Do-it-yourself wood moisture meter using a multimeter. Moisture meters for wood: review of the best models. How to make a moisture meter for wood with your own hands? Types of moisture meter models
The use of lumber and wood products with excess moisture leads to deformation wooden structures, loss of strength, development of fungus and mold. Humidity is the main controlled parameter at the production stage of wood materials. After processing round timber, the resulting timber is dried; at timber processing enterprises, moisture content is monitored in the laboratory. When the specified condition is reached, the wood is supplied to consumers and the distribution network. Moisture standards for commercial wood are determined by GOST.
To determine the moisture content of commercial wood, laboratory methods are used. Laboratory installations are installed at timber processing enterprises and allow measurements to be made with high accuracy. The method is based on determining the amount of moisture evaporated from wood samples. The testing process takes long time, requires the use of special equipment: thermostats, high-precision scales.
Wood is hygroscopic; during storage and transportation of the material, it absorbs moisture from the atmosphere. Before using timber, it is important to control its moisture content. Moisture meters are used to carry out express tests of wood.
A wood moisture meter is an electronic device that allows for express analysis of building materials and wood products.
Instruments for measuring wood moisture are distinguished by measurement methods:
- Conductometric - based on measuring electrical conductivity between two points - electrodes,
- Dielcometric – based on measuring the dielectric constant of a material,
- By definition of the reflectivity of IR radiation,
- By attenuation of microwave radiation when passing through the test sample.
"MEGEON 20502"
The most common are needle (conductometric) and non-contact (dielkometric) moisture meters. Devices that work with microwave and IR radiation are manufactured in a stationary design and are intended for use on wood processing production lines and in the production of particle boards (chipboards).
Needle moisture meter
The conductometric measurement method is used - the device measures the current flowing between electrode needles embedded in the wood. The circuit of the device is simple, it includes: a power source, pointed electrodes, the current in the circuit is measured with a microammeter. Electrode needles have sizes from 15 to 25 mm and are made of hard metal, in the non-working position are closed with a protective cover. The distance between the electrodes is determined by the device developers.
The device determines the moisture content as a percentage, the result is reflected on the display and does not require recalculation. The duration of one change does not exceed 5 seconds. A feature of contact models is their limited range of application: maximum accuracy is achieved at humidity from 7 to 30%; at higher values, the error increases significantly. The accuracy of measurements using needle moisture meters is influenced by the type of wood. It is recommended to use for measurements on wood that has not been subjected to chemical treatment.
"SEM DT-125H"
The rules for determining the moisture content of lumber using conductometric moisture meters are established by GOST 16588-91 and are consistent with the system international standards ISO. Measurements are carried out in different places of the workpiece: the first - at a distance of 0.5 m from the end, the subsequent ones - every other linear meter. The needles are inserted vertically over their entire length; the line connecting the needles must be parallel or perpendicular to the wood fibers. The device is widely used when working with lumber: boards, beams, block houses that do not lose presentation after piercing.
- "MEGEON 20502", Russia,
- "ADA ZHT 125", Hong Kong,
- "SEM DT-125H", China.
"Condtrol Hydro-Tec"
The operating principle of non-contact devices is based on measuring the average value of the dielectric constant (insulation coefficient) using a microwave method. Water has high conductive properties. When the sample under study is placed in an induced electromagnetic field, a high-frequency current is generated. The current value is proportional to the humidity of the environment. Non-contact moisture meters use 3-30 MHz generators. A capacitor is included in the high-frequency circuit; the discharge rate of the capacitor depends on the dielectric constant of the medium. The device performs quite complex calculations and has a built-in microprocessor. In terms of the complexity of the device, a non-contact moisture meter is superior to needle moisture meters.
"MEGEON 20610"
The microwave method is universal and can be used to determine moisture in various materials. It can be wood, plywood, drywall, concrete, brick, plaster or cement screed. The measurement results depend on the type of wood and the properties of the material being measured. Modern non-contact moisture meters have an option in the menu to select the type of wood and type of material.
