Hand-Held Measuring Apparatus and Method for the Operation Thereof

Abstract

A mobile measuring apparatus for nondestructively determining a material measurement value that relates to a material property of a workpiece comprises a housing in which at least a first sensor device and a second sensor device are located, a control device, an evaluating device, and a device for the supply of energy to the measuring apparatus. The first sensor device has a nuclear magnetic resonance sensor and the second sensor device has a sensor based on dielectric and/or resistive methods. Information about the material property of the workpiece, in particular moisture present in the workpiece, is obtained by evaluating a measurement signal provided by the first sensor device, which information is intended for the optimized control of the second sensor device and/or optimized evaluation of measurement signals provided by the second sensor device.

Claims

1. A mobile measuring appliance for nondestructive determination of a material measurement value relating to a material property of a workpiece, comprising: a housing; a first sensor apparatus at least partially located in the housing; a second sensor apparatus at least partially located in the housing; a control apparatus configured to actuate the first sensor apparatus and/or the second sensor apparatus; an evaluation apparatus configured to evaluate at least one measurement signal supplied by the first sensor apparatus and/or the second sensor apparatus; and an apparatus for supplying energy to the measuring appliance, wherein the first sensor apparatus comprises at least one nuclear magnetic resonance sensor and the second sensor apparatus comprises at least one sensor based on dielectric and/or resistive methods, wherein an information item about the material property of the workpiece is obtained by evaluating the at least one measurement signal supplied by the first sensor apparatus, and wherein said information item is configured to optimize actuation of the second sensor apparatus and/or to optimize evaluation of the at least one measurement signal supplied by the second sensor apparatus.

2. The measuring appliance as claimed in claim 1, wherein: the at least one sensor of the second sensor apparatus is selected from the group consisting of capacitance sensors, microwave sensors, ultrasonic sensors, resistance sensors, conductivity sensors, ultra-broadband radar sensors, and broadband impulse radar sensors.

3. The measuring appliance as claimed in claim 1, wherein: the nuclear magnetic resonance sensor comprises a first apparatus configured to generate a first magnetic field, a second apparatus configured to generate a second magnetic field, the second magnetic field superimposing the first magnetic field, the control apparatus comprises at least one control unit configured to control the second apparatus, and the control unit is configured to modify the second magnetic field to generate pulse sequences.

4. The measuring appliance as claimed in claim 1, wherein: the nuclear magnetic resonance sensor comprises a detecting apparatus configured to detect a magnetic field change, and the detecting apparatus includes a reception coil configured to detect the magnetic field change.

5. The measuring appliance as claimed in claim 3, wherein: the first and second magnetic fields of the nuclear magnetic resonance sensor define a first sensitive region of the nuclear magnetic resonance sensor, and the first sensitive region is a layer-shaped region extending substantially parallel to and at a distance from a first housing side outside of the housing of the measuring appliance.

6. The measuring appliance as claimed in claim 5, wherein the first sensitive region of the nuclear magnetic resonance sensor is displaceable outside of the housing perpendicularly to the first housing side of the measuring appliance by 1 cm to 3 cm.

7. The measuring appliance as claimed in claim 5, wherein the second sensor apparatus has a second sensitive region extending substantially symmetrically in relation to a perpendicular to the first housing side of the measuring appliance along said perpendicular.

8. The measuring appliance as claimed in claim 7, further comprising: an influencing device configured to influence a direction of extent and/or a homogeneity and/or a geometry of the first sensitive region and/or of the second sensitive region.

9. The measuring appliance as claimed in claim 1, further comprising: a shielding device configured to minimize mutual interference influences among the sensor apparatuses.

10. The measuring appliance as claimed in claim 1, wherein the evaluation apparatus is configured to evaluate the at least one measurement signal to determine: a relative and/or absolute moisture content; a moisture gradient into the workpiece; binding states of the water forming the moisture; time-dynamic processes of the water forming the moisture; and/or further structurally relevant parameters including salt content, composition, density, and porosity of the material of the workpiece.

