FI128185B - Device and methods for moisture concentration measurements in pressed biomaterial - Google Patents

Abstract

The present disclosure concerns a moisture concentration measurement device with an elongated measurement probe (12) configured to be moved in a body of pressed biomaterial (151) when moisture concentration measurements are performed. Before or after the probe (12) is moved, the control unit (118, 119, 120) initiates a moisture concentration measurement and reads an initial moisture concentration value from the moisture sensor. The control unit (118, 119, 120) then calculates a moisture concentration correction factor based on correction variables which include at least the estimated dynamic force and the biomaterial. The control unit (118, 119, 120) can calculate an adjusted moisture concentration value by adjusting the initial moisture concentration value with the moisture concentration correction factor,

Description

DEVICE AND METHODS FOR MOISTURE CONCENTRATION MEASUREMENT IN PRESSED BIOMATERIAL

FIELD OF THE DISCLOSURE

The present disclosure relates to monitoring of pressed biomaterials, more particularly to moisture concentration measurements performed inside a body of pressed biomaterial. The present disclosure further concerns a moisture concentration measurement device with an elongated measurement probe configured to be moved in a body of pressed 10 biomaterial when moisture concentration measurements are performed. Moisture concentration is the primary variable of interest, but embodiments of this disclosure also relate to measurement of secondary correction variables such as dynamic force, temperature and penetration depth. These correction variables can be used to improve the accuracy of the moisture concentration measurement by facilitating calculations which 15 account for the influence of systematic measurement errors in the primary measurement variable.

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BACKGROUND OF THE DISCLOSURE

In this disclosure the term “pressed biomaterial” refers primarily to hay, straw, silage, haylage or baleage, which may, after harvesting, be pressed, baled and stored in tightly packed bales, or alternatively pressed and stored in a silage pit. After a storage period the pressed biomaterial may, for example, be used as animal feed, bedding for domestic animals or as fuel in bioenergy-based power generators. The silage, haylage, baleage hay 25 or straw may include plants such as alfalfa, timothy grass, clover, fescue, maize, reed canary grass, elephant grass or cereal grains such as barley, wheat or rice.

In a more general sense the term “biomaterial” also refers to materials such as peat, cotton, tobacco, hemp or hops. These materials can also be pressed and packed tightly for 30 storage, transportation or consumption. In some circumstances, such as naturally occurring peat bogs, the materials may have been pressed without human intervention.

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All of the above biomaterials may also be converted into chopped form by chopping, hacking or grounding before they are pressed and stored. Alternatively, they may be pressed and stored in unchopped form.

The apparatus and methods described in this disclosure are applicable in moisture concentration measurements performed in both chopped and unchopped biomaterial in pressed form. Biomaterial chop may have a fine composition, that is, it may contain small particles and/or short straws. Biomaterial chop may also have a rough composition, that is, it may contain large particles and/or long straws. In the present disclosure, the term 10 “coarseness” will be used as a general adjective for describing how fine or rough the composition of the biomaterial or the biomaterial chop is. Very finely chopped biomaterial has low coarseness, whereas unchopped biomaterial has high coarseness.

Pressed biomaterial can undergo physical, chemical and biological changes when it is 15 stored. Most of these changes depend on the moisture content of the biomaterial and on its internal temperature. The internal temperature is partly determined by the surrounding temperature, but fermentation processes may also increase the temperature internally. If the moisture concentration in the biomaterial deviates from the desired range, the biomaterial may be spoiled by moulding. Finally, the risk of fire also depends on moisture 20 content, on the presence of fermentation and on the surrounding storage conditions.

Moisture concentration measurement in storage can be used to assess all of the above risks.

Furthermore, the water content of pressed biomaterial influences its weight. The 25 biomaterial will contain a lot more water if it is harvested in rainy weather than if it is harvested in dry conditions. Consequently, when biomaterial has been pressed into a tightly packed body, the weight of the body may not be an accurate indicator of the actual amount of (dry) biomaterial, because some of that weight will be water. This is an important consideration in animal feed. The feeding can be planned with greater accuracy if the 30 amount of water present in the biomaterial can be taken into account when the nutritional value of a body of pressed biomaterial is estimated.

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Accurate quality control, preservability assessment and usage of pressed biomaterials require some knowledge of moisture concentrations and temperatures in the material. In traditional agriculture, this knowledge is experiential. In other words, it involves no direct measurements. A farmer may, for example, try to keep the moisture level in stored 5 biomaterial more or less constant by always restricting harvesting to sustained periods of dry weather. Practical experience may also have taught the farmer how long the biomaterial usually keeps before it spoils when harvested in favourable conditions.

Repeated measurement of moisture concentration and temperature in pressed and stored biomaterials facilitates much better control, planning and flexibility in the harvesting, storage and usage of biomaterials than mere experiential knowledge does. The information gained from measurements may, for example, be used to make informed adjustments in the order, manner and timing in which specific units of biomaterial are used. Harvesting may also be performed in varied weather conditions in the knowledge that any variation in moisture content produced by the weather can be subsequently measured and taken into account in the storage phase. Moisture concentration sensors have therefore been developed for pressed biomaterials.

Moisture concentration measurements, sometimes combined with temperature 20 measurements, are typically performed inside the body of biomaterial. A body of pressed biomaterial is often so dense that a thin and elongated measurement probe, usually with a pointed tip, is required to penetrate the body. Various elongated measurement probes with measurement sensors have therefore been developed for monitoring purposes.

Document US 7114376 discloses a moisture sensing system for a bale-loading vehicle. The system includes a measurement probe which penetrates the bale. The probe is equipped with an electric moisture sensor.

A problem with this measurement setup is that the density of the biomaterial may influence 30 the measurement result. A straightforward moisture or temperature measurement may give unreliable results because packing density affects the electrical properties of the biomaterial. It can have indirect effects on both moisture concentration and temperature measurements. Furthermore, bodies of pressed biomaterial may not be entirely

20165877 prh 21 -11-2016 homogenous in terms of density. The biomaterial may be packed more densely in some parts of the body than in others.

In this disclosure the term “density” means bulk density. This means that the primary 5 density variable of interest is not the quotient of the weight of a single straw, particle or piece of biomaterial and its volume, but rather how many kilograms of biomaterial lies within a given larger volume occupied by air and straws, particles or pieces of biomaterial.

This disclosure primarily discusses force measurements which are performed when a 10 measurement probe is pushed into a body of biomaterial. The term “thrust force” refers to the force between a measurement probe and a main unit when the probe is pushed into a body of biomaterial. However, force measurements may also be conducted when a measurement probe is withdrawn from a body of biomaterial. The term “withdrawal force” refers to the force between a measurement probe and a main unit when the probe is 15 withdrawn from a body of biomaterial. Furthermore, force measurements may also be conducted when a measurement probe is rotated in a body of biomaterial. The term “rotational force” refers to the force between a measurement probe and a main unit when the probe is rotated in a body of biomaterial. The composite term “dynamic force” encompasses all three of these forces: thrust force, withdrawal force and rotational force.

