The Best Moisture Meters: Shopping Guide and Recommendations (02/23)

The right air humidity is essential for a healthy and comfortable living climate. Humidity that is too high or too low has negative effects, especially on the skin and respiratory tract. The humidity meter is responsible for controlling and monitoring the air humidity.

In our humidity meter test 2023 you will find some important information that you should pay attention to if you want to buy a humidity meter. This should not only help you with your purchase decision, but also provide additional insights.

Summary

• With moisture meters or so-called hygrometers you can measure the moisture in the air as well as in natural building materials.
• There are different types of hygrometers, which differ in their application. Both analogue and digital hygrometers are available for purchase.
• The measuring range and the penetration depth are the most important purchase criteria. The wider and deeper the measurement, the more qualitative the moisture meter.

Moisture Meter: Our Choices

Guide: Questions you should ask yourself before buying a moisture meter

Decision: What types of hygrometers are there and which is the right one for you?

The term hygrometer comes from ancient Greek and is made up of “hyrós”, which means moist, and “métron” = measure.

Accordingly, this instrument determines the moisture content in the air. It is available in analogue or digital form. Since the Middle Ages, various methods have been used to measure the humidity of the air, but the results were inadequate.

The first hygrometer was the hair hygrometer. It was demonstrated in 1783 by Horace-Bénédict de Saussure, for which he used a blond woman’s hair. Over the years, new methods and procedures were developed to optimise these instruments.

What are the characteristics of an analogue hygrometer and what are its advantages and disadvantages?

Analogue or mechanical hygrometers are also called absorption hygrometers. These instruments contain an absorbent material that expands at high humidity and contracts at low humidity.

The analogue hygrometer must be calibrated regularly and before first use. If the instrument is not calibrated correctly, deviations of up to five percent will occur. The values can be inaccurate. The advantage of a digital hygrometer is that it does not need a power supply or batteries.

What are the characteristics of a digital hygrometer and what are its advantages and disadvantages?

Unlike analogue hygrometers, digital hygrometers have additional functions. Depending on the model, these devices can not only indicate the humidity value but also the temperature or the dew point. Others also have a function for measuring surface humidity.

Digital hygrometers measure more accurately and do not need to be calibrated. The display and various buttons make them very easy to use. However, in order to function, these hygrometers require a power connection or batteries.

Buying criteria: You can compare and evaluate humidity meters based on these factors

• Measuring range and penetration depth
• Power supply
• Functions

Measuring range and penetration depth

The measuring range is one of the most important purchase criteria. It determines the range that you can measure with a moisture meter in the air or in a certain material. High-quality devices generally have a wider measuring range. However, these models are also priced higher.

Humidity meters give the measured value in percent or in digit units. Percentages are usually used to indicate the humidity of the air. The proportional amount of humidity is displayed on the device.

Although the percentage readings are easier to understand, the digit readings are more accurate. To measure the humidity in building materials such as wood or masonry, the indication in digits is used. These instruments are calculated with the help of current voltage. One digit usually corresponds to 0.1 volts.

To classify the measurement results, a table is included with the purchase of the respective instruments.

The wider and deeper the measurement, the more qualitative the moisture meter.

The penetration depth is also an important criterion. It tells you how deep the sensors can penetrate into a material to determine a value. The penetration depth for most devices is between 1 and 40 mm.

Again, the deeper the sensors penetrate the material, the more accurate the measurement results.

Power supply

As we have already learned from the guidebook, digital hygrometers need a power supply or batteries. Analogue hygrometers, on the other hand, do not.

It is very important to know what kind of batteries the instrument needs. You will find this information in the product description. Most devices use button batteries for power supply.

These are smaller and lighter, but more expensive and harder to find in the right size. It is advisable to choose a moisture meter that uses regular AA or AAA batteries. They are not only cheaper to buy, but also easy to find.

Functions

To choose a suitable hygrometer, you should first know what purpose it will serve. This is because models with several functions are also correspondingly more expensive. Combined devices contain several functions. They can not only measure the humidity of the room but also serve as a thermometer, barometer or clock.

This means that the device can also be used to wake you up in the morning. However, these functions are only useful if they are placed in a visible location. With handheld devices, the minimum and maximum values are very helpful. This makes it much easier to find the place with the highest moisture content. This increases the accuracy.

The hold function allows you to record readings by keeping them on the display for longer. This function is very useful in narrow niches or hard-to-reach places. However, it is included with most devices.

Interesting facts about moisture meters

How does a moisture meter work?

There are different types of moisture meters so that the moisture content in the air or in natural building materials can be determined. For this reason, the measuring methods of the devices also differ.

In order to measure the moisture within the object to be measured, most models have electrodes. An electrical charge is thus sent into the object. The moisture content is thus determined based on the conductivity of the material.

However, you should bear in mind that different materials have special requirements with regard to moisture measurement, which subsequently also affects the functioning of the moisture meter.

To determine the moisture content of wood, you do not need a specific measuring method. But for building materials like cement or screed, you do.

These materials influence conductivity because they contain different substances and salts. For this reason, you need specific equipment to measure such objects.

What should be the recommended temperature and humidity per room?

Although everyone’s preferences are different, different temperature and humidity levels are recommended for different living spaces. These are explained in the following table:

Room	Recommended humidity	Recommended room temperature
Living room	40-60%	20 ° C
Bedroom	40-60%	18 ° C
Children’s room	40-60%	21 ° C
Kitchen	50-65%	18 ° C
Bathroom	50-65%	23 ° C
Basement	50-65%	13-15 ° C

The humidity values in the individual rooms differ depending on the season. In summer, the humidity content of the air is often very high. This is due to the fact that when the outside temperature is warm, the moisture-laden air from outside cools down inside the room.

As a result, the room humidity increases. In winter, on the other hand, the relative room humidity decreases because the cold air from outside is heated in the room.

How do I calibrate a hygrometer?

Analogue hygrometers must be calibrated before first use and at regular intervals thereafter to give correct readings. It is recommended to calibrate every fourth to sixth month.

If the humidity value of your immediate environment differs from the displayed reading, you should readjust the humidity meter. There are two different methods for calibrating analogue hygrometers:

Humidity rag method

This method involves wrapping the hygrometer in a damp cloth for about two hours. The meter should then read a value of 98 percent relative humidity. It is important to maintain a constant temperature. In addition, the readjustment should take place in a closed room.

Salt method

For this method you need a freezer bag, salt and a glass. First you put the hygrometer in a freezer bag. Fill the glass with a tablespoon of salt. Then you should pour water into the glass until it reaches a porridge-like consistency. Pour this into the freezer bag. When sealed, the moisture meter should show a value of 75 percent humidity after about two hours.

This procedure should also take place in a closed room. If the value displayed is not correct, you can correct it with the help of the adjusting screw.

How accurate are humidity meters?

Depending on the model and use, the accuracy of humidity meters can vary. With analogue hygrometers, we usually have to reckon with a deviation of up to five percent. Higher deviations can also occur if the hygrometer is not calibrated regularly.

In general, however, hygrometers are very accurate. It should be noted, however, that a different measuring method is needed depending on the use. Humidity readings may be misrepresented if you use the wrong instrument for your application.

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