Which sensor detects the amount of water vapor in air to support greenhouse plant growth?

• A. Humidity Sensor
• B. Rain Sensor
• C. Temperature Sensor
• D. Flow Sensor

Answer: (A)

The main idea here is sensing how much water vapor is present in the air to manage greenhouse conditions. A humidity sensor is designed to measure water vapor in the air, typically reporting relative humidity. Keeping the air at the right humidity helps control plant transpiration, nutrient uptake, and disease risk, and it’s often tied to other climate controls like vents, heaters, dehumidifiers, or misting systems.

The other sensors don’t measure atmospheric moisture: a rain sensor detects precipitation outside and isn’t used for indoor humidity control; a temperature sensor measures air temperature but not the amount of water vapor; a flow sensor tracks the rate of liquid flow in irrigation lines, not air humidity. So, for monitoring how humid the greenhouse air is to support plant growth, a humidity sensor is the appropriate choice.