Method for checking the suitability of an electrical circuit for operation in a potentially explosive environment, production method, and electrical circuit

Abstract

The invention relates to a method for checking the suitability of an electrical circuit (28) for operation in a potentially explosive environment, comprising the steps of: ascertaining at least two individual parameters (L, C) of the circuit (28), each of which correlates with another member of a group comprising electrical inductance, electrical capacitance and electrical resistance; determining a coupling parameter on the basis of the at least two electrical individual parameters (L, C); and verifying the suitability of the circuit (28) for operation in the potentially explosive environment on the basis of the coupling parameter. The invention also relates to a method for producing an electrical circuit (28), comprising the step of checking the electrical circuit (28) in this way. The invention also relates to an electrical circuit (28) which is checked and / or produced according to a method of this kind.

Description

[0001] Method for checking the suitability of an electrical circuit for operation in a potentially explosive atmosphere, manufacturing process and electrical circuit

[0002] The content of the German patent application DE 10 2023 206 910.5 is incorporated herein by reference.

[0003] The invention relates to a method for testing the suitability of an electrical circuit for operation in a potentially explosive environment. Furthermore, the invention relates to a method for manufacturing an electrical circuit. The invention also relates to an electrical circuit.

[0004] To verify the suitability of an electrical circuit for operation in a potentially explosive environment, it is common practice to conduct an experimental spark test. This requires the fabrication of a test sample of the electrical circuit. Fabricating the electrical circuit and conducting the spark test are time-consuming and costly.

[0005] It is an object of the invention to provide an improved method for checking the suitability of an electrical circuit for operation in an explosive environment, which method can be carried out in a particularly time-efficient and economical manner.

[0006] This object is achieved by a method having the features of claim 1. It has been recognized that the suitability of an electrical circuit for operation in a potentially explosive environment can be checked particularly time-efficiently and economically if the suitability is verified using a coupling characteristic value which is determined using at least two individual characteristic values ​​of the circuit, each of which correlates with another member of a group comprising an electrical inductance, an electrical capacitance, and an electrical resistance. The method can preferably be carried out largely, in particular completely, without experimental testing. In particular, production of the circuit for an experimental spark test can be partially, in particular completely, dispensed with.By using at least two individual parameters to determine the coupling parameter, electrical, particularly electromagnetic, and / or energetic coupling effects between these individual parameters describing the circuit can be taken into account. This makes the test result particularly reliable. An electrical circuit tested using this method is particularly safe in operation. Since experimental testing can be largely, and in particular completely, dispensed with, the test is time-efficient and cost-effective. Circuits tested using this method can be manufactured accordingly cost-effectively.

[0007] The at least two individual characteristic values ​​can relate to, in particular correspond to, at least one part, in particular one section and / or one component and / or one structural unit, of the circuit, in particular of the entire circuit, in particular its property, in particular its electrical property.

[0008] In particular, the method ensures the verification of the suitability of a mixed circuit for operation in a potentially explosive environment, wherein the circuit comprises at least two of the following circuit components: a current and / or voltage source, in particular with an internal resistance, a capacitor, or a coil. The source can be of any type that can preferably be described mathematically precisely. The method preferably considers all circuit components of a circuit, in particular how they are electrically connected to one another in the circuit and / or the number of these components.

[0009] Fundamentally, three ignition types can be distinguished that can lead to the ignition of a potentially explosive environment: ohmic ignition, capacitive ignition, which occurs due to energy stored in a capacitance that leads to an ignition spark, and inductive ignition, which occurs due to energy stored in an inductance that leads to an ignition spark. The term "ignition types" primarily refers to spark ignition types, i.e., those ignition types whose ignition effect is based on an ignition spark.

[0010] Preferably, the coupling characteristic is determined as the most unfavorable energetic state of the circuit with respect to one of the aforementioned ignition types. In particular, a corresponding coupling characteristic can be determined for each of the aforementioned ignition types. Based on the at least one coupling characteristic thus determined, the suitability of the circuit for operation in the potentially explosive environment can then be verified using the known ignition limit values, in particular ignition limit curves, for these ignition types.

[0011] Particularly preferably, the coupling characteristic is determined based on a temporal profile of the characteristic variable relevant to the respective ignition type, in particular the capacitively or inductively stored energy. In an oscillating circuit formed by the circuit, excitation and / or damping effects can be taken into account. The coupling characteristic is preferably determined as the maximum, in particular the absolute value, of the temporal profile of this relevant variable. Thus, the most unfavorable energetic state of the circuit over time can be determined during suitability verification.

[0012] The determination of the at least one coupling characteristic value can be carried out analytically, in particular purely analytically, and / or numerically, in particular by means of numerical simulation of the circuit.

[0013] According to a further aspect, the verification of suitability is carried out taking into account the dependence of the generation of an ignitable spark on the temporal course of the coupling characteristic value, in particular the ignition energy, in particular the ignition current and / or the ignition voltage.

[0014] If none of the coupling parameters exceeds the permissible limit for the respective ignition type, the circuit is considered intrinsically safe. By verifying the suitability of the circuit for use in the potentially explosive atmosphere based on at least one coupling parameter, the unsuitability of a circuit, which only arises due to overlapping effects, can be reliably identified. On the other hand, unnecessarily high safety factors can be avoided due to improved predictability of the ignition behavior. Correlating values ​​​​are understood to mean that they are interdependent, in particular that they have a known, in particular mathematically describable, relationship to one another, in particular that they are linearly dependent on one another, in particular that they correspond to one another.

