Humidity meter: how to works and their principles

Humidity is a presence of water vapor in the air but Humidity Meter is needed for Humidity sensing for human comforting and control systems in the industries. Humidity Meter is two different types and their sensing and working principle depend on the Psychometric.

The Terminologies:

Humidity Meter uses simple Psychometric measures that study the thermodynamics of the air calculating the amount of water vapor present in terms of other gases concentration in air in terms of temperature and pressure. Several terminologies are used for Humidity measurement in accordance with Humidity Meter. The most common ones are Dew/Frost point (D/F PT), Parts per Million (PPM), Relative Humidity (RH). Relative humidity as the name suggests measures the relative ratio of mass vapor pressure to saturated mass vapor pressure. Dew Point is generally used in high Industrial processes and control system when dry gas comes into act. It measures the temperature at which the water vapor in a gas transforms into a liquid. All these terms are related to each other and have a certain range of working.

Humidity Sensing and Principles:

Humidity Meters sense humidity in various methods. Thus the Humidity Meters or sensors are divided majorly into two types- Relative Humidity Sensors and Absolute Humidity Sensors. Hygrometers are the term used for such instruments that use relative humidity sensor as their working principles. Dewpoint Hygrometers, Dry and Wet bulb Hygrometers and Electronic Hygrometers are common. In last few years, Electronic Hygrometers has been the real talk.

Capacitive Sensors:

The sensors on an Electronic Hygrometer can be of two types Resistive and Capacitive. The dielectric material is basically kept between a pair of electrodes that forms a capacitor. Capacitive sensors have their dielectric material as a plastic or polymer with the dielectric constant ranging from 2 to 19. At absence of moisture, this sensor gives the value of capacitance. In case of room temperature the dielectric constant is almost 80 thus absorption of water vapor increases capacitance. The amount of moisture present in sensor and the sensor capacitance is the real working principle in a capacitive sensor in a Humidity Meter. The electrode is formed of gold or platinum and is placed in an Alumina substrate. The polymer layer that gets deposited on the Humidity meter measures the humidity. The polymer layer acts as the dielectric.

Resistive Sensors:

It uses resistance values of the sensor element according to the change in humidity. Conductors are made of gold and printed by Ruthenium Oxide and made in a shape of a twisted comb forming an electrode. The polymeric film is applied and is measured according to movement of ions. The movement of ions in and out depicts the resistance of the sensors.

Uses:

Humidity meters have huge applications at both Industrial level and Domestic Levels. In Medical industry, humidity control is very much required for sterilizers, biological equipment, incubators, respiratory equipment and so on. In semiconductor industry humidity controlling has used during water processing. Humidity Meters are needed for dryers, ovens, paper and textile processing, chemical gas purification and in agricultural plantations. In domestic level is used to check humidity level in the air, used in ovens and for cooking control.