EP3526928A1

EP3526928A1 - Method for transferring data between an automation field device and a communication box

Info

Publication number: EP3526928A1
Application number: EP17761235.5A
Authority: EP
Inventors: Simon Gerwig; Harald SCHÄUBLE; Wolfgang Brutschin
Original assignee: Endress and Hauser SE and Co KG
Current assignee: Endress and Hauser SE and Co KG
Priority date: 2016-10-13
Filing date: 2017-08-29
Publication date: 2019-08-21
Also published as: CN109923831A; WO2018068941A1; CN109923831B; US20190268038A1; DE102016119548A1; US10840973B2

Abstract

The invention relates to a method for transferring data between an automation field device (2) and a communication box (4), wherein the method comprises the following steps: voltage modulation of the supply voltage (U_v) of the field device (2) by the communication box (4) such that a first communication signal (5) is produced and the supply voltage (U_v) has the first communication signal (5); demodulation of the first communication signal (5) from the supply voltage (U_v) applied to the field device (2) by means of the two-wire line (3) such that the first communication signal (5) is separated from the supply voltage (U_v); current modulation of an output current (I_A) of the field device by the field device (2) such that a second communication signal (6) is produced and the output current (I_A) has the second communication signal (6); demodulation of the second communication signal (6) from the output current (I_A) by the communication box (4) such that the second communication signal (6) is separated from the output current (I_A).

Description

Method for data transmission between a field device of

Automation technology and a communication box

The invention relates to a method for data transmission between a field device of automation technology and a communication box, a field device of automation technology and a communication box.

In process automation technology as well as in production automation technology, field devices are usually used which serve to detect and / or influence process variables. Measuring devices or sensors, such as level gauges,

Flowmeters, pressure and temperature measuring devices, pH redox potential measuring devices, conductivity measuring devices, etc., which record the corresponding process variables level, flow, pressure, temperature, pH or conductivity. To influence process variables are actuators, such as valves or pumps, via which the flow of a liquid in a pipe section or the level can be changed in a container.

A large number of such field devices are manufactured and distributed by the Endress + Hauser Group.

In addition, it is also customary in automation technology to construct and connect the field devices in a so-called two-wire technique, so that the energy supply and the communication of the process variable between the field devices can take place via a single pair of lines (two-wire line).

Such field devices have for this purpose an analog current or voltage output, for example a 4 to 20 mA current output or a 0 to 10 V voltage output. Only the transmission of the process variable or the measured value is possible via this current or voltage output. If an additional data transmission between the participants connected to the two-wire line is desired, the HART protocol, for example, is used. By means of the HART communication, the field devices can be very flexibly parameterized and put into operation or read out additional determined and stored measured values or data. The HART protocol enables bidirectional communication even in a potentially explosive environment via a point-to-point transmission of at least two subscribers. In this case, an FSK method (Frequency Shift Keying) is used, that for

Differentiating the binary states uses different frequencies of a sinusoidal signal (eg Bell 202 standard: "0" 2200 Hz, "1" 1200 Hz). The discretized and digitized data are provided by a special modem, which is in each case Participants must be present in a Hart protocol using the FSK method transmitted and received.

However, the components used for realizing a HART communication, in particular the FSK modem, require a relatively large amount of space and, moreover, are also relatively expensive, which is undesirable particularly in the case of field devices that are inexpensive to produce.

It is therefore an object of the invention, a cost-effective and possible

to propose space-saving communication method.

The object is achieved by a method for data transmission between a field device of automation technology and a communication box, wherein the communication box is connected to the field device via a two-wire line and via the two-wire line, a supply voltage is applied to the field device to provide the field device with energy, the method includes the following steps:

Voltage modulation of the supply voltage of the field device through the communication box, so that a first communication signal is generated and the supply voltage comprises the first communication signal;

Demodulation of the first communication signal from the over the

Two-wire line to the field device applied supply voltage, so that the first communication signal is disconnected from the supply voltage; Current modulation of a Ausgansstromes of the field device by the field device, so that a second communication signal is generated and the Ausgansstrom has the second communication signal;

Demodulating the second communication signal from the output stream through the communication box such that the second communication signal is separated from the output stream.

According to the invention, a method is proposed in which data can be communicated via the current consumption of the field device and its supply voltage. For this purpose, a communication box is introduced into a two-wire line between the field device and a supply unit. About the communication box is

The invention modulates a request in the form of a first communication signal to the supply voltage and demodulates the request in the field device. The response in the form of a second communication signal is modulated onto an output current of the field device and this is demodulated again in the communication box. The data to be communicated are modulated one to one, ie without change, to the supply voltage and not, as with others Communication method, such as HART, in which Frequency Shift Keying (Frequency Shift Keying) occurs, usually, for the purpose of data transmission changed.