To carry out measurements, the sensor of the device is pressed against the surface with a force of 1.0-1.5 kg, the measurement is carried out within 10-15 seconds. Humidity measurement range is from 4 to 85%, scanning depth is 20-30 mm.
The TOP 3 popular models include:
- "Condtrol Hydro-Tec", Russia,
- "MEGEON 20610", Russia,
- "Testo 635-2", Germany.
DIY psychrometer and moisture meter for wood
When equipping a carpentry workshop, it is necessary to know the air humidity in the room and be able to control the quality of raw materials. You can make devices to monitor these parameters with your own hands.
The simplest psychrometer is a device for determining air humidity, which can be made within 30 minutes. To do this, you need two ordinary room alcohol thermometers. Thermometers can be placed on the wall or on special stand. The main condition is that for one thermometer, the expansion flask with alcohol must be wrapped in a damp cloth. Thermometer readings will be different: the drier the surrounding air, the lower the temperature the “wet” thermometer will show. As air humidity increases, the difference in readings will be less. More accurately, the humidity in the workshop can be determined using a special table available on the Internet.
The Internet offers many schemes for making moisture meters with your own hands. If you calculate the cost of components, the cost of homemade products will be comparable to the cost of the simplest industrial designs. Experienced craftsmen they do without moisture meters, determine the moisture content of wood by indirect signs: by the color and elasticity of the chips, by sound - when hit with a carpenter's mallet, dry wood makes a characteristic ringing sound, and other signs.
Basic selection options
Wood moisture meters are available to the mass consumer, various models have their 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 compact, have an LCD display, an intuitive interface and are equipped additional options: temperature measurement, storing results, automatic shutdown, etc.
Features various types 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%. When taking 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, 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.
When buying lumber for construction or the manufacture of furniture, windows or other products, many people want to receive high-quality and reliable material. But often purchased wood turns out to be under-dried, which as a result leads to its cracking, deformation or damage due to the development of the rotting process.
The question of how to check the moisture content of wood is relevant and remains so. Moisture meters are mainly used to measure humidity. For both industrial and domestic purposes. Below is a table showing the density different varieties wood And then, let's look at the technique of how to determine the moisture content of wood without a moisture meter in 2 ways.
How to determine wood moisture content without a moisture meter?
For those who do not know how to determine the moisture content of wood, you can use special tables. From them, knowing the type of wood, you can determine its density. These tables summarize indicators obtained as a result of laboratory studies using special diagnostic research equipment.
Knowing that each type of wood is unique in structure, weight and density, and using tabular data, you can determine the moisture content of a particular sample in the field. What is important for further implementation heat treatment.
Below we will consider how to determine the moisture content of wood, based on tabular values and using simple measurements:
- The first step is to measure the mass and volume of the sample. These manipulations are performed in the usual ways using the simplest devices.
- The density of the material is calculated using formulas. In this case, it is necessary to remember about the error, which in any case will arise due to the difference in the places where the trees grow. In some it is greater, in others it is lower.
In addition, humidity may vary depending on different parts tree. For example, in the trunk it is about 50% for pine and 60% for spruce. The branches, being less massive, and due to regular airflow, contain no more than 56 for pine, and 46 for spruce.
The tops of trees contain up to 60% moisture, and the bark accumulates from 36 to 67. Taking into account all these indicators, it is necessary to determine the average for all parts of the tree in order to further use the obtained value in calculating intermediate values.
Undoubtedly, the most important indicator in construction using lumber is the moisture content of the wood; the methods for determining it involve taking certain measurements. The first step is to determine the absolute humidity. As practice shows, this is more of a theoretical indicator that reflects the amount of water in the remaining volume of wood. It is determined by the following formula:
The next step is to determine the moisture content of the wood at the time of testing, taking into account the calculated relative humidity. Calculations are carried out using the following formula:
In addition to the types of moisture described above, there are also 2 types of moisture found in the thickness of wood. These include free moisture and bound moisture. In the first case, water is located in the cell cavities and intercellular space. Bound moisture is located inside the cell walls, making it difficult to remove from them and remaining inside.
