Automation field device

Abstract

The invention relates to an automation field device (F) comprising: - at least four connection pins (1, 2, 3, 4) for connecting the field device (17); and - a field device electronics unit (16) designed to be operated at least in two operating states, the field device electronics unit (16) also being designed, in a first operating state, to provide a 4-20mA signal via a first and a second connection pin (1, 2) and, in a third operating state, to be supplied with the supply voltage via the first and a third connection pin (1, 2) and to enable digital communication via the fourth connection pin (4), the field device electronics unit (16) also being designed to be configured such that it is operated / operable selectively in one of the at least two operating states, the field device electronics unit also comprising a computing unit, in particular a microcontroller, which operates with a cycle frequency, and the field device electronics unit also being designed to set the cycle frequency on the basis of the operating state selected / to be configured and / or to adapt the cycle frequency to said operating state.

Description

[0001] Field device in automation technology

[0002] The invention relates to a field device in automation technology and a method for operating a field device in automation technology.

[0003] In automation technology, particularly in process automation technology, field devices are often used to record and / or influence process variables. Sensors such as level gauges, flow meters, pressure and temperature gauges, pH / redox potential meters, conductivity meters, etc., are used to record process variables and measure the corresponding process variables: level, flow, pressure, temperature, pH value, or conductivity. Actuators such as valves or pumps, which can be used to change the flow of a liquid in a pipe section or the fill level in a container, are used to influence process variables. Field devices are essentially all devices that are used close to the process and that provide or process-relevant information.In the context of the invention, field devices are understood to include, in particular, remote I / Os, radio adapters or, in general, devices that are arranged at the field level.

[0004] A large number of such field devices are manufactured and distributed by Endress + Hauser.

[0005] For historical reasons, these are usually connected to a higher-level unit, such as a PLC control unit or control system, via a two-wire cable (i.e., a cable with two separate wires). The two-wire field devices are designed in such a way that the measured or manipulated values ​​are communicated, i.e., transmitted, as process variables via the two-wire cable in the form of a 4-20 mA loop current or current signal. In this case, the loop current of the two-wire cable is set to a specific value by the field device or higher-level unit according to the detected process variable.

[0006] Furthermore, the field devices can also be supplied with power via the two-wire cable in 2-wire operation. However, this only provides the field device with a very limited amount of power (usually less than 50 mW). Alternatively, if more power is required than can be provided to the field device via the two-wire cable, the field devices can also be connected via a three- or four-wire cable. This can be necessary, for example, if an increased measurement interval is required. When using a three- or four-wire cable, the power is transmitted via a separate pair of wires, and the measured or set value is transmitted via a third wire in the form of a 4-20 mA signal.

[0007] In addition to the "traditional" connection of field devices via a two-wire cable, where the measured or control values ​​are transmitted via a 4-20 mA signal, newer digital communication and transmission systems are increasingly emerging. One of these digital communication systems is IO-Link. IO-Link is a standardized communication system for connecting intelligent sensors and actuators, published in September 2013 under the name "Single-drop digital communication interface for small sensors and actuators" (SDCI).

[0008] Field devices, especially field device electronics, are usually manufactured by the field device manufacturer depending on whether they are later intended to transmit the measured or manipulated value via a 4-20 mA signal or via a digital communication interface, such as IO-Link. This means that the field device electronics in the field devices are designed in such a way that either 4-20 mA operation or IO-Link operation is possible. In addition, each field device electronics is also designed in such a way that it can be used for either two-, three-, or four-wire operation. This means that separate field device electronics must be manufactured for each variant, which in turn leads to a high degree of variance in the production of the field device electronics.

[0009] For this reason, field device manufacturers are moving towards developing and manufacturing a (single) field device electronics that can basically be used for all applications (2-wire, 3-wire, with / without digital communication, and / or pure 4-20 mA signal transmission) and can be configured for the specific intended application.

[0010] However, this also means that the field device or field device electronics must be designed and configured in such a way that it also functions in an operating state in which the lowest energy is available to the field device or field device electronics. As already explained, this is 2-wire operation, in which only a few tens of mW are available. At the same time, the field device or field device electronics must also enable digital communication in a different operating state, such as the IO-Link communication mentioned above.

[0011] It is therefore an object of the invention to propose a field device with uniform field device electronics that can be flexibly adjusted to the desired operating state and that ensures secure and robust digital communication can be carried out at least in one operating state. This object is achieved according to the invention by the field device of automation technology according to claim 1 and the method for operating a field device of automation technology according to claim 8.

