DE102016116452B4 - SIP measuring cell - Google Patents

Abstract

SIP measuring cell, comprising a sample holder (D1) with a receiving section for receiving a sample, a first measuring electrode holder (C2) with a first measuring electrode (C4) received therein and a second measuring electrode holder (C2') with a second measuring electrode (C4') received therein, wherein the sample holder (D1), first measuring electrode holder (C2) and second measuring electrode holder (C2') are each formed by separate modules which can be attached to and separated from one another, wherein the sample holder (D1) is dimensioned such that it can be inserted into a receiving section of the measuring electrode holders (C2, C2').

Description

The invention relates to a SIP measuring cell according to claim 1, a set comprising a SIP measuring cell, a SIP measuring method, a method for producing a SIP measuring cell and the use of a SIP measuring cell.

A SIP measuring cell is made of EN 10 2006 014 066 B3 known. “SIP” stands for “spectral induced polarization”. A SIP measuring cell is a device for determining frequency-dependent, particularly complex electrical properties of samples (e.g. rocks or solid building materials) using a 4-point arrangement. The specific electrical resistance has long been used in rock and borehole geophysics to determine and characterize conductive structures and materials. Spectral induced polarization (SIP) is particularly aimed at the complex electrical properties (in the low frequency range). SIP enables an extended rock characterization with regard to the electrical and/or hydraulic conductivity and/or pore structures and/or interface processes of a (mineral) matrix-pore fluid system.

Spectrally induced polarization (SIP) is one of the geoelectrical methods of applied geophysics. It is used for measurements in the field as well as for measurements in the laboratory. A signal with a predetermined shape (often sinusoidal or rectangular) is fed into the subsurface or sample via feed electrodes, while an electrical potential is tapped via measuring electrodes. SIP measurements are typically carried out in a frequency range from 1-2 mHz to several kHz (e.g. up to 20 kHz or up to 100 kHz). Due to the polarization properties of the sample (e.g. rock or subsurface), a phase shift (which can be measured in mrad = milliradians, for example) occurs between the fed-in current and the measured voltage signal. There are now established models for the causes of the polarization effect that can be used to explain it (membrane polarization and electrode polarization).

In order to be able to correlate the SIP data with other rock physical quantities or estimates (e.g. regarding porosity or mineral and clay content), several measurements are (usually) required. In combination with classic, interdisciplinary laboratory and field analysis (e.g. mineralogical investigations, hydrogeological investigations, field geophysics), an empirical connection can then be established between the model ideas and measured rock characteristics.

The usual SIP measuring cells, such as those according to EN 10 2006 014 066 B3 , or according to the similarly designed DE 42 08 953 A1 , but require a considerable amount of effort to carry out the measurement.

It is therefore an object of the present invention to propose a SIP measuring cell and a SIP measuring method, wherein a measurement should be comparatively easy to carry out.

This object is achieved in particular by a SIP measuring cell according to claim 1.

According to a core idea of the invention, the sample holder is designed in such a way that it can be adapted to the sample to be held. In the prior art (such as EN 10 2006 014 066 B3 ), inflexible (rigid) sample holders are used and the sample is adapted (in terms of size and material or geometry) (e.g. by cutting or sawing).

Due to this adaptation process in particular, measurement methods using SIP measuring cells according to the state of the art are comparatively complex, and in particular time-consuming. Another disadvantage is that the sample has to be "modified" and is thus essentially "falsified". According to the invention, it was also recognized that this adaptation of the sample is particularly complex because the sample has to be adapted as precisely as possible to the corresponding sample holder in order to carry out a precise measurement, otherwise currents flow in a gap between the sample and the inner wall of the sample holder (or the sample holder) and can falsify the measurement result (sometimes considerably). It must be taken into account that the electrolyte in such a gap usually conducts much better than the sample to be measured, which can lead to considerable errors. A fundamental aspect of the present invention is therefore that, in contrast to the previous procedure, the sample is no longer adapted to the SIP measuring cell, but rather the other way around, the SIP measuring cell and in particular the sample holder to the sample.

In principle, the receiving section can be changed in terms of a cross-sectional shape (for example from circular to elliptical or polygonal, in particular square). Alternatively or additionally (if necessary while maintaining the cross-sectional shape) a diameter of the receiving section can be increased and/or reduced. In In any case, the recording section can be adapted to the sample.