11. The measuring appliance as claimed in claim 5, further comprising: an input apparatus configured to input working parameters and arranged in or on a second housing side of the measuring appliance.

12. The measuring appliance as claimed in claim 11, further comprising: an output apparatus configured to output working parameters and/or evaluation results and arranged in a second housing side of the measuring appliance.

13. The measuring appliance as claimed in claim 12, wherein: the first housing side of the measuring appliance lies opposite the second housing side, the second housing side is configured to receive the input apparatus and/or the output apparatus, and the second housing side is arranged on a rear side of the measuring appliance.

14. The measuring appliance as claimed in claim 1, wherein the control apparatus has an operating mode in which specifications relating to the workpiece are specified by user inputs and/or are made available to the measuring appliance.

15. The measuring appliance as claimed in claim 12, wherein the control apparatus has an operating mode in which output parameters of the output apparatus are specified and/or are made available to the measuring appliance.

16. A method for nondestructive determination of a material measurement value relating to a material property of a workpiece with a mobile measuring appliance, the method comprising: obtaining at least one first information item about the material property of the workpiece with at least one first sensor apparatus including a nuclear magnetic resonance sensor; obtaining at least one second information item about the material property of the workpiece using at least one further sensor apparatus of the mobile measuring appliance, the at least one further sensor apparatus based on dielectric and/or resistive methods; and optimizing actuation of the second sensor apparatus and/or optimizing evaluation of measurement signals supplied by the second sensor apparatus based on the first information item.

17. The method as claimed in claim 16, further comprising: calibrating the second sensor apparatus and/or calibrating the measurement signals supplied by the second sensor apparatus based on the first information item obtained by the first sensor apparatus.

18. The method as claimed in claim 16, wherein the at least one first information item obtained with the first sensor apparatus is based on a moisture present in the workpiece, and the method further comprises: determining the dry permittivity of the workpiece with the at least one first information item.

19. The method as claimed in claim 16, further comprising: carrying out a parallel and/or quasi-parallel and/or series measurement with the first sensor apparatus and the second sensor apparatus.

20. The method as claimed in claim 16, wherein the second sensor apparatus uses at least one sensor based on dielectric and/or resistive methods selected from the group consisting of capacitance sensors, microwave sensors, ultrasonic sensors, resistance sensors, conductivity sensors, ultra-broadband radar sensors, and broadband impulse radar sensors.

Description

DRAWINGS

[0126] The invention is explained in more detail in the subsequent description on the basis of exemplary embodiments depicted in the drawings. The drawing, the description and the claims contain numerous features in combination. Expediently, a person skilled in the art will also consider the features on their own and combine these to give further meaningful combinations. In the figures, the same or similar reference signs denote the same or similar elements.

[0127] In detail:

[0128] FIG. 1 shows a perspective illustration of a configuration of the mobile measuring appliance according to the invention,

[0129] FIG. 2 shows a view of the second housing side of the same configuration of the measuring appliance according to the invention,

[0130] FIG. 3 shows a schematic side view of the same configuration of the measuring appliance according to the invention,

[0131] FIG. 4 shows a schematic and simplified illustration of an embodiment of the components forming the first sensor apparatus and the second sensor apparatus, and the electromagnetic fields generated therewith, and

[0132] FIG. 5 shows a schematic illustration of a measurement method of the measuring appliance according to the invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0133] FIG. 1 and FIG. 2 show two views of an exemplary embodiment of the hand-held measuring appliance 10 according to the invention, in a perspective illustration and in a simplified, schematic plan view.

[0134] The hand-held measuring appliance 10 embodied in an exemplary manner comprises a housing 12, an input apparatus in the form of actuation elements 14, suitable for switching the hand-held measuring appliance on and off, for starting and configuring a measurement process and for entering working parameters, and an output apparatus in the form of a display 16 for outputting working parameters and/or evaluation results. For transportation purposes and for the guidance thereof, the hand-held measuring appliance 10 comprises a handle 18. The handle 18, the actuation elements 14 and the display are situated on a second housing side 20 of the measuring appliance 10, which typically faces the user when the measuring appliance is operated.

