Circuit arrangement for connecting a protective conductor to at least two liquid-carrying lines and method for testing a protective conductor connection

Abstract

Circuit arrangement for connecting protective conductors to at least two liquid-carrying lines (11, 12), wherein the circuit arrangement has a plurality of protective devices for electrical contacting, which are designed such that with each protective device for electrical contacting an electrical connection to a liquid in the line (11, 12) can be established, characterized in that each liquid-carrying line (11, 12) is assigned at least two protective devices (16A, 16B; 17A, 17B) for electrical contact, and the at least two protective devices (16A, 16B) for electrically contacting a liquid-carrying line (11) are each electrically connected to another protective device (17A, 17B) for electrically contacting another liquid-carrying line (12).

Description

[0001] The invention relates to a circuit arrangement for connecting the protective conductor to at least two fluid-conducting lines, in particular to at least two fluid-conducting lines that extend from the interior of a housing of a medical device, in particular the housing of a blood treatment device, to the outside. Furthermore, the invention relates to a medical device with a housing and at least two fluid-conducting lines and to such a circuit arrangement, as well as to a method for checking the protective conductor connection to at least two fluid-conducting lines that extend from the interior of a housing of a medical device, in particular the housing of a blood treatment device, to the outside.

[0002] Medical devices, especially blood treatment devices, require special electrical protection measures to comply with electrical safety regulations. For power supply, medical devices are equipped with a power supply unit with a central protective conductor connection, which is connected to the protective conductor system of the fixed electrical installation, which is at earth potential. The safety inspection (STK) of medical devices includes testing the electrical resistance of the protective conductor connection.

[0003] One protective measure for complying with electrical safety regulations (IEC 60601-1) in dialysis machines is the attachment of an electrical protective device to the fluid-carrying lines of the fluid section, in order to establish an electrical connection to the fluids contained in the fluid lines. This protective device can be designed as a tubular body made of an electrically conductive material to which the fluid line is connected. The tubular body, also referred to as a grommet, is connected to a protective conductor or equipotential bonding via a connecting line. The grommet can also be inserted into a recess in the housing to lead a fluid line out of the housing. In known dialysis machines, only a single such protective device is assigned to each fluid line for contacting.

[0004] Common blood treatment devices, especially dialysis machines, have an extracorporeal blood circuit and a dialysis fluid section or dialysis fluid circuit. The extracorporeal blood circuit comprises the blood chamber, and the dialysis fluid section comprises the dialysis fluid chamber of a dialyzer (filter), which is divided into two chambers by a semipermeable membrane. The dialyzer is generally a replaceable unit that is easily accessible and attached to the outside of the dialysis machine's housing.

[0005] Dialysis machines can be equipped with a device for producing dialysis fluid from fresh water and concentrates, located within the housing. Fresh dialysis fluid is supplied to the dialysis fluid chamber from the device for producing dialysis fluid via a dialysis fluid supply line, and used dialysis fluid is removed from the dialysis fluid chamber via a dialysis fluid discharge line. Since the dialyzer is not located within the housing of the dialysis machine, the dialysis fluid lines must be routed from the inside of the housing to the outside.

[0006] DE 10 2013 107 323 A1 describes an extracorporeal blood treatment device comprising a line leading to a dialyzer for supplying dialysate, a line leading from a dialyzer for discharging dialysate, and a substituate line for supplying substituate to the extracorporeal blood circuit. The extracorporeal blood treatment device has a potential equalization device in each of the dialysis fluid supply line, the dialysis fluid discharge line, and the substituate line. The potential equalization devices comprise a sieve insert made of an electrically conductive material, completely enclosed in a sieve housing, to which a grounding cable is connected. The grounding cables of the potential equalization devices arranged in the fluid-carrying lines lead to a common ground point.

