EP4139753A1

EP4139753A1 - Automation field device

Info

Publication number: EP4139753A1
Application number: EP21720235.7A
Authority: EP
Inventors: Simon Gerwig; Christian Strittmatter; Bernd Strütt
Original assignee: Endress and Hauser SE and Co KG
Current assignee: Endress and Hauser SE and Co KG
Priority date: 2020-04-23
Filing date: 2021-04-19
Publication date: 2023-03-01
Also published as: CN115398357A; DE102020111125A1; WO2021213958A1; US20230168655A1

Abstract

The invention relates to an automation field device (17), at least comprising: - at least a first, a second and a third connection pin; - field device electronics (16), which are designed such that the field device electronics can be operated either in a two-conductor mode or in a three-conductor mode. The field device electronics have an energy supply unit (6), which is designed to provide internal energy supply exclusively by means of the fed current in the two-conductor mode. In the three-conductor mode, an additional auxiliary current is to be fed to the field device electronics by means of an additional single-wire line (15c) to be connected to the third connection pin, and the energy supply unit (6) is also designed to provide the internal energy supply by means of the fed current and the fed additional auxiliary current. Furthermore, the field device electronics (16) are designed to use the additionally fed auxiliary current for internal energy supply only if the current fed by means of the two-wire line is not sufficient for the internal energy supply.

Description

Field device of automation technology

The invention relates to a field device in automation technology and a system in automation technology.

In automation technology, in particular in process automation technology, field devices are often used that are used to record and / or influence process variables. Sensors, such as level measuring devices, flow measuring devices, pressure and temperature measuring devices, pH redox potential measuring devices, conductivity measuring devices, etc., which detect the corresponding process variables level, flow rate, pressure, temperature, pH value and conductivity, are used to record process variables. Actuators such as valves or pumps, via which the flow of a liquid in a pipe section or the level in a container can be changed, are used to influence process variables. In principle, all devices that are used close to the process and deliver or process the process-relevant information are referred to as field devices. In connection with the invention, field devices are also understood to mean, in particular, remote I / Os, radio adapters or, in general, devices that are arranged on the field level.

A large number of such field devices are manufactured and sold by Endress + Hauser.

For historical reasons, these are usually connected via a two-wire line, ie a line with two separately formed wires, to a higher-level unit, for example a control unit PLC or control system. The two-wire field devices are designed in such a way that the measurement or control values are communicated, ie transmitted, analogously as process variables via the two-wire line in the form of a 4-20 mA loop current or current signal. In this case, a loop current of the two-wire line is set to a specific value by the field device or the superordinate unit in accordance with the recorded process variable. The measuring range is mapped linearly to the 4-20 mA current signal. Furthermore, the field devices are also supplied with energy via the two-wire line. In this case, one also speaks of two-wire field devices. Usually, a supply voltage between 10-35 V is applied to two-wire field devices. This means that the two-wire field device has a fault current of <3.6 mA and a minimum input voltage of, for example

10 V a maximum possible supply power of <36 mW is available.

Alternatively, in the event that more energy is required than can be provided to the field device via the two-wire line, the

Field devices can also be connected via a three-wire line. This eliminates the need to restrict the supply of power, as is the case with the two-wire line. In order to be able to implement the different modes of operation (two-wire or three-wire operation), there are different field device electronics that are integrated into the field device during manufacture. This means that the field device manufacturers have to provide different field device electronics or variances depending on the operating requirements.

It is therefore an object of the invention to show a possibility of how manufacturing variances can be reduced.

The object is achieved according to the invention by the field device of automation technology according to claim 1 and the system of automation technology according to claim 7.

The field device according to the invention in automation technology comprises at least: at least one first, second and third connection pin for the

Connection of internal field device electronics to an external voltage source;

- The field device electronics which is set up to be able to be operated either in a two-wire operation or a three-wire operation, the field device electronics in two-wire operation via a A current is to be supplied to the two-wire line to be connected to the first and second connection pin and the field device electronics have a first data and / or energy supply path which leads the current internally from the first to the second connection pin, the field device electronics having an energy supply unit which is set up to to realize an internal energy supply exclusively through the supplied current in two-wire operation, with the field device electronics in three-wire operation being supplied with an additional auxiliary current via an additional single-wire line to be connected to the third connection pin, and the field device electronics having a second energy supply path that internally transfers the additional auxiliary current from the first to the leads third connection pin, wherein the energy supply unit is further set up to implement the internal energy supply by the supplied current and the supplied additional auxiliary current, whereby i the field device electronics (is also set up to use the additionally supplied auxiliary current for the internal energy supply only if the current supplied via the two-wire line is not sufficient for the internal energy supply.