[0015] According to one aspect of the invention, at least one of the individual characteristic values ​​can correspond to an electrical inductance of the circuit, in particular of an individual component arranged in the circuit and / or a structural unit with at least two inductive components. The electrical inductance can be embodied as an inductive component in the circuit, for example in the form of a coil, in particular a primary coil for establishing an inductive energy and / or signal connection with a secondary coil. The energy stored in an electrical inductance can cause an ignition spark to be prevented, in particular if a conductor connected to it has a line break.

[0016] Signals can, in principle, contain a non-negligible amount of energy. Signals can be used to transmit analog and digital information, for example, enabling data transmission.

[0017] According to a further aspect of the invention, at least one of the individual characteristic values ​​can correspond to an electrical capacitance of the circuit, in particular of an individual component arranged in the circuit and / or a structural unit with at least two capacitive components. An ignition spark to be prevented can arise due to the electrical energy stored in the electrical capacitance, for example, if a short circuit occurs between the conductors connected to the capacitive component and / or the capacitive structural unit. The coupling characteristic value is preferably determined based on the electrical inductance of the circuit and the electrical capacitance of the circuit. The coupling characteristic value can, in particular additionally, be determined based on the electrical resistance.

[0018] According to a further aspect of the invention, at least one of the individual electrical characteristics correlates with a total electrical value of at least one section, in particular a component, of the circuit, in particular of the entire electrical circuit. The total electrical value of the entire circuit is understood to mean, for example, the total inductance and / or the total capacitance and / or the total electrical resistance of the circuit, in particular between an operating voltage contact and a ground contact of the circuit.

[0019] According to a further aspect of the invention, determining the coupling characteristic value comprises determining the electrical energy stored in the circuit. Storable electrical energy is preferably understood to be the electrical energy that is stored, in particular maximally, in the circuit during intended operation, in particular with the predetermined operating voltage, in an inductance and / or in a capacitance. Electrical energy is stored in the inductance in the form of a magnetic field. The inductance converts the energy stored in the magnetic field by means of its windings, inducing an induction voltage and changing the magnetic field over time.The electrical energy can be calculated, for example, based on the electrical inductance, in particular the current flowing through the inductance, and / or based on the electrical capacitance, in particular the voltage applied to the capacitance. The at least one coupling characteristic of the component, in particular the assembly, in particular the circuit, can be determined theoretically, in particular based on data sheets, and / or experimentally, in particular by measurements.

[0020] According to a further aspect of the invention, when determining the coupling coefficient, it is taken into account that the electrical energy that can be stored inductively and / or capacitively in the circuit is inconvertible into the other energy form, in particular in the event of a fault, in particular is completely inconvertible into one of the possible energy forms. A corresponding conversion can take place in the electrical circuit, in particular by having an electrical resonant circuit in which the electrical energy is cyclically exchanged between an inductance and a capacitance. Preferably, the coupling coefficient is determined in such a way that it takes into account the total electrical energy that can be stored in the circuit, in particular inductively and capacitively.Preferably, both variants are considered during testing: that the entire stored energy is present as inductive energy and / or as capacitive energy. In particular, the more critical case for explosion protection is tested. By allocating the entire electrical energy storable in the circuit to the inductance and / or capacitance, a particularly critical condition is tested. An electrical circuit tested in this way is particularly reliable and safe in operation.

[0021] The electrical circuit preferably comprises at least one, in particular at least two, electrical energy storage devices, in particular at least one inductor and / or at least one capacitor. The electrical circuit can comprise exclusively electrical energy storage devices, in particular free energy storage devices of a different type, for example electrochemical energy storage devices, in particular accumulators, or energy storage devices of a different type, such as electrochemical or chemical energy storage devices.

[0022] According to a further aspect of the invention, verifying the suitability of the circuit for operation in the potentially explosive environment comprises comparing the coupling characteristic with a coupling limit. The coupling limit can be a maximum voltage, in particular for a given capacitance, and / or a maximum current, in particular for a given inductance. The coupling limit preferably corresponds to a maximum energy storable in the circuit, in particular during intended use, at which the circuit can still be considered suitable for operation in a potentially explosive environment. For example, the coupling limit corresponds to the sum of the energies stored in the inductances and capacitances of the circuit.The coupling limit value can, for example, be a maximum of 10 pJ, in particular a maximum of 40 pJ, in particular a maximum of 60 pJ, in particular a maximum of 100 pJ, in particular a maximum of 200 pJ, in particular a maximum of 1 mJ, in particular a maximum of 100 mJ, in particular a maximum of 500 mJ, and / or at least 10 pJ, in particular at least 20 pJ, in particular at least 50 pJ.

[0023] The energies stored in the inductances and capacitances of the circuit are also referred to below as the inductive and capacitive energies stored in the circuit. In such an energy analysis, the inductances and capacitances of parasitic components are preferably also taken into account, i.e., in particular, the inductive and capacitive components of, in particular, all, components and / or conductors or lines and / or a circuit board.

[0024] According to one aspect of the invention, the suitability of the circuit for operation in the potentially explosive environment is verified taking into account a safety factor. The safety factor can be identical or different for the storable inductive and / or capacitive energy. The safety factor can be in a range from 1 to 10, in particular from 1.2 to 5, in particular from 1.5 to 3.