[0007] The invention is based on the object of specifying an improved protective conductor concept. In particular, the invention is based on the object of providing a circuit arrangement with which the electrical safety of medical devices, in particular dialysis machines, can be improved with relatively low technical effort. Furthermore, the invention is based on the object of creating a medical device with an improved protective conductor connection. Another object of the invention is to simplify the testing of the protective conductor connection and to provide a method that allows the testing of the protective conductor connection in a simple manner using the circuit arrangement according to the invention.

[0008] These objects are achieved according to the invention with the features of the independent patent claims. The dependent claims relate to advantageous embodiments of the invention.

[0009] The circuit arrangement according to the invention has a plurality of protective devices for electrical contacting, which are designed such that an electrical connection to a liquid in the line can be established with each protective device for electrical contacting. Such protective devices for electrical contacting can be designed, for example, as tubular bodies, to whose end pieces the liquid-carrying lines can be connected. The end pieces can be designed as connectors to which hose lines can be connected. For example, the hose lines can simply be pushed onto the end pieces. However, it is also possible for the end pieces to have plugs or sockets or other connectors. The protective devices can also be designed as a housing feedthrough.The electrical connection to the fluid in the fluid line can be established by the protective devices being made of an electrically conductive material, particularly metal. However, the protective devices can also be made of a non-electrically conductive material if they have electrically conductive inserts, particularly metal pieces, that are in contact with the fluid.

[0010] The circuit arrangement according to the invention is characterized in that each fluid-conducting line is assigned at least two protective devices for electrical contact. Consequently, two protective measures (MOP: "Means of Protection") are implemented for each fluid-conducting line. This improves electrical safety without requiring other measures, such as additional design measures to increase air or creepage distances and / or for improved electrical insulation. The overall safety for a patient connected to the fluid-conducting lines is increased because the lines are connected to a protective conductor or a protective potential using two independent measures.

[0011] The circuit arrangement according to the invention is further characterized in that the at least two protective devices for electrically contacting a liquid-conducting line are each electrically connected to another protective device for electrically contacting another liquid-conducting line. Consequently, one of the at least two protective devices for electrically contacting assigned to one liquid-conducting line is electrically connected to one of the at least two protective devices for electrically contacting assigned to the other liquid-conducting line, while another of the at least two protective devices for electrically contacting assigned to one liquid-conducting line is electrically connected to another of the at least two protective devices for electrically contacting assigned to the other liquid-conducting line.

[0012] The advantage of electrically connecting the protective devices assigned to the two fluid-carrying lines is that if the protective conductor connection of one fluid-carrying line fails, for example, due to a wire break, this line is still connected to the protective conductor or equipotential bonding via the protective conductor connection of the other fluid-carrying line. This increased redundancy leads to increased patient safety.

[0013] Further advantages of the circuit arrangement according to the invention become apparent when the fluid lines extend from the interior of the housing to the exterior, i.e., when they penetrate the housing wall. Then, of the at least two protective devices for electrical contacting associated with each fluid-conducting line, at least one protective device for electrical contacting is associated with a line section of the fluid-conducting line located inside the housing, and at least one protective device for electrical contacting is associated with a line section of the fluid-conducting line located at least partially outside the housing.A preferred embodiment provides that a protective device for electrically contacting a fluid-conducting line, which is assigned to the line section of one fluid-conducting line located inside the housing, is electrically connected to a protective device for electrically contacting another fluid-conducting line, which is assigned to the line section of the other fluid-conducting line located at least partially outside the housing. The protective devices assigned to the line section of the fluid-conducting line located inside the housing are each connected to a protective conductor or equipotential bonding via an electrical connecting line.

[0014] A line section lies at least partially outside the housing with respect to the position of its associated protective device if the protective device is located partly inside the housing and partly outside the housing. This is particularly the case if the protective device is mounted as a housing feedthrough in the housing wall and the electrical contact of the protective device is preferably made at the part of the protective device facing into the housing interior. In this embodiment, cable connections that penetrate the housing are avoided. A protective device designed as a housing feedthrough can be mounted electrically insulated from the housing, for example by means of circumferential insulators.