According to one aspect of the invention, in order to achieve the above object, a SIP measuring cell (preferably of the type described above) is proposed, comprising a sample holder (in particular the above sample holder) with a receiving section (in particular the above receiving section) for receiving the sample, a first measuring electrode holder with a first measuring electrode received therein and a second measuring electrode holder with a second measuring electrode received therein, wherein the sample holder, first measuring electrode holder and second measuring electrode holder are each formed by separate modules that can be attached to one another and separated from one another. A core idea of this aspect lies in the modular design of the SIP measuring cell. Different modules are basically also in the EN 10 2006 014 066 B3 described. However, there was no consideration of providing sample holders and a first and second measuring electrode holder, each designed as (separable) modules. On the contrary, a modular structure was proposed in which the measuring electrodes are arranged between the individual modules so that they can be replaced accordingly (if they are damaged). In the present case, on the other hand, the aim is that the entire sample holder or measuring electrode holder is replaceable. The respective measuring electrode is arranged (integrally) in the measuring electrode holders. The measuring electrode is therefore held (alone) by the corresponding measuring electrode holder and not between two flanges, as in the prior art. The separate modules can be plugged into or into one another. For example, the sample holder is dimensioned so that it can be plugged into a corresponding receiving section of the first and/or second measuring electrode holder. The first and/or second measuring electrode holder is preferably (apart from the measuring electrodes and electrical connections and connections for the measuring electrodes) in one piece, in particular monolithic. The sample holder (in particular the sample sleeve) can preferably consist of a one-piece (monolithic) body or two one-piece (monolithic) bodies, for example a (in particular elastic) sleeve and a feed device surrounding the sleeve. Overall, the second aspect also follows the basic idea of the invention, namely adapting the SIP measuring cell to the sample and not the other way around. The modular design makes this particularly easy to do, since (if the sample is initially "unsuitable") the corresponding module (for example the sample holder) can simply be removed and replaced with a suitable module. Overall, this means that a SIP measurement can be carried out effectively and easily.

The receiving section (eg a receiving sleeve) can be made at least partially from an electrically insulating material. A specific resistance of the insulating material is preferably more than 10 ⁶ Ω * m, more preferably more than 10 ¹⁰ Ω * m, more preferably more than 10 ¹² Ω * m, possibly more than 10 ¹⁶ Ω * m. The receiving section is preferably made from a chemically inert material.

The receiving section is particularly preferably made of an elastic material, in particular rubber, preferably silicone rubber. The elastic material's modulus of elasticity is preferably less than 100 N/mm ² , more preferably less than 50 N/mm ² , even more preferably less than 20 N/mm ² . The modulus of elasticity can also have a minimum value of 1 N/mm ² , preferably 4 N/mm ² . Such an elastic receiving section can effectively adapt the receiving section to the sample. If the sample is, for example, slightly larger in diameter than the inner diameter of the receiving section (in a relaxed state), the receiving section can be adapted to the sample in a simple manner by stretching. If the sample is, for example, slightly smaller in diameter than the inner diameter of the receiving section, the receiving section can be adapted to the sample by compressing it (for example with a clamp device). In any case, gaps between the inner wall of the receiving section and the sample can be avoided (or at least significantly reduced), so that the current has to run through the sample.

Overall, a reliable measurement can be carried out quickly.

An inner cross-section of the receiving section can be (circularly) cylindrical (in the relaxed state). This allows for easy adaptation to the sample.

The sample holder preferably comprises an infeed device, in particular a clamp device, such as preferably a hose clamp device, in order to be able to effect a radially inwardly directed pressure loading of the receiving section. The infeed device can generally have a (circumferential) band, in particular a metal band, which can form a loop, the size of which can be adjusted by a corresponding adjustment device (e.g. comprising an adjustment screw). In particular, the sample holder is designed as a rubber sleeve (i.e. with a cylindrical rubber body and at least one feed device running around the rubber body, in particular comprising a metal band). In any case, the sample holder can be easily adapted to the sample. This simplifies the measurement.

