Hygrometers, and Handling the Humidity

November 08, 2024

What is a hygrometer, and how does it measure humidity?

Hygrometers are a weather instrument that measure water vapour in the air otherwise known as humidity levels. Hygrometers are widely useful for aiding in seed germination, monitoring and maintaining living conditions and protecting materials including wood and leather.

Hygrometers are used in a variety of places for many different reasons, these are,

Meteorology:

Meteorologists use hygrometers to help predict weather changes, relative humidity levels and precipitation patterns. That show up on our weather apps daily.

Gardening and Agriculture:

Hygrometers are essential to greenhouse, land and allotment management. Monitoring humidity levels helps aid in optimum seed germination and overall crop health and yield. During seed germination humidity can be helpful especially during initial germination, however high levels of humidity when seedlings begin to grow is not optimal. This is because seeds will not be able to perform a process called ‘transpiration’ properly, a process of releasing oxygen through their stomata’s (tiny pores on the leaf). If this cannot happen the roots will suffocate and eventually die. To help keep humidity levels low, a small fan on medium or low has been proven effective at maintaining optimum humidity levels during seed germination.

Museums:

Museums use hygrometers to monitor moisture levels to protect valuable items such as artefacts and artwork. Items that area typically featured in museums are rare and usually old, therefore they can be or become fragile, requiring proper maintenance and care. Monitoring various humidity levels in museums is vital for the attraction’s success. As various areas will require different levels of optimum humidity, and the way to monitor these levels is the usage of hygrometers.

Homes:

Hygrometers are also useful to monitor humidity levels in your home, displaying to you how much moisture there is inside your home, understanding humidity can help reduce condensation and mould in your home whilst also protecting your health and especially young children and babies to ensure sufficient and safe air quality. Indoor humidity should sit between 40-60% relative humidity. If humidity levels drop lower than this, airborne viruses can remain infectious five times longer.

How do they measure humidity?

There are different types of hygrometers available, at ClimeMET we provide a wet and dry bulb hygrometer and a dial hygrometer.

Masons Wet and Dry Bulb Hygrometer cm3505

The Masons wet and dry hygrometer consists of two thermometers, one wet with a wick attached over the bulb of the thermometer (like a sock) and one dry. Humidity is measured by the increase in the difference between the wet bulb and the dry bulb. Using the Hygrometric conversation table that comes with your hygrometer, you can determine % relative humidity. You do this by:

Recording current temperatures shown on both thermometers.
Subtract the wet temperature from the dry temperature, this is your depression of the wet bulb.
Using the dry temperature and wet bulb depression, refer to the chart and read at the point where the two values meet on the conversion table.

Our Hygrometer Dial measures differently, and is widely used both indoors and outdoors.

Hygrometer Dial CM4303:

Our aneroid hygrometer dial displays a scale with the measurement range of 0-100% relative humidity. The outer scale displayed on the dial measures %RH to the nearest 10% and the inner scale measures the nearest 5%RH.

A spiralled metal spring mechanism expands and contracts depending on %RH. This spiral expands during periods of high humidity and contracts during periods of low humidity. The needle pointer at the front of the dial is attached to this mechanism and moves as the spiral spring expands and contracts, displaying the %RH on the dial face.

FAQs:

What is a hygrometer?
A hygrometer is an instrument used to measure the moisture content or the humidity level in the air. It provides readings to help monitor and control humidity in various environments.

Why is measuring humidity important?
Measuring humidity is crucial for various reasons, including:
Maintaining comfortable indoor humidity levels.
Preventing respiratory issues and allergies caused by mould and dust.
Protecting materials and products like wood, paper, and electronics from moisture damage.
Ensuring optimal conditions in manufacturing, food storage, and other industrial processes.

How often should I check my hygrometer?
It's recommended to check your hygrometer regularly, especially in environments where understanding humidity levels are essential, such as greenhouses, museums, or industrial settings. Regular checks ensure accurate readings, and optimal humidity control.

What is relative humidity?
Relative humidity is the most common measurement of humidity, it’s the percentage of moisture in the air compared to the maximum amount of moisture the air can hold at a specific temperature, and displayed as a percentage.