What You Need To Know Before Buying a Humidity Meter

Humidity sensors also called hygrometers, measure and report the relative humidity in the air. They can be used in homes for people with illnesses related to humidity; as part of home heating, ventilating, and air conditioning (HVAC) systems; in wine cellars or humidors. Humidity sensors can also be used in meteorology stations to predict and report weather, cars, office and industrial HVAC systems.

There is a wide range of humidity meters in the market, and sometimes be a real challenge to buy humidity meter that will work best for you. From simple hair hygrometers, polymer sensors, mirror dew point hygrometers to the exotic Lyman-alpha or infrared hygrometers, the range of available humidity sensors is really wide.

We present you the main types of humidity meters that are most popular and most widely used:

  • Relative Humidity Sensor – this hygrometer is based on an electronic component that absorbs water vapour according to the humidity of air and changes electrical impedance. It usually has the form of a “probe” attached by a cable or directly to electronics unit to display the humidity reading.
  • Condensation Principle Hygrometer – uses cooling to introduce controlled condensation. The temperature at which this happens is measured and displayed as dew or frost point.
  • “Dew-point” probe – a hygrometer based on an electronic sensor which changes electrical capacitance on absorbing water, capable of measuring trace levels of water vapour in dry gases. It is often scaled in units of frost point (dew point) and that is where its name comes from.
  • Psychrometer – this is a hygrometer which uses evaporative cooling as a humidity measure. It is also called wet-and-dry hygrometer and it is compared against one sheathed in a wet wick in moving air. The paired temperature values are used to find the humidity calculating or using tables.
  • Mechanical Hygrometer – uses change in length of hair or other organic material to measure humidity. Some types record on a chart driven by batteries or clockwork. Some very basic types are not powered at all. Nowadays, electronic sensor-based humidity meters are preferred, but many mechanical hygrometers remain in use for room monitoring.
  • Chilled mirror dew point hygrometer - offer one of the highest humidity measurements. They are virtually indestructible. It is one of the most precise methods of determining the water vapor content of a gas above 5% RH. It is recommendable to buy humidity meter in cases when you need precise measurements. This type can be easily cleaned. Use it when the gas sample has contaminants and particulates which could damage other types of humidity sensors.