[0025] According to a further aspect of the invention, the coupling limit is a predetermined limit for an individual characteristic value. The limit for the individual characteristic value can be taken, for example, from a design specification, in particular a design standard, in particular the European standard EN 60079-11. Alternatively, the limit can be determined experimentally. The permissible limit for the respective ignition type can also be derived, in particular implicitly and / or explicitly, using software. By determining the coupling characteristic value based on the at least two individual characteristic values ​​and comparing this with a predetermined limit for an individual characteristic value, the suitability of the circuit for the potentially explosive environment can be ensured in a particularly reliable manner.For example, the coupling limit corresponds to a maximum permissible storable inductive energy, with the coupling characteristic corresponding to the total energy storable in the circuit, in particular the sum of the inductive energy and the capacitive energy. A further object of the invention is to provide an improved method for manufacturing an electrical circuit for operation in a potentially explosive environment, which method can be implemented particularly time-efficiently and economically.

[0026] This object is achieved by a method comprising the steps of creating a circuit design, determining a test result by checking the suitability of the circuit design for operation in a potentially explosive environment according to the above description, and releasing or not releasing the circuit design depending on the test result. The advantages of the manufacturing method preferably correspond to the advantages described above in connection with the verification method. The method can be further developed by at least one of the features described above in connection with the verification method.

[0027] According to one aspect of the invention, the circuit according to the circuit design is released for production, in particular manufactured, if the review, in particular the verification, shows that the circuit according to the circuit design is suitable for operation in the potentially explosive environment.

[0028] If the review, in particular the verification, reveals that the circuit according to the circuit design is not suitable for operation in the potentially explosive environment, the circuit design is preferably supplemented with an ignition suppression means. The ignition suppression means can be designed to prevent an ignition effect in the event of a fault, in particular in the circuit and / or in a line connected to the circuit. According to one aspect of the invention, the ignition suppression means comprises at least one, in particular at least two, in particular at least three, in particular at least five, and / or a maximum of 15, in particular a maximum of 12, in particular a maximum of 10, in particular a maximum of five, in particular a maximum of two, diodes, in particular rectifier diodes, in particular Schottky diodes, and / or Zener diodes, and / or electrical resistors.The at least one diode is preferably designed to limit a voltage in the circuit and / or in a line connected to the circuit to a predetermined limit voltage.

[0029] According to a further aspect of the invention, the circuit is a component of a plug-in connection part and / or a counter-plug-in connection part for the inductive transmission of energy and / or signals, in particular for a measuring device.

[0030] According to a further aspect of the invention, the circuit of the connector part comprises a primary coil for inductive coupling with a secondary coil. The secondary coil can be a component of the mating connector part. A sensor is preferably connected to the mating connector part in a signal-transmitting, in particular energy-transmitting and / or data-transmitting, and / or mechanical, in particular flexibly and / or rigidly, manner.

[0031] It is a further object of the invention to provide an improved electrical circuit for operation in a potentially explosive environment, which is particularly safe in operation and economical to manufacture. This object is achieved by an electrical circuit that is tested according to a method as described above and / or manufactured according to a method as described above. The advantages of the circuit preferably correspond to the advantages described above in connection with the testing method and / or the manufacturing method. The method can be further developed by at least one of the features described above in connection with the testing method and / or the manufacturing method.

[0032] The electrical circuit is preferably a component of a measuring system with at least one sensor and / or a signal processing device and / or a connection device for the inductive transmission of energy and / or signals, in particular a plug-in connection part, preferably comprising the primary coil, and / or a mating plug-in connection part, preferably comprising the secondary coil for the inductive exchange of energy and / or signals with the primary coil.

[0033] Further features, details, and advantages of the invention will become apparent from the following description of several embodiments with reference to the figures. They show:

[0034] Fig. 1 A perspective, partially sectioned view of a measuring system with a connection device for the inductive transmission of energy and / or signals, comprising a plug connection part with an ignition suppression means for preventing an ignition effect in the event of a fault and a counter-plug connection part, Fig. 2 a schematic view of the connection device in Fig. 1 with the plug connection part and the counter-plug connection part,

[0035] Fig. 3 is a schematic diagram of the mating connector part in Fig. 1 with a sensor circuit connection for forming a signal connection with a sensor and a secondary coil for inductive coupling with the connector part, in particular a primary coil of the connector part,

[0036] Fig. 4 a schematic diagram of the connector part in the

[0037] Fig. 1, wherein the ignition suppression means comprises two diodes, in particular two Schottky diodes, and a resistor, which are contacted in the electrical circuit between an amplifier device and a power conditioning device of the plug-in connection part,

[0038] Fig. 5 is a schematic diagram of a plug-in connection part according to a further embodiment, wherein the ignition suppression means comprises a single diode, in particular a Schottky diode and a resistor,

[0039] Fig. 6 is a schematic diagram of a signal processing device according to a further embodiment, comprising an ignition suppression means with a diode, in particular a Schottky diode, and a resistor, or

[0040] Fig. 7 is a schematic diagram of a signal processing device according to a further embodiment, comprising an ignition suppression means with two diodes, in particular a Schottky diode and a Zener diode, and a resistor.

[0041] A first embodiment of a measuring system 1 with a connection device 2 and a sensor 3 connected thereto is described with reference to Figs. 1 to 4.

[0042] Sensor 3 is designed as a pH sensor. Sensor 3 can alternatively or additionally be designed as a redox sensor, a conductivity sensor, an oxygen sensor, a temperature sensor, a pressure sensor, and / or a sensor for other process-related parameters. The sensor can have an optical, an inductive, and / or an electrode-based measuring device.

[0043] The connection device 2 comprises a plug-in connector part 4 and a mating plug-in connector part 5 that can be reversibly connected thereto. The sensor 3 is preferably rigidly connected to the mating plug-in connector part 5, in particular to a housing 6 of the mating plug-in connector part 5.