Preferably, a first feed electrode receiving device, in particular a first electrolyte tank, preferably at least partially closable with a lid and/or at least partially transparent, is provided with and/or for receiving a first feed electrode. Alternatively or additionally, a second feed electrode receiving device, in particular a second electrolyte tank, preferably at least partially closable with a lid and/or at least partially transparent, can be provided with and/or for receiving a second feed electrode. In general, however, the first and/or second feed electrode can also be provided and arranged in other ways. Preferably, the first and/or second electrolyte tank is/are completely transparent. A lid of the first and/or second electrolyte tank, if provided, can be (in particular completely) transparent. The first and/or second electrolyte tank can be (at least substantially) cuboid-shaped. The first and/or second electrolyte tank can have a (flat) base surface on which it/they can be placed on a surface. The lid of the first and/or second electrolyte tank can be designed such that it covers a top side of the electrolyte tank completely or at least 50% or 70% (in other words, it is designed to be comparatively large). This makes it easy to fill the respective tank with electrolyte or to replace the feed electrodes. A wall of the first and/or second electrolyte tank facing the sample can have an (in particular circular) opening for receiving the first or second measuring electrode holder. A height of the first and/or second electrolyte tank can preferably be at least 1.5 times, even more preferably at least 2 times as high as a height of the first measuring electrode holder and/or the second measuring electrode holder and/or the sample holder. The first and/or second feed electrode is preferably detachably received in the corresponding feed electrode receiving device (electrolyte tank). This makes it easy to replace the respective measuring electrode. By making the respective electrolyte tank or, in general, the respective feed electrode receiving device transparent, a visual inspection can be carried out in a simple manner in order to be able to identify any problems (such as washing out of the sample or similar). On the one hand, a lid can prevent or at least reduce evaporation of the electrolyte (and thus possibly falsification of its composition) and, on the other hand, still provide easy access to the interior of the electrolyte tank. Furthermore, the fill level of the electrolyte tank(s) can be easily determined (if the tank is transparent). In general, markings that indicate a specific fill level can be attached to the first and/or second electrolyte tank (for example, horizontal lines).

The first and/or second feed electrode can be designed as a mesh electrode and/or made (at least partially) from platinum and/or aligned coaxially with the receiving section of the sample holder. When designed as a mesh electrode, a comparatively homogeneous field can be generated in a simple manner (and at the same time it is possible to look through the electrodes). When aligned coaxially with the receiving section, the advantage is that (in a state in which no sample is introduced) an (at least essentially) homogeneous field is generated that is particularly easy to control and allows measurements that are comparatively easy to evaluate. This further improves the measuring method (and indeed with simple means) (particularly with regard to measurement accuracy).

Preferably, a fixing device and/or a sealing device is provided (which can optionally be formed by the same structures), which have a first and a second feed element and are designed such that the individual components of the SIP measuring cell are fixed to one another and/or sealed against one another by moving the first and second feed elements towards one another. In particular, the individual components of the SIP measuring cell can be sample holders, first measuring electrode holders and second measuring electrode holders or, if appropriate, sample holders, first measuring electrode holders, second measuring electrode holders, first feed electrode receiving device and second feed electrode receiving device (e.g. electrolyte tank). Using such a fixing and/or sealing device, the individual elements can be fixed and/or sealed against one another using simple means and extremely quickly. A basic idea here is that a pressure is applied inwards at the ends of the SIP measuring cell (or a corresponding force is applied inwards), so that the individual elements are held together and corresponding sealing surfaces (or seals) are pressed together. It is particularly preferred that the sample holder and/or the first measuring electrode holder and/or the second measuring electrode holder be made of an elastic material (in particular with the E-modulus values as suggested above in connection with the sample holder or its receiving section). The inwardly directed force allows the elastic contact surfaces to be sealed or fixed against each other in a simple manner. Overall, an extremely simple assembly or simple sealing of the SIP measuring cell is achieved. This further simplifies the measurement.

The first and/or second measuring electrode holder can be designed (at least substantially) as a (circular) cylinder. In a preferred embodiment, ends of the first and/or second measuring electrode holder that face the sample holder have an (annular) groove or (annular) step that is designed to receive an edge of the sample holder in order to easily enable a connection between the sample holder and the first or second measuring electrode holder and to be able to easily create a seal.

Preferably, a sealing device (in particular the sealing device as described above) is provided and designed to compress the sample holder in the axial direction. Such compression in the axial direction simultaneously stretches (extends) the sample holder in the radial direction, so that it becomes thicker overall and is thus pressed against a sample held in the sample holder (or so that an inner wall of the sample holder moves towards the sample and thus the tightness between the sample holder and the sample is increased), which improves the measurement results. Overall, a seal between the sample and a wall of the sample holder is made possible in a simple manner.