[0015] This protective conductor concept with a "crosswise" connection of the protective devices allows for a particularly simple inspection of all protective conductor connections of a liquid-conducting line using only resistance measurements, which can be carried out without opening the housing. This is because two independent measuring points are created on the externally accessible protective devices, which are assigned to the section of the liquid-conducting line located outside the housing. Furthermore, this protective conductor concept ensures that the lines are earthed even if one of the electrical connecting lines to the protective conductor or equipotential bonding is interrupted. Earthing is then established via the other connecting line. Thus, a single measurement can be used to determine whether all liquid-conducting lines are connected to the protective conductor via at least one protective device.

[0016] The method according to the invention for checking a protective conductor connection to at least two liquid-carrying lines that are led from the interior of a housing of a medical device to the outside, with the circuit arrangement according to the invention, provides that the electrical resistance between the protective devices for electrical contacting, which are assigned to the line sections of the liquid-carrying lines located outside the housing, and the protective conductor or potential equalization is measured.

[0017] In one embodiment, the housing of the medical device is made of an electrically conductive material, with the protective conductor or equipotential bonding being electrically connected to the housing. If the protective conductor or equipotential bonding is electrically connected to an electrically conductive housing, the electrical resistance between the external protective devices for electrical contact and the housing can be easily measured without having to open the housing, since all measuring points are accessible from the outside.

[0018] An alternative embodiment provides a housing for the medical device made of an electrically non-conductive material, with the protective conductor or potential equalization being electrically connected to an externally accessible electrical measuring contact point on the electrically non-conductive housing. In this embodiment, the electrical resistance between the external protective devices and the measuring contact point can be easily measured. Alternatively or additionally, the electrical resistance between the external protective devices and the protective contact in the power plug of the medical device can be measured.

[0019] The protective conductor or equipotential bonding can be connected to the protective conductor system of a fixed electrical installation.

[0020] The at least two fluid-carrying lines can be part of a fluid system of the medical device, also referred to as a hydraulic system. A medical fluid, in particular dialysate, can be located in the fluid-carrying lines. The medical device can have a first fluid-carrying line and a second fluid-carrying line, wherein the two fluid-carrying lines form a fluid circuit that can comprise a supply line and a return line. The fluid circuit can be created by connecting the ends of the fluid lines to one another. The connection can be made by means of a short-circuit piece or a dialyzer (filter). In a dialysis machine, the fluid system can comprise the dialysis fluid supply line leading to the dialyzer (filter) and the dialysis fluid discharge line leading from the dialyzer (filter).

[0021] In the following, several embodiments of the invention are described in detail with reference to the drawings.

[0022] They show: Fig. 1 shows a part of the housing of a dialysis machine with the circuit arrangement according to the invention in a highly simplified schematic representation, Fig. 2 a protective device for contacting in an enlarged view, Fig. 3 a section of the housing with a measuring contact point of an alternative embodiment of the circuit arrangement according to the invention, Fig. 4 a schematic representation of a further embodiment of the circuit arrangement according to the invention, Fig. 5 shows a further embodiment of the circuit arrangement according to the invention, in which all protective devices are arranged inside the housing, Fig. 6 shows a further embodiment of the circuit arrangement according to the invention, in which all protective devices are arranged inside the housing, and Fig. 7 a protective device designed as a housing feedthrough in a schematic representation.

[0023] Fig. Figure 1 shows the components of a blood treatment device essential to the invention as an example of a medical device in a highly simplified schematic representation. In the present embodiment, the blood treatment device is a dialysis machine.

[0024] The dialysis machine has a housing 1 made of an electrically conductive material (metal housing). The housing 1 can consist of several housing parts 1A, 1B. In addition, the dialysis machine has a Fig. 1 comprises a dialyzer 2, shown only schematically, which is divided by a semipermeable membrane 3 into a blood chamber 4 and a dialysis fluid chamber 5. The dialyzer 2 can be attached to a holder 6 provided on the outside of the housing 1. A blood supply line 7 leads to the blood chamber 4 of the dialyzer 2, and a blood discharge line 8 branches off from the blood chamber 4. The blood chamber 4 and the blood supply and blood discharge lines 7, 8 form the extracorporeal blood circuit.