[0135] For the purposes of supplying the hand-held measuring appliance 10 with energy, the appliance has a recess on the first housing side 40 (also referred to as rear side of the measuring appliance below) lying opposite to the second housing side 20 on the rear side of the appliance, said recess preferably being provided to receive power-grid-independent energy stores 22, in particular batteries or rechargeable accumulators. The appliance presented in an exemplary manner comprises lithium ion accumulators, the high energy and power density of which is advantageously suitable for supplying the measuring appliance with energy. In an alternative embodiment, the energy store 22 may also be housed in the handle 18 of the measuring appliance 10. Preferably, the apparatus for supplying energy comprises a detachable interlocking and/or force-fit connection interface such that the energy store 22 (in general, also a plurality of energy stores) is (are) arrangeable in a removable and interchangeable manner. Moreover, the energy store 22 may be supplied with energy from a power grid and may be charged within and/or outside of the measuring appliance.

[0136] A position determination apparatus of the hand-held measuring appliance comprises four wheels 24 in the exemplary embodiment, by means of which the hand-held measuring appliance 10 may be displaced along the surface 44 of a workpiece 42 (cf. FIG. 3). Sensors which are sensitive to rotation of the wheels 24 capture a movement of the measuring appliance 10 and a traveled distance and therefore allow measurement results to be related with a position of the measuring appliance, in particular in relation to the workpiece 42. In an alternative embodiment of the measuring appliance 10, the position determination apparatus may comprise an optical displacement transducer instead of the wheels. Additionally, even more sensors, in particular inclination sensors, angle sensors, translation sensors, acceleration sensors and rotational-rate-sensitive sensors, may be present for determining the position more precisely. After placing the hand-held measuring appliance 10 onto the surface 44 of a workpiece 42 to be measured, for example on a wall or a concrete floor, the change in position of the hand-held measuring appliance as a consequence of displacing the appliance on the workpiece is ascertained. These position data are forwarded to an evaluation apparatus 30 for further evaluation. Particularly advantageously, multidimensional representations of the measurement results, for example, in particular, in the form of a map and/or a pseudo-three-dimensional representation, may be generated by means of the position-dependent measurement and evaluation of a workpiece.

[0137] Further components of the measuring appliance 10, in particular a first sensor apparatus 32 comprising a nuclear magnetic resonance sensor 32′, a second sensor apparatus 60 comprising an ultra-broadband radar sensor 60′, a control apparatus 28 for actuating the first sensor apparatus and the second sensor apparatus, an evaluation apparatus 30 for evaluating at least one measurement signal supplied by the first sensor apparatus and/or the second sensor apparatus, and a data communication interface 54 connected to the control and/or evaluation apparatus, are housed on a carrier element 26, in particular on a system circuit board or printed circuit board within the housing 12 (see, in particular, FIG. 2).

[0138] The control apparatus 28 has control electronics comprising means for communicating with the other components of the measuring appliance, for example means for open-loop and/or closed-loop control of the first sensor apparatus and the second sensor apparatus and means for open-loop control of the measuring appliance. In particular, the control apparatus 28 comprises a unit with a processor unit, a memory unit and an operating program stored in the memory unit. The control apparatus 28 is provided to adjust at least one operating functional parameter of the measuring appliance depending on at least one input by the user, via the evaluation apparatus and/or via the data communication interface 54.

[0139] The nuclear magnetic resonance sensor 32′, which is explained in more detail in FIG. 4, is provided for exciting nuclear magnetic resonance of nuclear spins of atomic nuclei in the material of the workpiece 42. According to the invention, the measured resonance signal is used at least for the nondestructive determination of a moisture measurement value of the workpiece, in particular in accordance with the measurement depth of the sensor for determining a moisture measurement value in the workpiece 42, i.e. for ascertaining information items which, inter alia, relate to a relative and/or absolute moisture content, a moisture gradient into the workpiece, binding states of the water forming the moisture and/or time-dynamic processes of the water forming the moisture. Here, the measurement depth is in particular down to 1 cm, advantageously down to 2 cm, particularly advantageously down to 3 cm into the workpiece. The nuclear magnetic resonance signal of the nuclear spins of the atomic nuclei excited in the material of the workpiece 42 is detected by means of a reception coil of the nuclear magnetic resonance sensor 32′. The generated measurement signal, in particular the amplitude and/or relaxation times thereof, is forwarded to the evaluation apparatus 30, by means of which it is evaluated and prepared by means of evaluation routines and forwarded to an output apparatus 16 and/or the control apparatus 28 and/or a data communication interface 54.