In other words, the term “dynamic force” refers to the force acting between an elongated probe and the main unit to which the probe is attached when the probe is moved, as explained in more detail below. This force will be partly determined by the characteristics of the biomaterial, both around the tip of the probe and along the submerged length of the 25 probe. It will also be partly determined by how the operator pushes, pulls or rotates the main unit.

Force measurements may also be conducted when the probe is stationary in the body of biomaterial, for example to check if the operator keeps leaning against the device after the 30 probe has come to a halt. The measured force will in this case be called “static force”.

Moisture measurements are typically conducted in pressed biomaterial either as capacitive or resistive electronic measurements where different parts of the probe constitute

20165877 prh 21 -11-2016 measurement electrodes and the biomaterial which surrounds the measurement probe constitutes the dielectric / resistor whose electric property is measured. This electric property varies with moisture concentration, but it also varies with the density of the biomaterial surrounding the probe. Capacitance increases with increased bulk density 5 because the permittivity of water and biomaterial is greater than the permittivity of air. A volume of high bulk density biomaterial has less air, more water and more biomaterial than a volume with low bulk density. Resistance, on the other hand, decreases with increased bulk density, because a larger area of biomaterial touches the electrodes and because a higher area of biomaterial touches the biomaterial that touches the electrodes, causing an 10 effect similar to connecting more parallel resistors to an electrical circuit.

Moisture concentration measurements in biomaterials may therefore be disturbed by systematic errors arising from the unknown density of the biomaterial or density variations in the biomaterial. A common method for negating systematic errors is to calculate 15 correction factors which estimate the magnitude of the systematic error. A moisture concentration correction factor can be used to adjust the measured moisture concentration values either upward or downward. An adjusted moisture concentration value, which is more representative of the true moisture concentration in the pressed biomaterial than the initially measured value, is thereby obtained.

However, systematic errors arising from density are not easily corrected because biomaterial density is often neither easily measurable nor constant. Some bodies of biomaterial, such as bales, can be weighted and their volume can be measured. However, it would usually be inconvenient to load the bodies on and off a scale every time a moisture 25 measurement is conducted. Furthermore, a density value obtained from weighting the entire body of biomaterial is only an average value, but biomaterial density can vary in a pressed body. Moisture concentration measurements are also preferably conducted at several depths in one body of biomaterial.

Thrust force measurements have therefore been implemented as a useful proxy for density measurements in moisture concentration measurement devices for biomaterials. Thrust force measurements can be readily integrated to an elongated moisture measurement probe by connecting one end of the probe to a force transducer. The additional force

20165877 prh 21 -11-2016 measurement functionality can thereby be added to a probe-based moisture measurement device without adding any large components to the device.

Document RU 1816107 discloses a humidity sensing device for fibrous materials with a measurement probe and a force indicator. When the probe is fully buried in the material, the material puts pressure on both the probe and one side of the casing. Due to this pressure the base plate moves. The force corresponding to this movement can be approximately read from a LED indicator with four adjacent lamps.

A problem with the device disclosed in RU 1816107 is that it is only usable in measurements where the probe becomes fully buried in the biomaterial and the biomaterial exerts a constant pressure on the moisture concentration measurement device. These conditions could, for example, be obtained if the moisture concentration measurement device is placed at the bottom of a container and the biomaterial is placed on top. However, the disclosed method is not, for example, usable in moisture concentration measurement devices where a human user thrusts the probe into a body of biomaterial. No static force remains between the handle and the probe after the thrust has finished and the user lets go of the device. The device disclosed in RU 1816107 can only perform a moisture measurement at one depth: when the probe is fully buried. Furthermore, the moisture measurement is performed between the tip of the probe and one side of the casing where the counter-electrodes are located. The local moisture concentration in the small portion of biomaterial which surrounds the probe cannot be measured.

BRIEF DESCRIPTION OF THE DISCLOSURE

An object of the present disclosure is to provide an apparatus and a method for solving the above problems.

The objects of the disclosure are achieved by methods and apparatuses which are characterized by what is stated in the independent claims. The preferred embodiments of the disclosure are disclosed in the dependent claims.

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The embodiments in this disclosure are based on the idea of localized measurements.

Moisture is often not distributed homogenously in a body of pressed biomaterial. Moisture measurements are therefore often conducted at several depths in one body of biomaterial when the total amount of water present in the material is estimated. This requires 5 measurement probes with relatively small moisture sensors which facilitate localized measurements in the material surrounding the probe. Moisture sensors may preferably be placed close to the outermost tip of the probe to maximize the available penetration depth.

Moisture concentration correction factors based on force measurements are specific to a 10 certain biomaterial and coarseness. In other words, no general correlation can be established across all biomaterials between force measurements and the moisture concentration correction factors which should be applied to avoid systematic errors. Appropriate moisture concentration correction factors must therefore be established experimentally for each specific biomaterial and coarseness, as described in more detail 15 below.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the disclosure will be described in greater detail by means of preferred 20 embodiments with reference to the accompanying drawings, in which:

Figure 1 illustrates a moisture concentration measurement device applicable in all embodiments.

Figure 2 illustrates a measurement method according to a first and fourth embodiment

Figure 3 illustrates the measurement method according to the first and fourth embodiments 25 in more detail.

Figure 4 illustrates the results of a thrust force measurement.

Figure 5 illustrates the results of a calibration experiment.

Figure 6 illustrates a measurement method according to a second and fourth embodiment.

Figure 7 illustrates the results of simultaneous thrust force and penetration depth 30 measurements.

Figure 8 illustrates a measurement method according to a third and fourth embodiment.

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DETAILED DESCRIPTION OF THE DISCLOSURE

Figure 1 illustrates a moisture concentration measurement device for pressed biomaterials. The illustrated components have not all been drawn to the same scale. A dotted line separates the inside of a body of biomaterial 151 from its surroundings 150. The device comprises a main unit with an inside and an outside. In the device shown in Figure 1, the main unit is coextensive with the casing 11.

An elongated measurement probe 12 consists of an inside portion which is inside the main unit, that is, inside the casing 11, and an outside portion which is outside the main unit, that is, outside the casing 11. The outside portion of the elongated measurement probe 12 is configured to be moved in a body of pressed biomaterial 151.

The inside portion of the elongated measurement probe 12 is connected to the main unit through a force transducer which is configured to measure the force acting between the probe and the main unit. To facilitate force measurements, the probe 12 must be at least to some extent mobile along the measurement axis (the x-axis in Figure 1) in relation to the main unit.