[0025] The dialysis machine has a dialysis fluid circuit 9, which includes a device 10 for producing dialysis fluid from fresh water and concentrates. A dialysis fluid supply line 11 leads from the device 10 for producing dialysis fluid to an inlet of the dialysis fluid chamber 5, and a dialysis fluid discharge line 12 leads from an outlet of the dialysis fluid chamber 5 to this device 10 or an outlet.

[0026] The dialysis fluid supply line 11 and the dialysis fluid discharge line 12 penetrate the wall of the housing 1 and each have a line section 11A or 12A located inside the housing, which is referred to below as the inner line section, and a line section 11B or 12B located outside the housing, which is referred to below as the outer line section.

[0027] In addition, the dialysis machine has a power supply unit 14 which comprises a protective conductor or a potential equalization 15 which can be connected to the protective conductor system of a fixed electrical installation (not shown) via the protective contact of the mains plug of the dialysis machine.

[0028] The fluid system of the dialysis machine can include additional components, such as actuators or sensors.

[0029] All technical equipment of the dialysis machine requires special safety measures, which are described below.

[0030] The dialysis fluid supply line 11 is assigned two protective devices 16A, 16B for electrical contacting, which are designed such that each protective device can establish an electrical connection to the fluid in the line 11, in particular to the dialysate flowing to the dialysis fluid chamber 5 of the dialyzer 2. One inner protective device 16A is arranged on the inner line section 11A, while the other outer protective device 16B is arranged on the outer line section 11B. The dialysis fluid discharge line 12 is also assigned two protective devices 17A, 17B for electrical contacting in order to establish an electrical connection to the fluid in the line 12, in particular to the dialysate flowing from the dialysis fluid chamber 5 of the dialyzer 2.One inner protective device 17A is again arranged on the inner line section 12A, while the other outer protective device 17B is arranged on the outer line section 12B. The dialysis fluid supply and discharge lines 11, 12 are flexible hose lines.

[0031] Fig. Figure 2 shows an enlarged view of one of the protective devices 16A, 16B or 17A, 17B (MOP: Means for Protection) for electrical contacting. The protective device (MOP) has a tubular body 18 made of an electrically conductive material. For example, the protective device can be designed as a metal grommet. The two end pieces 19, 20 of the tubular body 18 each have a circumferential bead 19A, 20A. The respective ends of the dialysis fluid supply and discharge lines 11, 12 are pushed onto the end pieces 19, 20 of the tubular body 18. An electrical connection part 21 is provided on the tubular body 18, which serves to connect electrical lines in order to establish an electrical connection to the tubular body and the fluid flowing through the tubular body, in particular the dialysate.Instead of just one connector to which multiple lines can be connected, the tubular body can also be provided with multiple connectors, each of which can be connected to one or more lines. Fig. 1 shows the connection of the connecting cables to a protective device with only one connecting part.

[0032] The two inner and outer protective devices 16A, 16B and 17A, 17B of the dialysis fluid supply and discharge lines 11, 12 are interconnected as follows. The inner protective device 16A or 17A of one fluid line 11 or 12 is electrically connected to the outer protective device 16B or 17B of at least one other fluid line 11 or 12. In the present embodiment, the inner protective device 16A of the dialysis fluid supply line 11 is electrically connected to the outer protective device 17B of the dialysis fluid discharge line 12 via a connecting line 22, while the inner protective device 17A of the dialysis fluid discharge line 12 is electrically connected to the outer protective device 16B of the dialysis fluid supply line 11 via a connecting line 23.Furthermore, the internal protective device 16A of the dialysis fluid supply line 11 is connected to the protective conductor or equipotential bonding 15 via a connecting line 24, while the internal protective device 17A of the dialysis fluid discharge line 12 is connected to the protective conductor or equipotential bonding 15 via a connecting line 25. Consequently, the protective devices 16A, 16B and 17A, 17B assigned to the individual fluid lines 11, 12 are independently connected to earth with low resistance. The respective connecting lines 22, 23, 24, 25 are connected to the connection parts 21 of the protective devices. However, the protective devices 16A, 17A can also each have two separate connection parts for connecting the respective lines 22 and 24 or 23 and 25.