[0140] The ultra-broadband radar sensor 60′ is advantageously used to emit an electromagnetic signal which penetrates deep into the material of the workpiece 42, the workpiece-internal reflections and/or scattering of said signal being measured by the sensor. A measurement signal generated by this sensor is evaluated by the evaluation apparatus 30, and so a moisture measurement value, in particular depth-resolved moisture measurement values, is/are obtained. In particular, the measurement depth of the ultra-broadband radar sensor 60′ is down to 10 cm, advantageously down to 15 cm and particularly advantageously more than 15 cm.

[0141] The evaluation apparatus 30 for evaluating at least one measurement signal supplied by the first sensor apparatus and/or the second sensor apparatus, optionally also for evaluating measurement signals from further sensor apparatuses of the hand-held measuring appliance 10, comprises, in particular, an information input, information processing and an information output. Advantageously, the evaluation apparatus 30 consists at least of a processor and a memory with an executable operating program stored thereon, and allows evaluation of at least a measurement signal of the nuclear magnetic resonance sensor 32′ and/or a measurement signal of the ultra-broadband radar sensor 60′ and determination of moisture measurement values in relation to the workpiece. Particularly advantageously, the evaluation apparatus has stored correction tables and/or calibration tables, which render it possible to interpret, convert, interpolate and/or extrapolate the evaluation results and calibrate the measuring appliance, in particular the evaluation routines, in respect of a workpiece material.

[0142] According to the invention, an information item relating to the moisture of the workpiece, obtained by means of the nuclear magnetic resonance sensor 32′, may be used to influence, preferably optimize, particularly preferably calibrate the evaluation of a measurement signal supplied by the ultra-broadband radar sensor 60′. As a result of this, an evaluation of measurement signals supplied by the second sensor apparatus which is adapted to the conditions of the workpiece and hence optimized may be facilitated. Hence, it is particularly advantageously possible to relate relative moisture measurement values from the ultra-broadband radar sensor 60′ directly to absolute moisture measurement values which are measured by means of the nuclear magnetic resonance sensor, and hence absolute moisture measurement values up to a maximum measurement depth corresponding to the maximum measurement depth of the ultra-broadband radar sensor 60′ are obtained (cf. FIG. 5).

[0143] Furthermore, an information item relating to the moisture of the workpiece, obtained by means of the nuclear magnetic resonance sensor 32′, may be used to realize an optimized actuation of the second sensor apparatus, in particular of the ultra-broadband radar sensor 60′, by way of the control apparatus. By way of example, physical and/or technical control parameters and characteristics such as voltages, currents, pulse durations, powers, emission directions of the ultra-broadband radar sensor 60′ may be subject to closed-loop and/or open-loop control depending on the information item.

[0144] The evaluation results are output by the evaluation apparatus 30 for further use via the control apparatus 28, either for transmitting the data to the data communication interface 54 or directly to a user of the measuring appliance 10. In particular, an output to a user may be effected by means of illustration on the display 16. The output on the display 16 may be carried out graphically, numerically and/or alphanumerically, for example in the form of a measurement value, a measurement curve, a signal profile, a time profile, as image data or in a gradient representation and in a combination thereof. Alternatively or additionally, a representation by means of a signal indication is possible, in particular by way of e.g. a light-emitting diode which evaluates a target variable, for example by way of color coding (e.g. red, yellow, green).