An exemplary force transducer may include a spring 13 with a known spring constant. The spring 13 may encircle a portion of the probe 12 inside the main unit, as illustrated in Figure 1. A first end 131 of the spring may be fixed to a support structure 14, which may in turn be fixed to the casing 11. A second end 132 of the spring, which may be mobile in relation to the support structure 14, and thereby mobile in relation to the main unit, may be in contact with the probe 12 for example through a small metal plate 15 which has been welded to the probe 12. The plate 15 may compress the spring 13 in the negative xdirection when the probe 12 is thrust into a body of biomaterial. In addition to transmitting the forces acting on the probe 12 to the spring 13, metal plate 15 may be used to prevent the probe 12 from rotating around the x-axis.

The force transducer illustrated in Figure 1 can also be converted to measure the pull force required to withdraw the probe 12 from the body of biomaterial 151. The plate 15 may, for example, be permanently attached to the second end 132 of the spring and the spring may

20165877 prh 21 -11-2016 be given more room to expand in the positive x-direction. Alternatively, the plate 15 or an equivalent structure could be in contact with two separate springs, one for measuring the pushing force during the thrust, and another for measuring the pulling force during withdrawal. The two springs could both encircle the inside portion of the probe.

Alternatively, one or both of them could be placed aside from the inside portion of the probe 12 and mechanically linked to the probe with suitable mechanical means.

The force transducer may also include a magnet 16 which is attached to the probe 12 and thereby at least partly mobile in relation to the casing. The force transducer may further 10 include a Hall sensor 17 for detecting the movement of the magnet 16. The Hall sensor 17 may be fixed to the casing. When the movement of the magnet 16 is measured by Hall sensor 17 and the spring constant of the spring 13 known, the momentary force acting on the probe 12 along the measurement axis can be calculated.

The moisture concentration measurement device illustrated in Figure 1 is primarily intended to be a handheld device. A human operator may grab the main unit by wrapping one or two hands around the casing 11, and thrust the probe 12 into a body of biomaterial. The main unit may also comprise a handle attached to the casing to facilitate a more secure grip.

However, the same measurement principle can be implemented also in a machineoperated moisture concentration measurement device. In this case the device may not have the kind of casing illustrated in Figure 1. Instead the main unit in the measurement device may be incorporated with other parts of the machine. The main unit will 25 nevertheless still comprise an inside and an outside and the probe will consist of a corresponding inside portion and an outside portion.

The outside portion of the elongated measurement probe 12 comprises at least one moisture sensor configured to measure a moisture concentration value in the pressed 30 biomaterial surrounding the moisture sensor. The moisture sensor is preferably placed close to the tip 18 of the probe 12 to maximize the available measurement depth, but it could be placed anywhere along the length of the probe. The moisture sensor may comprise a first measurement electrode 19 on the outer surface of the probe and a second

20165877 prh 21 -11-2016 measurement electrode 110 at the tip of the probe. These two electrodes may be separated by dielectric tube 111. The dielectric tube 111 may be made of glass fibre. It should preferably not absorb any moisture.

Throughout this disclosure, the word “local” will refer to a section 112 of biomaterial which surrounds that portion of the probe 12 where the moisture sensor is located. This “local” section consists of the biomaterial which affects the electrical measurement performed by the moisture sensor. The physical extent of this “local” section will vary from one biomaterial to another, and it may also depend on the coarseness and density of the 10 biomaterial. The sensor can be calibrated without knowing how far from the sensor the “local” section extends in each case.

The expression “local dynamic force” refers throughout this disclosure to the force which was applied to the measurement probe 12 when the tip 18 penetrated through, or was 15 withdrawn from, or rotated in, the section 112 of biomaterial which became the “local” section when the probe came to a halt. This local dynamic force is not always directly evident in the measurement data from the force transducer, but it can be estimated from the data with the methods described below. The local dynamic force may be estimated from measurements where frictional forces act on the entire submerged length of the 20 probe. In some, but not all embodiments, the local dynamic force may be estimated from the average frictional force along the submerged length of the probe.

The moisture sensor may be a capacitive sensor which uses the surrounding section of biomaterial 112 as a dielectric between the two measurement electrodes 19 and 110. As 25 is well known in the art, the dielectric constant of biomaterials changes as a function of moisture concentration.

Alternatively, the moisture sensor may be a resistive sensor which uses the surrounding section of biomaterial 112 as the resistor between the two measurement electrodes 19 30 and 110. As is well known in the art, the resistance also changes as a function of moisture concentration.

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The measurement results obtained from the moisture sensor and the force transducer may be memorized by a human user, who may then perform calculations to account for systematic errors in the moisture concentration measurement. However, preferably the moisture concentration measurement device comprises a computer device with a control 5 unit configured to calculate an adjusted local moisture concentration value in response to receiving at least moisture concentration values from the moisture sensor and force values from the force transducer. The control unit may perform the required calculations automatically and present the results to a human user or store them in a memory unit.

The moisture concentration measurement device may also comprise an interface unit. The interface unit may comprise a display 113, a keyboard 114, a touchscreen, microphones, loudspeakers, or other devices which facilitate user interaction with the control unit. The control unit may be a part of a computer device which is preferably located inside the casing 11. The control unit may, for example, comprise several circuit boards 118, 119 and 120 in various parts of the moisture concentration measurement device.

The control unit may comprise circuitry for implementing audio/video and logic functions on the interface unit. The control unit may also comprise one or more data processors. The control unit may be connected to a memory unit where computer-readable data or 20 programs can be stored. The memory unit may comprise one or more units of volatile or non-volatile memory, for example EEPROM, ROM, PROM, RAM, DRAM, SRAM, firmware or programmable logic. The control unit may be linked to data communication means for transferring data to remote nodes, where it may be stored or presented.

The probe 12 is preferably hollow to facilitate transmission of measurement signals. Communication wires 116 may connect the circuit board 120 in the probe to the circuit boards 118 and 119 in the casing. The dielectric tube 111 preferably also contains an internal electric wire 117 which facilitates electric contact and measurement between the two electrodes 19 and 110.

In addition to the mentioned components, the moisture concentration measurement device may at least comprise mechanical components which provide rigidity and structural support to the device. It is especially important that the probe is so strongly supported that it cannot be tilted in relation to the casing. Structural support components are important because the forces which act on the probe when it is thrust into or withdrawn from a body of biomaterial can be on the order of a thousand Newtons. However, since these components are not central to the described measurements they will not be described 5 further in this disclosure.

First embodiment

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In a first embodiment illustrated in Figure 2, this disclosure relates to a method for 10 performing a moisture concentration measurement in a body of pressed biomaterial with a moisture concentration measurement device (21, 22, 23). In the method, the outside portion of the elongated measurement probe is moved in a body of pressed biomaterial and the control unit reads force measurement values from the force transducer, and estimates from the force measurement values the local dynamic force (24). The control 15 unit may also store the force measurement values in a memory unit. Before or after the probe is moved, the control unit initiates a moisture concentration measurement and reads an initial moisture concentration value from the moisture sensor. The control unit then calculates a moisture concentration correction factor based on correction variables which include at least the estimated local dynamic force and the type of biomaterial (25).