A dry board differs from a wet board:
- weight,
- color,
- smell,
- ringing - if you hit it
How to measure wood moisture content scientifically?
There is also a second way to find out humidity. It consists of studying a prototype measuring 20x20x30 mm. In this case, the sample is taken not from the very edge, but further from it at a distance of 30-50 cm. As a rule, in this zone it is maximum and was not subject to natural evaporation.
To measure the moisture content of wood, the gravimetric method is used; the cut sample is weighed on a scale with high accuracy. At the next stage, the sample is placed in a drying cabinet, in which the temperature is maintained at 101-104 degrees. The heat treatment procedure continues for 6 hours. The sample is then removed and weighed again and returned to the cabinet.
The results obtained in this way are entered into a summary table. If the second measurement leads to a similar result from the first case, then the wood is considered completely dry.
See also:
Contents Transport humidity indicator Wood is the most demanding in terms of time aging and temperature conditions building material. With high-quality drying, it becomes strong and durable, and also makes the structure attractive. appearance on long term. But all this applies to dry lumber. If moisture remains in the wood, it may not even reach the consumer and turn blue, become covered […]
Contents Wood moisture content Initial wood moisture formula: To obtain high-quality lumber that will be minimally subject to linear changes under the influence of moisture environment, it is necessary to organize proper drying of the material. But for this, sometimes it is necessary to first calculate the moisture content in the wood structure at the actual moment. Wood moisture First of all, you need to understand the very concept [...]
Content Relative humidity wood calculation methods Wood is a hygroscopic material that absorbs a large amount of water and in some species the percentage of moisture is up to 70% of total weight and volume, filling all pores and channels. To correctly determine practical use For this or that type of lumber, the concept of relative absolute humidity was invented. First, […]
Information about wood moisture content is very important for correct construction technological processes woodworking Too high humidity of wood materials is fraught with the danger of biological damage to wood, as well as subsequent drying out wooden parts and their warping during operation in conditions elevated temperatures and low air humidity. Wood that is too dry becomes quite brittle, difficult to deform and bend, and difficult to cut.
Control of the lumber drying process is inextricably linked with the need current control wood moisture content. There are different methods measuring moisture content in wood and wood materials: gravimetric, conductometric, induction, microwave, infrared.
The weight method is the most accurate of the above. It is designed to evaluate wood moisture content in a laboratory setting and requires five to eight hours to obtain a result. From the test material (board), at a distance of 300-500 mm from the end, a sample 10-12 mm thick is sawed off (along the wood fibers), which is thoroughly cleaned of burrs and immediately weighed on a laboratory scale with an accuracy of 0.001 g. Then the sample is placed in an electric drying cabinet and dried at a temperature of 100-105°C. During the drying process, the sample is periodically removed from the drying cabinet and weighed. The first weighing is performed five hours after placing the sample in the cabinet, the rest - every one to two hours. The wood reaches a completely dry state when the sample mass ceases to change. The difference in the mass of the wet and dry sample (sample), related to the mass of the absolutely dry sample, shows the moisture content of the wood at the time of the first weighing.
Accelerated drying-weight method provides for drying samples at a temperature of 120±2°C in ovens with forced circulation. The drying time in this case is 2-2.5 hours. The final mass of the samples is determined after cooling them in room conditions within 2-5 minutes.
An express method for determining wood moisture content by weight is also known. Thin shavings are removed from the lumber or workpiece using a sharp chisel, which are immediately weighed with high precision and placed in a drying oven. After the chips are completely dry for a few minutes, they are cooled and weighed again. With high weighing accuracy, high accuracy of moisture determination is achieved. One unit houses precision analytical balances, a heater and fan, as well as an electronic unit for recording measurement results and calculating humidity. To obtain the most objective result, the sample should first be split, and then the chips should be removed from the surface of the inner part of the sample.