[0033] Earthing of both the dialysis fluid supply line 11 and the dialysis fluid discharge line 12 is ensured even if one of the two lines 24 or 25 is interrupted between the internal protective devices 16A or 17A and the protective conductor or equipotential bonding 15.

[0034] The protective conductor or potential equalization 15 is connected via a further connecting line 26 to the housing 1, which in the present example consists of an electrically conductive material ( Fig. 1). If the housing 1 is not made of an electrically conductive material, for example, a plastic housing, the housing has an externally accessible measuring contact point 27, which is connected to the protective conductor or potential equalization 15 via a connecting line 40. Fig. 3 shows this measuring contact point 27 in a schematic representation.

[0035] A PE conductor on a metallic part, in this case a metal grommet through which a conductive fluid, particularly dialysate, flows, is considered a single protective measure (MOP) according to the IEC 60601-1 standard. The additional independent PE conductor on the same part, if mechanically attached independently to this part, represents a further protective measure (MOP) according to this standard. The connection of two independent protective conductors primarily serves to improve electrical safety, particularly in the hydraulics area. One advantage of the safety concept is the simplified safety-related inspection (STK).

[0036] A method for testing a protective conductor connection using the circuit arrangement according to the invention is described below. For safety control (STK), a first measurement is taken of the resistance between the outer protective device 16B of the dialysis fluid supply line 11 and the housing 1 ( Fig. 1) or the measuring contact point 27 of the housing 1 ( Fig. 3) and with a second measurement, the resistance between the outer protective device 17B of the dialysis fluid discharge line 12 and the housing 1 or the measuring contact point 27 of the housing 1 is measured. In Fig. 1, the independent measuring points on the protective devices are designated by reference numerals 28, 29. The safety check can be performed using the measuring instruments commonly used in the field. Since all measuring points 28, 29 are accessible from the outside, the housing does not need to be opened. A resistance measurement between measuring points 28, 29 allows the wiring to be checked. If the resistance between measuring points 28, 29 is high, it can be concluded that one of the lines 22, 23, 24, 25 is open. An additional measurement of the electrical resistance between measuring points 28 or 29 and the protective contact in the power plug of the dialysis machine can be used to determine whether a proper connection to the protective conductor system of the electrical installation can be established.

[0037] Fig. 4 shows a schematic representation of a further embodiment of the circuit arrangement, which differs from that described with reference to the Fig. 1 to 3 differs in the connection of the individual protective devices. The corresponding parts are provided with the same reference numerals. In the alternative embodiment, the inner protective device 16A of one liquid-conducting line 11A is connected via a connecting line 22' to the inner protective device 17A of the other liquid-conducting line 12A, while the outer protective device 16B of one liquid-conducting line 11A is connected via a connecting line 23' to the outer protective device 17B of the other liquid-conducting line 12A. The inner protective devices 16A, 17A are connected via a connecting line 24 to a Fig. 4, which is connected to the protective conductor, while the outer protective devices 16B, 17B are electrically connected via a connecting line 25 to a second star point (not shown) which is connected to the protective conductor. Here too, in the event of a protective conductor failure, i.e. in the event of an interruption in one of the lines 24, 25 leading to one of the two independent star points connected to the protective conductor, the liquid-carrying lines are still earthed via the redundant star point connection. However, in this embodiment, not all measuring points are accessible from the outside. For this reason, a measuring point 30 is provided on the housing 1, which is electrically connected via a line 31 to the inner protective device 17A of the one liquid-carrying line 12A.In addition, a further measuring point 30' can be provided, which is electrically connected via a line 31' to the internal protective device 16A of the other liquid-carrying line 11A. The line 31' of the alternative or optional measuring point 30' is shown in dashed lines. By measuring the resistance between the two measuring points 30, 30', the resistance between the two internal protective devices 16A, 17A can be measured from the outside and a possible fault can be narrowed down. If, for example, the resistance between the two measuring points 30, 30' is low-ohm, the resistance between the measuring point 30 or 30' and the one in . Fig. 4, but the protective conductor (not shown) has a high resistance, this can be inferred from a fault in the electrical connection between the internal protective devices 16A, 17A and the protective conductor. A fault in the electrical connection between the internal protective devices 16A, 17A results in the resistance between one measuring point and the protective conductor being low-resistance and the resistance between the other measuring point and the protective conductor being high-resistance.

