FI108163B - Method and arrangement for measurement of the water vapour which diffuses into or out of a material - Google Patents

Description

108163

Method and apparatus for measuring water vapor diffusible from or to a material

The invention relates to a method according to the preamble of claim 1. The invention also relates to a device according to the preamble of claim 10.

Methods and devices of this kind are used to measure diffusible water vapor from a material. The rate of moisture evaporation and the rate of absorption, from which the diffusion coefficient and the moisture flux can be calculated, are measured from the surface of the material. In particular, methods and devices are used to measure the drying or wetting rate of structures.

According to the prior art, equilibrium moisture content of structures has been measured by measuring both the inside and the surface of the material. Of course, surface measurement techniques have the advantage that the material itself does not need to be physically damaged. Moisture volatility from the surface of the material has been measured mainly by methods based on the use of measuring chambers placed on the surface of the material to be measured. The side facing the measuring chamber of the measuring material is open, but otherwise it is made steam-tight. The measuring chamber also comprises a measuring container containing a moisture-absorbing material, such as calcium chloride. The measurement is done by weighing and installing the measuring box entering the measuring chamber * · “· 20 into the measuring chamber and then placing the measuring chamber tightly against the material surface * .1.1 with the open side facing the material surface. From the material, the volatile moisture on the open side of the measuring chamber diffuses into the measuring chamber and is absorbed into the measuring box. After the measuring time, typically about 72 hours, the measuring chamber is removed from the surface and the moisture absorbing measuring cup inside is weighed.

• · · • »· 25 The amount of moisture evaporated from the material can be calculated from the increase in the mass of the measuring container during the measurement. Based on evaporated moisture, measuring area and measuring time, rough conclusions can be drawn about the amount of water contained in the evaporating material, the equilibrium moisture content of the material and the rate at which the moisture evaporates.

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The method based on the weights of the moisture-absorbent box is prone to error. The measurement error is typically caused by a weighing error, moisture leaks during measurement, and the fact that the measurement method measures the integral of moisture absorption throughout the measurement period. In most cases, during the initial period of measurement, diffusion is determined by the surface layer of the substance to be measured, the moisture content of which is strongly influenced by the ambient humidity during the few days prior to measurement. Only at the end of the measurement is the amount of diffusion affected by the equilibrium moisture content of the substance to be measured. Thus, in this measurement principle, the uncertainty of the initial measurement period is the greatest source of fundamental error. Another disadvantage of the methods based on the weighing of the moisture-absorbing boxes is their long measuring time. The measurement time can be, for example, 1-5 days.

U.S. Patent 4,066,068 describes a method and apparatus for measuring the volatile moisture flow from a surface. The method and apparatus are particularly intended for measuring the moisture content of the skin. The method is based on the use of 15 open tubular protective housings at each end. The first end of the protective case is placed against the surface of the skin and the other end is left free from contact with the ambient air. As the moisture evaporates, the moisture in the air near the surface of the skin grows higher than the humidity in the surrounding air. This causes a moisture gradient to the air inside the enclosure. The moisture gradient is measured in the enclosure. 20 with two moisture sensors positioned at two points deflected in the normal direction of the skin surface. The temperature gradient in the enclosure is measured with »» two temperature sensors placed in a similar manner. From the measured moisture and temperature gradients, the diffusion equations can be used to calculate the moisture flow evaporated by the skin surface *.

The method described in U.S. Patent 4,066,068 is suitable for measuring moisture exchange between the material and its environment under prevailing environmental conditions. The method could thus be applied to the measurement of structural humidity mainly ';' determines the rate at which moisture is transferred from the surface of the structure to the ambient air: under prevailing conditions. No actual solution for measuring structural humidity is disclosed in the publication. A further problem with the device disclosed in the publication is that ambient air currents can cause turbulence inside the protective housing 3 108163. In turbulent or flowing air, the humidity flow is no longer solely determined by the diffusion flow, and the device may end up with an erroneous measurement result.

The object of the invention is to eliminate the above-mentioned drawbacks and to provide a completely new method and device for measuring the moisture evaporated or absorbed by the material.

