as phytopathology, require a Boolean
interpretation of leaf wetness data such as whether or not water is present. A
Boolean threshold is determined by analyzing a few days of time series data.
Consider time series data in FIGURE
, which were obtained at 5 Vdc
excitation. The sensor yields ≈445 mV when dry, ≈475 mV when frosted, and
>475 mV when wet. Therefore, a Boolean wetness threshold of 500 mV
should serve well for interpreting these data.
FIGURE 7-3. Typical LWS response
Duration of leaf wetness can be determined either by post processing of data,
or by programming the datalogger to accumulate time of wetness based on the
Boolean threshold. Accumulation of dust and debris, such as avian fecal
matter, will change the Boolean threshold. So, while having the datalogger
accumulate time of leaf wetness, or time of frost, may be convenient, assurance
of data quality requires retention of the base mV measurements.
Collect data frequently enough to capture changes in surface
wetness. A sample frequency of 15 minutes or less is usually
necessary to accurately capture leaf wetness duration.
NOTE
8
Содержание LWS
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