In a specific embodiment, the feed electrode receiving devices (in particular the electrolyte tanks) can be guided on one or more rails. This allows the positioning of the feed electrode receiving devices (in particular the electrolyte tanks) relative to one another to be varied in a simple and well-defined manner (namely along the rails). This allows the SIP measuring cell to be adapted quickly and easily.

The first and/or second measuring electrode can be designed as a ring electrode and/or consist of a material that is slightly polarizable (possibly non-polarizable) and/or be integrated into a wall of the associated measuring electrode holder, in particular such that the respective measuring electrode is set back relative to adjacent sections of the wall of the respective measuring electrode holder (in its entirety). The first and/or second measuring electrode is preferably arranged such that even the points (sections) closest to the sample or the receiving space for the sample are set back relative to the adjacent sections of the wall of the respective measuring electrode holder. This effectively prevents contact with the sample and yet enables (direct) contact with the electrolyte.

The above object is further achieved in particular by a set comprising a SIP measuring cell of the type described above and at least one additional sample holder and/or at least one additional first measuring electrode holder and/or at least one additional second measuring electrode holder and/or at least one additional first feed electrode receiving device and/or at least one additional second feed electrode receiving device. The respective additional holders or receiving device(s) preferably differ from the corresponding holder or corresponding receiving device(s) still provided in terms of a shape and/or a material quality and/or a dimension, in particular in terms of a length and/or a diameter, in particular an inner diameter, and/or in terms of a connection geometry. Such a set allows the SIP measuring cell to be adapted to the sample quickly and easily. If, for example, it turns out that a sample holder provided in the SIP measuring cell is too small for the sample to be measured, a larger-sized sample holder from the set can be used and inserted instead of the original sample holder. In this example, an adapted first and/or second measuring electrode holder can also be used (if this is necessary or advantageous). In general, identical components can also be replaced, for example if a component (e.g. one of the measuring electrode holders) is damaged.

The above-mentioned object is further achieved in particular by a SIP measuring method using a SIP measuring cell, in particular of the type described above, wherein the individual elements of the SIP measuring cell are fixed and sealed by axially moving a first end towards one another in the direction of a second end. This allows the individual elements to be fixed and/or sealed in a simple manner.

The above-mentioned object is further achieved, in particular, by a method for producing a SIP measuring cell, preferably of the type described above, further preferably by providing a set of the type described above, wherein a sample holder and/or a first measuring electrode holder and/or a second measuring electrode holder and/or a first feed electrode receiving device and/or a second feed electrode receiving device is/are replaced by an additional sample holder or an additional first measuring electrode holder or an additional second measuring electrode holder or an additional first feed electrode receiving device or an additional second feed electrode receiving device, wherein the replaced holder/receiving device differs from the newly installed holder/receiving device in terms of a shape and/or a material quality and/or a dimensioning, in particular in terms of a length and/or a diameter, in particular an inner diameter and/or in terms of a connection geometry.

The above-mentioned object is further achieved by the use of a SIP measuring cell for determining at least one frequency-dependent, in particular complex, electrical property of a sample, in particular a rock sample and/or a building material by means of a 4-point arrangement.

Overall, the SIP measuring cell is characterized by a modular design, so that the measuring conditions can be (quickly) adapted to the sample material (and not, as previously, the other way around). Furthermore, the measuring and/or feed electrodes (which largely determine the measurement accuracy and the quality of the SIP data) can be exchanged or replaced in just a few steps.

Measuring and/or feed electrodes can be made of Pt, PtCl, Ag or AgCl or comprise these materials.

The first and/or second measuring electrode holder can be inserted into the corresponding feed electrode holder (electrolyte container).

The first and/or second feed electrode receiving device (electrolyte container) can have a fastening frame in which the respective feed electrode can be arranged. This allows damaged feed electrodes to be removed relatively quickly.

A sample holder (sleeve) made of silicone rubber enables an (almost) perfect sealing of the outer peripheral surface (surface) of the sample against edge currents and can therefore significantly improve the data quality. The sample holder (sleeve) allows any sample geometry (in terms of diameter, length, cross-sectional shape) to be taken into account without the measuring cell having to be completely redesigned (or the sample having to be adapted and thus in principle distorted).