[0012] The field device according to the invention for automation technology comprises: at least four connection pins for connecting the field device; field device electronics which are designed to be operated in at least two operating states, wherein the field device electronics are further designed to provide a 4-20 mA signal via a first and second connection pin in a first operating state, and to be supplied with the supply voltage via the first and a third connection pin in a third operating state and to enable digital communication via the fourth connection pin or to provide a first switching output at the fourth connection pin, wherein the field device electronics are further designed to be configured such that they are / can be operated selectively in one of the at least two operating states, wherein the field device electronics further comprise a computing unit, in particulara microcontroller which operates at a clock frequency and wherein the field device electronics are further configured to set or adapt the clock frequency based on the selected / to-be-configured operating state.

[0013] The present invention proposes a field device with field device electronics that supports multiple operating states, a first operating state being a pure 2-wire operating state in which a 4-20 mA signal is provided via the first and second connection pins. This 4-20 mA signal transmits both data and power (< 50 mW), and a third operating state being a 3-wire operating state in which the field device electronics is supplied with the supply voltage and enables digital communication. According to the invention, the field device electronics is configured to adapt a clock frequency of a computing unit to the operating state for which or to which the field device electronics is or is to be configured, in order to enable digital communication in the third operating state (and pure 2-wire operation with correspondingly little available power in the first operating state).

[0014] An advantageous embodiment of the field device according to the invention provides that the field device electronics are further configured to be supplied with a supply voltage via the first and third connection pins in a second operating state and to enable digital communication via the fourth connection pin or to provide a first switching output on the fourth connection pin, wherein the second operating state further provides that a second switching output is provided on the second connection pin and / or wherein the third operating state further provides that a 4-20 mA current output is provided on the second connection pin.

[0015] A further advantageous embodiment of the field device according to the invention provides that the field device electronics are further configured to recognize, depending on the connection assignment of the connection pins, the operating state to which it should or will be configured and to set the clock frequency based on the operating state to be configured.

[0016] A further advantageous embodiment of the field device according to the invention provides that the field device electronics are further configured to increase the clock frequency in the case that they are to be or are to be configured to the second or third operating state compared to the case that they are to be configured to the first operating state in order to enable digital communication via the fourth connection pin.

[0017] A further advantageous embodiment of the field device according to the invention provides that the field device electronics are further configured to reduce the clock frequency in the case that they are to be or are to be configured to the first operating state compared to the case that they are to be configured to the second or third operating state.

[0018] A further advantageous embodiment of the field device according to the invention provides that the field device electronics are further configured to increase or decrease the clock frequency by at least a factor of 2, preferably at least by a factor of 2.5, particularly preferably at least by a factor of 3.

[0019] A further advantageous embodiment of the field device according to the invention provides that the digital communication comprises IO-Link communication, APL communication, or PA / FF communication. APL stands for Advanced Physical Layer.

[0020] In addition, the field device electronics can also be configured to automatically detect whether digital communication, particularly in the case of IO-Link communication, is or should be carried out via the fourth connection pin, or whether the fourth connection pin is used as the first switching output. In particular, it can be provided that the automatic detection takes place depending on a device connected to the fourth connection pin. The invention further relates to a method for operating a field device in automation technology according to one or more of the previously described embodiments, wherein the method comprises the following steps:

[0021] Recognize which connection assignment is present on the connection pins of a field device electronics;

[0022] Determining an operating state in which the field device electronics is to be operated based on the detected connection assignment;

[0023] Configuring the field device electronics in such a way that a clock frequency of a computing unit, in particular a microcontroller, is adapted to the operating state determined based on the pin assignment.

[0024] The invention is explained in more detail with reference to the following drawings. It shows:

[0025] Fig. 1 : a block diagram of a field device according to the invention with field device electronics which is designed to be operated in a first operating state,

[0026] Fig. 2: a block diagram of the field device according to the invention with the field device electronics, which is designed to be operated in a second operating state, and

[0027] Fig. 3: a block diagram of the field device according to the invention with the field device electronics, which is designed to be operated in a third operating state.

