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Rain Sensors – A Good Bet for Irrigation Controllers


A rain sensor or switch is a device that gets activated by rainfall. It serves as an effective water conservation device when linked to an automatic irrigation system that’ll shut down on its own when it rains. It’s a useful mechanism to have in residential, commercial, and industrial setups alike.

In the paras that follow, you’ll get to know about the various kinds of rain sensors in use.

Rain Sensors – Types and Functionality

The rain sensor has gone through various stages of evolution in recent years to reach where it is today. Nowadays, it is possible to find different kinds of rain sensors that come packaged with their own set of features and benefits. Here are the three most common types of rain sensors available in the market.

Water Collection Basin

The oldest type of irrigation rain sensor, which is utilized till date, comprises of a water-collecting cup or basin that doubles up as a rain gauge. Once a pre-defined amount of water gets collected in the basin, the heaviness of the water turns off the entire irrigation system by making a switch trip. The issue with this variant of the rain sensor is that it fails to discriminate between debris and rain that fills the container. The watering cycle can be prematurely interrupted in this system.

Rain Sensors Working on the Concept of Conductivity

Second generation rain sensors have adopted the principle of conductivity. In this system, the bottom of the basin contains two electrodes. As and when the water level touches the electrode, a circuit is completed and this leads to the tripping of a switch. In this case, the heaviness of any debris will not cause the switch to trip. However, the debris may displace water, thereby making the switch drop prematurely even if a light shower takes place.

Hygroscopic Disk

The third type of rain sensor is the most popular in the lot and discards the catch basin. It comprises of hygroscopic disks made of synthetic materials that are quite similar to cork; they tend to expand when wet. Alan Lander from Hydro Dynamics Corp (https://hydrodynamicscorp.com/) says that you can save money on watering your lawn by installing a rain sensor, so that your irrigation system will not turn on if the ground is already wet. In this rain sensor, the expanded disk automatically triggers a switch once a pre-defined quantity of rainfall takes place. The hygroscopic disks have proved to be reliable and precise.


While choosing a rain sensor, it’s essential to check the power it draws among other things. You may want to check out wireless sensors that are easy to install and do not have any wires that may get damaged over time. The mounting hardware and their versatility have to be considered as well. If you’ve been looking for an effective lawn irrigation system that’s affordable and functional alike, it’s a good idea to opt for the sensors using the hydrodynamics principle. Check them out to get an effective irrigation system at the earliest.

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