The electrolyte containers can be made of glass and/or acrylic glass, particularly transparent acrylic glass. This makes it relatively easy to read the fill level (for example with the help of a marking) in order to be able to react to evaporation effects during longer series of measurements. Furthermore, if the fluid conductivity changes, it can be checked whether this was caused by evaporation (level change) or by dissolution from the sample. Leaching or solution components of sample materials can also be detected by simple visual inspection.

Overall, a modular design is proposed for improved (optimized) ease of maintenance. The individual modules can be adapted or optimized for SIP measurements (for example by using non-conductive or non-polarizable materials). In principle, adaptation is made to the sample material and not the other way around. High variability and flexibility is made possible by the simple adaptation of the SIP measuring cell to different sample materials and sample geometries. The data quality can be easily improved by reducing external interference.

In one embodiment, the sample holder, first measuring electrode holder and second measuring electrode holder are arranged between the feed electrode receiving devices (electrolyte tanks). The electrolyte tanks can be connected to one another via the measuring electrode holders and the sample holder (due to the electrolyte contained therein).

In general, the measuring electrodes can be in contact (directly) with the electrolyte, but without touching the sample material to be examined (thereby avoiding measurement errors).

In an alternative embodiment, the first and/or measuring electrode holders can be equipped with point electrodes, in particular to meet (variable) sample material requirements. If the electrolyte tanks and/or the associated lids are (at least partially) transparent, evaporation as well as dissolution and/or precipitation effects can be quickly identified.

In a specific embodiment, the entire SIP measuring cell has a modular design so that (routine) maintenance, cleaning and the replacement of defective or damaged components can be carried out quickly and easily.

Further embodiments emerge from the subclaims.

• 1 Das allgemeine Messprinzip einer 4-Punkt-SIP-Messung anhand eines Vergleichsbeispiels;
• 2 eine erfindungsgemäße SIP-Messzelle gemäß einem Ausführungsbeispiel in einer schematischen Ansicht;
• 3 die SIP-Messzelle gemäß 2 in einer perspektivischen Ansicht;
• 4 eine perspektivische Schnittansicht der SIP-Messzelle gemäß 3;
• 5 eine Seitenansicht der SIP-Messzelle gemäß 3;
• 6 eine Schnittansicht entlang der Längsachse der SIP-Messzelle gemäß 5;
• 7 eine Frontansicht der SIP-Messzelle gemäß 3;
• 8 eine Draufsicht der SIP-Messzelle gemäß 3; und
• 9 einen vergrößerten Ausschnitt der SIP-Messzelle.

The invention is described below using an embodiment example, which is explained in more detail using the figures. Here:

• 1 The general measuring principle of a 4-point SIP measurement using a comparison example;
• 2 an inventive SIP measuring cell according to an embodiment in a schematic view;
• 3 the SIP measuring cell according to 2 in a perspective view;
• 4 a perspective sectional view of the SIP measuring cell according to 3 ;
• 5 a side view of the SIP measuring cell according to 3 ;
• 6 a sectional view along the longitudinal axis of the SIP measuring cell according to 5 ;
• 7 a front view of the SIP measuring cell according to 3 ;
• 8th a top view of the SIP measuring cell according to 3 ; and
• 9 an enlarged section of the SIP measuring cell.

In the following description, the same reference numbers are used for identical and equivalent parts.

In 1 The 4-electrode measuring principle of a SIP measurement is described in more detail using a comparative example. A current generator 20 generates a current signal I (typically in the mA range), which is fed in via two electrolyte tanks B2, B2' filled with electrolyte or via two feed electrodes B6, B6' arranged in the electrolyte tanks. The range of measuring frequencies taken into account can be from 1 mHz, in particular 2 mHz, up to 20 kHz or 100 kHz. A voltage signal V _mat that drops across a sample can be tapped via measuring electrode connections C3, C3' arranged on a sample holder D1. The sample or the sample material is shown schematically here as an equivalent resistor 10. The current signal I can then be determined via a shunt resistor 30. During the measurement, the impedance Z _mat of the sample material can therefore be determined (for each measuring frequency) from the measured voltage V _mat and the measured current I _g as follows: $${\text{Z}}_{\text{mat}}={\text{V}}_{\text{mat}}/{\text{I}}_{\text{G}}.$$

The measured current I _g results from the voltage drop V across the shunt resistor 30 as follows: $${\text{I}}_{\text{G}}=\text{V}/{\text{R}}_{\text{shunt}}.$$

If we now use the equation to calculate the sample impedance Z _mat , we get R _shunt as the ohmic resistance value: $${\text{Z}}_{\text{mat}}={\text{R}}_{\text{shunt}}*\left({\text{V}}_{\text{mat}}/\text{V}\right).$$

This sample impedance or the complex conductivity derived from it exhibits a pronounced frequency dependence for many natural materials, which can be used to characterize the material (physically and/or mineralogically or chemically).

