Humidity Meters (Hygrometers)

The purpose of a hygrometer is for monitoring or measuring the moisture content of the air to decipher humidity. The calculations of the various measurements of humidity can be quite complex. As such, we aim to keep our instruments as simple to use as possible. The range is full of specialised features and benefits to ensure we have the right tool for the job. 

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Temperature and Humidity Data Loggers

Looking to record temperature and humidity over expansive periods? What you need is a humidity data logger. Using these devices is simple. You begin by choosing a logging interval (This is how often you want to take a measurement and can range form every second to every hour). You then place the device in the desired area and begin recording. Through either an LCD display or PC software the results are viewable. This offers visual representation of all logged points during the measurement period.

Data loggers are essential in transportation and storage of temperature and humidity sensitive goods. Without one, complying with strict regulations can be next to impossible. Regulations governing such activity requires traceable logs for the entire storage duration. If humidity isn't required you may find our temperature data loggers more useful.

Hygrometer and Humidity Meter Features & Applications

The product list below contains all our thermo-hygrometers including our hand-held and free-standing models. Our free standing models are perfect for consistent placement in an office or working environment. The large LCD displays are viewable from distance allowing easy use. Our free-standing models have become the most popular in our range. Their simplicity and large display has made them a staple in many workplace environments. They have become preferable over simple thermometers for offices due to their better representation of environmental conditions for a small cost. Our hand-held models are great for delivering one-off, single results. They are excellent for HVAC, clean rooms and air streams. Our pen-type and pocket thermo-hygrometers offer a compact approach. They are ideal for workmen on the move and feature impact resistance casings.

Our more complex models measure dew-point and wet-bulb and also increase in accuracy. They have a mixture of features such as a min/max memory and data hold functions. We also offer the unique infrared thermo-hygrometer for surface targeting.

Humidity Data Logger Important Features

When choosing a device make sure you account for three important features. The capacity, logging interval and measurement period. The capacity is how many readings the device can hold. Within our selection of products, this ranges from 16,000 to 250,000+ readings. Every user should compare this with the logging interval. This will give you the measurement period. At every 10 seconds a user would use 16,000 readings in just short of 2 days. The larger capacity data loggers would allow roughly 30 days of continuous recording. Make sure you choose a model that will cover the measurement period required.

Thermo-Hygrometers / Temperature and Humidity Meters

The prefix thermo is a reference to the hygrometers ability to measure temperature. Most humidity measurements return relative humidity as a standard value. Relative humidity is relative to the current temperature. As such you should expect both measurements on any humidity meter you buy. Don't go getting confused by jargon, all humidity meters are thermo-hygrometers.

Hygrometer Readings

Humidity meters can display many different measurements dependant on the specification of the model. The guide below explains the most common readings you a likely to find on our products.

Relative Humidity

Relative humidity is represented by the %RH symbol and is the most commonly used measure of humidity. We define relative humidity as the amount of water vapour in the air compared to the greatest possible amount at that temperature. For example, 50 %RH would mean simply that 50% of the maximum amount of water vapour is currently in the air. Remember, this is relevant to the temperature. The higher the temperature, the more water vapour can be held in a given volume of air. This means that the air is fully saturated when at 100 %RH. This is when condensation would begin to form on surfaces.

RH readings are provided by all humidity meters in the ATP range.

Dew Point Calculation

Dew point becomes easy to understand once we understand relative humidity. It is a measure of the temperature required for condensation to begin forming if the amount of water vapour were to remain constant. Like relative humidity, the device measures the amount of moisture in the air but instead returns the temperature at which the relative humidity would be at 100% saturation. This is when water vapour begins to condense from the air. Any temperature higher than the dew point indicates that the moisture would stay in the air as vapour. This calculation is important in applications such a building where condensation causes damp which can cause mould and structural problems.

Dew point is available on a select number of our hygrometers

Wet Bulb Calculation

The wet-bulb temperature is very similar to the dew point and is often confused. The dew point is the temperature required to hit 100% relative humidity with the current amount of water vapour in the air. In comparison wet-bulb is the temperature the environment would have at 100% RH if it were cooled by adding water vapour (evaporating) into it.

At 100% relative humidity the dew point, wet-bulb and actual temperature are all the same. At lower humidity levels the dew point will always be the lowest temperature as water vapour is not added. The wet-bulb temperature will be in between the two showing the lowest temperature possible in current ambient conditions.

A selection of models are available with the wet-bulb function.

For advice about which hygrometer equipment is best suited to your application contact our Technical Support Team. Please call direct: 01530 566804 or email: For sales please call: 01530 566800 and if you would prefer you can contact us by email on

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