The invention is based on the measurement of moisture flow by determining a moisture gradient in a closed measuring chamber. The moisture content shall be measured at at least one point. The temperature at each humidity measurement point is also preferably measured by a temperature sensor integrated in the humidity sensor. The invention is also based on placing on the opposite side of the measuring chamber, on the opposite end, either a moisture source which releases moisture into the air space of the measuring chamber or a moisture binding device which binds itself from the air space of the measuring chamber. The moisture gradient is calculated from the moisture gradient, and the moisture flow and / or its variation is analyzed to determine the drying or wetting rate of the material to be measured. The equilibrium moisture content of the material to be measured can be deduced from the drying rate. Further, if equilibrium moisture is measured from within the material at a suitable depth, typically 2 to 4 cm, the permeability of the material can be determined. This information can also be used to predict. behavior of the equilibrium moisture content of the structure, for example, when the material dries or wets or when the material is coated. The method can also take into account 20 possible thermal gradients and their convection by measuring "" · temperature at both ends of the diffusion path and collapsing the effect of convection f · :: by computation.

More particularly, the method of the invention is characterized in what is set forth in the characterizing part of claim 1. The device according to the invention, in turn, is characterized by what is stated in claim 10. characterizing part.

The invention provides significant advantages.

V. The invention can improve the accuracy and speed of structural humidity measurement.

Compared to the method for measuring structural humidity 108163 4 based on the change in mass of the water-absorbing material, the invention significantly speeds up and refines the moisture measurement. Namely, by the method according to the invention, the diffusion measurement can be made, for example, in 15 minutes. Due to the speed of measurement, several measuring points can be used or, for example, the necessary humidity measurements of the building can be made during one visit of 5 persons.

The invention also has further advantages or advantageous embodiments.

If, in connection with the invention, a moisture source, such as a dampened blanket, is used in the measuring chamber in place of the moisture binder, the moisture absorption capacity of the material can also be measured.

10 If, when using a moisture binder or a moisture source, the moisture diffusion current is measured immediately after placing the meter on the surface to be measured, the maximum evaporation capacity of the surface or, respectively, the maximum moisture absorption capacity under that measurement condition can be determined. As the measurement continues, the evaporation and moisture absorption properties of the material can be determined.

15 The time dependence of the moisture flow can be used to determine the equilibrium moisture content and permeability of the material to be measured.

If desired, equilibrium humidity can be easily and simply assured by measuring a certain depth from the material being measured, whereby the material to be measured; permeability can be calculated by the measured equilibrium moisture diffusion and material * ·. . 20 based on sensor measurement data.

If the invention is to monitor the drying of the building material and to measure the moisture content of the material, the invention provides an excellent method for the construction of building materials. * for evaluating coatability.

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BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be illustrated by way of example and with reference to the accompanying drawings.

Figure 1 shows a cross-section of one measuring device according to the invention.

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The general measurement principle of the invention is that a substantially vapor-tight measuring chamber is formed above the surface to be measured, the humidity of which can be diffused from the surface to be measured to the other end of the chamber or vice versa. The moisture content of the air is determined at least at two of the 5 measuring chamber points and the moisture flow through the measuring chamber is calculated from the results. The determination is made by measurement. Alternatively, the moisture flow can also be determined by measuring the moisture content at only one point on the surface of the material and assuming it is known at the other end of the measuring chamber.

The measuring device according to Fig. 1 comprises an open end 10 and a cylindrical body 1 with a measuring chamber 7 inside thereof. temperature and humidity sensors 5, 6 disposed near the first and second ends of the housing 1 in the measuring chamber 7 and in the measuring chamber 7. Figure 15 also shows the material 8 whose moisture is being measured. Moisture is measured by placing the measuring device against the surface 9 of the material 8. The moisture-binding or releasing surface of the humidity binder 3 or the moisture source 13, in turn, is the surface 10. The measuring device also comprises a calculating unit and the necessary conductors for supplying the measurement data to the calculating unit. However, these elements are not shown in Figure 1.

The function of the body 1, together with the cover 2, is to define on the surface 9 to be measured: a substantially vapor-tight measuring chamber 7. In addition, the body 1 supports some parts of the measuring device. The shape of the measuring chamber 7 itself, and thus of the body 1, has very few fundamental restrictions. However, when measuring plane surfaces, the edges at the first end of the frame 1 must be as smooth and smooth as possible in one of the 25 levels in order to achieve good sealing between the frame 1 and the surface 9 to be measured.