The proposed communication method can be used, for example, in the production for programming the field device and during the final adjustment and the so-called load check. Furthermore, it is also possible via the communication method to connect the communication box to the field device in a data-conducting manner and to connect the communication box with further functionalities, e.g. Radio communications,

equip the field device with these functionalities as well.

An advantageous embodiment of the invention provides that the

Voltage modulation of the supply voltage a voltage value of

Supply voltage is varied such that the supply voltage having the first communication signal.

A further advantageous embodiment of the invention provides that the

Current modulation of the output current of the field device, a current value of the

Output current is varied such that the output current is the second

Communication signal has.

An advantageous embodiment of the invention provides that for the demodulation of the first communication signal from the supply voltage DC voltage components of the supply voltage are filtered out by the field device. An advantageous embodiment of the invention provides that the first and / or the second communication signal are generated according to a UART protocol, SPI or an MC protocol.

The object is further achieved by a field device of automation technology, which can be connected to a two-wire line for power supply, comprising: a demodulation unit having a capacitance, wherein the capacitance separates a first communication signal, which is modulated onto the supply voltage of the field device, from the supply voltage, so that the first communication signal is available to the field device;

a modulation unit that is set up, a second one

To modulate the communication signal to an output current of the field device, so that the second communication signal via the output current of the

Field device is transferable. An advantageous embodiment of the field device according to the invention provides that the demodulation unit and / or the modulation unit has no modem, in particular no FSK modem, or to have to separate the first communication signal from the supply voltage and / or to modulate the second communication signal.

A further advantageous embodiment of the field device according to the invention provides that the demodulation unit consists of the capacitance. Because of that

Demodulation unit consists solely of a capacity, can be the

Integrate demodulation unit particularly simple and space-saving in the field device or realize.

A further advantageous embodiment of the field device according to the invention provides that the field device is adapted to transmit a process variable via a loop current, in particular a 4 to 20mA loop current, wherein a means for current regulation, in particular a current regulator, sets the loop current according to the process variable and the current-regulating means is part of the modulation unit and further configured to modulate the second communication signal to the loop current so that the loop current comprises the second communication signal.

An alternative embodiment of the field device according to the invention provides that the field device is adapted to transmit a process variable via a voltage signal, in particular a 0 to 10 V voltage signal, wherein the

Modulation unit is designed such that a first terminal with a second connection for the two-wire line via a means for current regulation, which

in particular has a controllable resistor, is connected and the means modulates the second communication signal to an internal current of the field device as an output current. The object is also achieved by a communication box for data transmission with a field device of automation technology, wherein the communication box can be connected to the field device via a two-wire line, and has the following:

a modulation unit that is configured to perform a voltage modulation of a voltage signal of the two-wire line, so that the voltage signal of the two-wire line to a first communication signal to

Having data transmission;

a demodulation unit configured to generate a current signal of

Demodulate a two-wire line, so that a second communication signal of the communication box is available. In addition, the object is also achieved by a system of automation technology, which is a field device according to one of the previously described embodiment, a communication box according to the previously described embodiment and a

Two-wire line, which connects the field device with the communication box and over which the field device is supplied with energy has.

An advantageous embodiment of the system according to the invention provides that the communication box has at least one further functionality in order to also equip the field device with this functionality, the communication box exchanging data with the field device according to the method described above in relation to the further functionality Provide that the communication box is formed on the at least one further functionality to a connection of the communication box via a radio protocol or a

to allow wired protocol and the communication box with the

Field device exchanges data related to the radio protocol or the wired protocol.

The invention will be explained in more detail with reference to the following drawing. 1 shows a schematic representation of the system according to the invention, comprising a field device, a communication box and a two-wire line.

1 shows a schematic representation of the system 1 according to the invention, which is a field device 2 of automation technology, a communication box 4 for

Data transmission and a two-wire line 3 has.

The communication box 4 and the field device 2 are connected in a data-conducting manner via a two-wire line 3. Via the two-wire line 3, the field device 2 is supplied with a supply voltage Uv, for example. By a power adapter, which is not shown in Fig. 1. About the two-wire line 3 is next to the

Energy supply also the transmission of a process variable, which by the

Field device 2 is detected, to one, also not shown in Fig. 1, higher-level unit, for example. A PLC instead. It goes without saying that in the case that the field device 2 acts as an actuator, via the two-wire line 3, a transmission of the

Control value from the parent unit to the field device 2 takes place.