[0145] For the purposes of determining a moisture measurement value of a workpiece, in particular in a workpiece, the measuring appliance 10 is positioned with the first housing side 40 thereof, i.e. with the appliance rear side, in a planar fashion in the immediate vicinity of the workpiece 42, in particular contacting the surface 44 of the latter. In the process, the magnetic fields 34, 36 generated by the nuclear magnetic resonance sensor 32′ and the electromagnetic radiation of the ultra-broadband radar sensor 60′ emerge through the first housing side 40 from the measuring appliance 10 and penetrate into the workpiece 42, with the first sensitive region 38 and the second sensitive region 62 coming to rest in the workpiece (see, in particular, FIG. 3). Positioning the measuring appliance 10 in the immediate vicinity of the workpiece surface 44 facilitates determining absolute moisture measurement values, in particular up to 10 cm, advantageously up to 15 cm and particularly advantageously more than 15 cm, into the workpiece 42.

[0146] FIG. 3 depicts the embodiment according to the invention of the hand-held measuring appliance 10 from FIGS. 1 and 2 in a simplified schematic side view. The nuclear magnetic resonance sensor 32′ comprises two apparatuses for generating magnetic fields, in particular a permanent magnet arrangement 46, 46′ (cf. FIG. 4) which generates a first magnetic field 34 and a radiofrequency coil 48 (cf. FIG. 4) which generates a second magnetic field 36. The nuclear magnetic resonance sensor 32′ is configured in such a way that the first magnetic field 34 is aligned substantially parallel to the first housing side 40 while the second magnetic field 36 is aligned substantially perpendicular to the magnetic field lines of the first magnetic field 34. The two magnetic fields superpose in an extended region, in which, in particular, the sensitive region 38 of the nuclear magnetic resonance sensor 32′ is situated as well, in particular as a layer-shaped region.

[0147] The ultra-broadband radar sensor 60′, which is provided for emitting electromagnetic radiation and for detecting signals reflected and/or scattered in the interior of the workpiece, has a second sensitive region 62 which is identical with the solid angle of the maximum sensitivity of the sensor (direction of extent). The second sensitive region 62 extends symmetrically with respect to a perpendicular in relation to the first housing side of the measuring appliance, along which the first sensitive region 38 of the nuclear magnetic resonance sensor 32′ may advantageously be displaced as well.

[0148] With the first housing side 40, the hand-held measuring appliance 10 is positioned in such a way in the immediate vicinity of a workpiece 42 to be examined that the distance between the first housing side 40 and the workpiece surface 44 is minimized. What this achieves is that the magnetic fields 34, 36 of the nuclear magnetic resonance sensor 32′ and the electromagnetic radiation of the ultra-broadband radar sensor 60′ penetrate into the workpiece and the first sensitive region 38 and the second sensitive region 62 come to rest in the workpiece 42.

[0149] By varying the second magnetic field 36 generated by the second apparatus, i.e., in particular, by varying the radiofrequency coil 48 and/or varying the frequency and/or varying the current and/or varying the voltage in the radiofrequency coil 48, it is possible to vary the first sensitive region 38 in terms of its distance from the first housing side 40 and hence modify the distance of the sensitive region 38 in the workpiece from the surface 44 thereof. Alternatively and/or additionally, the nuclear magnetic resonance sensor 32′ may be repositioned, in particular repositioned mechanically, in the housing 12 of the hand-held measuring appliance 10 in such a way that the distance between the nuclear magnetic resonance sensor 32′ and the first housing side 40 is varied and consequently the distance of the first sensitive region 38 in the workpiece 42 from the surface 44 of the latter is also varied. Depth profiles of the moisture measurement values may be created particularly advantageously in this manner.

[0150] According to the invention, an information item relating to the moisture of the workpiece, obtained by means of the nuclear magnetic resonance sensor, may be used to influence, preferably optimize, particularly preferably calibrate the evaluation of a measurement signal supplied by the ultra-broadband radar sensor 60′. As a result of this, an evaluation of measurement signals supplied by the second sensor apparatus 60 which is adapted to the conditions of the workpiece and hence optimized may be facilitated. Hence, it is particularly advantageously possible to relate relative moisture measurement values from the ultra-broadband radar sensor 60′ directly to absolute moisture measurement values which are measured by means of the nuclear magnetic resonance sensor 32′, and hence absolute moisture measurement values up to a maximum measurement depth corresponding to the maximum measurement depth of the ultra-broadband radar sensor 60′ are obtained (cf. FIG. 5).

