Method for determining a calibration specification, method for determining an absolute humidity, and NMR measuring device

Abstract

A method determines a calibration specification specifying a functional correlation between an NMR measurement variable, determined using an NMR measuring device, for a material to be analyzed and a humidity contained in the material to be analyzed. The method includes provision of a relaxation curve of the material having a known humidity; determination of a relaxation time distribution from the relaxation curve provided; and determination of an approximate relaxation time distribution relative to at least one other humidity. The at least one other humidity is less than the known humidity. The method further includes reconstruction of another relaxation curve from the approximate relaxation time distribution; determination of an expected NMR measurement variable from the reconstructed other relaxation curve for the at least one other humidity; and determination of the calibration specification as a function of the humidity contained in the material, in accordance with the determinable NMR measurement variable.

Claims

1. A method for determining a calibration specification for use with an NMR measuring device, the calibration specification specifying a functional relationship between an NMR measurement variable, which is determined using the NMR measuring device, of a material to be analyzed and a humidity contained in the material to be analyzed, the method comprising: identifying a relaxation curve of the material, the material having a known humidity; determining a relaxation time distribution from the identified relaxation curve of the material; determining an approximated relaxation time distribution relating to at least one other humidity, the at least one other humidity less than the known humidity; reconstructing another relaxation curve from the approximated relaxation time distribution; determining an expected NMR measurement variable from the reconstructed another relaxation curve for the at least one other humidity; and determining the calibration specification as a function describing the humidity contained in the material as a function of the NMR measurement variable.

2. The method as claimed in claim 1, wherein the identified relaxation curve of the material is a transverse relaxation curve.

3. The method as claimed in claim 1, wherein the known humidity is at least 50% of a saturation humidity of the material.

4. The method as claimed in claim 1, further comprising: determining the relaxation time distribution by inverse Laplace transformation from the identified relaxation curve of the material.

5. The method as claimed in claim 1, further comprising: calculating the approximated relaxation time distribution relating to the at least one other humidity by multiplying the determined relaxation time distribution by a Heaviside step function H(τ.sub.c(θ.sub.i)−τ), wherein τ.sub.c(θ.sub.i) is selected such that an integral s(θ.sub.1)=∫ρ(τ,θ.sub.i)dτ is less by a fraction 1−θ.sub.i/θ.sub.ref than s(t,θ.sub.ref), wherein τ is time, wherein θ.sub.i is the at least one other humidity, wherein θ.sub.ref is the known humidity, wherein ρ(θ.sub.i) is the approximated relaxation time distribution, and wherein s(t,θ.sub.ref) is the identified relaxation curve of the material.

6. The method as claimed in claim 1, further comprising: calculating approximated relaxation time distributions relating to a multiplicity of humidities.

7. A method for determining an absolute humidity of a material to be analyzed, using an NMR measuring device, comprising: specifying a material to be analyzed using an input apparatus of the NMR measuring device; recording an NMR measurement variable of the specified material, using the NMR measuring device; providing a calibration specification as a function of the specified material; determining the absolute humidity using a functional relationship, specified in the calibration specification, between the recorded NMR measurement variable of the specified material and a humidity contained in the material analyzed, wherein the calibration specification specifies the functional relationship between the NMR measurement variable and the humidity contained in the material to be analyzed, wherein the calibration specification is determined by: identifying a relaxation curve of the specified material, the specified material having a known humidity; determining a relaxation time distribution from the identified relaxation curve of the specified material; determining an approximated relaxation time distribution relating to at least one other humidity, the at least one other humidity less than the known humidity; reconstructing another relaxation curve from the approximated relaxation time distribution; determining an expected NMR measurement variable from the reconstructed another relaxation curve for the at least one other humidity and determining the calibration specification as a function describing the humidity contained in the specified material as the function of the NMR measurement variable.

8. The method as claimed in claim 7, further comprising: outputting the absolute humidity which has been determined for the specified material using an output apparatus of the NMR measuring device.

