What is the best method to test a rain sensor?

The best method to test a rain sensor is to simulate rain and observe if the system shuts off. This approach directly assesses the functionality of the rain sensor in real-world conditions. By simulating rainfall, you can verify whether the sensor accurately detects moisture and sends a signal to the irrigation system to shut off when sufficient water has been detected. This test ensures that the sensor responds promptly and effectively to prevent unnecessary irrigation during wet conditions, functioning as intended.

The other options may provide useful information, but they do not effectively test the sensor's operational capability. Checking rain gauge readings can indicate rainfall amounts but does not confirm whether the sensor itself is functioning correctly. Inspecting wiring for damage is a good maintenance practice but will not directly test the sensor's effectiveness in detecting rain. Similarly, adjusting the sensitivity settings may help optimize performance, but unless the sensor is tested under actual simulated rainfall conditions, it is difficult to ascertain whether it operates properly.