[0044] The housing 6 of the mating connector part 5 has a thread 7, in particular an external thread. The thread 7 is designed for fastening the mating connector part 5 to a measuring point. The thread 7 is designed in particular such that the mating connector part 5 can be attached to a measuring chamber wall such that the sensor 3 is arranged in the measuring chamber and the mating connector part 5 is arranged at least partially outside the measuring chamber. The measuring chamber wall is sealed by the mating connector part 5, in particular a sealing element, preferably in a fluid-tight, in particular gas-tight manner. The housing 6 of the mating connector part 5 has a tool engagement 8 for rotating the mating connector part 5, in particular for screwing the thread 7 to the measuring chamber wall.

[0045] The mating connector part 5 is described in further detail with reference to Figs. 1 to 3. The mating connector part 5 comprises an electrical secondary circuit 9, which is preferably formed at least partially, in particular predominantly, on a secondary circuit board 10. A secondary coil 11 is arranged in the secondary circuit 9. The secondary coil 11 is a component of an inductive coupling path for the transformer-based transmission of energy and / or signals.

[0046] The secondary coil 11 is wound on a secondary coil body 12, in particular a hollow cylindrical one. A central recess 13 of the secondary coil body 12 is cylindrical.

[0047] The secondary circuit 9 has a sensor circuit connection 14 for establishing a power and / or signal-transmitting connection with the sensor 3. The sensor circuit connection 14 is designed to supply the sensor 3 with power and to transmit sensor signals. For this purpose, the sensor circuit connection 14 comprises a plurality of, in particular at least three, in particular at least four, connection contacts, which are preferably connected to a corresponding mating connection contact of the sensor 3, in particular integrally connected, in particular soldered.

[0048] The secondary circuit 9 preferably further comprises at least one of the following devices: a secondary power conditioning device 15 for providing at least one supply voltage, in particular at least two supply voltages, and / or a secondary rectifier device 16 for rectifying an alternating voltage induced at the secondary coil 11 and / or a secondary communication device 17, in particular a modulator / demodulator module and / or a modem module, for exchanging energy and / or signals via the secondary coil 11 and / or a sensor communication device 18 for exchanging data with the sensor 3 and / or a sensor signal conditioning device 19, in particular with an analog-to-digital converter, for conditioning the sensor signals. The sensor communication device 18 can be a component of a digital module for processing digital data.

[0049] The mating connector part 5, in particular the secondary power conditioning device 15 and / or the secondary rectifier device 16, can have a secondary ignition suppression means 20.1, 20.2 for preventing an ignition effect in the event of a fault by limiting a maximum electrical power that can be transmitted to the secondary coil 11 and / or the sensor circuit connection 14.

[0050] For the mechanical connection of the plug-in connector part 4 with the mating plug-in connector part 5, these parts interact in the manner of a plug connection. A reversibly detachable closure means 5a, in particular a bayonet lock, prevents the plug connection from being released, particularly accidentally.

[0051] The measuring system 1 and the plug-in connection part 4 are described in further detail with reference to Figs. 1, 2 and 4. The plug-in connection part 4 has a housing 21. A cylindrical projection 22 is arranged on the housing 21 and is designed to engage in the cylindrical recess 13 of the mating plug-in connection part 5, in particular the housing 6 of the mating plug-in connection part 5. A primary coil 23 of the plug-in connection part 4 is arranged in the cylindrical projection 22 and is inductively coupled to the secondary coil 11 when the plug-in connection part 4 is in engagement with the mating plug-in connection part 5, in particular when the cylindrical projection 22 is in engagement with the recess 13.

[0052] A connecting cable 24 is provided on the plug-in connector 4. The connecting cable 24 preferably establishes a signal connection to a signal processing device 25 of the measuring system 1. The connecting cable 24 is preferably firmly connected, in particular not detachable without damage, to the housing 21 of the plug-in connector 4. In particular, the connecting cable 24 can be connected to the housing 21 in a fluid-tight, in particular gas-tight, manner.

[0053] The signal processing device 25 is preferably designed to supply the connection device 2, in particular the plug-in connection part 4 and / or the mating plug-in connection part 5 and / or the sensor 3, with electrical energy and / or signals, in particular via the connecting cable 24. The signal processing device 25 is designed to exchange data, in particular to receive sensor signals and / or to transmit control signals, with the plug-in connection part 4. The signal processing device 25 can have a user interface 26 for inputting and outputting information, in particular with a display means for displaying information, in particular the sensor signals, and / or a communication module 27, in particular a radio module, for the wired and / or wireless exchange of data, in particular with a control room and / or a central computing system.

[0054] The connector part 4 is designed for the inductive transmission of energy and / or signals, in particular electrical power and / or signals, in a potentially explosive environment. The connector part 4 has an electrical circuit 28 with a circuit connection 29. The primary coil 23 is arranged in the circuit 28. The connecting cable 24 contacts the circuit connection 29.

[0055] The circuit connection 29 comprises an operating voltage contact 29.1, a reference potential contact 29.2, a first signal line contact 29.3, and a second signal line contact 29.4. The reference potential contact 29.2 is also referred to as the ground contact, abbreviated GND. An operating voltage intended to supply power to the measuring system 1, in particular to the connecting device 2, in particular to the plug-in connector part 4, is applied between the operating voltage contact 29.1 and the reference potential contact 29.2. The operating voltage contact 29.1 and the reference potential contact 29.2 are also referred to as power supply contacts 29.1, 29.2. The plug connection part 4 comprises a power conditioning device 30 in the circuit 28. The power conditioning device 30 is connected, in particular directly connected, to the operating voltage contact 29.1 and the reference potential contact 29.2.The power conditioning device 30 can be designed to provide at least one, in particular at least two different, voltage levels.

