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today I would like to show you the rain detector on our meteo station, how it works and how to integrate.
Measurement principle
There are several ways and technologies to detect raining. A simple technology is to measure the ohmic resistance between two wires on a surface with rain drops. Such rain detectors has a meander wiring surface perpendicular to the sky. The disadvantages of this technique are, that the wires are exposed to the erosive climate. That reduces the lifetime of the sensor. Furthermore any pollution can cause a long term drift.
A similar technology is to detect rain drops using a capacitive measurement principle same as a touch pad on a laptop. The surface has a similar meander structure as the detector before but the surface is coated to protect the sensing area and to extend the lifetime by this way.
When rain drops fall on the surface a change of the capacitance is measured between two electrodes (meander wired) and the internal electronic switchs an internal relay on. A device internal heating function drys the drops over a longer time out.
Such a rain detector is the Kemo M152K
This sensor principle detects rain as far as rain drops falls on the surface. But it cannot measure a rain volume per square meter.
How to set up and connect to RMS?
The sensor is powered by 12V to supply the internal electronic and the permanent heating function .
The other two wires (internal from the switch of the relay) must be connected to a digital input of a Mini Logger (RMS-MDI-868/915).
Setup on our experimental meteo station
How to integrate into the RMS?
Add the Mini Logger RMS-MDI (Click on Tools -> Setup -> Devices -> New -> Wireless device -> Select gateway …).
After adding, the RMS shows a 0-(OFF) or 1-(ON) status for Rain or Dry.
Now it is meaningful to define an individual message for both statuses. For that click on Tools -> Setup -> Measuring points -> Choose the RMS-MDI and define the Settings.
Here you can define the display text individual.
The chart appears as follows:
Application
The customer can use rain sensors in combination with a warning or alarming function by SMS, telephone and email to react faster (e. g. to protect something) or to control automated e. g. to open/close windows or shutter.