After calculating the moisture concentration correction factor, the control unit can calculate an adjusted moisture concentration value by adjusting the initial moisture concentration value with the moisture concentration correction factor (26). This adjustment usually means either division or multiplication with the correction factor. The control unit can then 25 store the adjusted local moisture concentration value in the memory unit and/or present it to a user (27).

Figure 3 illustrates this first embodiment in more detail. As mentioned above, the measurements are conducted with a moisture concentration measurement device in a 30 body of pressed biomaterial. Measured variables and other known information is shown in white boxes in Figure 3. Values calculated from measurement results are shown in light grey boxes. Correlations obtained from calibration experiments before the actual

20165877 prh 21 -11-2016 measurement was conducted are shown in dark grey boxes. The same colouring scheme will be applied in figures 6 and 8 below.

The primary measurement variable is the local moisture concentration in the region of biomaterial which surrounds the moisture sensor. The electrical properties (capacitance / resistance) of the biomaterial depend on moisture concentration, so the measured electrical property (31) can be converted into initial local moisture concentration value (33) with calibration data (32).

Separate calibrations are typically required for different biomaterials and degrees of coarseness (38). The calibrated correlation 32 may, for example, be calculated by measuring moisture concentration with the measurement device, and with a reference method, in several different bodies of biomaterial with varying moisture content. The reference method may, for example, be one where samples of biomaterial are obtained by boring and then weighted before and after a heat treatment in which the moisture evaporates. The result of the calibration 32 is an approximate correlation between sensor response and local moisture concentration.

As already mentioned above, the initial local moisture concentration value 33 may be influenced by systematic errors which cannot be circumvented either by repeated sampling or more accurate calibration. For example, sensor response is affected by the density of the biomaterial. As indicated in Figure 3, a moisture concentration correction factor 34, which accounts for this systematic error at least approximately, can be used to calculate an adjusted local moisture concentration value 35. This adjusted value 35 should be closer to the true local moisture concentration in the biomaterial than the initial value 33.

In this first embodiment, the moisture concentration correction factor 34 is calculated only from a thrust force measurement (36). The control unit may measure from the force transducer the force by which probe 12 acts on the main unit (in the direction of the x-axis) 30 when the probe is thrust into the body of biomaterial. In accordance with Newton’s third law, this force is equal to the force which the probe exerts on the biomaterial.

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The force transducer may be sampled repeatedly and the control unit may store the measured force values in a memory unit. The thrust force is thereby stored as a function of time. The resulting data may be referred to as a “dynamic force signal”.

The user may initiate a measurement by inputting start commands to the control unit through the interface unit. Alternatively, the control unit may be programmed to automatically monitor the force signal and to initiate a measurement based on the recorded force values. The force transducer indicates zero force until the tip of the probe is pressed against the outer surface of the biomaterial, so the force signal reliably indicates the 10 moment when a thrust is about to begin. The force drops back to zero when the probe is inside the body of biomaterial, the thrust is finished and the user lets go of the device.

Thrust force can be interpreted as a proxy for biomaterial density. The denser the biomaterial, the more thrust force is required to push the probe through the biomaterial. In 15 other words, the density of the biomaterial affects the frictional force which impedes the movement of the probe through the biomaterial. At any given moment during the thrust, the primary determinant of the frictional force is the local density of biomaterial around the tip of the probe because the tip must open a channel in the biomaterial through which the probe can move. However, smaller frictional forces acting along the entire submerged 20 length of the probe also contribute to friction.

The type and coarseness of the biomaterial also affect the frictional force. Type and coarseness are assumed to be known to the user who performs the measurement. The user may enter this data into the measurement device by using the interface unit, for 25 example by making selections in a type / coarseness menu which the control unit displays on the screen. The control unit may then retrieve the calibrated correlation 37 which corresponds to the selected biomaterial type and coarseness.

This first embodiment concerns moisture concentration measurements where the density 30 of the studied body of biomaterial is known or assumed to be homogenous throughout the body. The magnitude of this density is unknown. In homogenous bodies of biomaterial the static frictional force is often larger than the kinetic frictional force because it is easier for the tip of the probe to penetrate the next layer of biomaterial when the tip is moving than

20165877 prh 21 -11-2016 when it is at rest. In other words, a greater force is required to start a thrust than to maintain it once the probe is moving.

A stronger push is therefore usually required to exceed a static friction threshold than to keep the probe in motion. This usually holds true both when the probe penetrates through the outer surface of the biomaterial and when a stationary probe is put in motion after it has already penetrated the biomaterial and come to a halt.

The submerged surface area of the probe gradually increases as it penetrates deeper into 10 the biomaterial. Both the static and the kinetic frictional force will gradually increase when they begin to act on a longer section, and thereby a larger area, of the probe. The magnitude of this effect depends on the biomaterial density.

This disclosure is primarily concerned with situations where the moving force is provided 15 by human muscle power. The apparatus shown in Figure 1 is intended to be a handheld device which is easy to operate by hand. In other words, a human typically moves the probe in a body of biomaterial when a moisture concentration measurement is performed. A moisture concentration measurement device where the thrust is provided by machine power could be implemented with the same measurement principles. The movements 20 performed by the operator could then be automated.

The control unit may be programmed to advise the operator through the interface unit that a reliable density correction requires a steady thrust performed with a force which remains relatively constant. When the operator then puts the probe in motion in a homogenous 25 body of biomaterial, the measured dynamic force signal will typically first contain a peak corresponding to the static friction threshold. After that the dynamic force may remain approximately steady. This steady-state dynamic force is interpreted as a proxy for the density of the biomaterial in this first embodiment. At the end of a thrust the dynamic force may momentarily increase if the operator tries to keep the probe going as deep as possible. 30 After that it falls close to zero.

One example of a thrust force measurement in a homogenous bale of hay is shown in Figure 4. The graph shows that the thrust force initially rose to about 140N to overcome

20165877 prh 21 -11-2016 the static frictional threshold. The thrust force then obtained values which average approximately 11 ON as the probe moved through the biomaterial. The thrust force then increased again at the end before the operator finished the thrust.

In relatively homogenous bodies of material, the local dynamic force 39 may be estimated from the dynamic force signal in Figure 4 for example by calculating the average of the thrust force on the steady-state plateau, which in the example shown in Figure 4 extends from about 2,4 s to 2,8 s.

The dynamic force supplied by a human operator may not always be as steady as in Figure 4. The operator may push the probe in an irregular manner. Human anatomy may in certain body positions prevent the operator from supplying a constant force to the device. A steady-state plateau may therefore not always be present in the thrust force data.

The control unit may also be programmed to check the form of the recorded dynamic force signal and refrain from calculating a density correction if the signal is very irregular, with no clear plateau which could be interpreted as the steady state thrust force. The control unit may do so by automatically setting the moisture concentration correction factor to one if the data is irregular. The control unit may be programmed to alert the operator through 20 the interface unit that a density correction could not be conducted because the thrust force was not steady.