According to the invention, a field device is proposed which can be operated both in two-wire and in three-wire operation. This is made possible by an internal, uniformly designed field device electronics in the field device, which, depending on the operating requirements, is provided by three external connection pins either only with a two-wire line or, if necessary, with a cable. can also be contacted with a single-wire line. Due to the uniform design of the field device electronics as a combination circuit of two-wire and three-wire circuits, the variance of the field device electronics can be reduced, since only one field device electronics is required for both operating modes.

An advantageous embodiment of the field device according to the invention provides that the field device electronics furthermore have a first and a second diode, the first diode being introduced into the first data and / or energy supply path in such a way that a cathode of the first diode is directed towards the electronics supply unit and wherein the second diode is introduced into the second energy supply path in such a way that a cathode of the second diode is also directed towards the electronics supply unit, so that in the event that a voltage applied to the cathode of the first diode falls below a specific voltage value, the second diode is switched on.

A further advantageous embodiment of the field device according to the invention provides that the field device electronics also have a galvanic separation introduced into the second energy supply path, which is designed to provide a potential-free output voltage after the galvanic separation and wherein the field device electronics are also designed in such a way that the potential-free output voltage of the Supply electronics supply unit. In particular, the embodiment can provide that the field device electronics furthermore have a chopper which is introduced into the second energy supply path and which serves to convert a DC voltage applied on the input side into a square-wave AC voltage applied on the output side, and the field device electronics are also designed in such a way that the output-side AC voltage of the galvanic isolation to feed. In particular, the embodiment can also provide that the field device electronics furthermore have a voltage regulator connected upstream of the chopper, which is designed to regulate a voltage across the first and third connection pin.

A further advantageous embodiment of the field device according to the invention provides that the field device electronics furthermore have a 4-20 mA current control unit and are designed in such a way that at least part of the current is passed through the 4-20 mA current control unit, the 4-20 mA current control unit being set up to to set the current according to a 4-20mA standard both in two-wire operation and in three-wire operation.

The invention further relates to a system of automation technology, at least comprising: - A field device of automation technology according to one of the preceding claims;

- A voltage source arranged outside the field device;

- A two-wire line which connects a positive pole of the voltage source to the first connection pin with a first wire and a negative pole of the voltage source to the second connection pin with a second wire.

An advantageous embodiment of the system according to the invention provides that an external load resistor is introduced into the connection of the minus pole of the voltage source with the second connection pin.

Another advantageous embodiment of the system according to the invention also has a single-wire line which connects the minus pole of the voltage source to the third connection pin.

The invention is explained in more detail with reference to the following drawings.

It shows:

1 shows a field device with field device electronics that are connected to a voltage source via two connection pins by means of a two-wire line, and

2: the field device with the field device electronics which is connected to a voltage source via three connection pins by means of a three-wire line.

The field device of automation technology 17 shown in FIGS. 1 and 2 comprises a uniformly designed internal field device electronics 16, via which an optional connection to a two-wire or a three-wire line is possible. The field device electronics 16 are thus designed so that the field device 17 can be operated either as a two-wire or three-wire field device, depending on the circumstances or installation situation in an automation system.

To connect the field device 17, the field device electronics 16 have at least three connection pins 1, 2, 3 via which either the two or Three-wire line can be connected. In the exemplary embodiment shown in FIG. 1, the field device has, by way of example, four connection pins 1,

2, 3, 4 on. The field device electronics also include an EMC filter 5, which 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 energy supply, a microprocessor 7 for the internal control of the field device electronics 16, a sensor - Or actuator element 8 for detecting or setting a measurement or control value, a shunt resistor 9 and a 4-20 mA current control unit 10 which, together with the shunt resistor 9, sets or modulates a 4-20 mA current signal.

In addition, the field device electronics 16 can include a display and / or input unit 11, for example in the form of a touch display. Via the display and / or input unit 11, for example, measured or set values can be displayed or the field device 17 can be parameterized.

The field device electronics 16, which are uniformly designed according to the invention, can be operated in different operating states. On the one hand, the field device electronics 16 can be set up in which

To be operated two-wire operation and in addition it can also be set up or can be operated in a three-wire operation. Fig. 1 shows an example of a two-wire operation in which the

Field device electronics 16 is connected via a two-wire line 15 to an external voltage source 19 and an external load resistor 18 connected in series with the voltage source 19. In two-wire operation, the field device electronics 16 are connected to the outside of the via a first connection pin 1 and a second connection pin 2