[0151] FIG. 4 depicts the components of an embodiment of the nuclear magnetic resonance sensor 32′ according to the invention and of the ultra-broadband radar sensor 60′ in a simplified and schematic illustration. Two permanent magnets 46, 46′ which are arranged perpendicular to the first housing side 40 and antiparallel in relation to one another generate a first magnetic field 34, in particular a static magnetic field, which extends substantially parallel to the surface of the first housing side 40. This first magnetic field provided for aligning the nuclear spins of the atomic nuclei present in the material sample has, for example, in particular, a magnetic field strength of 0.5 tesla, with the permanent magnets being produced from a neodymium iron boron alloy. In this exemplary embodiment, the second apparatus for generating the second magnetic field is formed by a radiofrequency coil 48. As soon as current flows through this coil, an electromagnetic field, in particular the second magnetic field 36, is generated. The two magnetic fields superpose in a region which lies substantially outside of the housing 12 of the measuring appliance 10. The sensitive region 38 of the nuclear magnetic resonance sensor 32′ likewise lies in the superposition field of the magnetic fields 34 and 36. Depending on the frequency of the radiated-in electromagnetic field 36 and the static magnetic field strength of the first magnetic field 34, the sensitive region is defined by an area in an ideal case, in which the magnetic field strength of the first magnetic field 34 is constant and, in particular, has a defined magnitude. In reality, the area in fact has a layered shape on account of non-exact frequencies. Since the magnetic field lines 34 do not extend exactly parallel to the first housing side 40, the sensitive region 38 is therefore also curved in a manner corresponding to the magnetic field lines as a consequence thereof. The curvature and form of the first magnetic field 34, and hence of the sensitive region 38, may be influenced and, in particular, homogenized using further means, for example a shim coil 56 and/or magnetic shielding 58.

[0152] The ultra-broadband radar sensor 60′ is depicted as an electrically conductive surface, in particular depicted as a metal sheet. The second sensitive region 62 of the ultra-broadband radar sensor 60′ corresponds to the chief emission direction of the sensor and therefore spans an emission cone which may penetrate deep into the workpiece in the case of suitable positioning of the measuring appliance.

[0153] FIG. 5 schematically depicts a possible measurement process using the measuring appliance according to the invention. Starting with the measurement by the nuclear magnetic resonance sensor 32′ in step 64, volume components V.sub.m of the water forming the moisture are ascertained as a function F.sub.1 of the measurement depth z.sub.m of the discrete layers m=1 . . . a in the workpiece for various measurement depths z.sub.m (m=1 . . . a) into the workpiece up to the maximum measurement depth z.sub.a of the nuclear magnetic resonance sensor:

V.sub.1 . . . a=F.sub.1(z.sub.1 . . . a).  (1)

The second sensor apparatus 60, here using the example of a radar sensor 60′, allows measurement signals S|.sub.1 . . . b to be measured in the workpiece up to the maximum measurement depth

[00001]$z_b=\underset{m=1}{\overset{b}{.Math.}}.Math.d_m$

or the radar sensor, depicted in step 66. In the special case where d.sub.m is constant for various m, the maximum measurement depth may be simplified to z.sub.b=b.Math.d.sub.m. The measurement signal S|.sub.1 . . . b substantially depends (functional relationship F.sub.2) on the radar frequency f, the layer thicknesses d.sub.m and the complex-valued effective material permittivities ∈.sub.eff,m thereof (V.sub.m, d.sub.m, ∈.sub.eff,m, etc. represent parameters of in each case a single layer):

S|.sub.1 . . . b=F.sub.2(f,d.sub.1 . . . b,∈.sub.eff,1 . . . b)=F.sub.3(f,d.sub.1 . . . b,∈.sub.T,∈.sub.water,V.sub.1 . . . b)=F.sub.4(d.sub.1 . . . b).  (2)

Alternatively, the measurement signal may also be expressed as a function (F.sub.3) of the radar frequency f, the layer thicknesses d.sub.m, the dry permittivity ∈.sub.T of the material of the workpiece, the permittivity ∈.sub.water and the volume component V.sub.m of the water forming the moisture at the corresponding measurement depth.