The control unit may also be programmed to explicitly instruct the operator to release the moisture concentration measurement device when the thrust is finished. If the device is 25 not released and the operator keeps leaning against the device after the probe has stopped, the control unit may falsely interpret this static force as the steady-state dynamic force, and the density correction may be erroneous.

The moisture concentration measurement method according to this first embodiment may 30 be performed multiple times in one thrust if the operator pushes the probe into the biomaterial in sequences. If the thrust occurs in multiple sequences, the homogeneity assumption only needs to apply to each step separately. In other words, the body of biomaterial may be assumed to consist of several layers of varying density, but the density

20165877 prh 21 -11-2016 in each layer may be assumed to be homogeneous and each step may cover one homogeneous layer. The truth of these assumptions may depend on how the control unit instructs the operator and on how much the operator knows about the body of biomaterial which is measured. However, it should be remembered that very short partial thrusts may 5 not produce a clear steady-state dynamic force plateau from which a local dynamic force could be reliably estimated.

The control unit may initiate a new moisture concentration measurement every time the force signal falls below a certain threshold value. This will be discussed in more detail 10 below in the fourth embodiment below.

When the local dynamic force 39 has been estimated from the dynamic force signal, a calibrated correlation 37 between thrust force and moisture concentration is needed to calculate the moisture concentration correction factor 34. These calibration experiments 15 are performed beforehand and are present in the moisture concentration measurement device merely as tabulated data. The calibration procedure is nevertheless described here briefly to clarify the idea.

The correlation 37 is specific to each biomaterial, so separate calibration experiments must 20 be performed for each biomaterial with each degree of coarseness. Unchopped hay will here be used as an illustrative example. The correlation data from the calibration experiment is presented in Figure 5. Prior to this experiment, the moisture sensor had been calibrated for hay measurements in the calibration 32 which was described above.

In the experiment shown in Figure 5, several bales were taken as samples from the same harvest lot and measured with the sensor. The bales were at the same moisture and had the same (relatively low) bulk density. The bales were then pressed further to create various higher density samples with the same moisture concentration. All samples initially had a moisture content (mass percentage) close to 16.2 %, which was measured with a 30 standard oven drying moisture determination method. The steady state and moisture sensor response were measured in each sample.

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The measurement results are shown in Figure 5. As seen in the figure, the moisture sensor response correlates with the required thrust force. The true moisture concentration was 16.2% in all samples, but the sensor indicates significantly higher values in the pressed samples. An approximately linear relationship can be detected between the systematic 5 error and the thrust force. Thrust force is again interpreted as a proxy of hay density.

The correlation specified in box 37 in Figure 3 is usually linear, but it may in some cases be nonlinear. A table of moisture concentration correction factors 34, which relate the estimated steady state dynamic force 39 of a certain magnitude to systematic errors of a 10 certain magnitude, can be calculated from the exemplary data in Figure 5 with standard methods. This calibration procedure is merely exemplary, and many other methods could also be used for establishing the correlation 37 between thrust force and the densitydependent systematic error in the moisture sensor response.

Force vs correction factor relationships can be obtained for a multitude of biomaterials with different degrees of coarseness through repeated calibration experiments. They may be stored in the memory unit before the device is used. When the user performs a measurement, the control unit may prior to the measurement ask the user to input which type of biomaterial is about to be measured, and the approximate coarseness of the 20 biomaterial. Having obtained this information, the control unit may retrieve the corresponding calibration relationship 37 from the memory unit. After a moisture concentration measurement and a dynamic force measurement have been performed, the initial local moisture concentration 33 can be adjusted with the moisture concentration correction factor 34, for example by either multiplying or dividing the value 33 with the 25 value 34. The result is an adjusted local moisture concentration value 35, which is closer to the correct local moisture concentration value than the value 33 because the systematic error arising from unknown biomaterial density has been at last approximately corrected.

Second embodiment

In a second embodiment, this disclosure relates to a method where a motion sensor, configured to measure the motion of the elongated measurement probe in a body of pressed biomaterial, is also included in the moisture concentration measurement device.

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With this modification, penetration depth can also be used as a correction variable when systematic errors arising from density variations are corrected. In this embodiment the control unit reads motion measurement values from the motion sensor. The control unit may store these motion measurement values in the memory unit.

After initiating a moisture concentration measurement, the control unit calculates a penetration depth value from the stored motion measurement values. The penetration depth value may, for example, express the depth to which the tip of the probe has penetrated the body of biomaterial. The control unit can then include the penetration depth 10 value in the correction variables which are used to calculate the moisture concentration correction factor. In other words, the control unit is additionally configured to calculate an adjusted moisture concentration value in response to receiving penetration depth values from the motion sensor.

The motion sensor may, for example, be an acceleration sensor on the circuit board 120 which is located inside the probe 12. The penetration depth of the probe 12 in biomaterial 151 can then be calculated (as a function of time) from the measured acceleration data. The force signal may be used to initiate the motion measurement when a thrust begins.

The motion sensor may also be an infrared proximity sensor placed on the side of the casing which is closest to the biomaterial surface. The probe penetration depth can then be obtained directly from the proximity data. Again, the beginning of a thrust may be identified from the force signal. A proximity measurement may be performed at any time, regardless of whether the probe is moving or stationary. In other words, if the motion sensor is a proximity sensor, the motion measurement does not necessarily have to be performed simultaneously with the thrust. When the time-dependence of the penetration depth during the thrust is of interest, the proximity sensor may be monitored during the thrust.

Figure 6 illustrates the second embodiment in more detail. Boxes 31,32, 33 and 38 have the same reference numbers as in the first embodiment because their content is unchanged. The calibrated correlation between force and moisture sensor response 37 may also be the same as in the first embodiment. The thrust force measurement 36 is also

20165877 prh 21 -11-2016 performed in the same manner as in the first embodiment, but the operator is not instructed to keep the thrust force constant. One benefit of this second embodiment is that the operator can perform the thrust as he or she pleases.

The motion sensor measurement is indicated in Figure 6 with box 69. The control unit may continuously read motion measurement values from the motion sensor and calculate a penetration depth signal from these values. The penetration depth signal indicates the depth to which the probe has penetrated in the biomaterial as a function of time.

Whereas the method described in the first embodiment was applicable primarily to homogenous bodies of biomaterial, the method in this second embodiment is applicable even to non-homogenous bodies of pressed biomaterial. The reason for this is that the motion measurement data enables more versatile methods for estimating the local dynamic force.

In a non-homogenous body of biomaterial the frictional force will vary. As in the first embodiment, a static frictional force always opposes the onset of probe movement. After the static threshold has been overcome, there will be a dynamic frictional force which resists the thrust. However, the magnitude of this dynamic frictional force may depend on 20 the density of the biomaterial which surrounds probe. It will depend particularly strongly on the density of the biomaterial surrounding the tip of the probe because this is where frictional forces are the strongest.