Field device located voltage source 19 connected in order to supply a current. In two-wire operation, the supplied current is used to communicate both the 4-20 mA current signal for the transmission of a measurement or control value and also enables an internal energy supply for the field device electronics. In order to supply the current I supplied via the first connection pin 1 to the electronics supply unit 6, the field device electronics have a first data and / or energy supply path 6a (indicated by a thick line in FIG. 1), which connects the first connection pin 1 via the EMC filter 5 connects to the electronics supply unit 6. the

Electronics supply unit 6 is set up to implement an internal energy supply through the supplied current I and the other internal electronic components, such as the display and / or input unit 11, the sensor or actuator element 8 and / or the microprocessor 7, with energy to supply. Furthermore, the supplied current I or the parts that are not routed to the internal shunt resistor 9 via the electronics supply unit are routed through further connection paths via the current control unit 10 and / or the microprocessor 7. The current control unit 10 is set up to set the current in accordance with the 4-20 mA standard. For example, in the event that the field device is designed as a sensor, ie has a sensor element 8, the current via the 4-20 mA current control unit 10 together with the shunt resistor 9 according to a process variable detected by the sensor element, all the more to a higher-level unit ( not shown in Fig. 1) to be transmitted. In order to enable two-wire operation, a switchover unit 14 is provided which is configured in such a way that the current I coming from the shunt resistor 9 via a 4-20 mA output path 9a is conducted to the second connection pin 2.

2 shows an example of a three-wire operation in which the field device electronics 16 are connected to a minus pole of the voltage source 19 via an additional single-wire line 15c. The single-wire line 15c is connected via a third connection pin 3 of the field device electronics 16. The additional line 15c allows additional energy to be supplied to the field device electronics 16 via the first and third connection pins 1, 3. According to the invention, the field device electronics 16 are designed to provide the additional energy available between the first and third connection pins 1, 3 as required to the other internal electronic components of the field device electronics when the energy that can be generated by the supplied current is not sufficient for the internal energy supply.

Through the additional connection of the negative pole of the voltage source to the third connection pin by means of the single-wire line, the field device electronics can be provided with an additional current for generating energy. The field device electronics are designed in such a way that the additional current is rectified via a second energy path 6b (indicated by a thick line in FIG. 2), which serves as a pure energy path, and from the first connection pin to the energy supply unit and back again to the third connection pin to be led. A rectifier 20 is introduced into the second energy path to rectify the additional current.

However, since when the additional single-wire line 15c is connected between the third connection pin 3 and the minus pole of the voltage source 19, the third connection pin is lower in terms of voltage or potential than the second connection pin, which is connected to ground, the field device electronics also include a Galvanic isolation 13 introduced into the second energy path, so that an output voltage after galvanic isolation is floating or floating and can be fed to the electronics supply unit 6, which is related to the ground of the field device electronics 16, for internal energy supply. The difference in the voltage or the potential between the second and third connection pin can also fluctuate as a function of the external load 18 and / or the current provided by the 4-20 mA current control unit 10.

Furthermore, the field device electronics comprise a chopper 23, which serves to convert a DC voltage applied on the input side into a square-wave AC voltage applied on the output side, so that AC voltage on the output side can then be transformed via the electrical isolation 13.

The chopper 23, the rectifier 20 and the galvanic separation 13 can be implemented both as independent electronic components and in a single electronic component.

Optionally, the field device electronics 16 can also have a voltage regulator 12 connected upstream of the chopper 23, which is designed to stabilize a voltage U present across the first and third connection pins 1, 3 so that it can be fed to the electronics supply unit 6 for power supply.

In order to be able to use the additional energy as required, ie only when the energy obtained from the current supplied via the two-wire line or the stabilized voltage U is insufficient to supply the internal components with sufficient energy, the field device electronics 16 includes a diode arrangement . The diode arrangement consists of a first diode 21a, which is introduced into the first data and / or energy supply path 6 in such a way that a cathode of the first

Diode 21a is directed to the electronics supply unit 6 and a second diode 21b, which is introduced into the second energy supply path 6b in such a way that a cathode of the second diode 21b is also directed to the electronics supply unit 6, so that in the event that the cathode of the first diode applied stabilized voltage U falls below a specific voltage value Usp, the second diode 21b is or are switched on. The specific voltage value Usp is dependent on the design or dimensioning of the field device electronics 16 and is essentially determined by the voltage U stabilized by the voltage regulator 12, the specific voltage value Usp being selected to be greater than the stabilized voltage U, ie Usp> U. The specific voltage value Usp is usually greater than the stabilized voltage U by the forward voltage of the second diode. For example, the field device electronics can be dimensioned such that the operating voltage made available for the electronics supply unit 6 The stabilized voltage U of the voltage regulator is approx. 15 V and the specific voltage value is approx. 15.7 V, the second diode having a forward voltage of approx. 0.7 V. The demand-dependent connection offers the advantage that the field device electronics can be reduced in temperature during operation with an active current output.