2 shows a SIP measuring cell according to an embodiment of the present invention. The measuring cell has two electrolyte tanks B2, B2', between which there are measuring electrode holders C2, C2' with measuring electrode connections C3, C3' and a sample holder D1 for holding the sample material. The electrolyte tanks B2, B2' have covers B1, B1'. A current I is generated in a generator 20, fed in via feed electrodes B6, B6' and measured via the shunt resistor 30. The measuring electrode holders C2, C2' hold the measuring electrodes C4, C4' (see 9 ). The (ring-shaped) measuring electrodes C4, C4' do not touch the sample. Furthermore, the measured voltage is tapped from the outside of the sample holder D1 (sample sleeve), so that falsification of measurement results can be avoided.

3 shows the 2 only schematically shown SIP measuring cell with further details in an oblique view. The SIP measuring cell is (completely) modular, symmetrical and also divisible. The two electrolyte tanks B2, B2' run on parallel arranged rails A1, A1', which are held by (two each) guide sleeves A6, A6' or, in general, guide elements (per tank side). According to the design, the sleeves A6, A6' are hexagonal (but they can also have other shapes). At the end of the guide rails There are feed elements, in particular comprising rods A4, A4' (counter rods), which can be held by nuts A2, A2' and washers A5, A5'.

After a sample has been installed or the measuring electrode holders C2, C2' and the sample holder D1 have been assembled, the measuring cell can be clamped in place, particularly firmly, using the adjustment elements (rods A4, A4' or counter rods). This simultaneously seals the sample holder D1 against leaks at a connection to the measuring electrode holders C2, C2' by (geometrically) expanding a material of the sample holder D1.

The sample holder D1 comprises an (elastic) sleeve D3 and a feed device (clamp device) D2 for compressing the sleeve D3 (see in particular 4 ).

According to the design, the electrolyte tanks B2, B2' and the lids B1, B1' are made of (transparent) acrylic glass. This makes it easy to detect possible chemical reactions or the resulting precipitation in the electrolyte tanks B2, B2' or on the feed electrodes B6, B6'. In addition, the fill level of the electrolyte can be easily checked without separating the SIP measuring cell from the test setup.

4 shows a sectional view of the SIP measuring cell from 3 . It can be seen that the measuring electrode holders C2, C2' are inserted into the walls B11, B11' of the electrolyte tanks B2, B2' via grooves (or corner recesses) B10, B10'. The feed electrodes B6, B6' are fixed via frames B4, B4' in a wall B3, B3' of the respective electrolyte tank B2, B2' (each using, for example, 4 screws, e.g. PMMA screws, B7, B7'). The feed electrodes B6, B6' and a tap B5, B5' are preferably connected to one another (conductively) by means of a (corrosion-resistant) wire bridge B8, B8'.

Openings B9, B9' can be seen on the wall B11, B11', through which the measuring electrode holders C2, C2' (directly) and the sample holder D1 (indirectly) are flanged.

The SIP measuring cell can be secured against leakage by means of a seal C1, C1' (O-ring) between the electrolyte tanks B2, B2' and the measuring electrode holder C2, C2'.

In addition, one can see in 9 a recess C5, C5' (ring-shaped recess) within the measuring electrode holders C2, C2', into which the measuring electrodes C4, C4' are inserted. The measuring electrodes C4, C4' can be connected to the measuring electrode connections C3, C3' via a hole (not shown in the figures) through the measuring electrode holders C2, C2'. The measuring electrode connections C3, C3' can be designed as banana plugs, for example.

5 shows a side view of the SIP measuring cell. The modular structure is clearly visible there. The SIP measuring cell therefore comprises the electrolyte tanks B2, B2', the measuring electrode holders C2, C2', the sample holder D1 and the guide rails A1, A1' (with the associated elements, such as guide sleeves A6, A6', rods A4, A4' together with nuts A2, A2' and washers A5, A5').

