Types of moisture meters - how they work, distinctive features

A moisture meter refers to an electronic instrument used to measure the moisture content as a percentage of the total weight of an object. Such devices help to carry out a qualitative analysis of various materials and most accurately assess their characteristics necessary for further storage and operation for their intended purpose. Therefore, moisture meters are essential to effectively monitor and maintain optimal productivity levels in many industries, including wood, agriculture and construction.

Peculiarities

A moisture meter is a device that measures the percentage of moisture in a gas or solid. Such a device can also be used for working with bulk materials. The well-known hygrometer (determiner of relative air humidity) is a special case of a moisture meter. The purpose of using such devices is varied: they allow you to control the microclimate and comply with technological requirements. Modern moisture measuring instruments are manufactured almost exclusively on an electronic component base.

This technique is especially important in industry, where many types of raw materials, semi-finished and finished products can absorb significant amounts of moisture from the air. It inevitably affects the quality of finished products, their durability, and sometimes even prevents you from getting at least a decent product. Therefore, very strict requirements are imposed on the moisture meter.

Due to the variety of applications, it is impossible to get by with just one version of such a device. And therefore, many varieties of such technology have appeared.

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Kinds

The market for such devices is large: from small compact moisture meters to huge devices with many different functions. Let's look at the two most popular types.

• Needle (contact) Designed for extremely accurate measurement of the moisture level of various lumber and wood products. Determination of humidity occurs by measuring and converting the electrical resistance of the material under study into a percentage using the conductometric method.
• Contactless. Designed for high-precision determination of the moisture level of wood products using the dielcometric method. The measurement takes place in several stages: the type of species is set on the device, it is leaned against the surface of the wood, a button is pressed and the measurement result is displayed on the indicator.

Basic selection options

Wood moisture meters are available to the mass consumer; different models have their own advantages and disadvantages. To work with lumber, you can limit yourself to a needle moisture meter; when making furniture, working with plywood, MDF and chipboard, it is better to choose a non-contact model. Modern models are compact, have an LCD display, an intuitive interface and are equipped with additional options: temperature measurement, storing results, automatic shutdown, etc.

Features of various types of moisture meters are:

• Needle moisture meters are the cheapest, they are simple and compact, and allow you to quickly take measurements. This type of meters has a significant error when the sample humidity exceeds 30%. During measurements, the integrity of the surface is compromised. The devices are designed to work with chemically untreated lumber.
• Non-contact moisture meters are more expensive, equipped with an electromagnetic field generator and processor, and consume more energy. The measurement accuracy is affected by surface roughness; on uneven surfaces the device produces significant errors. Non-contact moisture meters are multifunctional; the devices allow you to work with wood and other materials: sawdust, chipboard, concrete, MDF, plasterboard.

The consumer decides which moisture meter to choose depending on the tasks being solved.

Better needle hygrometers

Let's look at the best models of needle moisture meters for wood.

Benetech GM605

Inexpensive needle type hygrometer. It has a small body and a protective cover for electrodes. Thanks to this, it easily fits into your pocket and can be carried from place to place. It has raised notches on the sides that make it easier to hold the device.

The screen is minimalistic and does not display any information other than the research result. It is indicated as a percentage.

For material with different degrees of wetting, different operating modes must be used. They are selected with the “Set” button. There are four such modes in total:

• 1 – for measuring wood with a humidity level of up to 24%;
• 2 – for measuring wood with a humidity level of up to 30%;
• 3 – for measuring wood with a humidity level of up to 37%;
• 4 – for measuring wood with a moisture level above 40%.

The device operates only at positive temperatures. You can only measure the moisture level not only in wood, but also in any other building materials: brick, concrete, polymer boards.

The main disadvantage of the model is that with high humidity of the object under study, the error in readings increases. Already at 50% - 60% they may be incorrect.

The device is powered by two standard AAA batteries. The compartment for them is located in its rear part. Batteries are included in the delivery package.

The cost of the device ranges from 1,000 to 1,500 rubles.

Smartsensor AR971

A more expensive version of the hygrometer, which will cost about 2,500 rubles. Outwardly, it is very similar to the Benetech GM605, but has one significant difference - it is capable of measuring materials with a high moisture content. Correct readings are possible at humidity levels up to 70% - 75%.

For different conditions it is also necessary to select different modes. There are also four of them here, only they have a wider range of values.

The needles are noticeably thinner than on cheap models. They do not need to be placed deep into the tree - 1 - 1.5 millimeters is enough.

The screen is black and white. It has LED backlighting that allows you to work even in low light conditions.

The electrodes are also covered with a protective cover, which protects them from damage.

It is possible to save readings in the device’s memory.

Power supply is from a 9 V Krona battery. It is not included in the delivery package.

TK100

A professional universal hygrometer that can measure any humidity in any material in almost any conditions. The price of the device is appropriate - from 8,000 to 9,000 rubles.

The error of readings does not exceed 0.5% - 0.6%. Moreover, such values ​​are maintained at humidity levels up to 80%.