[0056] The plug connection part 4 has a communication device 31, in particular a modulator-demodulator module and / or modem module, for exchanging energy and / or signals via the primary coil 23.

[0057] The plug connection part 4 can have a control device 32, in particular a digital module, in particular comprising an electronic processing unit. The control device 32 is designed to control the data transmission between the circuit connection 29 and the primary coil 23, in particular the communication device 31.

[0058] The plug connection part 4 has an amplifier device 33. The amplifier device 33 comprises an electrical resonant circuit 34. The resonant circuit 34 comprises the primary coil 23 and at least one capacitor 35.1, 35.2. Furthermore, the amplifier device 33 comprises a switch 36, in particular an electronic switch, in particular a transistor.

[0059] A supply inductance 37 is connected upstream of the resonant circuit 34. The supply inductance 37 is arranged along the electrical line between the power conditioning device 30 and the resonant circuit 34, in particular the switch 36, in particular is electrically contacted, in particular connected in series with them. The supply inductance 37 is designed such that the resonant circuit 34 is damped as little as possible by the supply inductance 37. For this purpose, the supply inductance 37 should be dimensioned as high as possible. However, in order to avoid efficiency losses as much as possible, the electrical resistance of the supply inductance 37 should also be reduced. Since the available installation space is limited, a preferred range results for the supply inductance 37 with regard to its electrical inductance, namely from 0.01 mH to 1 H, in particular from 0.1 mH to 100 mH, in particular from 1 mH to 10 mH, in particular from 3 mH to 7 mH.This applies in particular if a carrier signal frequency for switching the primary coil 23, which is generated in particular by means of the switch 36, lies in a range from 10 kHz to 10 MHz, in particular from 100 kHz to 1 MHz, in particular from 150 kHz to 400 kHz.

[0060] The switch 36 is in signal connection with the control device 32. The communication device 31 is in signal connection with the primary coil 23.

[0061] For voltage smoothing, a smoothing capacitor 38 can be connected to the circuit terminal 29, in particular to the operating voltage contact 29.1 and / or to the supply inductance 37, in particular on the side of the circuit terminal 29.

[0062] According to an alternative embodiment, the capacitor 38 may represent the total capacitance of the electrical circuit 28. According to this alternative, the capacitor 38 is not necessarily present in the form of a single component or at the position shown within the circuit 28.

[0063] The plug connection part 4 has an ignition suppression means 39 in the circuit 28 for preventing an ignition effect in the event of a fault by limiting a reaction of the electrical energy to the circuit terminal 29

[0064] The components of the circuit 28, in particular of the plug-in connection part 5, are preferably arranged at least partially, in particular predominantly, in particular completely, on at least one, in particular a single, primary circuit board 40. In particular, the ignition suppression means 39 and the amplifier device 33 are arranged on the primary circuit board 40.

[0065] The ignition suppression means 39 is preferably arranged between the operating voltage contact 29.1 and / or the reference potential contact 29.2, in particular in a parallel circuit to the amplifier device 33 and / or the current conditioning device 30.

[0066] The ignition suppression means 39 has an electrical resistor 41, which is arranged in particular in a series circuit between the current conditioning device 30 and the amplifier device 33.

[0067] The ignition suppression means 39 comprises two diodes 42.1, 42.2, in particular rectifier diodes, in particular Schottky diodes. These are arranged, in particular directly, between the circuit terminal 29, in particular the operating voltage contact 29.1, and / or the power conditioning device 30, and the amplifier device 33, on the one hand, in particular directly, in particular electrically contacted. Furthermore, they are electrically conductively connected, in particular directly, to the ground contact 29.2, in particular arranged in a parallel circuit with the amplifier device 33.

[0068] The ignition suppression means 39 configured in this way prevents the electrical energy stored in the circuit 28, in particular in the amplifier device 33, from having a reactive effect on the circuit terminal 29. In particular, the maximum voltage that can be generated between the power supply contacts 29.1, 29.2, in particular the maximum voltage that can be generated by the amplifier device 33, is limited. This prevents a voltage that could lead to an ignition spark from being reached at the circuit terminal 29.

[0069] The design of the ignition suppression means 39 with the resistor 41 limits the maximum electrical power that can be transmitted, particularly from the amplifier device 33, to the circuit terminal 29. The resistor 41 is optional.

[0070] The redundant design of diodes 42.1 and 42.2 is also optional. Multiple redundancy of diodes 42.1 and 42.2, particularly double redundancy and triple redundancy, ensures particularly high operational reliability.

[0071] The measuring system 1, in particular the connection device 2, in particular the plug connection part 4, advantageously ensure that an ignition effect is reliably prevented in the event of a fault, in particular in the event of a break in the connecting cable 24 or in the event of improper use.

[0072] The amplifier device 33 ensures signal transmission between the plug connection part 4 and the mating plug connection part 5 in a particularly reliable and robust manner. However, the resulting higher electrical energy that can be stored by the plug connection part 4 is potentially sufficient to provide an ignition effect, particularly in the connecting cable 24. The ignition suppression means 39 advantageously ensures that a reaction of the electrical energy stored in the plug connection part 5 to the circuit connection 29 is reliably prevented. The ignition suppression means 39 reliably prevents the energy required for spark ignition and / or thermal ignition from being released to the circuit connection 29, particularly to the connecting cable 24. The plug connection part 4 can be operated safely and reliably in potentially explosive environments.