For the transmission of data going beyond that, for example for parameterization, between the communication box 4 and the field device 2, the communication box 4 has the following: A first terminal pair 13 for input-side connection of the two-wire line 3, so that the communication box 4 via the two-wire line 3 to a supply unit, such as a transmitter power supply, not shown in Fig. 1, is connected.

A second terminal pair 14 for output side connection of the

Two-wire line 3, so that the communication box 4 is connected via the two-wire line 3 to the field device 2.

A modulation unit 11, which is arranged between the first and the second terminal pair 13, 14 in the communication box 4. The modulation unit 11 is set up such that a voltage modulation or an amplitude modulation of a voltage signal of the two-wire line 3 takes place in accordance with a first communication signal 5 for data transmission. This can, for example, by one or more diodes, which has a

Switch, in particular a controllable field effect transistor, short-circuited, be realized. About the controllable switch and the diode or diodes, the first communication signal to the voltage signal of

Two-wire line modulated. The voltage signal is thus available to the field device 2 as a supply voltage at the second connection terminal pair 14 of the communication box 4, so that the first communication signal 5 is transmitted via the two-wire line 3 to the field device 2. That by the

1 is represented by a "01010" signal at the input of the field device 2. A demodulation unit 12 which is arranged between the first and the second terminal pair 13, 14 in the communication box 4. The demodulation unit 12 is set up so that one of the second

Terminal pair 14 connected two-wire line 3 derived current signal is demodulated. For this purpose, the demodulation unit 12 preferably comprises a resistor, which is arranged between the first and the second terminal pair such that the current signal flows through the resistor, and an operational amplifier, which consists of a through the

Resistance generated voltage drop generates the second communication signal. The second transmitted by the current modulation

Communication signal 6 is shown by way of example in FIG. 1 by a "1010" signal.

In principle, the communication box 4 can also be equipped with a different functionality than the parameterization. For example, it can have a radio module, so that data can be exchanged wirelessly with another device via the radio module of the communication box 4 and the data between the communication box and the field device wired, according to the inventive method, be replaced.

For transmission of the additional data, a corresponding field device 2 has the following:

A terminal pair 15 for connecting the two-wire line 3. About the connected two-wire line 3, the field device 2 is supplied with energy. In the example shown by way of example in FIG. 1, the field device 2 is supplied with a voltage of 24 V.

A demodulation unit 7 with a capacity 8 which is that of the

Communication box 4 on the supply voltage V _s modulated first communication signal 5 demodulates or separates. The capacitor 8 can be formed, for example, by a capacitor or a plurality of capacitors connected in series and / or in parallel. The first communication signal 5 is thus available after the capacitor 8 without a modem, in particular without a FSK modem, and can, for example, by a microcontroller

be further processed. 1 shows by way of example the simplest case in which the demodulation unit 7 requires only a single capacitance 8, for example in the form of a capacitor. In contrast to the communication methods known from the prior art, in particular HART, it is thus possible to realize a space-saving and cost-effective data transmission.

A modulation unit 9, which is adapted to a second

To modulate communication signal 6 to an output current I _{A of} the field device, so that the second communication signal 6, which serves, for example, as a response signal to the first communication signal 5, via the

Output current I _{A of} the field device 2 to the communication box 4 is transferable. For this purpose, the modulation unit 9 performs a current modulation of

Output current l _A or an amplitude modulation of the output current. In the example shown by way of example in FIG. 1, the field device 2 is designed as a two-wire or two-wire field device according to the 4 to 20 mA standard, and a process variable detected by the field device 2 is applied via a loop current generated by a current regulator 10 is adjustable, transmitted. For this purpose, the current controller 10 receives in the normal measurement mode, for example from the microprocessor, a current setpoint value, which represents the process variable, and regulates the loop current to a value corresponding to the current setpoint value. According to the invention, the current regulator 10 is also part of the modulation unit and is further adapted to apply the second communication signal 6 to the

to modulate according to the process variable loop current. Essentially, the current controller adds the second one

Communication signal to the loop current to be set. It is also conceivable, however, an alternative embodiment of the field device 2 such that the process variable is not transmitted via a loop current, but via a voltage signal. For example, the process variable can be represented by a 0 to 10V

Voltage signal to be transmitted. In field devices according to this embodiment, no current regulator is provided for adjusting the current. Due to this, the modulation unit has a means for current regulation, wherein the means comprises a first

Connection of the terminal pair with a second connection of the

Connecting terminal pair connects. By the means, the second

Communication signal 6 are modulated on a self-current of the field device. The means may comprise, for example, a resistor and a field effect transistor, wherein the field effect transistor is arranged in series with the resistor, so that the current flowing through the resistor is modulated by the field effect transistor.

