EP2068103A2 - Measuring module for quick measuring of electrical, electronic and mechanical components at cryogenic temperatures and measuring device with such a measuring module - Google Patents

Abstract

The module (10a) has a contact element (5b) fastened to a part of a partition wall between a measuring chamber (4) and a cooling chamber (3) and thermally insulated from an outer wall of the module, where a local thermal connection is produced from the measuring chamber to the cooling chamber. A contacting device changes a heat flow in a hermetically closed condition of the module, where the heat flow between a cooling head (1b) of a single stage cryocooler and the contact element is either produced or strongly increased or interrupted or strongly reduced using the contacting device. An independent claim is also included for a measuring device comprising devices for supplying and pumping a fluid into/from a hollow space of a connecting element.

Description

The invention relates to a measuring module for measuring and testing a measuring object with an evacuable measuring chamber for receiving the measured object and a contact element, wherein the measuring object is thermally connected during the measuring and / or testing process with a first contact surface of the contact element, and at least one cold head which can be thermally connected to a second contact surface of the contact element, wherein the cold head can be cooled down to cryogenic temperatures by means of a cryocooler consisting of at least one cold stage, and wherein the contact element consists of thermally highly conductive material, and the first and second Contact surface lie on opposite sides of the contact element, and wherein the cold head and the contact element during the measuring and / or testing process are in an evacuated environment and are thermally conductively connected to each other.

Such a measuring device is known from [2].

Durch Verkleinerung der Temperatur T von metallischen Leitern verkleinert sich auch dessen Widerstand R, so dass das Produkt R·T and damit die thermische Rauschspannung V_R besonders stark reduziert wird. Deshalb wird dieses Kühlverfahren heute für empfindliche Messgeräte und Sensoren genutzt, wie sie z.B. in der NMR-Spektroskopie [1] vorkommen. Man erreicht dort eine markante Verbesserung der Messempfindlichkeit, d.h. des Signal-zu-Rausch-Verhältnisses (= SI-NO).By cooling, the thermal noise of electronic components can be reduced. The thermal noise is caused by statistical movements of the charge carriers and by irregular, temperature-dependent lattice vibrations, which are transmitted to the charge carriers by collisions. It manifests itself by a noise voltage V _R at the ends of electrical conductors. In an ohmic resistance R which is at the temperature T, the noise voltage in the frequency range Δ f is given by [3], [4]: $$\left|V_R\right|=\sqrt{4\mathit{kRT}\cdot \mathrm{\Delta }f}\mathrm{in\; which}k=\mathrm{1:38}\cdot {10}^{-23}\mathrm{Ws}/\mathrm{K}\left(=\mathrm{Boltzmann}-\mathrm{constant}\right)$$

By reducing the temperature T of metallic conductors and its resistance R decreases, so that the product R · T and thus the thermal noise voltage V _{R is} particularly reduced. Therefore, this cooling method is used today for sensitive measuring devices and sensors, such as those found in NMR spectroscopy [1]. There is achieved a marked improvement in the measurement sensitivity, ie the signal-to-noise ratio (= SI-NO).

For the development of such meters or sensors with cooled electrical and electronic components, therefore, suitable electronic and electrical components (e.g., cables, resistors, transistors, etc.) must be previously assessed and subjected to quality inspection (e.g., thermal cycling). For this purpose, test facilities are needed that allow individual electronic components and entire electronic circuits to be cooled to their use and test temperature, with the aim of identifying their properties and specifications and performing quality tests on them.

The simplest and most widely used method for cooling to cryogenic temperatures is with the aid of liquid nitrogen (LN2) or, more rarely, with liquid helium (LHe). The components to be measured (electronic components or circuits, mechanical components or combinations thereof) are immersed in a Dewar vessel filled with LN2 or LHe and cooled. Quality checks (eg temperature cycling tests) and / or the determination of electrical or mechanical properties of components can be carried out in this way.