9. An NMR measuring device, comprising: an NMR sensor; and a control apparatus configured to control the NMR measuring device and to evaluate an NMR measurement variable from an NMR measurement signal recorded by the NMR sensor, wherein the control apparatus is configured to determine a calibration specification for use with the NMR measuring device, the calibration specification specifying a functional relationship between the NMR measurement variable of a material to be analyzed and a humidity contained in the material to be analyzed, by (i) identifying a relaxation curve of the material, the material having a known humidity, (ii) determining a relaxation time distribution from the identified relaxation curve of the material, (iii) determining an approximated relaxation time distribution relating to at least one other humidity, the at least one other humidity less than the known humidity, (iv) reconstructing another relaxation curve from the approximated relaxation time distribution; (v) determining an expected NMR measurement variable from the reconstructed another relaxation curve for the at least one other humidity, and (vi) determining the calibration specification as a function describing the humidity contained in the material as a function of the NMR measurement variable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure is explained in more detail in the description below with the aid of exemplary embodiments represented in the drawings. The drawings, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them to form other useful combinations. Reference signs which are the same or similar in the figures denote elements which are the same or similar.

(2) In the drawings:

(3) FIG. 1 shows a perspective representation of one configuration of the mobile NMR measuring device according to the disclosure,

(4) FIG. 2 shows a plan view of a first housing side of one configuration of the NMR measuring device according to the disclosure,

(5) FIG. 3 shows a method flowchart of one embodiment of the method according to the disclosure for determining a calibration specification,

(6) FIG. 4a shows an exemplary relaxation curve s(t,θ.sub.ref) for the humidity θ.sub.ref,

(7) FIG. 4b shows a relaxation time distribution ρ(θ.sub.ref) calculated for the relaxation curve s(t,θ.sub.ref) represented in FIG. 4a,

(8) FIGS. 4c,d respectively show an approximated relaxation time distribution ρ(θ.sub.1) and ρ(θ.sub.5) calculated from the relaxation time distribution ρ(θ.sub.ref) represented in FIG. 4b by multiplying by a Heaviside step function H(τ.sub.c(θ)−τ),

(9) FIG. 4e respectively shows a reconstructed relaxation curve s(t,θ.sub.1) and s(t,θ.sub.5) relating to the relaxation time distributions ρ(θ.sub.1) and ρ(θ.sub.5) represented in FIGS. 4c,d,

(10) FIG. 5 shows a method flowchart of one embodiment of the method according to the disclosure for determining an absolute humidity of a material to be analyzed.

DETAILED DESCRIPTION

(11) FIG. 1 and FIG. 2 show two views of an exemplary embodiment of the handheld energy-autonomous NMR measuring device 10 according to the disclosure, in a perspective representation and in a simplified schematic plan view, respectively.

(12) The NMR measuring device 10 explained by way of example comprises a housing 12. Accommodated in the housing 12, there is an input apparatus 14 in the form of actuation elements 14′, suitable for turning the NMR measuring device 10 on and off, for starting and configuring a measurement process and for input of working parameters. An output apparatus 16 for output of information which has been determined and for output of working parameters is furthermore provided in the form of a display screen 16′ in the housing 12. The NMR measuring device 10 has a handle 18 for transport and for guiding it. The handle 18, the actuation elements 14′ and the display screen 16′ are located on a first housing side 20 (also “front side”) of the NMR measuring device 10, which typically faces toward the user during operation of the NMR measuring device.