Some information about the moisture content of wood can be obtained without the use of instruments by examining thin shavings removed with a sharp chisel. Wood chips with high humidity become easily deformed when crushed. Dry chips will crumble and break. Wood that is too wet cuts very easily, and on the sample you can see a wet mark from a cut with a chisel.
Other methods for measuring wood moisture require the use of special devices - moisture meters. The most common are moisture meters that measure the electrical resistance between needles embedded in wood (conductometric method). The current passing through the wood under test is amplified and then measured with a microammeter, the scale of which is calibrated as a percentage of the wood's moisture content. Resistance depends on the moisture content of the wood, as well as the density and temperature of the material. Electric moisture meters quite reliably determine wood moisture content in the range from 7 to 30%, but the results of measuring humidity above 30% suffer from a large error.
An electric moisture meter can be used to remotely measure the moisture content of wood in a drying chamber. To reliably judge the moisture content of a whole board, it is necessary to take measurements in large number points along the length and width of the board and take the average of the obtained values. Control samples with sensor needles embedded in them are placed inside the stack, and meter is outside the camera. When making such measurements, corrections must be made for the actual temperature of the wood. However, experience shows that the remote measurement method does not give accurate results, in particular due to the fact that the sensor needles deliver excess heat to the wood in buried areas. Due to drying of the wood in these places, the contact between the sensor and the material is broken, and the readings of the device are distorted.
Measurement error with modern electric moisture meters, which are equipped with testing scales different breeds wood: beech, spruce, maple, larch, oak, pine, etc., is 1-2% abs. in the range from 0 to 30%.
As a note: absolute error is determined in the measured values themselves, and relative error - in fractions of the measured value. For example, with an absolute error of ±2% for a humidity of 18%, we can assume that the real humidity is 16-20%. Under these conditions, the relative error will be 2 x 100/18 = 11.1%.
The induction (dielcometric) measurement method is based on the use of electromagnetic waves and determination of the dielectric constant of wood, which depends on the moisture content in it. The dielectric constant of a material is a value that shows how many times the capacitance of the capacitor increases if the air gap between the plates is replaced with a gasket of the same thickness made of this material. The dielectric constant depends on the frequency of the current and the moisture content of the wood. With increasing moisture content of wood, the dielectric constant along the fibers increases, which is especially noticeable at current frequencies up to 100 Hz.
The voltage from the inductive type sensor, which is a flat radiating circuit installed inside the moisture meter housing under the digital display, is supplied to a digital voltmeter located on the front board of the device.
Non-contact induction moisture meters are insensitive to wood temperature, which allows you to work without temperature correction tables. Such moisture meters operate in the range of 5-45% wood moisture content with an accuracy of 1-1.5% abs. and take into account the density of the measured wood. The great advantage of the induction method is that the measurement duration does not exceed 5 s. When the measurement result goes beyond the upper limit of the required humidity range, the device sounds a sound signal.
Induction moisture meters, the measurement principle of which is based on the relationship between the dielectric properties of a wet material and the amount of moisture it contains, are produced by many companies, including the Russian Interpribor and MetronX.
Rice. 1. Express thermal conductivity meter and
humidity building materials IVTP-12
In domestic practice, the portable digital moisture meter VSKM-12U, designed to assess the moisture content of various building materials, including wood, has been widely used. Now it is being replaced by an express meter for thermal conductivity and humidity of building materials, IVTP-12 (Fig. 1). The operation of the device is based on correlation connections between dielectric and physical properties capillary-porous bodies.
The humidity measurement range of this device is from 0.3 to 60% with an error of 1.5-2.5% abs. The depth of the control zone is not less than 50 mm, the duration of one measurement is no more than 10 s.