The disadvantages of this method are that the lowest cryogenic temperature is given by the boiling point of the liquid gas 77K at LN2 and 4.2K at LHe), and the specimens are exposed to extreme thermal stresses due to the high cooling rates. In addition, condensate and ice may form on the test specimens.

In a more advanced cooling method, the object to be cooled is attached to a thermally well-conductive contact element which is cooled by a cooling medium (e.g., LN2 or LHe) to the desired temperature. To keep the thermal losses small, the whole assembly is housed in an evacuated chamber, which also prevents the formation of condensation and ice [2]. However, such systems are efficient only at temperatures just above the boiling point of the cooling medium. If specimens need to be tested well above the boiling point (but far below room temperature), then this must be achieved by heating the contact element additionally, which in turn leads to increased loss of cooling medium and increased costs (especially if the cooling medium is LHe). Another disadvantage here is that the user always has to rely on the cooling medium and must always ensure that there is sufficient reserve of it. In addition, such a system has the disadvantage that the user must understand how to deal with cryogenic liquids.

In addition, measuring modules are known in which the cooling is not carried out by a cryogenic cooling medium, but by a cryocooler with a closed cooling circuit [2]. The disadvantage of this measuring module is that the cryocooler must first be switched off and then followed by a long wait until the cryocooler has warmed up sufficiently, and the chamber in which the specimen is located can be opened.

Based on this prior art, it is the object of the invention to propose a measuring module and a measuring device with which such long waiting times can be avoided in order to make the cooling of the measuring objects more user-friendly.

This object is achieved in that the cryocooler including cold head is housed in a cooling chamber, which is spatially separated from the measuring chamber and independently of this is evacuated that the contact element thermally insulated from the outer wall of the measuring module attached part of a partition between the measuring chamber and the cooling chamber is and makes a local thermal connection from the measuring chamber to the cooling chamber, and that a contacting device is provided for changing the heat flow in the hermetically sealed state of the measuring module, with the help of the heat flow between the cold head and the contact element either made or greatly enlarged, or interrupted or greatly reduced.

With the measuring module according to the invention, a cooling process without cryogenic liquids can be realized, wherein the test temperature of the measured objects within the given temperature range can be freely selected by the variably adjustable heat flow between the cold head and the contact element.

The cryocooler may remain cold during cooling or warming up of the measurement object. The cooling rates for the measurement object can thus be shortened compared to the prior art by about the specified by the cryocooler manufacturer cooling time of the cryocooler, because the cryocooler does not need to be cooled again. The typical cooling time of a cryocooler is between about 40 and 60 minutes. In addition, an unnecessary thermal load of the cryocooler is avoided.

The separate chambers for the measurement object and the cryocooler also allow optimal thermal isolation between the measuring chamber and the cooling head.

The cooling rate .DELTA.T _K / .DELTA.t and the warm-up rate .DELTA.T _W / .DELTA.t are freely adjustable with the measurement module according to the invention and can be chosen so that the measurement object is not damaged.

In addition, the desired cooling cycles can be carried out automatically, with their number being freely selectable.

The measuring module according to the invention is easy to use and allows easy mounting and changing of the measuring objects.

Preferably, the contacting device according to the invention comprises a pneumatic, hydraulic or electric drive, or a combination thereof, or a manual drive with which the cold head and the contact element can be mechanically moved towards or away from each other, wherein the cold head and the contact element either pressed against each other or spatially be separated so that the heat flow between them is increased or decreased. The drive allows both the contacting of the measuring object with the cooling head over the two contact surfaces of the contact element as well as the separation of the same contact in a simple and fast manner.

Alternatively, the contacting device may comprise a connecting element which is arranged between the cold head and the contact element and permanently in close thermal communication with the cold head and the contact element, wherein the connecting element has at least one cavity which can be filled with a well-conducting fluid at cryogenic temperatures whereby the thermal conductivity of the connecting element and thereby also the heat flow between the cold head and the contact element can be changed. This also shortened cooling times and warm-up times can be realized, which can be dispensed with movable mechanical components, resulting in a structurally very simple solution.