• · · • · ·

The measuring chamber 7, on the other hand, in the direction of the surface 9 to be measured, can in principle * be of any shape. However, the preferred forms of fabrication are rectangle, square and especially circle. Otherwise, the measuring chamber 7 is preferably shaped such that the measuring chamber 7 in the measuring position extends in the normal direction of the surface 9 to be measured and is uniform in cross-section. The measuring chamber 7 is thus preferably in the form of e.g. a cube or a cylinder.

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In principle, however, the measuring chamber 7 may be tapered, widened, or deformed as it moves from the first end to the second end of the measuring chamber 7, but regular shape facilitates modeling of the diffusion phenomenon and thus measurement. The diffusion path, which can be defined as the path 5 inside the measuring chamber 7 from the measuring surface 9 at the first end of the frame 1 to the other end of the frame 1, is preferably flat and parallel to the normal surface 9 to be measured. The direction of the diffusion paths may also be the opposite of that described above. The measuring chamber 7 thus functions as a diffusion chamber.

The material of the housing 1 must be substantially water-and-vapor-free and highly heat conductive material so that the measuring chamber 7 itself will have a minimal effect on the measurement. Water or vapor adsorption to the surface of the material must be low or non-existent. Suitable materials are, for example, aluminum, steel or polytetrafluoroethylene. The body 1 can also consist of two different materials, one of which is water-free. In this case, the parts adjacent to the measuring chamber 7 of the body 1 are covered with water-free material.

In the device type shown in Fig. 1, the dimensions of the body 1 may, depending on the application, be e.g. such that the cylinder forming the measuring chamber 7 is 6-10 cm in height and 5-10 cm in diameter.

; In turn, the lid 2 is shaped so that it can be sealed against the frame 1. Cover ^! 20 2 can be done, for example, by pressing to fit. If the body 1 is cylindrical, the cover 2 may also be threaded. Cover * ♦ · • ·. ·: ·. The connection between the body 2 and the body 1 need not necessarily be vapor-tight if the connection is not limited to the diffusion path of the measuring chamber 7 but is located behind e.g. The cover 2 also forms a space in which the humidity binder 3 or the • ♦: T: 25 humidity source 13 can be located. Alternatively, a moisture binder 3 or a moisture source. 13 may be designed for insertion into body 1 or between body 1 and: ': cover 2. Also, in the advantageously shaped measuring chamber 7, the surface 10 to be measured and the moisture-binding or releasing surface 10 are parallel.

In designing the moisture binder 3 and the moisture source 13, respectively, it is essential that the moisture-binding or releasing surface 10 cover substantially the entire cross-section of the diffusion path 7 108163. When using a preferred shape measuring chamber 7, such a design avoids the formation of a moisture gradient 3 or a moisture gradient inside the measuring chamber 7 parallel to the surface 10 of the moisture source 13. The humectant of the humectant binder 3 may be, for example, silica gel, calcium chloride or the like. It is essential that the moisture binder 3 is capable of absorbing moisture at least at the same rate at which the surface 9 to be measured releases it. The moisture binder 3 should also be able to absorb moisture evenly over the entire surface 10 area. The moisture source 13 of the moisture source 13, in turn, may be, for example, a dampened blanket. Essential to the moisture source 13 is that it is capable, if necessary, of releasing moisture at at least the same rate at which the surface 9 to be measured can bind this at the other end of the diffusion path. The moisture source 3 should also be capable of releasing moisture evenly over the entire surface 10 area.

The function of the seal 4 is to insulate the part near the first end of the measuring chamber 7 in a substantially vapor-tight manner from the air surrounding the measuring device. The preferred material 15 and the preferred dimensions of the seal depend on the dimensions of the measuring chamber 7 and the material 8 to be measured and the smoothness of its surface 9. If the diffusion of water in the material being measured is rapid, the seal 4 must be wide enough along the material 8 past the seal 4 to reduce the significance of the diffusible moisture flow. Mostly; t: The seal 4 may be e.g. rubber and about 5-10 mm wide.

The temperature and humidity sensors 5, 6 are preferably of the type in which the temperature *: **: sensors are integrated with the humidity sensors. This allows accurate measurement of the temperature of the · ·: .v humidity sensor, which in turn monitors the ambient temperature. If separate humidity and temperature sensors are used. *, The temperatures of the humidity and temperature sensors may differ, resulting in an incorrect measurement result.

