Humidity Meters and Hygrometers | Action Instruments

What is Humidity?

Humidity is the presence of water vapour in air (water in a gaseous form) which is not visible to the human eye. Humidity measurement taken by a hygrometer are used to predict condensation or frost and is used in psychrometric calculations to get a dew point, Dry Bulb Temperature or Wet Bulb Temperature, Enthalpy etc..

Humidity effects many things in our day to day lives.

The presence of humidity will effect the perceived temperature and a higher humidity does make the average person feel hotter. The Humidex was created to describe a comfort level by calculating temperature and humidity together to give a scale of comfort.

Electronics are effected by humidity levels with most electronic devices having a minimum and maximum temperature and humidity specified, but despite these figures there are extensive. Electro mechanical devices will have extended lifespan if humidity is controlled within a specific range.

Food and pharmaceutical industry are very reliant on a controlled humidity environment. Due to higher humidity being advantageous for bacterial, mold and mildew growth.

Measurement of humidity can be perceived with a few techniques:

Absolute humidity:

Is the water content in air and measured in grams per cubic meter. An easy way to explain this measurement is as if you were able to extract all the moisture from air in cubic meter into a liquid form and then weight it.

Relative humidity:

Measured as a percentage 0% to 100% of the current absolute humidity relative to the highest point for a specific temperature At 100% the air would often be referred to as saturated. In essence water vapour is at equilibrium and no more evaporation would occur when water in liquid form is exposed to this air that has 100% relative Humidity. It is in this state that dew, fog or frost is likely to form.

Specific humidity:

The ratio of the mass of water vapour to the total mass of the moist air parcel.

How do we measure Humidity with hygrometer or Humidity Meter?

There are various methods to measure Humidity, and are commonly referred to as Hygrometers. These include wet and dry bulb Hygrometers, dew point hygrometers, hair tension hygrometers, captivate or resistive relative humidity sensors. As a distributor of Rotronic who predominantly focus on Relative Humidity Meters through captive sensors. These humidity sensors consist of a substrate on which a film of polymer is deposited between electrodes, which forms a capacitor. The sensor will absorb water vapour from the air and will find and equilibrium between sensor and air. The result is that the capacitance change as humidity increases or decreases.