Preferably, the contact element comprises a heat exchanger, which is operated with a cryogenic fluid, in particular liquid nitrogen or liquid helium, and serves for precooling of the contact element. The main advantage This embodiment is a high cooling rate for measurement objects having a high heat capacity, so that the cooling time can be further shortened.

In a particularly preferred embodiment of the measuring module according to the invention, at least one temperature sensor and at least one heater are provided, which serve to regulate the temperature of the contact element. Further temperature sensors can also be attached to the measurement object, so that its temperature can be measured and regulated directly.

Moreover, it is advantageous if the cryocooler has two stages, each with a cold head, wherein the cold head of the first stage is thermally connected to a heat exchanger, which serves for the liquefaction of nitrogen gas. This embodiment has the advantage that the cryofluid required for the pre-cooling is generated autonomously, i. no longer needs to be purchased externally.

The invention also relates to a measuring device with a measuring module according to the invention described above, wherein the contact element is thermally insulated from the external environment of the measuring module. For example, the contact element may be fastened at one end of the bellows-shaped separating wall between the measuring chamber and the cooling chamber, whereby it is thermally insulated from the outer wall of the measuring module.

Advantageous is a measuring device which comprises a measuring module with a connecting element which is arranged between the cold head and contact element and permanently in close thermal communication with the cold head and the contact element, wherein the connecting element has at least one cavity, and wherein devices for supplying and pumping a are provided at cryogenic temperatures highly conductive fluid into and out of the cavity of the connecting element, whereby the heat flow between the cold head and the contact element can be increased or decreased.

Particularly advantageous is a measuring device comprising a measuring module, in which the cryocooler has two stages, each with a cold head, wherein the cold head of the first stage with a heat exchanger, which is used for liquefaction of Nitrogen gas is used, is thermally connected, and wherein the first stage of the cryocooler is connected via the heat exchanger with a nitrogen separator, through which the nitrogen gas can be obtained directly from the air and fed to the heat exchanger.

Further advantages of the invention will become apparent from the description and the drawings. Likewise, the features mentioned above and those listed further can be used individually or in any combination. The embodiments shown and described are not to be understood as exhaustive enumeration, but rather have exemplary character for the description of the invention.

Fig. 1a

eine erfindungsgemäße Messeinrichtung mit einem einstufigen Kryokühler im nicht kontaktierten Zustand;

Fig. 1b

eine erfindungsgemäße Messeinrichtung mit einem einstufigen Kryokühler im kontaktierten Zustand;

Fig. 2a

eine erfindungsgemäße Messeinrichtung mit einem einstufigen Kryokühler und einem Wärmetauscher im nicht kontaktierten Zustand;

Fig. 2b

eine erfindungsgemäße Messeinrichtung mit einem einstufigen Kryokühler und einem Wärmetauscher im kontaktierten Zustand;

Fig. 3a

eine erfindungsgemäße Messeinrichtung mit einem zweistufigen Kryokühler und einem Wärmetauscher im nicht kontaktierten Zustand;

Fig. 3b

eine erfindungsgemäße Messeinrichtung mit einem zweistufigen Kryokühler und einem Wärmetauscher im kontaktierten Zustand;

Fig. 4

eine erfindungsgemäße Messeinrichtung mit einem einstufigen Kryokühler und einem Verbindungselement mit variabler thermischer Leitfähigkeit;

Fig. 5a

eine Messeinrichtung nach dem Stand der Technik, bei der die Abkühlung des Kontaktelementes mittels einer Kryoflüssigkeit erfolgt; und

Fig. 5b

eine Messeinrichtung nach dem Stand der Technik, bei der die Abkühlung des Kontaktelementes mittels eines Kryokühlers erfolgt.