When two temperature and humidity sensors 5, 6 are used, these are placed in the measuring device with the first sensor 5 located near the surface 9 to be measured and the second sensor 6. : near the surface 10 of the moisture binder 3 or the moisture source 13. Distance of the sensors 5, 6

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the above surfaces may be e.g. 2-5 mm. The distance of the sensor 5 from the surface 9 is minimized.

• ·: ': The sensors 5, 6 can be hung, for example, in the middle of the diffusion paths, and the suspension can be made, e.g. The hangers also comprise the necessary wires for transferring the measurement information from the sensor to the calculating unit.

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The transducers 5, 6 should be selected such that their cross-section does not form a significant part of the cross-section of the measuring chamber, i.e. the area of the diffusion path. Otherwise, the selection of sensors 5, 6 is influenced by e.g. the required measurement accuracy and range.

The measuring method according to the invention uses, for example, a measuring device as described above. In the method, a diffusion chamber 7 is formed above the surface 9 of the material 8 to be measured and sealed against the surface 9 to be measured. When forming or after forming diffusion chamber 7, a vapor-binding surface 10 is formed on the opposite side of the diffusion chamber 7 when measuring the evaporation chamber. This creates a substantially undisturbed diffusion path in the diffusion chamber and conditions at which the first and second ends of the diffusion chamber have surfaces of varying humidity 9, 10. The humidity tends to equalize between the surfaces 9, 10 and the air against them. direction. The moisture gradient, in turn, causes moisture to diffuse from the humid end to the drier end of the diffusion chamber air space.

After forming the diffusion chamber 7, the partial pressure Pw of the water vapor at two points is determined from the airspace of the diffusion chamber. The first of the measuring points is located: /. i 20 near the surface 9 to be measured and the other near the surface 10 which absorbs or releases moisture.

The partial vapor pressure Pw for water vapor can be determined, for example, by measuring the relative humidity Rh and the temperature T, and calculating the partial vapor pressure Pw for these vapors. '· * * The partial pressure Pw of the water vapor can then be calculated from the formula:: ·! ·! PwCn = £ flP- * PmCO [hPa], (1) 100 l »« 25 with partial pressure of saturated water vapor. The partial pressure \: of saturated water vapor, in turn, is obtained, for example, from the table or from the formula: '': 7.5 »r (oc)

Pws (T) = 6.1078 * 10r (° C) + 237-3 ° C [hPa]. (2) 9108163

If the water vapor pressure in the first measurement point PW1 is different from water vapor pressure at the second measuring point M, the measuring points represent the vapor pressure levels is the diffusion W. the diffusion W of the diffusion chamber 7 from the first end to the second end may be reduced to 5 vapor pressure difference, the measurement points represent the vapor pressure levels, the distance L, diffuusiotien cross-sectional area A and the water vapor permeability u by. The vapor permeability of water vapor in air is 174 ng / s * m * Pa. When using the device of Fig. 1, A is the bottom surface area of the cylinder and L is the distance between the measuring points in the height of the cylinder. The diffusion current W is given by the above units using the equation: 10 V = 3.6 * 10 '[g / h], (3)

If moisture is transferred from the material being measured 8 to the moisture binders 3, the diffusion current W calculated from formula 3 is positive. If, on the other hand, a moisture source 13 is used to transfer moisture to the material 8 to be measured, the diffusion current W calculated from formula 3 is negative.

If the surface 9 of the material 8 to be measured can transmit or receive moisture, the diffusion current W begins to form immediately after the diffusion chamber 7 is formed. Initially, however, the diffusion current cannot be reliably measured, since the v: humidity gradients in the air space of the diffusion chamber 7 and between the surfaces 9 and 10 and these; This step takes about 30 to 600 seconds, depending on the case * * 20. The equilibration step is typically followed by a phase of high diffusion flow, whereby the surface 9 of the material 8 evaporates strongly into the air dried by the moisture binder 3. The moisture of the surface 9 of the material 8

. . also, as the diffusion current W decreases, it decreases rapidly. Diffusion current W

decrease over time typically occurs exponentially, A * e'B * '- • ·, 25. When measuring the diffusion current W in this time range, about 30 to 600 seconds ;; After the formation of the diffusion chamber 7, the maximum evaporation capacity of the surface to be measured under the prevailing humidity conditions can be determined.