(13) For the energy supply of the NMR measuring device 10, the NMR measuring device 10 comprises, on the second housing side (not represented in detail here) opposite the first housing side 20 on the rear side of the device, a recess which is used to receive energy storage units (not represented in detail here) independent of an electrical supply network in the form of rechargeable accumulators. Because of the energy storage unit independent of an electrical supply network, the NMR measuring device 10 can at least temporarily be operated energy-autonomously, i.e. independently of an electrical supply network, and therefore in particular without a cable. The NMR measuring device 10 presented by way of example has lithium-ion accumulators, the high energy density and power density of which are advantageously suitable for the energy supply of the NMR measuring device 10. Preferably, the energy supply apparatus comprises a releasable form-fit and/or force-fit connection interface, so that the energy storage unit (in general also a plurality of these) can be arranged removably and replaceably. Furthermore, the energy storage unit may be supplied with energy from an electrical supply network and charged in and/or outside the NMR measuring device 10.

(14) On a support element 22, in particular a system circuit board or printed circuit board, inside the housing 12, further component parts of the NMR measuring device 10 are accommodated, in particular an NMR sensor 24, a control apparatus 26 for controlling the NMR measuring device 10 and for evaluating NMR measurement signals delivered by the NMR sensor 24, as well as a data communication interface 28 connected to the control apparatus 26 (see in particular FIG. 2). The control apparatus 26 is intended to carry out the two proposed methods according to the disclosure, and to this end comprises a memory having an executable operating program stored therein. In particular, the control apparatus 26 is used to evaluate at least one NMR measurement signal delivered by the NMR sensor 24, in particular to evaluate and provide a relaxation curve s(t,θ.sub.ref) of a material 34, to determine a relaxation time distribution ρ(θ.sub.ref) from the relaxation curve s(t,θ.sub.ref) provided, to determine an approximated relaxation time distribution ρ(θ.sub.i), in particular on the basis of and by using the relaxation time distribution ρ(θ.sub.ref) provided, to reconstruct a relaxation curve s(t,θ.sub.i) from the approximated relaxation time distribution ρ(θ.sub.i), to determine an expected NMR measurement variable A from a reconstructed relaxation curve s(t,θ.sub.i), and to determine a calibration specification as a function θ(A) describing the humidity θ as a function of an NMR measurement variable A which can be determined (by means of the NMR measuring device 10).

(15) In addition, the control apparatus 26 is used to evaluate at least one NMR measurement signal delivered by the NMR sensor 24, in particular to record an NMR measurement variable A of the material 34 to be analyzed, to provide a calibration specification as a function of a specified material 34, and to determine the absolute humidity θ by using the functional relationship specified in the calibration specification.

(16) In one alternative exemplary embodiment, the control apparatus 26 may also be intended only to carry out one of the two methods proposed, i.e. either to carry out the method for determining a calibration specification or to carry out the method for determining an absolute humidity θ of a material 34 to be analyzed.

(17) The control apparatus 26 has control electronics comprising means for communication with the other component parts of the NMR measuring device 10, for example means for controlling and regulating the NMR sensor 24, an evaluation apparatus independent of the control apparatus 26, a data communication interface 28, or the like. The control apparatus 26 comprises in particular a unit having a processor unit, having a memory unit and having an operating program stored in the memory unit. The control apparatus 26 is intended to adjust at least one operating functional parameter of the NMR measuring device 10 as a function of at least one input by a user, by an optionally provided evaluation apparatus and/or by the data communication interface 28.

(18) The NMR sensor 24 is intended to excite a nuclear magnetic resonance in atomic nuclei of the material 34 to be analyzed. The NMR sensor 24 is intended in particular to measure an NMR measurement signal, in particular a relaxation curve s(t,θ.sub.i).

(19) FIG. 3 shows a method flowchart which depicts an exemplary embodiment of the method according to the disclosure for determining an in particular material-specific calibration specification, the calibration specification specifying a functional relationship between an NMR measurement variable A, which can be determined using the NMR measuring device 10, of a material 34 to be analyzed and a humidity θ contained in the material 34 to be analyzed.

(20) In method step 100, the material 34, for which a corresponding calibration specification is intended to be determined, is adjusted to a known humidity θ.sub.ref. This method step is, for example, carried out by using a drying cabinet. In one exemplary embodiment, the humidity θ.sub.ref may, for example, be 100% of the saturation humidity of the material 34.