Show it:

Fig. 1a

a measuring device according to the invention with a single-stage cryocooler in the non-contacted state;

Fig. 1b

a measuring device according to the invention with a single-stage cryocooler in the contacted state;

Fig. 2a

a measuring device according to the invention with a single-stage cryocooler and a heat exchanger in the non-contacted state;

Fig. 2b

a measuring device according to the invention with a single-stage cryocooler and a heat exchanger in the contacted state;

Fig. 3a

a measuring device according to the invention with a two-stage cryocooler and a heat exchanger in the non-contacted state;

Fig. 3b

a measuring device according to the invention with a two-stage cryocooler and a heat exchanger in the contacted state;

Fig. 4

a measuring device according to the invention with a single-stage cryocooler and a connecting element with variable thermal conductivity;

Fig. 5a

a measuring device according to the prior art, in which the cooling of the contact element is effected by means of a cryogenic liquid; and

Fig. 5b

a measuring device according to the prior art, in which the cooling of the contact element is effected by means of a cryocooler.

Fig. 5a shows a measuring device according to the prior art. A measuring module 10 'is used for cooling, measuring and testing a measuring object 6. The measuring object 6 to be cooled is fastened to a thermally highly conductive contact element 5' , which is cooled by a cooling medium (eg LN2 or LHe) to the desired temperature. In order to keep the thermal losses small, the whole assembly is housed in an evacuated chamber 4 ' , whereby the formation of condensation and ice is avoided. The desired measurement temperature can be controlled, for example, by means of a controller 36, a heater 7 and temperature sensors 35a, 35b . In order to increase the efficiency or to minimize the loss of cooling medium, in addition, the supply of the cooling medium via valves 12, 13 are regulated.

5 b shows a further known from the prior art measuring device, which differs from the in 5a differs in that the cooling is not carried out by a cryogenic cooling medium, but by a cryocooler 1a with a closed cooling circuit. A measuring module 10 " comprises a cold head 1b and a contact element 5". The cold head 1 b can be cooled down to cryogenic temperatures by means of the cryocooler 1 a comprising at least one cold stage. The contact element 5 "is made of material with good thermal conductivity and is positioned between the measuring object 6 and the cold head 1 b. These components are located in an evacuated environment during the measuring and / or testing process and are connected to one another in a thermally conductive manner.

The cold head 1 b, which is cooled by the first cooling stage of the cryocooler 1 a with a specific cooling power, is fixedly connected to a contact element 5 "which ideally assumes the temperature of the cold head 1 b without thermal load then the test object 6 to be tested are mounted. The temperature of the contact element 5 "or of the measurement object 6 can be controlled with the controller 36, heater 7 and temperature sensors 35a, 35b.

Fig. 1a, 1b show a first embodiment 10a of a measuring module according to the invention. In contrast to the known devices, the measuring module 10a according to the invention comprises a two-chamber system with a cooling chamber 3 and a measuring chamber 4, which can be evacuated independently of one another. In the cooling chamber 3 is the cryocooler 1 a with its cold head 1 b and a closed cooling circuit. As the cryocooler 1a, a Stirling, a Gifford-McMahon or a Pulse-Tube cooling apparatus may be used. The cooling chamber 3 is evacuated during the measuring operation and thereby isolated the cryocooler 1 a thermally from its surroundings.

The measuring object 6 to be measured are located in the likewise evacuated measuring chamber 4 and is fixedly connected to a contact element 5b on a first contact surface 9a . The contact element 5b is formed as part of the partition wall between the two chambers 3, 4 and serves as a local thermal connection from the cooling chamber 3 to the measuring chamber 4. The contact element 5b is fixed to a thermally insulated to the outer wall of the measuring module body.