Consequently, even if the probe is in motion it may encounter a new friction threshold when 25 it begins to penetrate a portion of biomaterial where the density is higher. This means that the measured dynamic force may exhibit peaks which correspond to sections where the tip penetrated denser biomaterial, and troughs which correspond to sections where the tip penetrated sparser biomaterial.

When motion measurements are utilized, the stoppage point of the thrust can be determined directly from the motion data. In other words, the control unit can disregard any lingering static force which the operator may apply to the device after the probe has already come to a halt in the biomaterial.

20165877 prh 21 -11-2016

Figure 7 shows data from exemplary measurement conducted in a non-homogenous body of hay with a moisture concentration measurement device which comprises both a force transducer and a motion sensor. The solid line shows the dynamic force signal scaled to the axis on the left. The dotted line shows the penetration depth as a function of time. This is the penetration depth signal and it is scaled to the axis on the right.

The operator performed the thrust shown in Figure 7 in two stages. In the first stage the thrust force reached an initial peak at about 1,1 seconds as the probe quickly penetrated 10 with strong force just over 40cm into the body of biomaterial. Then the thrust stalled for about half a second until the operator again applied a force strong enough to move the probe a further 10-15 cm inward. At 2,1 - 2,3 seconds the operator tried to push the probe deeper, but it did not move any further. The operator then gradually relaxed the thrust force and let go of the device. Thrusts in non-homogenous bodies of biomaterial often show 15 variation in the thrust force.

As in the first embodiment, a moisture concentration measurement is performed after the probe has stopped. The control unit may be programmed to initiate a moisture concentration measurement only if the dynamic force is below a certain threshold value.

The control unit may also be programmed to refrain from showing measurement results until the operator has ceased to apply force to the probe.

Taking Figure 7 as an example, the temporary stall after 1,2 seconds may not have been sufficient to initiate a moisture concentration measurement because the applied thrust 25 force remained relatively high, above 100 N. When the thrust force gradually declined after

2,5 seconds, a moisture concentration measurement may have been conducted.

As mentioned before, the strongest friction component arises at the tip of the probe because it must penetrate and push aside new layers of biomaterial. The question of 30 interest in Figure 7 is how high the thrust force was just before the probe stopped and a measurement was initiated. The force applied in the final moments before the probe came to a stop indicates with good accuracy how large the frictional force was in the section of biomaterial which the probe penetrated in the final stage of the thrust. This section of

20165877 prh 21 -11-2016 biomaterial is the local section which surrounds the tip of the probe when the moisture concentration measurement is performed. As before, local dynamic force is a proxy for local biomaterial density.

The control unit may estimate the local dynamic force from the penetration depth and dynamic force signals as follows. The control unit can determine the moment when the probe comes to a halt directly from the penetration depth signal. The control unit may then wait for the dynamic force signal to fall below a certain predetermined limit to ensure that no further movement is forthcoming. This predetermined limit may be selected based on 10 the type of biomaterial and its coarseness. It may, for example, be 10 N, 20 N, 50 N or higher. Alternatively or complementarily, the control unit may wait for a predetermined time after the probe has come to a halt before initiating a measurement. This time may, for example, be 1 sec, 2 sec, 5 sec or higher.

When the dynamic force has fallen below the predetermined limit, the control unit may perform a measurement with the moisture concentration sensor and simultaneously identify the last local thrust force maximum which was recorded in the thrust force signal before the probe came to a halt. In the exemplary data shown in Figure 7, the last local maximum which can be identified in the dynamic force signal before the halt at 2,2 seconds 20 is just below 700 N. The control unit may select the last local thrust force maximum as the estimate of the local dynamic force 610 in Figure 6.

As in the first embodiment, the frictional force may increase gradually as the probe penetrates further into the biomaterial due to the increasing length and area upon which 25 the frictional force acts. The penetration depth signal may also be used to calculate a correction for this increase in the frictional force. This may be done experimentally by measuring the force signal when a measurement probe is withdrawn from various biomaterials. The frictional force which depends on penetration depth can be more reliably determined in withdrawal than in penetration. A calibrated correlation 611 can thereby be 30 determined between penetration depth and the depth-dependent frictional force. The control unit may use this correlation to estimate the local dynamic force 610 at a certain penetration depth more accurately.

20165877 prh 21 -11-2016

Another way to measure the depth-dependent frictional force is to add to the measurement device a force transducer for detecting rotational force. When the probe is submerged into the biomaterial at a given depth, the frictional force which resists rotation is directly proportional to the frictional force which resists translation. Both of them depend on the 5 penetration depth in the same manner. The same correlation between penetration depth and depth-dependent frictional force can therefore be obtained by recording the required rotation force at various depths. The control unit may be programmed to instruct the operator to rotate the probe.

The second embodiment may also be implemented with a method which combines both elements presented above. In other words, the control unit may adjust the last local force maximum (recorded in the dynamic force signal before the probe came to a halt) with a penetration factor which accounts for the increase in frictional force due to deeper penetration. The need for more complex analysis of this kind depends on the desired measurement accuracy and on the type of biomaterial and its coarseness.

After a moisture concentration measurement and dynamic force measurement have been performed, the initial local moisture concentration 33 can be adjusted with the moisture concentration correction factor 64, for example by either multiplying or dividing the value 20 33 with the value 64. The result is an adjusted local moisture concentration value 65, which is closer to the correct local moisture concentration value than the value 33 because the systematic error arising from the unknown local biomaterial density has been at last approximately corrected.

Third embodiment

In a third embodiment, this disclosure relates to a method where a temperature sensor is provided in the outside portion of the elongated measurement probe. After initiating a moisture concentration measurement, the control unit reads a temperature value from the 30 temperature sensor. The control unit may store the temperature value in the memory unit.

The control unit can then include the penetration depth value in the correction variables which are used to calculate the moisture concentration correction factor. In other words, the control unit is then additionally configured to calculate an adjusted moisture

20165877 prh 21 -11-2016 concentration value in response to receiving temperature values from the temperature sensor.

The temperature sensor may be located on the circuit board 120 which is inside the probe.

Figure 8 illustrates the measurement methodology employed in this embodiment. Boxes

31,32, 33, 36, 37 and 38 are the same as in the first and second embodiments. Boxes 69, 610 and 611 are the same as in the second embodiment.

The control unit measures the local temperature 811 with the temperature sensor after it 10 has initiated a moisture concentration measurement. The control unit may sometimes directly accept this measured temperature value as the estimated local temperature 812. However, the kinetic friction experienced by the probe during the thrust can heat the probe significantly, at least in denser biomaterials. If many thrusts are performed in quick succession, the temperature sensor may give readings which are more than 10K higher 15 than the true temperature of the biomaterial.