[0038] Fig. 5 shows a schematic representation of a further embodiment of the circuit arrangement, which differs from that described with reference to the Fig. 1 to 3 in that all protective devices 16A, 16B and 17A, 17B are arranged within the housing 1. The corresponding parts are again provided with the same reference numerals. In this embodiment, two measuring points 32', 33 are provided on the housing 1, which are electrically connected to the protective devices 16B, 17B of the two liquid-carrying lines 11A and 12A via lines 34', 35. In addition, two further measuring points 32, 33' can be provided, which are electrically connected to the protective devices 16A and 17A via lines 34, 35'. The lines 34, 35' of the optional measuring points 32, 33' are shown. By measuring the resistances between the measuring points 32, 33 and the protective conductor, it can be checked whether the earthing is correct.If four measuring points 32, 33 and 32', 33' are provided, the electrical resistance between the protective devices 17A and 16B or the protective devices 16A and 17B can also be measured, and a possible fault can be localized without opening the housing.

[0039] Fig. 6 shows a schematic representation of a further embodiment of the circuit arrangement, which differs from that described with reference to Fig. 4 in that all protective devices 16A, 16B and 17A, 17B are arranged within the housing 1. The corresponding parts are again provided with the same reference numerals. In this embodiment, two measuring points 36, 37 are provided on the housing 1, which are electrically connected via lines 38, 39 to the protective devices 17A, 17B of one of the two liquid-conducting lines 12A. In addition, two further measuring points 36', 37' can be provided, which are electrically connected via lines 38', 39' to the protective devices 16A, 16B of the other liquid-conducting line 11A. The lines 38', 39' of the alternative or optional measuring points 36', 37' are shown in dashed lines. The earthing can be checked with the measuring points connected to the outside using the resistance measurements described above.

[0040] Fig. Figure 7 shows a highly simplified schematic representation of a protective device designed as a housing bushing. This protective device 16B', 17B' can be one of the two protective devices 16B or 17B shown in the Fig. 1 to 6. In this embodiment, the housing 1 can be made of an electrically conductive material. If the protective device comprises a body made of an electrically conductive material through which liquid flows, this body is preferably electrically insulated from the electrically conductive housing.

[0041] In the embodiments described above, the individual measuring points can be designed like the measuring contact point, which is described with reference to Fig. 3 is described.

[0042] The inventive concept can also be used for inputs and outputs / interfaces of the extracorporeal blood circuit.