The heat flow between the cold head 1 b and the contact element 5 b is changed by mechanically moving towards or away from one another by means of a pneumatic, hydraulic or electric drive 8, a combination thereof, or by manual drive, the cold head 1 b and the contact element 5 b and that thereby the cold head 1 b and the contact element 5 b are pressed against each other ( Fig. 1 b) or spatially separated ( Fig. 1a ), so that the heat flow between them large resp. gets small. In the first case, the cold head 1 b contacted the contact element 5 b at a second contact surface 9b and the contact element 5b is cooled together with the measurement object 6 by the cryocooler to the desired temperature. In the second case, the contact between the cold head 1b and the second contact surface 9b of the contact element 5b is disconnected, so that the contact element 5b together with the measurement object 6 are reheated without the cryocooler 1a having to be switched off beforehand.

The controller 36 with connected heater 7 and temperature sensor 35a allows control of the temperature of the contact element 5b and thus of the measurement object 6 to the desired value. For warming up, the drive 8 moves the contact element 5b away from the cold head 1b and thereby interrupts the heat flow between them ( Fig. 1 b) , The heater 7 then allows a rapid warming of the contact element 5b and the measuring object 6. The cryocooler 1a continues running, and the cold head 1 b cools, since it is no longer thermally loaded, to the lowest possible temperature. The user is not dependent on cryogenic liquids in this embodiment.

An improved embodiment 10b of the measuring module according to the invention is shown in FIG Fig.2a and Fig.2b shown. It leads to a massive reduction of the cooling times and differs from the previous embodiment in that a contact element 5a is provided with a heat exchanger through which a cryogenic liquid (LN2 or LHe) flows, thereby allowing pre-cooling of the contact element 5a and of the measurement object 6 , The inlet valve 12 and the outlet valve 13 control the flow of the cooling medium. During the cooling process, the valves 12 and 13 are opened, and the existing in a Dewar vessel 11 cryogenic liquid is pressed, for example by generating an overpressure in the Dewar vessel 11 by insulated lines in the heat exchanger of the contact element 5a, whereby this is pre-cooled. The cooling times down to the boiling point of the cryogenic liquid are massively shortened in this way compared to a cooling with the cryocooler alone (eg a Gifford-McMahon cryocooler).

As soon as the contact element 5a has reached the temperature of the cryogenic liquid, the valves 12 and 13 are closed again. The drive 8 then moves the Contact element 5a down and connects this thermally with the cold head 1 b (see 2b ). The temperature of the contact element 5a is measured with the temperature sensor 35a and can then be controlled by the heater 7.

To warm up the contact element 5a is moved by means of the drive 8 upwards, whereby its thermal contact with the cold head 1 b is interrupted again (see 2a ). Subsequently, the heater 7 allows an accelerated warming of the contact element 5a and thus also of the measurement object 6. In this cooling method, however, care should always be taken to ensure that there is always sufficient cryogenic fluid in the dewar vessel 11.

Another embodiment 10c of the measuring module according to the invention is shown in FIG 3a and 3b illustrated. This embodiment differs from that in FIG Fig.2a and Fig.2b in that a two-stage cryocooler 2a is used, and that the first stage of this cryocooler 2a serves to liquefy N2 gas in order to produce the contact element 5a already in the variant of FIG 3a and 3b is shown to pre-cool. An inlet valve 20 controls the inflow of air to a nitrogen separator 21. The nitrogen already present in the air is first separated from the remaining gases by means of the nitrogen separator 21, before it is led to a heat exchanger 22 and liquefied there. The heat exchanger 22 is thermally connected to a cold head 2b of the first stage of the cryocooler 2a, whereby it is cooled down to the required temperature. The liquefied nitrogen is then passed by means of a pump 23 through an outlet valve 24 , which serves to control the nitrogen liquefied in the heat exchanger 22, and conveyed into the dewar vessel 11. The valves 20, 24 allow the switching on and off of nitrogen liquefaction. If the valves 12, 13 for pre-cooling of the contact element 5a are opened or closed, then the valves 20, 24 are closed or opened. A cold head 2c of the second stage of the cryocooler 2a takes over the contacting of the contact element 5a analogous to the cold head 1 b in Fig. 2a, 2b ,

Figure 4 shows a further variant of the measuring module according to the invention, in which no moving mechanical parts needed within the vacuum range become. The heat flow between the cold head 1 b and the contact element 5 b is changed by the fact that between both elements, a connecting element 31 is installed, which is permanently in close thermal connection with the cold head 1 b and the contact element 5 b. The connecting element 31 has at least one cavity into which a well-conducting at cryogenic temperatures gas is pressed or pumped out again, whereby the heat flow between the cold head and the contact element is large resp. gets small.