[0028] Basically, Figures 1 to 3 all show a field device 17 with field device electronics 16 that is uniformly designed in terms of hardware. The uniformly designed field device electronics each comprise four connection pins 1, 2, 3, 4 via which the field device 17 can be connected accordingly in an automation system, an EMC filter 5 that is connected downstream of the connection pins 1, 2, 3, 4 to protect the field device 17 from possible EMC interference, an electronics supply unit 6 for the internal power supply, a microprocessor or microcontroller 7 for the internal control of the field device electronics 16, a sensor or actuator element 8 for detecting or setting a measured or set value, a load resistor 9 and a 4-20mA current control unit 10 that, together with the load resistor 9, sets a current value I.In addition, to enable IO-Link operation, the field device electronics 16 has an auxiliary circuit 12 for forming first and second auxiliary paths 12a, 12b and an IO-Link unit 13 for enabling IO-Link communication. The IO-Link unit 13 is connected to the fourth connection pin 4 via the EMC filter by a first output path 13a, so that bidirectional IO-Link communication can take place via the fourth connection pin 4. Furthermore, the IO-Link unit 13 is connected to the third connection pin 3 via the EMC filter 5 by a supply path 13b, and to the first connection pin 1 via the EMC filter 5. The IO-Link unit 13 is additionally connected to the second connection pin 2 via a switching unit 14 and the EMC filter 5.The switching unit 14 is designed such that the second connection pin 2 can be operated either as a second switching output Q2 or as a current output (active or, in two-wire operation, passive) at which a 4-20 mA signal is output. The configuration of the switching unit 14 can be performed, for example, by the microprocessor. This can, for example, control the auxiliary circuit via a control signal, which forwards the control signal to the switching unit.

[0029] Additionally or alternatively, the configuration can be performed via IO-Link communication, e.g., via an IO-Link master connected to the fourth connection pin 4. This can be done, for example, during the assembly of the field device 17 by the field device manufacturer.

[0030] To enable control of the IO-Link unit 13 and the auxiliary circuit 12, the microprocessor is connected to the IO-Link unit 13 via a first and a second control line 7a and 7b, and to the auxiliary circuit 12 via a third control line 7c. To compensate for possible voltage level differences between the microprocessor 7 and the IO-Link unit 13, a first level converter 15a can be incorporated into the first control line 7a and a second level converter 15b into the second control line 7b.

[0031] Furthermore, the field device electronics can include a display and / or input unit 11, for example in the form of a touchscreen. The display and / or input unit 11 can be used, for example, to display measured or manipulated values ​​or to configure the field device 17.

[0032] The uniformly designed field device electronics 16 allows it to be operated in different operating states. The different operating states are shown in Figs. 1 to 3, where for clarity the inactive electrical connections are marked with dashed lines, the electrical connections used for data transmission are marked with a thin line, the electrical connections used for power transmission are marked with a medium line or a medium-thick line, and the electrical connections used for power and data transmission are marked with a thick line. Firstly, the field device electronics 16 can be configured, as shown in Fig. 1, so that it is operated in a first operating state, a pure 4-20 mA two-wire operation. In this case, a two-wire line is connected to the first and second connection pins 1 and 2 in order to apply a connection voltage to the field device electronics 16.A current I is supplied to the electronics supply unit 6 via the EMC filters 5 with a first data and / or power supply path or 4-20mA path 6a, which in the first operating state represents a 4-20mA input path (indicated by a thick line in Fig. 1).

[0033] In the first operating state, the supplied current I feeds the electronics supply unit 6 on the one hand so that it can provide the internal operating voltage and on the other hand the current I carries a signal in the form of a 4-20 mA signal, via which a measured or control value can be transmitted. For example, if the field device is designed as a sensor, i.e. has a sensor element, the current can be set via the 4-20 mA current control unit 10 together with the burden resistor 9 in accordance with a process variable detected by the sensor element in order to be transmitted to a higher-level unit (not shown in Fig. 1). In order to enable pure 4-20 mA two-wire operation, the switching unit 14 is configured such that the current I coming from the burden resistor 9 via a 4-20 mA output path 9a is guided to the second connection pin 2.Due to the pure 4-20 mA two-wire operation, in which a connection voltage of approx. 17-20 is usually applied, a maximum energy of < 50 mW is available to the field device electronics.

[0034] The field device electronics 16 are further designed according to the invention to adapt a clock frequency of the microprocessor 7 for or to the first operating state, the pure 4-20 mA two-wire operation. For example, the field device electronics can be configured to lower or reduce the clock frequency in the first operating state compared to the third operating state, which will be described in more detail below. The specific clock frequency to which it is reduced depends significantly on the microprocessor 7. For example, the clock frequency in the first operating state can be reduced by at least 50%, preferably by at least 60%, particularly preferably by at least 66%, compared to the clock frequency in the second and / or third operating state, which will be described in more detail below.