The correct local temperature value may be estimated theoretically if the heat capacity of the probe and heat transfer rate from the biomaterial to the probe is known. However, it is usually more convenient to include temperature measurements in the calibration 20 experiment depicted in Figure 5, with motion sensing also included. When a moisture concentration measurement is subsequently performed in a biomaterial with unknown moisture properties, the measured dynamic force 36 and the measured motion 69 can be compared to a calibrated correlation 814 between (1) the force and motion recorded in the calibration experiment (and the history of these measurements, if multiple thrusts are 25 conducted in quick succession) and (2) the temperature sensor response recorded in the calibration experiment. An estimated correction can then be calculated to the measured local temperature 811 with the help of correlation 814.

A separate function for temperature measurement could also be programmed to the 30 control unit in the moisture concentration measurement device. The control unit may, for example, be programmed to check if the probe has remained stationary for a predetermined settling period. The settling period should be long enough to allow the temperature of the probe (or at least the tip of the probe) to equalize with the temperature of the surrounding biomaterial. The measured local temperature 811 may then be directly

20165877 prh 21 -11-2016 accepted as the estimated local temperature if the probe remained stationary for the duration of the settling period.

Many biomaterials have low heat conductivities. The heat capacity of the probe, on the other hand, can be quite large if it includes thick metallic parts. The required settling period may therefore have to be 10 minutes, 15 minutes, or longer. The control unit may explicitly instruct the operator to keep the probe stationary for the duration of the predetermined settling period. If the probe is put in motion before the settling period has expired, the control unit may revert to the previously described method where the local temperature 10 811 is estimated with the help of correlation 814.

Once the local temperature 812 has been estimated, a separate calibrated correlation 813 is invoked to estimate how much the electrical properties of the biomaterial change as a function of local temperature. The data required for this correlation can for example be 15 obtained in an experiment where a sample of biomaterial is cut or bored from a larger body, this sample is enclosed in an airtight enclosure and the probe is inserted into the sample through the enclosure. By putting the sample in a temperature chamber the moisture sensor response can be studied as a function of temperature. The airtight enclosure prevents water from evaporating during the measurement.

A new moisture concentration correction factor 84, whose input now includes dynamic force, motion and temperature measurements, may then be calculated. As in the preceding embodiments, the control unit may then use moisture concentration correction factor 84 and the initial local moisture concentration value 33 to calculate an adjusted moisture 25 concentration value 85. This adjusted moisture concentration value may be presented to the user through the interface unit and/or stored in memory.

As in the preceding embodiments, the control unit may be programmed to initiate a moisture concentration measurement only if the dynamic force is below a certain threshold 30 value. The control unit may also be programmed to refrain from showing measurement results until the operator has ceased to apply force to the probe.

20165877 prh 21 -11-2016

Fourth embodiment

As already indicated above, force measurements can also be conducted while a probe is withdrawn from a body of biomaterial which it has already penetrated, or while it is rotated 5 in a body of biomaterial which it has already penetrated.

A withdrawal may start from a position where the probe is fully submerged in a body of biomaterial, or from one where it is partially submerged. A rotation may also be performed at any depth in a body of biomaterial. In both measurements, frictional forces act along the 10 submerged length of the probe. Withdrawal and rotational force measurements differ from thrust force measurements in that there is no additional frictional barrier arising from forces acting on the pointed tip of the probe. In other words, in these measurements the probe moves in a channel which it has previously opened.

Force measurements conducted during withdrawal or rotation may be used to estimate the average density of biomaterial along the submerged length of the probe. In other words, the dynamic force may in this case, too, be interpreted as a proxy for biomaterial density.

Force measurements in withdrawal and rotation may be advantageously combined with 20 motion sensor measurements which indicate the momentary penetration depth.

Alternatively, if motion sensors are not employed, the control unit may be programmed to instruct the operator to perform a complete withdrawal from a position of full submersion, or a rotation at full submersion. The penetration depth at full submersion is known. The estimate of local dynamic force which is obtained from these measurements may be stored 25 and used in subsequent moisture concentration measurements conducted at other depths.

A force measurement conducted during withdrawal may, for example, involve steps where the probe is thrust into a body of biomaterial and a moisture concentration measurement is performed. Temperature measurements may also be performed, and the penetration 30 depth may be determined with the means specified above. When the moisture concentration measurement is finished, the probe may be withdrawn and the withdrawal force measured.

20165877 prh 21 -11-2016

The first peak in the withdrawal force measurement may be interpreted as the magnitude of the static frictional force acting along the submerged length of the probe. The average value of the dynamic force signal during the first 15cm of withdrawal may be interpreted 5 as an average of the dynamic frictional force acting along the submerged length of the probe. The static or dynamic frictional force acting along the submerged length of the probe may be assumed to be proportional to the average density of biomaterial along the submerged length of the probe. Either of these measured force values may be taken as an estimate of the local dynamic force when an adjusted moisture concentration value is 10 calculated with any of the methods presented in the first three embodiments. The withdrawal force measurements may be repeated at several depths. A local dynamic force estimate obtained at one depth may be used for moisture concentration measurements conducted at other depths as well, even close to the surface of the body of biomaterial where new withdrawal measurements may not be possible.

A separate calibrated correlation may be experimentally established for withdrawal force measurements in each biomaterial and for each degree of coarseness. Calibrated correlations may be determined between withdrawal force and moisture sensor response in the manner exemplified in Figure 5 above. The moisture concentration correction factor 20 may then be calculated from this correlation once the withdrawal force has been measured, in the manner exemplified in the preceding embodiments.

A force transducer for measuring rotational force should be added to the moisture concentration measurement device if rotational force measurements are conducted. A 25 rotational force transducer may, for example, comprise a torsional spring. A moisture concentration measurement device may comprise both one or more translational force transducers, such as the one illustrated in Figure 1, and one or more rotational force transducers.

A force measurement conducted during rotation may, for example, involve steps where the probe is thrust into a body of biomaterial and a moisture concentration measurement is performed. Temperature measurements may also be performed and the penetration depth may be determined with the means specified above. Before or after these measurements, the operator may be instructed by the control unit to rotate the probe in

20165877 prh 21 -11-2016 the body of biomaterial by rotating the main unit. The main unit may be equipped with rotation handles or bars which make it easy for the operator to apply a rotational torque about the x-axis illustrated in Figure 1. The force signal is measured from the rotational force transducer.

The main unit may comprise a positional sensor from which the control unit may obtain data for verifying that a rotation has taken place. These sensors may, for example, include a magnetometer or a MEMS acceleration sensor. The first peak in the rotation force measurement may be interpreted as the magnitude of the static frictional force acting along 10 the submerged length of the probe. The average value of the force signal during the first degrees of rotation may be interpreted as the average of the dynamic frictional force acting along the submerged length of the probe.

The static or dynamic frictional force acting along the submerged length of the probe may 15 be assumed to be proportional to the average density of biomaterial along the submerged length of the probe. Either of these measured force values may be taken as an estimate of the local dynamic force when an adjusted moisture concentration value is calculated with any of the methods presented in the first three embodiments. The rotational force measurements may be repeated at several depths. A dynamic force estimate obtained at 20 one depth may be used for moisture concentration measurements conducted at other depths as well.