[0073] The connecting cable 24 can be shielded. The connector part 4 and / or the mating connector part 5, in particular the circuit 28 and / or the secondary circuit 9, can be potted. In particular, the respective circuit 9, 28 can be potted in a fluid-tight, in particular gas-tight manner. The respective housing 6, 21 can be filled, in particular completely, with a potting compound. This particularly reliably prevents an ignition effect in the area of ​​the connector part 4 and / or the mating connector part 5. A method for testing the suitability of an electrical circuit 28 for operation in a potentially explosive environment is described below, in particular with reference to the circuit 28 of the connector part 4:

[0074] The suitability of the electrical circuit 28 for operation in a potentially explosive environment is preferably checked at least partially, in particular completely, on the basis of individual characteristic values ​​L, C of the circuit 28. This allows cost-intensive experimental tests, in particular in a spark test chamber, to be avoided to the greatest extent possible, in particular completely.

[0075] First, a design for an electrical circuit is created. The circuit design corresponds to circuit 28 without the ignition suppression means 39. A first individual characteristic value L of this circuit design is determined, which correlates with an electrical inductance, in particular, corresponds to the electrical inductance of the supply inductor 37. A second individual characteristic value C of the circuit is determined, which correlates with an electrical capacitance of the circuit, in particular, the smoothing capacitor 38, and in particular corresponds to this.

[0076] The first and / or the second individual characteristic value L, C can alternatively be assigned to an electrical total value L to t, Ctot of the entire circuit, in particular the circuit design. For example, the first individual characteristic value L can correspond to a total electrical inductance Ltot of the circuit. The second individual characteristic value C can correspond to a total electrical capacitance Ctot of the circuit. A coupling characteristic is determined based on the first and second individual characteristic values ​​L, C. For this purpose, the electrical energy storable in the circuit, in particular in the supply inductance 37 and / or in the smoothing capacitor 38, is determined. The electrical energy storable in an inductance, in particular in its magnetic field, can be determined using the following equation, taking into account the current I flowing through the inductance:

[0077] EL = 0.5 I 2 L.

[0078] The electrical energy stored in a capacitor can be determined by taking into account the voltage U across the capacitor using the following equation:

[0079] Ec = 0.5 U 2 C.

[0080] To determine the suitability of an electrical circuit 28 for operation in a potentially explosive environment, energy limit values ​​EL,S, Ec,s can be specified, particularly in conjunction with corresponding design specifications. In particular, an energy limit value EL,S for the inductively storable energy EL and an energy limit value Ec,s for the capacitively storable energy Ec can be different. The energy limit value EL,S for the maximum permissible inductively stored energy EL can be lower than the energy limit value Ec,s for the maximum permissible capacitive energy Ec stored in the circuit 28, or vice versa.The coupling characteristic, which depends on the two individual characteristic values ​​L, C, can be determined based on the quotient of the stored inductive energy EL and the corresponding permissible energy limit EL,S and / or based on the quotient of the stored capacitive energy Ec and the corresponding permissible energy limit Ec,s, in particular based on the sum, in particular based on the inverse of the sum, of these quotients. In other words, a safety factor can be determined by taking into account the distance between the stored energies EL, EC of both energy forms and the respective energy limit EL,S, Ec,s.

[0081] A particularly preferred embodiment for determining the coupling characteristic value is based on the assumption that the energy EL, EC stored in a specific energy form can be at least partially, in particular completely, converted into the other energy form. For example, the energy EL, EC stored in the electrical resonant circuit 34 can be present entirely as capacitive energy Ec, in particular in the capacitances 35.1, 35.2, or entirely as inductive energy, in particular in the primary coil 23, or can be distributed between an inductive and a capacitive energy form. The coupling characteristic value is preferably determined depending on whether the electrical energy EL, EC that can be stored inductively and / or capacitively in the circuit 28 can be converted into the other energy form.

[0082] The coupling characteristic can be determined based on the highest form of energy stored in the circuit, for example, the inductive energy EL or the capacitive energy Ec. Alternatively, the coupling characteristic can be determined based on the sum of the total electrical energy that can be stored in the circuit 28, in particular during normal operation of the circuit and / or in the event of a fault, in particular comprising the inductive energy EL and the capacitive energy Ec. The coupling characteristic determined in this way can be compared with the lowest of the energy limit values ​​EL,S and / or Ec,s in order to verify the suitability of the circuit 28 for operation in the potentially explosive environment.

[0083] In particular, a safety factor can be determined as the quotient of the energy limit value EL,S, Ec,s and the coupling characteristic, in particular the sum of the storable energies EL, EC. Preferably, the suitability of the circuit 28 for operation in the potentially explosive environment is verified as suitable, in particular as intrinsically safe, if the resulting safety factor is at least as large as a predetermined safety limit value. The safety limit value is preferably at least 1.5, in particular at least 2, in particular at least 2.5, in particular at least 3.

[0084] The safety limit can also be called the coupling limit.

[0085] The energy limit values ​​Eps and Ec,s disclosed in standard EN 60079-11 are particularly suitable for the individual inductive and capacitive energy forms, particularly for the corresponding individual characteristic values ​​L and C. For example, the inductive energy limit value EL,S is 40 pJ, especially for an inductance current of 0.3 A. The capacitive energy limit value Ec,s can be 158.6 pJ, especially for a capacitor voltage of 5.6 V.