[0035] By reducing the clock frequency of the microprocessor 7, the power consumption of the microprocessor 7 is reduced, enabling safe operation of the field device electronics 16 with the maximum available energy of < 50 mW. By reducing the clock frequency and the associated reduction in power consumption, it is also possible to apply a lower connection voltage to the field device electronics 16 configured for the first operating state. For example, a connection voltage of less than 15 V may be sufficient, whereas otherwise, i.e., without adjusting the microprocessor's clock frequency, 17 V would normally be applied.

[0036] Furthermore, the field device electronics 16, as shown in Fig. 2, can be configured to operate in a second operating state. In the second operating state, the field device electronics 16 is supplied with a supply voltage via the first and third connection pins 1, 3. The IO-Link unit 13 and the electronics supply unit 6 are supplied via the first data and / or power supply path or 4-20 mA path 6a, which represents a pure supply path in the second operating state (indicated by a medium-thick line in Fig. 1). As a supply voltage, for example, a voltage of greater than 15 V, preferably greater than 20 V, particularly preferably approximately 24 V, can be applied to the first and third connection pins 1, 3, so that the field device electronics configured for the second operating state has sufficient energy available compared to the first operating state.

[0037] Furthermore, in the second operating state, IO-Link communication is enabled via a fourth connection pin 4, or alternatively, a first switching output Q1 is provided if IO-Link communication is not intended or cannot take place. In addition, a second switching output Q2 can be provided on the second connection pin 2 in the second operating state. For this purpose, the switching unit 14 switches between the 4-20 mA output path and a third output path 13d. In the second operating state, the field device electronics 16 is supplied via an internal auxiliary supply path, which can be routed via a reference diode 12c. However, this requires a supply voltage approximately 10 V higher. The reference diode 12c can be part of the auxiliary circuit 12. The auxiliary supply path comprises the third control line 7c, the second auxiliary path 12b, and an eighth auxiliary path 9b.

[0038] Furthermore, the field device electronics 16 can be configured to operate in a third operating state, as shown in Fig. 3. In the third operating state, the field device electronics 16 is again supplied with the supply voltage via the first and third connection pins 1, 3. Likewise, in the third operating state, IO-Link communication is enabled via the fourth connection pin 4, or the first switching output Q1 is provided if IO-Link communication is not to be or cannot take place. Additionally, in the third operating state, a 4-20 mA current output can be provided at the second connection pin 2. In the third operating state 18, an external (outside the field device) burden resistor can be connected between the connection pin 3 and the connection pin 2. In this case, the field device electronics is supplied via the 4-20 mA current I, which is supplied to the first connection pin 1.If no external burden resistor 18 is connected between the connection pins 2 and 3, the field device electronics 16 is supplied via the internal auxiliary supply path in the third operating state, just as in the second operating state.

[0039] The field device electronics 16 can further be configured to automatically detect, in both the second and third operating states, whether IO-Link communication with an external IO-Link master should take place via the fourth connection pin 4 or whether the fourth connection pin should be used as the first switching output Q1. For automatic detection, the field device electronics 16 can, for example, be configured to monitor the fourth connection pin 4 to determine whether it is briefly pulled to an inverting switching state by the external IO-Link master.

[0040] Additionally or alternatively, the field device electronics 16 can be configured to deactivate the second connection pin 2 in both the second and third operating states, so that neither the second switching output Q2 is available in the second operating state nor the 4-20 mA current output is available in the third operating state. Deactivation can be achieved, for example, through a software configuration, e.g., by setting a corresponding parameter in the field device electronics.

[0041] The field device electronics 16 can further be configured to adjust the clock frequency of the microprocessor for or to the second and / or third operating state. For example, the field device electronics can be configured to increase the clock frequency in the second and / or third operating state compared to the first operating state. As already mentioned, the specific clock frequency to which the increase is made depends largely on the microprocessor.

[0042] For example, the clock frequency in the second and / or third operating state can be increased by at least 50%, preferably by at least 60%, particularly preferably by at least 66%, compared to the clock frequency in the first operating state.