Furthermore, the field device electronics can have a fourth connection pin 4, in particular for communication purposes. The field device electronics can be designed, for example, in such a way that digital communication, in particular IO-Link communication, is possible via the fourth connection pin 4.

List of reference symbols

1 First connection pin

2 Second connection pin

3 Third connection pin

4 Fourth connection pin

5 EMC filters

6 Electronics supply unit

6a First data and / or energy supply path

6b Second pure energy supply path

7 microprocessor

8 sensor or actuator element

9 Internal shunt resistance

9a 4-20mA output path

10 4-20mA current control unit 11 Display and / or output unit 12 Voltage regulator

13 Galvanic isolation

14 Switching unit

15 Two-wire line 15a First wire of the two-wire line 15b Second wire of the two-wire line 15c Additional single-wire line

16 Field device electronics

17 Field device in automation technology

18 External burden

19 External voltage source

20 Rectifier 21a First diode 21b Second diode 21a 22 Connection paths 23 Chopper U Stabilized voltage Specific voltage value

Claims

1. Field device of automation technology (17), at least having:

- At least one first, second and third connection pin for connecting internal field device electronics to an external voltage source (19);

- The field device electronics (16), which is set up to be able to be operated either in a two-wire operation or in a three-wire operation, the field device electronics in two-wire operation having to be supplied with a current via a two-wire line (15) to be connected to the first and second connection pin (1, 2) and the field device electronics (16) have a first data and / or energy supply path (6a) which internally leads the current from the first to the second connection pin, the field device electronics having an energy supply unit (6) which is set up to supply a internal energy supply to be realized exclusively through the supplied current, the field device electronics in three-wire operation having to be supplied with an additional auxiliary current via an additional single-wire line (15c) to be connected to the third connection pin, and the field device electronics (16) having a second energy supply path (6b) which provides the additional Auxiliary current leads internally from the first to the third connection pin, the energy supply unit (6) also being set up to implement the internal energy supply through the supplied current and the supplied additional auxiliary current, the field device electronics (16) also being set up to provide the additional The auxiliary current supplied should only be used for the internal energy supply if the current supplied via the two-wire line is not sufficient for the internal energy supply.

2. Field device of automation technology according to claim 1, wherein the field device electronics further comprises a first and a second diode (21a, 21b), wherein the first diode is introduced into the first data and / or energy supply path (6a) in such a way that a cathode the first diode is directed to the electronics supply unit (6) and wherein the second Diode is introduced into the second energy supply path (6b) in such a way that a cathode of the second diode (21b) is also directed towards the electronics supply unit (6), so that in the event that a voltage applied to the cathode of the first diode (21a) is below a specific voltage value falls, the second diode (21 b) is switched on.

3. Field device of automation technology according to one or more of the preceding claims, wherein the field device electronics furthermore have a galvanic separation introduced into the second energy supply path (6a)

(13), which is designed to provide a potential-free output voltage after the electrical isolation (13) and wherein the field device electronics (16) are also designed to supply the potential-free output voltage to the electronics supply unit (6).

4. Field device of automation technology according to the preceding claim, wherein the field device electronics (16) furthermore has a chopper (23) which is introduced into the second energy supply path (6a) and serves to convert a DC voltage applied on the input side into a square-wave AC voltage applied on the output side, and the

Field device electronics (16) are also designed in such a way that the output-side alternating voltage is supplied to the electrical isolation (13).

5. Field device of automation technology according to the preceding claim, wherein the field device electronics (16) further include a chopper

(23) has upstream voltage regulator (12) which is designed to stabilize a voltage present across the first and third connection pins (1, 3). 6. Field device of automation technology according to one or more of the preceding claims, wherein the field device electronics (16) further has a 4-20mA current control unit (10) and is designed such that at least part of the current is passed through the 4-20mA current control unit (10) is, the 4-20mA current control unit (10) is set up to to set the current according to a 4-20mA standard both in two-wire operation and in three-wire operation.

7. System of automation technology, at least comprising: a field device of automation technology according to one of the preceding claims;

- A voltage source (19) arranged outside the field device;

- A two-wire line (15) which has a first wire (15a) a plus pole of the voltage source with the first connection pin (1) and with a second wire (15b) a minus pole of the voltage source (19) with the second connection pin ( 2) connects.

8. System of automation technology according to the preceding claim, wherein an external load resistor (18) is introduced into the connection of the minus pole of the voltage source (19) with the second connection pin (2).

9. System of automation technology according to one of the two preceding claims, further comprising a single-wire line (15c) which connects the negative pole of the voltage source (19) to the third connection pin (3).