(21) In method step 102, an NMR measurement signal is recorded, in particular with an NMR sensor 24 of an NMR measuring device 10, and a relaxation curve s(t,θ.sub.ref) is determined therefrom. This relaxation curve s(t,θ.sub.ref) is subsequently provided to a computation unit of the device carrying out the method, in particular to the control apparatus 26 of the NMR measuring device 10. The NMR measurement signal, in particular the data on which it is based, may furthermore be preprocessed for evaluation, for example by smoothing, filtering, or the like. An exemplary relaxation curve s(t,θ.sub.ref) is represented in FIG. 4a.

(22) In method step 104, a relaxation time distribution ρ(θ.sub.ref) is determined, in particular calculated, by inverse Laplace transformation from the relaxation curve s(t,θ.sub.red provided. A relaxation time distribution ρ(θ.sub.ref) calculated for the relaxation curve s(t,θ.sub.ref) represented in FIG. 4a is represented in FIG. 4b.

(23) In method step 106, an approximated relaxation time distribution ρ(θ.sub.i) relating to at least one humidity θ.sub.i, with θ.sub.i<θ.sub.ref, is calculated by multiplying the relaxation time distribution ρ(θ.sub.ref) by a Heaviside step function H(τ.sub.c(θ)−τ), where τ.sub.c(θ) is selected in such a way that an integral
s(θ.sub.i)=∫ρ(τ,θ.sub.i)dτ
is less by a fraction 1−θ.sub.i/θ.sub.ref than the same integral for the humidity θ.sub.ref, i.e. than
s(θ.sub.ref)=∫ρ(τ,θ.sub.ref)dτ.

(24) In one embodiment of the method, this method step 106 may be repeated several times—indicated by a dashed repetition arrow in the method flowchart in FIG. 4—so that after full completion of method step 106 approximated relaxation time distributions ρ(θ.sub.i) relating to a multiplicity i of humidities θ.sub.i, with θ.sub.i<θ.sub.ref, have been calculated. In one exemplary embodiment, i is for example 9, i.e. including the relaxation time distribution ρ(θ.sub.ref) calculated from the relaxation curve s(t,θ.sub.ref) provided, there are in total 10 relaxation time distributions ρ(θ.sub.ref), ρ(θ.sub.1), . . . , ρ(θ.sub.9). FIGS. 4c and 4d respectively represent an exemplary approximated relaxation time distributions ρ(θ.sub.1) and ρ(θ.sub.5) calculated from the calculated relaxation time distribution ρ(θ.sub.ref) in FIG. 4b by multiplying by a Heaviside step function H(τ.sub.c(θ)−τ). In this case, θ.sub.1=0.9 (corresponding to 90% of the saturation humidity of the material 34) and θ.sub.5=0.5 (corresponding to 50% of the saturation humidity of the material 34), so that τ.sub.c(θ.sub.1) and τ.sub.c(θ.sub.5) are correspondingly selected in such a way that the integral
s(θ)=∫ρ(τ,θ)dτ
is less by a fraction 0.1 or 0.5, respectively, than
s(θ.sub.ref)=∫ρ(τ,θ.sub.ref)dτ.

(25) In the graphs represented, the reduction of the integral corresponds to a reduction of the area under the relaxation time distribution by the corresponding fraction 0.1 (by 10%) and 0.5 (by 50%), respectively.