You can examine not only wood, but also any other materials, including bulk materials (for example, sand). For this purpose, the device has steel probes 30 centimeters long. They can be immersed in bulk material to measure moisture content at depth.

For measuring wood, the probes have sharp tips. They are introduced into the material to a depth of 1 - 1.5 millimeters.

The measurement results are displayed on a black and white LCD screen with LED backlighting. They can be saved in the device memory.

The model is powered by four AAA batteries.

Review of popular models

As already written above, the domestic market offers a fairly wide selection of models of moisture meters from Russian and foreign manufacturers. In this section of the article we will talk about some of them.

"Control Hydro Pro"

Appearance of "Condtrol Hydro pro"

This model is a Russian development, its main technical characteristics are given in the table below:

The cost of the model according to Yandex.Market as of the third quarter of 2022 is:

Control Hydro Pro

"EM4806"

Appearance of "EM4806"

This model is produced (Germany), its main technical characteristics are given in the table below:

The cost of the model as of the third quarter of 2022 is 1,500 – 2,000 rubles.

"GMH 3830"

Appearance of "GMH 3830"

The model is produced by GREISINGER electronic GmbH (Germany), its main technical characteristics are given in the table below:

The cost of the model according to Yandex.Market as of the third quarter of 2022 is:

GREISINGER GMH 3830

"SEM DT-125N"

Appearance of "SEM DT-125N"

The moisture meter is made in China, its main technical characteristics are given in the following table:

The cost of the model according to Yandex.Market as of the third quarter of 2022 is:

SEM DT-125N

Non-contact devices

The dielcometric apparatus tests the material at a certain distance without violating its integrity. Its sensors are mounted on the working surface, replacing probes. High accuracy is ensured when quickly examining a sample, and it is also possible to store the research results in memory.

More expensive models allow scanning at a depth of 50 mm. It is advisable to use the device when it is necessary to perform a calculation based on the lower threshold of a parameter.

It also has the option to evaluate the temperature and humidity of the environment. This device is indispensable when analyzing solid and dense workpieces.

Harvia SAC92200

Harvia SAC92200

Country of origin: Finland. The body of the model is made of wood in eco-style. It has the shape of a rounded square, into which a clear dial is inserted, the measurement step of which is 10 units. The body material is birch. The model has a hair operating principle. Measuring range: pressure from 0 to 100%, temperature - from -15 to +55C° .

Advantages:

• nice design;
• low cost;
• high accuracy;
• ease of operation.

Main disadvantage:

• long period of response to changes in air humidity.

Laboratory and portable moisture meters

Grain moisture is measured in laboratory and field conditions; according to this, the entire variety of moisture analyzers is divided into laboratory and portable devices. But for moisture meters of any type, the most important characteristic is the accuracy of measurements.

The greatest accuracy in measuring grain moisture is provided by analysis based on the use of special drying ovens. To carry it out, a grain sample, previously ground, is dried for 40 minutes at a temperature of 130 degrees. The sample is then cooled and weighed. The difference between the mass of the sample before and after drying is the basis for calculating the percentage of moisture. But this method is only suitable for laboratory conditions.

Portable (portable) moisture meters for express analysis work based on measuring either the dielectric constant of a substance (dielectric moisture meters) or on the absorption of acoustic or electromagnetic vibrations by a grain sample (flow moisture meters).

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TFA 45.2033

TFA 45.2033

Country of origin: Germany. The mechanical type hygrometer is made in the shape of a circle. The case has a brass ring and an informative dial, which is divided into comfort zones. Measuring range: humidity from 0 to 100%, temperature from -15 to +55C°. The device has a wall mount.

Advantages:

• low cost;
• ease of operation;
• wall mounting option.

Main disadvantage:

• When direct sunlight hits the device, it gives readings with a large error.

Best models

If you need to measure grain moisture, the Fauna-M model is suitable. This is a microprocessor device designed for oilseeds and grains. “Fauna-M” can be used during harvesting, and when monitoring the quality of harvested grain, and during storage, and during express analyzes during processing. The device operates in a dielectric method, and the measurement results are displayed on an alphanumeric display with backlight. There is a sensor that determines the temperature of the grains; There is also a setting that compensates for errors caused by temperature changes.

By adjusting the calibration of the device, you can adapt it to a specific type of grain crop. Even in the most difficult cases, the measurement error will not exceed 1.5%. The system is designed to work with :

• wheat;
• soybeans;
• peas;
• sunflower;
• rapeseed;
• triticale;
• mustard;
• flax;
• 8 more crops;
• optionally with chickpeas, safflower and other grain plants.

Testo 606-1 is a moisture meter for measuring the water content in wood and building materials. The model is included in the federal state register. Its memory contains characteristic curves for various types of controlled substances and wood species. You can successfully explore:

• beech;
• cement beacons;
• maple;
• concrete mixture;
• brickwork;
• pine;
• plaster;
• larch;
• mortar;
• spruce.