As the measurement continues, the surface portions of the material 8 to be dried will no longer be capable of significantly releasing moisture by themselves. However, if moisture is present in the inner parts of the material 8 10 108163 to be measured, the moisture begins to move in the material 8 towards the inner surface 9. At this point, the diffusion current approaches the equilibrium current on the exponential curve in absolute values. This basic evaporation rate, in turn, describes the properties of the material 8. If the permeability of the material is known, the equilibrium moisture content of the material can be deduced from the 5 basic evaporation rates.

By measuring, in addition to the diffusion flow, the equilibrium moisture content of a material at a given depth d, the permeability of that material can be calculated from the equilibrium moisture, measurement depth, and sensor 5 reading from the formula: μ-— ~ - [kg * m'1 * s'Ii |, Pa'1], (4)

^ WM ~ ^ WS

10 where - μ is the water vapor permeability in the material, - W is the diffusion flux in kilograms per square meter per second, - Pym is the partial vapor pressure of water vapor measured at equilibrium with depth d, and "altaνΜ

The equilibrium range of the diffusion current is typically achieved in 5 to 30 minutes. Depending on the material ·. '·: 8 and the measuring arrangements, it may take * * more time to reach equilibrium. However, the achievement of equilibrium can be monitored by measuring the diffusion current • · ♦ · ♦ as a function of time. The equilibrium is reached when the absolute change in the diffusion current • · · * 20 is no longer significant.

: The equilibrium moisture content of a material is determined by the amount of water it contains and * · · v J its ability to bind water. Water retention is material specific. At the same time: at a water content, the equilibrium moisture content of the material with high water-binding capacity is:: lower than that of the material with low water-binding capacity. More specifically, 25 the moisture physics of structures and the properties of building materials are described in: '' Manual on Moisture Control in Buildings '' (ISBN: 0-8031-2051-6).

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When measuring the moisture-absorbing capacity of the surface 9, proceed as described above. The measurement differs in that the diffusion process is reversed.

The maximum evaporation or moisture absorption capacity of the surface 9 and the base evaporation rate or wetting rate of the equilibrium area can be determined by measuring these quantities 5 as described above. Alternatively, if the diffusion process can be described by an exponential equation, a sufficient number of points can be measured as a function of time to determine the exponential relation. The desired quantities can then be extrapolated from the resulting exponential equation.

However, the material 8 to be measured may not always follow the exponential 10 dependence. This may be due, for example, to the large size of the structure itself or to the fact that the material has high humidity gradients due to the moisture history prior to the measurement. Deviations due to the large structure can be caused, for example, by moisture conductors close to the measuring area, such as cracks or materials or joints that are highly conductive. Here, too, measurements can provide 15 valuable insights into structures, their moisture conditions and / or moisture behavior.

Solutions other than those described above may also be contemplated within the scope of the invention. As mentioned above, the configuration of the apparatus may be very different from that of the apparatus of Figure 1. You can also add more features to the device, or connect it to a computer. The method also does not •; 20 limit the material to be measured. The method can also be used to measure, for example, land.

• ·. . Measured Building Material 8, in turn, can be almost anything, eg concrete, · · · wood, brick, tile or gypsum, wood or chipboard. The object to be measured can also be the seam of different materials. The material 8 may be either a loose building material or. V. be an integral part of the structures.

The invention may also be applied so that the partial pressure of the water vapor is measured at only one point of the diffusion chamber 7. In this case, this measuring point should be close to the surface to be measured at t 1 '·' 9. The second partial pressure needed to calculate the diffusion current is calculated by • 1; thereby assuming that the relative humidity of the air in the diffusion chamber 7 at the surface 10 of the humidifier 3 is zero. Similarly, on the surface 10 of the moisture source 13, the relative humidity of the air can be assumed to be 100%. In order to improve the measuring accuracy 12 108163, instead of the assumed humidity values of 0% and 100%, different calibrated values may be used. The calibrated values can be, for example, between 1-3% and 97-99%. However, at least two measurement points are preferably used for good measurement accuracy. If desired, the measuring points can also be placed in 5 measuring devices, for example in three or four measuring planes, and also in such a way that each measuring plane has, for example, two, three or four separate sensors. The measurement level here refers to the assumed uniform humidity surfaces.