Claims

[1] Circuit arrangement for connecting protective conductors to at least two liquid-carrying lines (11, 12), wherein the circuit arrangement has a plurality of protective devices for electrical contacting, which are designed such that with each protective device for electrical contacting an electrical connection to a liquid in the line (11, 12) can be established, characterized by , that each liquid-carrying line (11, 12) is assigned at least two protective devices (16A, 16B; 17A, 17B) for electrical contact, and the at least two protective devices (16A, 16B;) for electrically contacting a liquid-carrying line (11) are each electrically connected to another protective device (17A, 17B) for electrically contacting another liquid-carrying line (12). [2] Circuit arrangement according to claim 1, characterized bythat of the at least two protective devices (16A, 16B; 17A, 17B) for electrical contacting, which are assigned to each liquid-conducting line (11, 12), at least one protective device for electrical contacting is assigned to a line section (11A, 12A) of the liquid-conducting line (11, 12) located inside the housing (1) of the medical device and at least one protective device for electrical contacting is assigned to a line section (11B, 12B) of the liquid-conducting line (11, 12) located at least partially outside the housing. [3] Circuit arrangement according to claim 2, characterized bythat a protective device (16A, 17A) for electrically contacting a liquid-conducting line (11, 12), which is assigned to the line section of the one liquid-conducting line located inside the housing, is electrically connected to a protective device (16B, 17B) for electrically contacting another liquid-conducting line (11, 12), which is assigned to the line section of the other liquid-conducting line located at least partially outside the housing. [4] Circuit arrangement according to claim 3, characterized by that the protective devices (16A, 17A) assigned to the line section of the liquid-carrying line located inside the housing are each connected to a protective conductor or a potential equalization (15) by means of an electrical connecting line (24, 25) for electrical contact. [5] Medical device with a housing and at least two liquid-carrying lines (11, 12), characterized by that the medical device has a circuit arrangement according to one of claims 1 to 4. [6] Medical device according to claim 5, characterized by that the at least two liquid-carrying lines (11, 12) are led from the interior of the housing to the outside. [7] Medical device according to claim 5 or 6, characterized by that the at least two liquid-carrying lines (11, 12) are part of a liquid system (9) of the medical device. [8] Medical device according to one of claims 5 to 7, characterized by that a medical liquid, in particular dialysate, is located in the at least two liquid-carrying lines (11, 12). [9] Medical device according to one of claims 5 to 8, characterized bythat the medical device has a first liquid-carrying line (11) and a second liquid-carrying line (12), wherein the two liquid-carrying lines form a liquid circuit (9). [10] Medical device according to one of claims 5 to 9, characterized by that the medical device is a blood treatment device, in particular a dialysis machine. [11] Medical device according to one of claims 5 to 10, characterized by that the housing (1) consists of an electrically conductive material, wherein the housing is electrically connected to the protective conductor or potential equalization (15). [12] Medical device according to one of claims 5 to 11, characterized by that the housing (1) consists of a non-electrically conductive material, wherein an externally accessible electrical measuring contact point (27) on the housing is electrically connected to the protective conductor or potential equalization (15). [13] Medical device according to one of claims 5 to 12, characterized by that the protective conductor or equipotential bonding (15) is connected to the protective conductor system of a fixed electrical installation. [14] Medical device according to one of claims 1 to 13, characterized by that at least one protective device (16A, 16B; 17A, 17B) is designed as a housing feedthrough. [15] Medical device according to claim 14, characterized by that the at least one protective device (16B', 17B') designed as a housing feedthrough is electrically insulated from a housing (1) made of an electrically conductive material. [16] Method for testing a protective conductor connection to at least two liquid-carrying lines (11, 12) which are led from the interior of a housing (1) of a medical device to the outside, with a circuit arrangement according to claim 3, characterized bythat the electrical resistance between the protective devices (16B, 17B) for electrical contacting, which are assigned to the line sections (11B, 12B) of the liquid-carrying lines located at least partially outside the housing, and the protective conductor or potential equalization (15) is measured. [17] Method according to claim 16, characterized by that the protective conductor or potential equalization (15) is electrically connected to a housing (1) made of an electrically conductive material, wherein the electrical resistance between the protective devices (16B, 17B) for electrical contacting, which are assigned to the line sections (11B, 12B) of the liquid-conducting lines (11, 12) lying at least partially outside the housing, and the housing (1) is measured. [18] Method according to claim 16, characterized bythat the protective conductor or potential equalization (15) is electrically connected to an externally accessible electrical measuring contact point (27) on a housing (1) made of an electrically non-conductive material, wherein the electrical resistance between the protective devices (16B, 17B) for electrical contacting, which are assigned to the line sections (11B, 12B) of the liquid-conducting lines (11, 12) lying at least partially outside the housing, and the measuring contact point (27) is measured.

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