[0154] The signal S|.sub.1 . . . b can be split into signal components S|.sub.1 . . . a and S|.sub.a+1 . . . b, with the latter signal component originating from layers beyond the maximum measurement depth z.sub.a of the nuclear magnetic resonance sensor 32′ (step 68):

S|.sub.1 . . . b=F(S|.sub.1 . . . a+S|.sub.a+1 . . . b).  (3)

By setting the signal components S|.sub.a+1 . . . b beyond the measurement depth of the nuclear magnetic resonance sensor 32′ to zero or by directly determining the surface-near reflection S|.sub.1 . . . a (for example by modeling the measurement data), it is possible to correlate the measurement values from the nuclear magnetic resonance sensor 32′ and those from the radar sensor 60′ for the measurement depth up to Z.sub.a and determine the dry permittivity ∈.sub.T in step 70:

[00002]$\begin{array}{cc}{\mathrm{.Math.}}_{\mathrm{eff},1.Math..Math.\mathrm{.Math.}.Math..Math.a}^{\alpha }=\left(1-V_{1.Math..Math.\mathrm{.Math.}.Math..Math.a}-\underset{i=1}{\overset{n}{.Math.}}.Math.V_i^{\prime }\right).Math.{\mathrm{.Math.}}_T^{\alpha }+V_{1.Math..Math.\mathrm{.Math.}.Math..Math.a}.Math.{\mathrm{.Math.}}_{1.Math..Math.\mathrm{.Math.}.Math..Math.a}^{\alpha }+\underset{i=1}{\overset{n}{.Math.}}.Math.V_i^{\prime }.Math.{\mathrm{.Math.}}_i^{\alpha }.& \left(4\right)\end{array}$

Here, V.sub.i′ and ∈.sub.i represent volume components and permittivities of further substance components in the material of the workpiece, for example capillary water, air inclusions, etc. The parameter α is determined by an underlying model.

[0155] If the dry permittivity ∈.sub.T is known, the signal component S|.sub.a+1 . . . b of the deeper layers may be evaluated in respect of volume component of the water of the moisture (step 72).

[0156] If the material density ρ is known, the volume components of the water of the moisture may be converted into mass components in step 74. The material density may emerge either by the user specifying the material of the workpiece or, alternatively, from a measurement using the nuclear magnetic resonance sensor 32′ in step 76 as well. Finally, the ascertained measurement values are output to the user (step 78), for example by means of a display 16, an LED, a color scale or via a data appliance, in particular a smartphone, connected wirelessly to the measuring appliance.

[0157] If the material is specified by the user, it is further possible to carry out corrections and/or calibrations of the measurement signals from the nuclear magnetic resonance sensor 32′ and/or from the radar sensor 60′ in step 80. By way of example, contributions of organic constituents of the workpiece to the measurement signals of the water forming the moisture may be taken into account by way of calibration tables.

[0158] Alternatively, it is possible to provide an appliance-internal calibration function, by means of which relevant parameters, in particular, for example, the dry permittivity, may be measured if a dry workpiece is present and stored in the appliance for further use such that a calibration of the measurement signals from the nuclear magnetic resonance sensor 32′ may be undertaken in step 80.

[0159] Furthermore, calibration data for calibrating the measurement signals or the evaluation thereof in step 80 may be obtained by inputting material parameters, in particular a layer sequence of the material building up the workpiece. Alternatively or additionally, these calibration data may also be derived from measurement signals from the nuclear magnetic resonance sensor 32′ or from the radar sensor 60′ in step 80.