6 shows a sectional view along the central longitudinal axis of the SIP measuring cell according to 5 . In particular, the positioning of the feed electrodes B6, B6' along an imaginary central axis "opening B9, B9' - measuring electrode holder C2, C2' - sample holder D1" can be seen in order to ensure that the electrical current spreads (as directly and as distortion-free as possible). In addition, the positioning of the measuring electrode connections C3, C3' and taps B5, B5' (feed points) on the top of the measuring cell can be seen in order to achieve quick and easy access when changing connections.

Due to the modular design of the entire SIP measuring cell, it can be dismantled quickly and without increased effort or tools. This increases the efficiency of maintenance, cleaning and repair tasks on the measuring cell and ensures quick reuse and minimal loss of measuring time. The feed and/or measuring electrodes can be made of a corrosion-resistant metal (e.g. platinum or silver) or contain such a metal.

7 shows the SIP measuring cell in a front view. It can be seen that the electrolyte tanks B2, B2' are secured by the rods A4, A4' (counter rods) using washers A5, A5' and nuts A2, A2'.

8th shows the SIP measuring cell from above. Here, the fixing of the entire measuring cell by the rails A1, A1' and the sleeves A6, A6' is once again clearly visible. The measuring electrode connections C3, C3' and taps (feed points) B5, B5' on the top are also visible.

The present embodiments are not intended to be limiting. The invention can in particular also be implemented with geometries and/or materials other than those described above.

At this point, it should be noted that all of the parts described above, viewed individually and in any combination, in particular the details shown in the drawings, are claimed as essential to the invention. Modifications to this are familiar to the person skilled in the art.

Reference list

A1, A1'

rail

A2, A2'

Mother

A4, A4'

pole

A5, A5'

Washer

A6, A6'

Guide sleeve

B1, B1'

Lid

B2, B2'

Electrolyte tank

B3, B3'

Wall

B4, B4'

Frame

B5, B5'

Tap

B6, B6'

Feed electrodes

B7, B7'

screw

B8, B8'

Wire bridge

B9, B9'

opening

B10, B910'

Groove

B11, B11'

Wall

C1, C1'

poetry

C2, C2'

Measuring electrode holder

C3, C3'

Measuring electrode connection

C4, C4'

Measuring electrode

C5, C5'

Recess

D1

Sample holder

D2

Clamp device

D3

Sleeve

I

Current signal

Vmat

Voltage signal

Zmat

Impedance

10

Equivalent resistance

20

Power generator

30

Shunt resistance

Claims (22)