If now the well-conducting gas at cryogenic temperatures (eg He) in the connecting element 31 or away, then increases or decreases, the thermal conductivity of the connecting element 31. When pressing in the gas is achieved in this way an increase in the heat flow between the contact element 5b and the cold head 1 b, so that the contact element 5b and with it also the measurement object 6 are cooled.

The connecting element 31 is connected via an inlet valve 33 to a gas pressure cylinder 37 and via an outlet valve 34 to a vacuum pump 32 . To cool the measuring object 6, the inlet valve 33 is opened, the outlet valve 34 is closed, and the connecting element 31 is filled with gas via the gas pressure cylinder 37. As a result, the thermal conductivity of the connecting element becomes large, and as a result, the contact element 5b and the measuring object 6 are cooled. When the measuring object 6 has reached the desired temperature, its temperature is controlled by the sensor 35 a and the heater 7.

For warming up the measurement object 6, the inlet valve 33 is closed and the outlet valve 34 is opened. Thereafter, the connecting element 31 is pumped empty with the vacuum pump 32, whereby the thermal conductivity of the connecting element 31 is again small, and the contact element 5 b can be reheated with the help of the heater 7 easily.

The inventive separation of the measuring chamber 4 and the cooling chamber 3 optimum isolation of the measuring chamber 4 from the cold head 1 b, 2c realized as soon as the cold head 1 b, 2c of the contact element 5a, 5b is moved away. The invention Measuring module 10a, 10b, 10c with the two-chamber system according to the invention has the advantage that the cryocooler 1a, 2a always remains cold during the cooling or warming up of the measurement object 6. As a result, the cooling rates for the measurement object 6 become shorter, because the cryocooler 1 a, 2 a does not have to be cooled down anew, and, moreover, an unnecessary thermal load of the cryocooler 1 a, 2 a is avoided. The measuring module according to the invention and thus also the measuring device according to the invention has a high flexibility, since the contact element 5a, 5b can be easily adapted or changed depending on the application.

References

1. [1] Patent EP 0 878 718 A1 : NMR measuring device with cooled measuring head
2. [2] http://www.lakeshore.com/desertcryo/custom/index.html
3. [3] JB Johnson, Thermal agitation of electricity in conductors, Phys. Rev., vol.32, pp. 97-109, 1928
4. [4] H. Nyquist, Thermal agitation of electricity in conductors, Phys. Rev., vol.32, pp.110-113, 1928

LIST OF REFERENCE NUMBERS

1a

single-stage cryocooler

1b

Cold head of the single-stage cryocooler

2a

Two-stage cryocooler

2 B

Cold head of the first stage of the two-stage cryocooler

2c

Cold stage of the second stage of the two-stage cryocooler

3

cooling chamber

4

measuring chamber

4 '

Chamber (prior art)

5a

Contact element with heat exchanger

5b

contact element

5 '

Contact element (prior art)

5 '

Contact element (prior art)

6

measurement object

7

stoker

8th

drive

9a

first contact surface of the contact element

9b

second contact surface of the contact element

10a

measurement module

10b

measurement module

10c

measurement module

10d

measurement module

10 '

Measuring module (prior art)

10 "

Measuring module (prior art)

11

Dewar

12

Inlet valve for pre-cooling

13

Exhaust valve for pre-cooling

20

Inlet valve for nitrogen liquefaction

21

nitrogen separator

22

Heat exchanger for nitrogen liquefaction

23

pump

24

Exhaust valve for the liquid nitrogen

31

connecting element

32

Vacuum pump

33

intake valve

34

Exhaust valve.