[0086] The temporal progression of the different energy forms can be taken into account when determining the coupling characteristic, for example, using a numerical simulation of circuit 28 or using a differential equation describing circuit 28. For the fault case of a circuit with a capacitance C, an inductance L, and a resistance R connected in parallel to a voltage source, the following second-order differential equation can be formulated, where Io indicates the initial value of the current I(t) flowing through the inductance:

[0087] The coupling characteristic value can be determined as the maximum, in particular the amount, of the temporal course of the inductive energy EL,max(t), in particular taking into account the above differential equation:

[0088] EL,max(t) = 0.5 (Imax(t)) 2 L.

[0089] Since the circuit design according to the schematic diagram in Fig. 4 cannot be verified as intrinsically safe without the ignition suppression device 39, a corresponding circuit design would not be approved. The circuit design is therefore supplemented with the ignition suppression device 39. Due to the ignition suppression device 39, the circuit 28 is then intrinsically safe and suitable for operation in potentially explosive atmospheres.

[0090] The circuit 28 is manufactured according to the circuit design supplemented by the ignition suppression means 39. In particular, the connector part 4 is manufactured with the circuit 28. The operation of the measuring system 1, the connection device 2, the connector part 4, and the ignition suppression means 39 is as follows:

[0091] The plug-in connector part 4 is initially separated from the mating plug-in connector part 5. The thread 7 is screwed to the measuring chamber wall. The sensor 3 is designed as a pH sensor and is arranged in the measuring chamber, in particular at a measuring point. The mating plug-in connector part 5 is ready for reversible connection to the plug-in connector part 4.

[0092] For the inductive transmission of energy and / or signals between the plug-in connector part 4 and the mating plug-in connector part 5, these are plugged onto one another. The primary coil 23, in particular the cylindrical projection 22 of the housing 21 of the plug-in connector part 4, is inserted into the secondary coil 11, in particular into the recess 13 of the housing 6 of the mating plug-in connector part 5. The plug-in connection is locked by means of the locking means 5a. The plug-in connection forms a mechanical connection between the plug-in connector part 4 and the mating plug-in connector part 5. At the same time, the arrangement of the primary coil 23 in the secondary coil 11 establishes a connection for the inductive transmission of energy and / or signals.

[0093] The connection device 2, in particular the plug-in connector part 4, is supplied with electrical energy via the circuit connection 29, in particular via the operating voltage contact 29.1 and the reference potential contact 29.2. The electrical energy is preferably provided by the signal processing device 25 and conducted to the circuit connection 29 via the connecting cable 24. The signal processing device 25 is preferably designed to be intrinsically safe in the sense of explosion protection, in particular electrical ignition protection.

[0094] The plug connector part 4 has components that store electrical energy. The amplifier device 33, in particular the feed inductance 37 and the capacitors 35.1, 35.2, the primary coil 23, and the smoothing capacitor 38 act as electrical energy storage devices. The stored energy can exert an ignition effect in the event of a fault, which is particularly independent of the intrinsically safe design of the signal processing device 25. The potential ignition effect results in particular from the energy storage capacity of the amplifier device 33, in particular the feed inductance 37, which has a comparatively high electrical inductance for energy-efficient signal transmission.

[0095] To reliably prevent an ignition effect in the event of a fault, the magnitude of any potential reaction of the stored electrical energy to the circuit connection 29 is limited by means of the ignition suppression means 39. The ignition suppression means 39 prevents, in particular, an ignition effect, in particular an ignition spark, from occurring in the event of a break in the connecting cable 24 or if the connecting cable 24 is disconnected from a connection point, for example, to the signal processing device 25, in violation of operating instructions.

[0096] The ignition suppression means 39 ensures voltage limitation between two, preferably between all, of the contacts 29.1 to 29.4. This reliably prevents, in particular, an inductance, in particular the supply inductance 37, from causing a voltage sufficiently high for spark ignition at the circuit terminal 29, in particular between two contacts 29.1 to 29.4.

[0097] The pass band of the diodes 42.1, 42.2 can be in a range from 0 V to 10 V, in particular from 0.1 V to 5 V, in particular from 0.2 V to 2 V, in particular from 0.5 V to 1 V.

[0098] Resistor 41 limits the current, in particular a maximum short-circuit current, and thus the electrical power. By limiting the electrical power, the spark energy released into the explosive environment can be reduced to a permissible level, in particular to the extent that the occurrence of an ignition spark is reliably prevented. In particular, resistor 41 dissipates part of the stored energy as waste energy.

[0099] The plug connection part 4 formed with the ignition suppression means 39 ensures in particular that an ignition effect in the area of ​​the connecting cable 24 is avoided.

[0100] The ignition suppression is further promoted in that the connecting cable 24 has a shield, in particular electrical and / or magnetic, and / or in that the circuit 28 is enclosed with an encapsulation, in particular a potting, in particular a potting made of a non-electrically conductive material, in particular a plastic material.

[0101] A further embodiment of a circuit 28a, in particular of the plug-in connection part 4, is described with reference to Fig. 5. The circuit 28a is shown in a highly simplified manner in Fig. 5. The circuit 28a differs from the previously described embodiment in the design of the ignition suppression means 39a. The ignition suppression means 39a has the electrical resistor 41 and a single diode 42.1. Schematically shown in the circuit 28a is a fault switch 36a, which is intended to simulate the effect of a short circuit or a line break. In reality, the circuit 28a is designed without this fault switch 36a. By means of the fault switch 36a, a particularly unfavorable fault case with regard to spark ignition can be explained or symbolized, which occurs in particular when the line 24 is interrupted at exactly the position of the fault switch 36a.Furthermore, the design and functioning of the circuit 28, in particular of the plug connection part 4, can correspond to those of the circuit 28 described above.