Thanks to the Hold option, reading measurements is simplified. The moisture meter from Testo lights up the screen and performs self-diagnosis if necessary. Other features worth noting:

• cover for protected storage;
• carrying strap;
• proprietary calibration protocol included;
• weight 0.09 kg;
• dimensions 0.119x0.046x0.025 m;
• error no more than 1%;
• measurement every second.

Condtrol Hydro-Tec is also an excellent moisture meter for working with wood and concrete. The device works very quickly. The design allows you to set the moisture content in the range of 2-65% in layers up to 0.02 m deep. The built-in sample library contains 20 types of wood, but not randomly, but divided into 9 groups. The manufacturer claims that Hydro-Tec is professional grade.

Therefore, it is readily used in woodworking, furniture, parquet, molding, window and door industries. The company warranty is given for 2 years. The device is included in the federal register. Requires a pair of AAA batteries to operate. The measurement takes no more than 1 second; and the relative air humidity during operation should not exceed 85%, permissible temperatures - 5-40 degrees above zero.

For wood and grain, Gann Hydromette Compact from Germany can be used. The German product can also work with sawn wood, fiber and particle boards no thicker than 0.025 m, gypsum and plaster. This needle-type moisture meter allows you to take into account the temperature of the material according to the table included in the delivery set. The moisture content of the plaster is indicated as a percentage of the dry mass. A 9 V dry cell or a rechargeable battery is used for power supply.

How to find out the moisture content of wood?

There are several methods for determining wood moisture content. But first you need to find out the type of plant and air moisture, since different trees have their own standards.

In order to measure the moisture of wood raw materials, as a rule, two methods are used: gravimetric or using an electrical device. Their indicators may differ slightly, but not significantly.

Weight

Measuring process:

1. To begin with, you need to cut off a piece 10–15 millimeters wide from the middle of the board with your own hands. It will serve as a control sample. The main thing at this stage is to take the block from the center of the board. There is no need to cut off the end part, as it has much less moisture.
2. Next, the fragment you cut yourself needs to be cleaned and weighed on a scale. The resulting figure is recorded. For example, let's call it "Ph". This will be the initial mass of the sample.
3. After weighing, this piece must be sent to a special dryer, a device with a temperature of about 100C°.
4. The first weighing is done by hand after five hours. All subsequent indicators are recorded at intervals of 1–2 hours.
5. Drying is carried out until the weight indicator begins to repeat. This means that the material has become completely dry. Let us denote the numerical indicator of the last sample as “Pc”.
6. Next, humidity can be determined using the formula:

W = (Ph-Pc) : (Pc x 100%)

W – percentage indicator; Ph – first weight; Pc – final weight.

Electric

It takes a lot of time to carry out weight measurements of wood. On average, this work takes about nine hours. But there is a way that allows you to determine the percentage of water in a tree much faster and more accurately.

It is much easier to determine the moisture content of wood raw materials using an electric moisture meter.

The operating principle of a moisture meter is based on a change in the electrical resistivity of a material depending on its humidity. The needle-electrodes of this device are inserted into the wood so that they are opposite each other. A current is passed through them, and the moisture meter shows the amount of water in this section of the tree. But since the moisture meter measures moisture only locally, it is better to repeat the measurement in several places.

How to determine the moisture content of wood without technical means?

Today, the amount of water in wood raw materials is determined using complex calculations and the latest instruments. But people have always been involved in construction. And somehow they managed without progressive methods and moisture meters.

A few simple recommendations on how to determine the moisture content of wood:

1. It is necessary to draw a line along the freshly cut fragment with a pencil. When the wood is wet, the line will turn blue after a while; if it is dry, it will not.
2. The shavings can “tell” about the amount of water in wood raw materials. If they are elastic, soft, and do not break when crushed, the tree is wet. Shavings of dry raw materials in your hand will break and crumble.
3. You can run a sharp metal object over the wood with your own hands. The condition of the material is determined by the trace left behind. Wet wood will have a wet mark.
4. You can determine the amount of moisture in wood raw materials by hitting it with a wooden object. If the sound is dull, the wood is wet; if the sound is thin and ringing, the wood is dry.
5. The dryness of the wood is also indicated by cracks at its ends. Wet material has fewer of them.

6. When sawing a board with your own hands, when moisture seeps into the hole, the wood contains a large amount of water and is unsuitable for work. Too dry raw materials crumble during such processing.

Wood moisture plays a huge role in construction and renovation. Damp wood will become deformed as it dries. To avoid this, you should only work with dry material.

Testing and Calibration

The simplest option is to wrap the device in a wet cloth and then in a plastic bag. Within an hour, in a tightly closed bag, the humidity will reach 96%. The readings will stop changing. If this does not happen or the device gives incorrect readings, it cannot be trusted. More precise adjustments can be made using table salt. It is poured into a saucer and diluted with water until completely dissolved.

The solution must have a high concentration. Then the saucer is placed in a tightly locked sealed box. A moisture meter is also placed there. After 8 hours the humidity will reach 75%. As soon as this happens, the device is removed and this value is set as quickly as possible.

To learn how to choose the right moisture meter for wood, see below.