SIP measuring cell, comprising a sample holder (D1) with a receiving section for receiving a sample, a first measuring electrode holder (C2) with a first measuring electrode (C4) received therein and a second measuring electrode holder (C2') with a second measuring electrode (C4') received therein, wherein the sample holder (D1), first measuring electrode holder (C2) and second measuring electrode holder (C2') are each formed by separate modules which can be attached to and separated from one another, wherein the sample holder (D1) is dimensioned such that it can be inserted into a receiving section of the measuring electrode holders (C2, C2'). SIP measuring cell according to Claim 1 , characterized in that the receiving section is at least partially formed from an electrically insulating material and/or from a chemically inert material and/or from an elastic material and/or that at least an inner cross section of the receiving section is cylindrical and/or that the sample holder (D1) has a feed device (D2) for a radially inwardly directed pressure application to the receiving section. SIP measuring cell according to one of the preceding claims, characterized in that a first electrolyte tank (B2) is provided with and/or for receiving a first feed electrode (B6) and/or a second electrolyte tank (B2') is provided with and/or for receiving a second feed electrode (B6'). SIP measuring cell according to one of the preceding claims, characterized in that a first (B6) and/or a second (B6') feed electrode is/are designed as a mesh electrode and/or is/are at least partially made of platinum and/or is/are aligned coaxially to the receiving section. SIP measuring cell according to one of the preceding claims, characterized in that a fixing and/or sealing device with a first and a second feed element is provided and is designed such that the individual components of the SIP measuring cell are fixed to one another and/or sealed against one another by moving the first and second feed elements towards one another. SIP measuring cell according to one of the preceding claims, characterized in that a sealing device is provided and is designed to compress the sample holder (D1) in the axial direction. SIP measuring cell according to one of the preceding claims, characterized in that feed electrode receiving devices can be guided on one or more rails (A1, A'). SIP measuring cell according to one of the preceding claims, characterized in that the first (C4) and/or second (C4') measuring electrode is/are designed as ring electrode(s) and/or consist of slightly polarizable material and/or are integrated in a wall of the associated measuring electrode holder (C2, C2'). SIP measuring cell according to one of the preceding claims, wherein a cross section of the receiving section is variable and wherein a diameter of the receiving section is enlargeable and/or reducible. Set comprising a SIP measuring cell according to one of the preceding claims and at least one additional sample holder and/or at least one additional first measuring electrode holder and/or at least one additional second measuring electrode holder and/or at least one additional first feed electrode receiving device and/or at least one additional second feed electrode receiving device, which differ in terms of a shape and/or a material properties and/or a dimensioning, and/or in terms of a connection geometry. SIP measuring method using a SIP measuring cell according to one of the Claims 1 until 9 , whereby the fixation and/or tightness of the individual elements of the SIP measuring cell is achieved by axially moving a first end towards a second end. Method for producing a SIP measuring cell according to one of the Claims 1 until 9 , wherein a sample holder is replaced by an additional sample holder and/or a first measuring electrode holder is replaced by an additional first measuring electrode holder and/or a second measuring electrode holder is replaced by an additional second measuring electrode holder and/or a first feed electrode receiving device is replaced by an additional first feed electrode receiving device and/or a second feed electrode receiving device is replaced by an additional second feed electrode receiving device, wherein the replaced holder/receiving device differs from the newly installed holder/receiving device with regard to a shape and/or a material properties and/or a dimensioning and/or with regard to a connection geometry. Use of a SIP measuring cell for measuring an induced polarization with more than one frequency, wherein the SIP measuring cell comprises: a sample holder (D1) with a receiving section for receiving a sample, wherein the receiving section is formed from an elastic material with an E-modulus of less than 100 N/mm ² , wherein a cross section of the receiving section is variable and/or wherein a diameter of the receiving section is enlargeable and/or reducible. Use according to Claim 13 wherein the SIP measuring cell comprises a first measuring electrode holder (C2) with a first measuring electrode (C4) accommodated therein and a second measuring electrode holder (C2') with a second measuring electrode (C4') accommodated therein, wherein the sample holder (D1), first measuring electrode holder (C2) and second measuring electrode holder (C2') are each formed by separate modules which can be attached to and separated from one another, wherein the first and second measuring electrodes are held by the associated first and second measuring electrode holders alone, respectively. Use according to Claim 13 or 14 , characterized in that the receiving section is at least partially formed from an electrically insulating material and/or from a chemically inert material and/or from an elastic material and/or that at least an inner cross section of the receiving section is cylindrical and/or that the sample holder (D1) has a feed device (D2) for a radially inwardly directed pressure application to the receiving section. Use according to any of the preceding Claims 13 until 15 , characterized in that a first electrolyte tank (B2) is provided with and/or for receiving a first feed electrode (B6) and/or a second electrolyte tank (B2') is provided with and/or for receiving a second feed electrode (B6'). Use according to any of the preceding Claims 13 until 16 , characterized in that a first (B6) and/or a second (B6') feed electrode is/are designed as a mesh electrode and/or is/are at least partially made of platinum and/or is/are aligned coaxially to the receiving section. Use according to any of the preceding Claims 13 until 17 , characterized in that a fixing and/or sealing device with a first and a second feed element is provided and is designed such that the individual components of the SIP measuring cell are fixed to one another and/or sealed against one another by moving the first and second feed elements towards one another. Use according to any of the preceding Claims 13 until 18 , characterized in that a sealing device is provided and is designed to compress the sample holder (D1) in the axial direction. Use according to any of the preceding Claims 13 until 19 , characterized in that feed electrode receiving devices can be guided on one or more rails (A1, A'). Use according to any of the preceding Claims 13 until 20 , characterized in that the first (C4) and/or second (C4') measuring electrode is/are designed as ring electrode(s) and/or consist of slightly polarizable material and/or are integrated in a wall of the associated measuring electrode holder (C2, C2′). Use of a SIP measuring cell according to one of the Claims 1 until 9 for measuring induced polarization with more than one frequency.