[0102] A further embodiment of a signal processing device 25a, in particular an electrical circuit 43 of the signal processing device 25a, is described with reference to Fig. 6. The circuit 43 is shown in a highly simplified manner in Fig. 6. For intrinsically safe design with regard to explosion protection, the signal processing device 25a has an ignition suppression means 44. The ignition suppression means 44 comprises an electrical resistor 41 and a diode 42.1. The resistor is arranged, in particular connected in series, between a voltage source 46 and a circuit terminal 45, in particular an operating voltage contact 45.1, of the signal processing device 21. The diode 42.1 is connected in parallel to the circuit terminal 45, in particular to the operating voltage contact 45.1 and a ground contact 45.2.The circuit 43 comprises a smoothing capacitor 38a and further electrical and / or electronic components, in particular an inductance 23a and / or a resistor 41a. Furthermore, the design and operation of the measuring system 1, in particular the signal processing device 25a, can correspond to the embodiments described above.

[0103] A further embodiment of a circuit 47 is described with reference to Fig. 7. The circuit 47 can be a component of a measuring system 1, a connection device 2, a signal processing device 25, and / or any other electrical or electronic device that is particularly intended for operation in a potentially explosive environment.

[0104] The circuit 47 has an electrical resistor 41 and a diode 42.1 corresponding to the embodiment described above, in particular with reference to Fig. 6. In addition, a further diode 48, in particular a Zener diode, is arranged in the circuit 47. The Zener diode 48 is arranged in parallel with the circuit terminal 45, in particular with the operating voltage contact 45.1 and the ground contact 45.2, in particular with regard to the resistor 41 on the side of the voltage supply 46. Otherwise, the design and operation of the circuit 47, in particular of the ignition suppression means 49, can correspond to the operation of the embodiments described above.

[0105] A circuit 28, 28a, 43, 47 designed and verified according to the method described above is particularly robust and safe for operation in a potentially explosive environment. The same applies to a connection device 2 formed therewith, in particular a plug connection part 4 formed therewith, and / or a signal processing device 25 formed therewith, and / or any other electrical or electronic device formed therewith.

Claims

Patent claims 1. A method for checking the suitability of an electrical circuit (28, 28a, 43, 47) for operation in an explosive environment, comprising the steps: 1.1 Determining at least two individual nucleus values ​​(L, C) of the circuit (28, 28a, 43, 47), each correlating with another member of a group comprising an electrical inductance, an electrical capacitance and an electrical resistance, 1.2 Determining a coupling nucleus value based on at least two electrical individual nucleus values ​​(L, C), and 1.3 Verify the suitability of the circuit (28, 28a, 43, 47) for operation in the potentially explosive atmosphere using the coupling germ value.

2. Method according to claim 1, characterized in that one of the individual nucleus values ​​(L) corresponds to an electrical inductance of the circuit (28, 28a, 43, 47).

3. Method according to claim 1 or 2, characterized in that one of the individual nucleus values ​​(C) corresponds to an electrical capacitance of the circuit (28, 28a, 43, 47).

4. Method according to one of the preceding claims, characterized in that at least one of the electrical individual nucleus values ​​(L, C) is compared with an electrical total value (L to t, Ctot) of the entire circuit (28, 28a, 43, 47).

5. Method according to one of the preceding claims, characterized in that determining the coupling characteristic value comprises determining an electrical energy (EL, EC) that can be stored in the circuit (28, 28a, 43, 47).

6. Method according to claim 5, characterized in that when determining the coupling characteristic value, it is taken into account that the electrical energy (EL, EC) which can be stored inductively and / or capacitively in the circuit (28, 28a, 43, 47) can be converted into the other energy form.

7. Method according to one of the preceding claims, characterized in that verifying the suitability of the circuit (28, 28a, 43, 47) for operation in the potentially explosive environment comprises comparing the coupling characteristic value with a coupling limit value (EL.S, Ec.s).

8. Method according to one of the preceding claims, characterized in that the verification of the suitability of the circuit (28, 28a, 43, 47) for operation in the potentially explosive environment is carried out taking into account a safety factor.

9. Method according to claim 8, characterized in that the coupling limit value (EL,S, Ec,s) is a predetermined limit value for an individual characteristic value (EL, ES).

10. Method for producing an electrical circuit (28, 28a, 43, 47) for operation in a potentially explosive atmosphere, comprising the steps: 10.1 Creating a circuit design, 10.2 Determining a test result by checking the suitability of the circuit design for operation in an explosive environment according to a method according to any one of the preceding claims, and 10.3 Release of the circuit design for producing the electrical circuit (28, 28a, 43, 47) depending on the test result.

11. The method according to claim 10, characterized by manufacturing the circuit (28, 28a, 43, 47) according to the approved circuit design.

12. Method according to claim 10 or 11, characterized by supplementing the circuit design in dependence on the test result with an ignition suppression means (39, 44, 49) for preventing an ignition effect in the event of a fault.

13. Method according to claim 12, characterized by supplementing the circuit design with an ignition suppression means (39, 44, 49) which has at least one diode (42.1, 42.2, 48) for limiting a voltage in the circuit (28, 28a, 43, 47) to a predetermined limit voltage.

14. Method according to one of claims 10 to 13, characterized in that the circuit (28, 28a, 43, 47) is a component of a plug connection part (4) for the inductive transmission of energy and / or signals, in particular for a measuring device (1).

15. Electrical circuit (28, 28a, 43, 47) which is tested according to a method according to one of claims 1 to 9 and / or is manufactured according to a method according to one of claims 10 to 14.

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