In addition to the task of quickly determining the moisture content of lumber and blanks (i.e. solid wood), in woodworking, the task of determining the moisture content of crushed wood and wood boards is no less urgent. For current and final control of products in slab production, special electric moisture meters are used. The DI-2M device is equipped with two sensors - for determining the moisture content of chips and slabs, as well as an electronic measuring unit with autonomous power supply. The sensor for measuring the moisture content of crushed wood is a detachable glass in which a sample of material is compacted between two disk electrodes using a press. Using these electrodes, the electrical resistance of the compacted material - chips or fibers - is measured. The sensor for measuring the moisture content of particle boards is a probe with four needles mounted on a handle. The electric moisture meter allows you to measure the moisture content of chips in the range from 5 to 25%, and the moisture content of particle boards in the range from 6 to 22%. Measurement error ±1-2% abs.
The operating principle of ultra-high frequency (microwave) moisture meters for bulk materials is based on a significant (tens of times) difference in the electrical properties of water and dry material. The moisture concentration is determined by the attenuation of microwave radiation passing through the layer of the analyzed material. In such moisture meters, a ribbon of material passes between the transmitting and receiving antennas. The transmitting antenna is connected to a microwave generator, the receiving antenna is connected to a measuring device. The higher the humidity of the analyzed material, the weaker the signal entering the measuring device. Microwave moisture meters allow you to measure humidity in a wide range (0-100%) with high accuracy. In Fig. Figure 2 shows a diagram of the M-Sens 2 moisture meter (manufacturer - SWR Engineering, Germany).
The moisture measurement method used in M-Sens 2 is based on the principle of absorption of microwave radiation by a material. The higher the moisture content of a material, the more microwave energy is absorbed by it and converted into heat, and the less is returned to the moisture sensor sensor. The reflected high frequency waves are converted and subjected to digital processing, which provides high resolution of the moisture meter. The structure of the material and the uniformity of moisture influence the measurement results, therefore the measured moisture content is reduced to an average value through the bulk density of the controlled material. To do this, a preliminary calibration of the device is carried out, during which reference data on the moisture content of the raw materials is entered into the sensor. Random changes in humidity caused by material heterogeneity and bulk density are eliminated by software tools. The bulk materials moisture sensor is equipped with a function for automatically compensating for changes in ambient temperature.
For measuring humidity bulk material Pass-through type moisture meters have been developed directly on the conveyor belt, for example the Moistscan MA-500 moisture meter (Fig. 3).
Its operating principle is based on measuring the phase shift and attenuation of microwave signals passing through the material and conveyor belt. The quality of the measurement does not depend on the size of the pieces of material and the speed of the conveyor belt. The moisture meter automatically compensates for the effects of changes in product feed rate when using a belt weight meter or an integral material layer thickness monitor. The thickness of the layer of the material under study can vary from 20 to 500 mm, the measured range of moisture content is 0-90%, the main error is 0.1-0.5%.
The German company GreCon produces the Moisture Analyzer MWF 3000 LD, which operates based on the principle of measuring microwave resonance. The measurements use the properties of the dipole nature of water molecules. The electromagnetic field is generated by a planar sensor and ensures the penetration of microwaves into the material to a depth of 30 to 100 mm (depending on the type of sensor). Changes in the resonant field are recorded by the sensor and transmitted to the processor. The resonant frequency of the microwave field changes depending on the moisture content of the material (the width of the resonance curve increases). Measuring field parameters allows you to separately evaluate the moisture content and density of the material. Irradiation does not cause heat or any chemical reactions in the wood. The measurements are effective regardless of the density, surface structure and color of the material. Due to the large depth of signal penetration, it is possible to record both bound and free moisture in wood. When using the test instrument different materials Calibration curves should be established in advance. The device is used in the production of wood panels in areas for drying chips or fibers, in areas for mixing components and forming a carpet, during quality control finished products. Measurement accuracy ±2%.
1 - sample, 2 - sensor, 3 - focusing mirror,
4 - rotating filter wheel, 5 - IR radiation source
Another principle for measuring the moisture content of different materials is implemented in the Spectra Quad infrared moisture meter (Fig. 4). Contactless measuring system, operating online, is equipped with an optical device for collecting measured parameters. The working tool is infrared radiation absorbed by wet material: the drier the material, the more infrared rays it will reflect.