35a

Temperature Sensor

36

controller

37

Gas bottle

Claims (8)

Measuring module for measuring and testing a measuring object (6) with an evacuable measuring chamber (4) for receiving the measuring object (6), with a contact element (5a, 5b), wherein the measuring object (6) during the measuring and / or testing process with a first contact surface (9a) of the contact element (5a, 5b) is thermally connected, and having at least one cold head (1b, 2b, 2c) which can be thermally connected to a second contact surface (9b) of the contact element (5a, 5b),
wherein the cold head (1b, 2b, 2c) can be cooled down to cryogenic temperatures by means of a cryocooler (1a, 2a) consisting of at least one cold stage,
wherein the contact element (5a, 5b) consists of thermally highly conductive material, and the first and second contact surface (9a, 9b) lie on opposite sides of the contact element (5a, 5b), and
wherein the cold head and the contact element (5a, 5b) are in an evacuable environment during the measuring and / or testing process and are connected to one another in a thermally conductive manner,
thereby countersigned,
that the cryocooler (1a, 2a) together with the cold head is accommodated in a cooling chamber (3), which is spatially separated from the measuring chamber (4) and can be evacuated independently of it,
the contact element (5a, 5b) is thermally insulated from the outer wall of the measuring module, is part of a partition wall between the measuring chamber (4) and the cooling chamber (3) and establishes a local thermal connection from the measuring chamber (4) to the cooling chamber (3) , and
a contacting device is provided for changing the heat flow in the hermetically closed state of the measuring module, with the aid of which the heat flow between the cold head (1b, 2b, 2c) and the contact element (5a, 5b) is either produced or greatly enlarged, or interrupted or greatly reduced can be. Measuring module according to claim 1, characterized in that the contacting device comprises a pneumatic, hydraulic or electric drive (8), or a combination thereof, or a manual drive, with which the cold head (1b, 2b, 2c) and the contact element (5a, 5b ) can be moved towards or away from each other mechanically, wherein the cold head (1b, 2b, 2c) and the contact element (5a, 5b) either pressed against each other or spatially separated, so that the heat flow between them is increased or decreased. Measuring module according to claim 1, characterized
that the contacting device comprises a connecting element (31) which is arranged between cold head (1b) and contact element (5b) and is permanently in close thermal connection with the cold head (1b) and the contact element (5b), and
in that the connecting element (31) has at least one cavity which can be filled with a fluid which conducts well at cryogenic temperatures, whereby the thermal conductivity of the connecting element (31) and thereby also the heat flow between the cold head (1b) and the contact element (5b) can be changed. Measuring module according to one of the preceding claims, characterized in that the contact element (5a) comprises a heat exchanger, which is operated with a cryogenic fluid, in particular liquid nitrogen or liquid helium, and serves for precooling of the contact element. Measuring module according to one of the preceding claims, characterized in that at least one temperature sensor (35) and at least one heater (7) is provided, which serve to regulate the temperature of the contact element (5a, 5b). Measuring module according to one of the preceding claims, characterized in that the cryocooler (2a) has two stages, each with a cold head (2b, 2c), wherein the cold head (2b) of the first stage with a heat exchanger (22) for the liquefaction of nitrogen -Gas serves, is thermally connected. Measuring device with a measuring module according to claim 3, characterized
in that devices (23, 37) for supplying and pumping out a fluid which conducts well at cryogenic temperatures are provided in or out of the cavity of the connecting element (31), whereby the heat flow between the cold head (1b) and the contact element (5b) can be increased or decreased. Measuring device with a measuring module according to claim 6 and 3, characterized in that the first stage of the cryocooler (2a) via the heat exchanger (22) is connected to a nitrogen separator (21) through which the nitrogen gas obtained directly from the air and the Heat exchanger (22) can be supplied.

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