(26) In method step 108, a relaxation curve s(t,θ.sub.i) is reconstructed from the respective approximated relaxation time distribution ρ(θ.sub.i), so that this method step 108 is also repeated several times—indicated by a dashed repetition arrow in the method flowchart in FIG. 4. For the two exemplary humidities θ.sub.1 and θ.sub.5, two exemplary relaxation curves s(t,θ.sub.1) and s(t,θ.sub.5) are represented in FIG. 4e. From the relaxation curves s(t,θ.sub.i) obtained in this way, here in the example of FIG. 4 s(t,θ.sub.1) and s(t,θ.sub.5), expected NMR measurement variables A.sub.i are subsequently determined in method step 110, i.e. here in the example A.sub.1 and A.sub.5, respectively. The NMR measurement variable A.sub.i is defined in this exemplary embodiment as an amplitude s(0,θ.sub.i) of the respective relaxation curve s(t,θ.sub.i). As an alternative or in addition, the relaxation curve s(t,θ.sub.i) may itself already be interpreted and used as an NMR measurement variable A.

(27) In method step 112, by using the expected NMR measurement variables A.sub.i which have been determined, the NMR measurement variable A.sub.ref relating to the humidity θ.sub.ref, and the corresponding humidities θ.sub.i and θ.sub.ref, the calibration specification is determined as a function θ(A) describing the humidity θ as a function of the NMR measurement variable A which can be determined. In the exemplary embodiment of FIG. 4, the 10 humidities θ.sub.1, . . . , θ.sub.9, θ.sub.ref are stored in an allocation table or in a calibration curve as a calibration specification as a function of the NMR measurement variables A.sub.1, . . . , A.sub.9 and A.sub.ref. In the application, i.e. when carrying out the method for determining an absolute humidity θ of a material 34 to be analyzed, by using an NMR measuring device 10, an NMR measurement variable A evaluated from an NMR measurement may therefore be used to determine the humidity θ by reading, interpolating or calculating the value of the associated humidity θ by using the calibration specification.

(28) In principle, the method according to the disclosure for determining an in particular material-specific calibration specification may be carried out for different materials 34, and in this way a material database which contains a multiplicity of material-specific calibration specification may be compiled.

(29) FIG. 5 shows a method flowchart which depicts an exemplary embodiment of the method according to the disclosure for determining an absolute humidity θ of a material 34 to be analyzed, by using an NMR measuring device 10.

(30) In a method step 200, a material to be analyzed is initially specified by using an input apparatus 14 of the NMR measuring device 10 used, for example as a result of an input or selection by a user. In one exemplary embodiment, the user explicitly indicates the material 34 to be analyzed, for example by their selecting the name of the material “concrete screed” (for example from a predetermined list).

(31) In method step 202—on the basis of the specified name of the material 34—a calibration specification is provided, as a function of the specified material 34, in particular to the control apparatus 26 of the NMR measuring device 10. The calibration specification relating to the material 34 to be analyzed is provided in this exemplary embodiment by a database query, in particular by using an Internet connection. The calibration specification called up from a database 300 (cf. FIG. 1) by means of the data communication interface 28 of the NMR measuring device 10 is forwarded to the control apparatus 26.

(32) In method step 204, an NMR measurement variable A of the material 34 to be analyzed is recorded by means of the NMR measuring device 10. In particular, in this case an NMR measurement signal is recorded by the NMR sensor 24 of the NMR measuring device 10, and a relaxation curve s(t,θ) is determined therefrom. This relaxation curve s(t,θ) is subsequently provided to the control apparatus of the NMR measuring device 10, and the NMR measurement variable A required for identifying an allocation in the calibration specification is determined therefrom, in analogy with the description of the method in FIG. 4, here defined as an amplitude s(0,θ).

(33) In method step 206, the absolute humidity θ is subsequently determined by using the functional relationship, specified in the calibration specification, between the NMR measurement variable A of the material 34 analyzed and the humidity θ expected in the material 34 analyzed.

(34) In method step 208, the results of the quantification of the absolute humidity θ is processed further by means of the control apparatus 26 of the NMR measuring device 10, in particular output by means of the output apparatus 16 of the NMR measuring device 10 to a user of the NMR measuring device 10. In this embodiment, a percentage, which indicates the concentration of the absolute humidity θ in the material, is output.