[0043] Due to the increase in the clock frequency of the microprocessor, the power consumption by the microprocessor is increased, but the microprocessor also works faster, so that with IO-Link communication via the fourth connection pin 4 it can be ensured that in the event of an external request from an IO-Link master a fast response can be given, i.e. a response that conforms to the specifications for IO-Link communication in terms of response time. In addition, the field device electronics 16 can be set up to recognize, depending on the connection assignment of the connection pins 1, 2, 3, 4, which operating state it should be or will be configured to and to set the clock frequency based on the operating state to be configured. In other words, the field device electronics 16 is set up to automatically recognize which connection pins are connected and to determine the desired operating state from this.

[0044] List of reference symbols

[0045] First connection pin

[0046] Second connection pin

[0047] Third connection pin

[0048] Fourth connection pin

[0049] EMC filter

[0050] Electronics supply unit a First data and / or power supply path / 4-20mA path

[0051] Microprocessor a First control line b Second control line c Third control line

[0052] Sensor or actuator element

[0053] Load resistor a 4-20mA output path b Eighth auxiliary path 0 4-20mA current control unit 1 Display and / or output unit 2 Auxiliary circuit 2a First auxiliary path 2b Second auxiliary path 2c Reference diode 3 IO-Link unit 3a First output path to connection pin 4 3b Second output path to connection pin 3 3c Supply path 3d Third output path to connection pin 2 4 Switching unit 5a First level converter between IO-Link unit and microprocessor 5b Second level converter between microprocessor and IO-Link unit 6 Field device electronics 7 Field device 8 External load resistor

[0054] Current 1 First switching output 2 Second switching output

Claims

Patent claims 1 . Field device of automation technology (F), comprising: at least four connection pins (1, 2, 3, 4) for connecting the field device (17); field device electronics (16) which are designed to be operated in at least two operating states, wherein the field device electronics (16) are further designed to provide a 4-20 mA signal via a first and second connection pin (1, 2) in a first operating state, and to be supplied with the supply voltage via the first and a third connection pin (1, 3) in a third operating state and to enable digital communication via the fourth connection pin (4) or to provide a first switching output (Q1) on the fourth connection pin (4), wherein the field device electronics (16) are further designed to be configured such that they are / can be operated selectively in one of the at least two operating states, wherein the field device electronics further comprise a computing unit, in particulara microcontroller which operates with a clock frequency and wherein the field device electronics are further configured to set or adapt the clock frequency based on the selected / to-be-configured operating state.

2. Field device of automation technology according to claim 1, wherein the field device electronics (16) is further configured to be supplied with a supply voltage via the first and the third connection pin (1, 3) in a second operating state and to enable digital communication via the fourth connection pin (4) or to provide a first switching output (Q1) on the fourth connection pin (4), wherein the second operating state further provides that a second switching output (Q2) is provided on the second connection pin (2) and / or wherein the third operating state further provides that a 4-20 mA current output (Q2) is provided on the second connection pin (2).

3. Field device of automation technology according to one or more of the preceding claims, wherein the field device electronics (16) is further configured to recognize, depending on the connection assignment of the connection pins (1, 2, 3, 4), the operating state to which it is to be or will be configured and to set the clock frequency based on the operating state to be configured.

4. Field device of automation technology according to one or more of the preceding claims, wherein the field device electronics (16) is further configured, in the case that it is to be or is to be configured to the second or third operating state, to reduce the clock frequency compared to the case that it is configured to the first operating state is to be configured in order to enable digital communication via the fourth connection pin (4).

5. Field device of automation technology according to one or more of the preceding claims, wherein the field device electronics (16) is further configured to reduce the clock frequency in the case that it is to be or is to be configured to the first operating state compared to the case that it is to be configured to the second or third operating state.

6. Field device of automation technology according to one or more of the preceding claims, wherein the field device electronics (16) is further configured to increase or decrease the clock frequency by at least a factor of 2, preferably at least a factor of 2.5, particularly preferably at least a factor of 3.

7. Field device of automation technology according to one or more of the preceding claims, wherein the digital communication comprises an IO-Link communication, an APL communication or a PA / FF communication.

8. A method for operating a field device of automation technology according to one or more of the preceding claims, wherein the method comprises the following steps: Detecting which connection assignment is present on the connection pins (1, 2, 3, 4) of a field device electronics (16); Determining an operating state in which the field device electronics (16) is to be operated based on the detected connection assignment; Configuring the field device electronics (16) such that a clock frequency of a computing unit (7), in particular of a microcontroller, is adapted to the operating state determined on the basis of the pin assignment.

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