The body 1 can also be shaped such that the actual cover 2 is not needed. This can be accomplished, for example, by providing an opening to the other end 10 of the measuring chamber 7 on the side of the body 1 through which the humidity binder 3 or the moisture source 13 can be inserted into the measuring chamber. Otherwise, the other end of the body 1 may otherwise be designed to be closed and vapor-tight. In this embodiment, the opening on the side of the body is closed by the moisture binders 3 or the moisture source 13. In the measuring method, the cover 2 can also be omitted if desired, if the opening on the other end of the body 15 is sufficiently covered by the moisture binders 3 or moisture. In this case, however, moisture binding becomes more saturated because it also binds moisture from outside the measuring chamber 7. Similarly, the moisture source 13 transfers part of its moisture to the outside air space.

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Claims (15)

A method of determining a diffusion flow of moisture diffusible from or to a surface of a material, comprising: diffusion flow through defined partial pressures, characterized in that - a moisture evaporating or absorbing surface is formed, and - a diffusion space is formed such that a substantially closed diffusion chamber is formed between the moisture evaporating or absorbing surface and the measured surface,! . wherein moisture can be transferred between the surface to be measured and the surface evaporating or absorbing moisture through the interior of the diffusion chamber. ·. *. by diffusion. ♦ · ♦ · · ♦ ♦ · * · · »: Y: 20 Method according to Claim 1, characterized in that: ·: T: the partial pressure of the water vapor is determined at least at the first measuring point by: · · · * ·: · '- measuring the relative humidity of the surrounding air, t:' · f - measuring the point ambient temperature and t 1 · ·:: - Calculate the partial pressure of the water vapor based on relative humidity and temperature 25. I4 108163 The method according to claim 2, characterized in that - at least one second point for determining the partial pressure of the water vapor is selected so as to be substantially adjacent to the humidity evaporating or attracting surface, and 5. relative to the humidifying air surrounding the measuring point. let's be known. Method according to one of Claims 1 to 3, characterized in that the moisture-evaporating surface is formed by placing an absorbent material, such as felt, on the opposite end of the measuring surface of the diffusion chamber. Method according to one of Claims 1 to 3, characterized in that the moisture-binding surface is formed by placing a moisture-absorbing material such as silica gel or calcium chloride on the opposite end of the measuring surface of the diffusion chamber. • 4 The method according to any one of claims 1 to 5, characterized in that the diffusion flow rate is determined at least at the first and second time from which. . the first moment is 0-5 minutes after the diffusion chamber is formed and M is at least one second 5-15 minutes after the diffusion chamber is formed. The method according to claim 6, characterized in that the diffusion current as a function of time is determined by fitting the determined instantaneous diffusion current values to an exponential curve. 15 108163 8. A method according to claim 7, characterized in that the equilibrium moisture content of the measured substance of known permeability is determined from the exponential curve. The method according to any one of claims 1 to 8, further comprising measuring the equilibrium moisture content of the material at a certain depth within the material, characterized in that: - substantially determining the partial vapor pressure of the material surface and 10. determining the permeability of the water vapor. Device for diffusible moisture from the surface (9) or surface (9) of the material (8). ·. 15 for determining a diffusion flow, comprising: - a measuring chamber (7), open at least partially from the first end of the body (1), at least partially within the body (1), with a diffusion path between the first and second ends of the body; 20. a humidity sensor (5) located inside at least one of the measuring chambers (7) and of a humidity sensor (5). - at least one temperature sensor (5) disposed inside the measuring chamber (7), characterized in that the device 25 comprises a humidity binder (3) fitted inside the measuring chamber (7) or a moisture source (3) to release moisture inside the measuring chamber (7). ) located at one end of the measuring chamber (7) or moisture source (3) or moisture source (3), and - at least one humidity sensor and a temperature sensor (5) arranged near the first end of the body (1) and spaced to the other end from a placed humidity binder (3) or a moisture source (3). Device according to Claim 10, characterized in that the device comprises an opening at one end of the body (1) and a cover (2) for closing this opening. to Device according to Claim 10 or 11, characterized in that the body (1) is cylindrical and made of a material substantially free of moisture, such as metal. Device according to one of Claims 10 to 12, characterized in that at least one humidity sensor and a temperature sensor (6) are arranged close to one end of the housing (1). 13 108163 Device according to one of Claims 10 to 13, characterized in that a seal (4) is attached to the body (1) for sealing the surface (9) of the open side (9) of the measuring chamber (7). against. The "W" 4 1 is substantially vapor-tight at its periphery (1, 2) to the measuring chamber (7). ♦ · * · '1 Device according to one of Claims 10 to 14, characterized in that it