The intensity of absorption of radiation of a certain wavelength is proportional to the moisture content in the material. A quartz-halogen source emits light in a specific wavelength range. Light from the source passes through rotating filters. Optical IR filters separate the light flux into measurement and reference beams, which are absorbed and not absorbed by the analyzed component. The reflected energy of the rays is converted into electrical signals, the level ratio of which is proportional to the value of the controlled parameter. Additional optical channels (internal beams) compensate for any instability of the optical and electronic components. Light passing through the filter is directed at the sample and is partially absorbed and partially reflected. The reflected light is collected and focused onto a sensor, the signal from which is proportional to the moisture content of the material.
In the production of wood products, it is important to use raw materials of a certain moisture content. To accurately determine the degree of drying of raw materials, a wood moisture meter is used. The compact assistant helps to avoid defects in production, and when building a house from timber, protects against purchasing low-quality material. We will discuss how the device is used, its devices and types in this short review.
Types of devices
Before the advent of a moisture meter, it was possible to determine the moisture content of wood only using GOST. The process took time and took place in several stages. A small piece was broken off from the product, and through complex laboratory tests and comparison of indicators, the exact moisture content was determined. With the advent modern devices the cons faded into the background.
Wood moisture meters are compact devices that allow you to determine the moisture content of raw materials in a few seconds. The device operates from resistivity wood of varying degrees of drying to electrical discharge.
Wood moisture meters have the following advantages:
- speed of the procedure;
- there is no need to damage the raw materials.
- the instrument error can reach 2-10%, which is significant for chamber drying;
- the high price of some moisture meters.
The error in the indicators is explained by the different density of the material, which also affects the resistance to electrical discharge. There are universal devices, for example, mg4d moisture meter and for a specific type of material: concrete, wood.
All devices, depending on the modification, are divided into types:
- needle-shaped;
- surface measurements;
- deep;
- contactless.
Let's consider each type from the point of view of the advisability of purchasing them for use at work and at home.
Compact devices with a small metal needle that sticks into the material. Measurements are carried out only at air temperatures above +1 degrees. At sub-zero temperature the percentage of measurement error increases. The accuracy of the moisture meter is 2%. For accuracy of indicators, the puncture is made in several places of the product.
- Compact, easily fits in your pocket.
- Low error.
- Damages the product.
- Practically does not detect humidity less than 5%.
Popular models include: CEM DT-1329, Benetech GM610.
Surface measurement
The surface measurement wood moisture meter has two small metal needles that are immersed inside, causing virtually no damage to the raw material. The percentage of error in indicators is no more than 0.2-0.5%. The model is designed specifically for working with wooden boards.
- Low error.
- Small size.
- It is not possible to measure material with a cross-section of more than 20 mm.
- The error increases when operating at temperatures below 0 degrees.
Among the models are: ASTM F2170, EM4806.
Depth measurement (probe)
Professional massive moisture meters with high accuracy of humidity readings. Suitable for working with timber, rounded and a simple log, large section boards. It is also used to determine the humidity in heaps of sawdust and wood chips.
Determines the amount of water throughout the entire structure of the tree, but requires careful operation. If the needle breaks, removing it from the material will be problematic. The device has a low error, within 0.5%, and operates at any temperature. Suitable for woodworking company.
- Accuracy of indicators across the entire structure of raw materials.
- Ability to work with material of any density and size.
- The massive device is not suitable for home use.
- High price.
Among the popular models are: DampMaster Pro, GMH 3830.
Non-contact (dielcometric)
Small humidity measuring device wooden products that should not be damaged: laminate, parquet board, plywood. The sensor is located directly on the device or fixed on top of the product.
- Compactness.
- Does not damage the product.
- Works with a range of specific wood types.
- High percentage of error.
Among the popular models, Hydro Pro stands out.