A separate calibrated correlation may be experimentally established for rotational force measurements in each biomaterial and for each degree of coarseness. Calibrated 25 correlations may be determined between rotational force and moisture sensor response in the manner exemplified in Figure 5 above. The moisture concentration correction factor may then be calculated from this correlation once the rotational force has been measured, in the manner exemplified in the preceding embodiments.

Further options

In all embodiments presented above, estimates of local dynamic force or local temperature obtained during one thrust / withdrawal may be re-used in calculations which are

20165877 prh 21 -11-2016 performed in subsequent moisture concentration measurements in the same body of biomaterial. The underlying assumption, which the control unit may present to the operator, is that the density or temperature distribution in the body of biomaterial (along the x-axis in Figure 1) is assumed to be the same in the subsequent measurements.

The control unit may be programmed to initiate new moisture concentration measurements at predetermined intervals but to refrain from initiating new measurements if the force signal exceeds a predetermined threshold value.

The predetermined time interval may correspond to the sampling frequency of the moisture concentration measurement device. A suitable sampling frequency and suitable methods for averaging moisture concentration measurements may be determined in laboratory experiments before the device is used. Alternatively, the sampling frequency and averaging method may be selected by the operator through the interface unit.

The motion sensor signal could also be used as the measurement trigger. The dynamic force signal and motion sensor signal can also be used together.

The criterion for initiating a moisture concentration measurement may therefore be that the 20 force signal is below a certain threshold value. If the criterion is met, the control unit may perform moisture concentration measurements and present them to the user, possibly after averaging. If the criterion is not met, the control unit may refrain from performing measurements and may, for example, on the interface unit show a blank screen to the operator until the force signal again drops and a new measurement can be performed.

The threshold value may, for example, be 10N, 20N or 50N. Different threshold values may be selected for different biomaterials. A threshold value of 50N may, for example, be selected on the experimentally tested assumption that a thrust force of, say, 49N, is insufficient for moving the probe in the biomaterial which is being measured. This threshold 30 value would allow the user to apply a static force of 49N to the device while the measurement is conducted, for example by leaning against the probe.

In thrust, withdrawal and rotation, the control unit may apply two separate threshold values, for example an upper limit for determining that the probe is likely to be in motion and a lower limit for determining that the probe has likely come to a halt after being set in motion.

Claims (10)

20165877 prh 09 -03- 2018 A humidity measurement device for printed biomaterial (151), wherein: - the device includes a main unit (11), - the device includes an elongated measuring tip (12) which includes an outer part 5 outside the main unit (11) and inside the main unit (11), - the inner part of the elongated measuring tip (12) is connected to the main unit (11) via a force transducer (13, 16, 17) arranged to measure the force acting between the measuring tip (12) and the main unit (11), 10 - the outer portion of the elongate measuring tip (12) includes at least one humidity sensor (19, 110) configured to measure the moisture density value of the printed biomaterial (151) surrounding the humidity sensor (19, 110), the device includes a control unit (118, 119, 120) configured to calculate a corrected moisture density value when the control unit has received at least 15 humidity density values from the humidity sensor (19, 110) and the force values from the force sensor (13, 16, 17). Device according to Claim 1, characterized in that the device also comprises a motion sensor arranged to measure the penetration depth of the tip portion (18) of the elongated measuring tip (12) in the printed biomaterial (12), and that the control unit (118, 119, 120) is further configured to calculate a corrected moisture density value when the control unit has received penetration depth values from the motion sensor. Device according to claim 1 or 2, characterized in that the outer part of the elongate measuring tip (12) also includes a temperature sensor configured to measure the temperature of the printed biomaterial (151) surrounding the elongated measuring tip, and The control unit (118, 119, 120) is further configured to calculate a corrected humidity density value when the control unit has received temperature values from the temperature sensor. 20165877 prh 09 -03- 2018 Device according to one of the preceding claims 1 to 3, characterized in that the device further comprises a user interface unit (113, 114) which enables the user to connect to the control unit (118, 119, 120). 5. A method for performing a moisture density measurement printed on a paragraph 5 biomaterials (151) with - a device comprising a main unit (11) and an elongated measuring tip (12) comprising an outer part outside the main unit (11) and an inner part inside the main unit (11), and an inner part of the elongated measuring tip (12) is connected sensor (13, 16, 17), which 10 is configured to measure the force acting between the measuring tip (12) and the main unit (11), characterized in that: - the outer part of the elongated measuring tip (12) comprises at least one humidity sensor (19, 110), 15 - operating a control unit (118,119,120) configured to read the measured values from at least the humidity density sensor (19, 110) and the force sensor (13, 16, 17), - transferring the outer portion of the elongated measuring tip (12) to the body of printed biomaterial (151), - the control unit (118, 119, 120) reads the force measurement values from the force sensor (13, 16, 20 17) and evaluate the local thrust force measurement values, - the control unit (118, 119, 120) initiates the moisture density measurement, reads the first moisture density value from the humidity sensor and calculates the moisture density correction factor based on correction variables containing at least the estimated local thrust and biomaterial, 25 - the control unit (118, 119, 120) calculates the corrected moisture density value by correcting the first moisture density value by a moisture density correction factor, and - the control unit (118, 119, 120) stores the corrected moisture density value and / or displays it to the user. The method according to claim 5, characterized in that 20165877 prh 09 -03- 2018 - using a motion sensor configured to measure the movement of the elongated measuring tip (12) in the printed biomaterial (151), - the control unit (118, 119, 120) additionally reads the good values from the motion sensor, - when the control unit (118, 119, 120) has started the moisture density measurement, the control unit (118, 119, 120) calculates the penetration depth from the stored goodwill values, and the control unit (118, 119, 120) further including the penetration depth in the correction variables when calculating the moisture density correction factor. Method according to one of claims 5 or 6, characterized in that - a temperature sensor is applied to the outer part of the elongated probe (12), - when the humidity density measurement has been started by the control unit (118, 119, 120), the control unit (118, 119, 120) reads the temperature value from the temperature sensor, the control unit (118, 119, 120) further including the temperature in the correction variables when calculating the moisture density correction factor. Method according to one of claims 5 to 7, characterized in that the control unit (118,119,120) reads the force measurement values from the force sensor (13,16,17) when the measuring tip (12) is inserted into the body of printed biomaterial (151). Method according to one of Claims 5 to 7, characterized in that the control unit (118,119,120) reads the force measurement values from the force sensor (13,16,17) when the measuring tip (12) is withdrawn from the body of printed biomaterial (151). Method according to one of Claims 5 to 7, characterized in that the control unit (118, 119, 120) reads the force measurement values from the force transducer (13, 16, 17) when the measuring tip (12) is rotated on the printed biomaterial (151).