Humidity Meter, Humidity Indicator, and Humidity Controller are three different types of devices used to measure, display, and control humidity levels in various applications.

Humidity Meter: A humidity meter, also known as a hygrometer, is a device used to measure the moisture content or relative humidity in the air. It typically provides a numerical value or percentage that represents the amount of water vapor present in the air relative to the maximum amount the air can hold at a given temperature. Humidity meters are widely used in weather monitoring, HVAC (Heating, Ventilation, and Air Conditioning) systems, industrial processes, agriculture, and indoor environments to assess and monitor humidity levels for various purposes.

Humidity Indicator: A humidity indicator is a device that visually indicates the humidity level in an environment using color changes or numerical readouts. These indicators are often used in packages or containers that need to maintain specific humidity conditions, such as in the storage of sensitive electronic components or certain products that can be affected by humidity. Humidity indicators are designed to provide a quick and easy way to determine whether the humidity inside a container is within the desired range or if protective measures need to be taken.

Humidity Controller: A humidity controller is a more advanced device that not only measures humidity levels but also has the capability to control and maintain humidity at a set target value. It typically works in conjunction with other equipment such as humidifiers or dehumidifiers to achieve the desired humidity level. Humidity controllers are commonly used in various industrial processes, greenhouses, storage facilities, and laboratories where precise control of humidity is essential for specific applications or to preserve sensitive materials.