Review of popular models
Let's take a closer look at the cost and technical characteristics of moisture meter models that have received positive reviews from professionals and amateurs.
EM4806
Compact moisture meter from the manufacturer STIHL for surface measurement of moisture in wood and concrete solutions. Universal probe meter with an electronic sensor. Used to measure moisture in wood and concrete at a depth of up to 40 cm. Non-contact device from Russian manufacturer Control. Used for measuring moisture in materials at a depth of up to 3.5 cm. Suitable for working with wood and concrete. The sensor is located in the device itself, which is applied to the surface being measured.
- Moisture measurement limit - from 2 to 65%;
- Weight - 200 g.
- Operates at temperatures from +4 to +40;
- The measurement error is within 1%.
- The cost of the device is 15,690 rubles.
Conclusion
Inexpensive needle or surface measuring instruments are suitable for home use. For office work, it is more advisable to purchase a probe or contactless device. Their price is higher, but they are more functional and allow you to work with various types wood
Tree - natural material, quite susceptible to humidity. It is capable of releasing and absorbing moisture depending on environmental conditions. When the microclimate remains unchanged, the wood moisture content tends to remain constant.
Determining wood moisture content largely depends on the type of wood. The most hygroscopic are pear, beech, and kempas. The most resistant are oak, bamboo, and merbau.
The use of wood for construction and renovation requires compliance with humidity standards. The term “moisture content” refers to the percentage of water to dry wood.
Humidity types
There are two types of humidity of wood raw materials: relative and absolute.
Absolute
This concept is characterized by the ratio of the mass fraction of moisture of a certain volume of wood to the weight of absolutely dry raw materials of the same size. There are established standards for this indicator state standards. According to them, the indicators of the absolute humidity meter of the board should be within 9%.
Relative
This is the percentage of moisture contained in the wood to the mass of wet wood. In wood raw materials, water is found in two forms: free and bound. They indicate the total amount of moisture in the raw material. The volume of bound moisture depends on the microclimate, as it is absorbed from the air. It is located in the cellular structure of the tree. It is because of this, depending on the humidity of the environment, that the material swells or shrinks. Bound water can only be removed by drying.
Free moisture does not lead to swelling, since the water in this case is in the intercellular structure of the wood. But thanks to it, the density of the material increases.
In addition, the type of wood raw material depends on the degree of its moisture content.
There are several types of wood moisture content:
Wet. This category includes a tree that for a long time exposed to water. In this case, the humidity meter reading is more than 100%.
Freshly cut. The moisture content of a recently felled tree is between 50-100%.
Room dry. This type of material has been in a heated building for a long time. Therefore, its number is in the range of 9–13%.
Air dry. This type includes wood that has been stored for a long time fresh air. Depending on environmental conditions, its indicator is in the range of 15–20%.
Absolutely dry. Such indicators can only be achieved by drying in a special device. The amount of water in this case is 0.
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 for different trees there are standards.
In order to measure the moisture of wood raw materials, as a rule, two methods are used: gravimetric or using electrical appliance. Their indicators may differ slightly, but not significantly.
Weight
For this method you will need:
very accurate scales;
Measuring process:
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.
After weighing, this piece must be sent to a special dryer, a device with a temperature of about 100C°.
The first weighing is done by hand after five hours. All subsequent indicators are recorded at intervals of 1–2 hours.
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”.
W = (Ph-Pc) : (Pc x 100%)
W – percentage indicator; Ph – first weight; Pc – final weight.
To get more reliable results, it is better to use two sample samples. 
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 the moisture meter is based on changing the specific electrical resistance material depending on its moisture content. 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 devices. But people have always been involved in construction. And somehow they managed without progressive methods and moisture meters.
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.
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.
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.
You can determine the amount of moisture in wood raw materials by hitting it with some kind of wooden object. If the sound is dull, the wood is wet; if the sound is thin and ringing, the wood is dry.
The dryness of the wood is also indicated by cracks at its ends. Wet material has fewer of them.
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.