By appropriately trained communication box 4 and the field device 2, thus a method for data transmission can be realized in a simple manner. The method for data transmission provides that in a first method step, the supply voltage V _{s of} the field device 2 is amplitude-modulated by the communication box 4, so that a first communication signal 5 is generated. The first communication signal 5 can be generated according to a UART, SPI or MC protocol. In a second method step, the supply voltage V _s applied via the two-wire line 3 to the field device 2 is demodulated so that the first communication signal 5 is obtained from the supply voltage V _s applied to the field device. The first communication signal 5 can subsequently

be further processed. For example, a microcontroller or microprocessor, the field device according to the means of the first communication signal. 5

transmitted parameter information parameterize the field device 2. In a third method step, a current modulation or an amplitude modulation of the output current I _{A of} the field device takes place by the field device, so that the

Output current has the second communication signal. The second

Communication signal 6 is thus transmitted via the output current I _A to the communication box 4. In a fourth method step, the communication box 4 demodulates the output current I _A , so that the second communication signal 6 from the

Output current l _{A is} disconnected and the communication box 4 is present for further processing. LIST OF REFERENCE NUMBERS

1 system of automation technology

2 field device

3 two-wire line

4 communication box

5 First communication signal

6 Second communication signal

7 demodulation unit of the field device

8 capacity

9 modulation unit of the field device

10 means for current regulation, e.g. a current regulator

1 1 Modulation unit of the communication box

12 Demodulation box of the communication box

13 First terminal pair of the communication box

14 Second terminal pair of the communication box

15 terminal pair of the field device

U _v supply voltage

IA output current

Claims

claims

1. A method for data transmission between a field device (2) of

Automation technology and a communication box (4), the

Communication box (4) with the field device (2) via a two-wire line (3) is connected and via the two-wire line (3) a supply voltage (U _v ) to the field device (2) is applied to supply the field device (2) with energy The method includes the following steps:

Voltage modulation of the supply voltage (U _v ) of the field device (2) by the communication box (4), so that a first communication signal (5) is generated and the supply voltage (U _v ), the first communication signal (5);

Demodulation of the first communication signal (5) from the over the

Two-wire line (3) to the field device (2) applied supply voltage (Uv), so that the first communication signal (5) from the supply voltage (U _v ) is disconnected;

Current modulation of a Ausgansstromes (l _A ) of the field device by the field device (2), so that a second communication signal (6) is generated and the

Having Ausgansstrom (l _A), the second communication signal (6);

- Demodulation of the second communication signal (6) from the output current

() through the communication box (4) so that the second communication signal (6) is disconnected from the output stream (I _A ).

2. The method of claim 1, wherein for the voltage modulation of

Supply voltage (Uv) is a voltage value of the supply voltage (Uv) is varied such that the supply voltage (U _v ), the first communication signal (5).

3. The method of claim 1 or 2, wherein the current modulation of Ausgansstromes (l _A ) of the field device (2) a current value of the output current (l _A ) is varied such that the output current (l _A ), the second communication signal (6).

4. The method according to one or more of the preceding claims, wherein for the demodulation of the first communication signal (5) from the supply voltage (V _s ) DC components of the supply voltage through the field device (2)

be filtered out.

5. The method according to one or more of the preceding claims, wherein the first and / or the second communication signal (5, 6) are generated according to a UART protocol, an SPI protocol or an MC protocol.

6. Field device of automation technology, which is connectable to a two-wire line (3) for supplying energy, comprising:

a demodulation unit (7) having a capacitance (8), wherein the capacitance (8) separates a first communication signal (5), which is modulated onto the supply voltage (V _s ) of the field device (2), from the supply voltage (V _s ), so that the first communication signal (5) is available to the field device (2); a modulation unit (9) arranged to have a second one

Communication signal (6) to an output current (l _A ) of the field device (2) to modulate, so that the second communication signal (6) via the

Output current (l _A ) of the field device (2) is transferable.

7. Field device according to claim 6, wherein the demodulation unit (7) and / or the

Modulation unit (9) has no modem, in particular no FSK modem, or

to separate the first communication signal from the supply voltage and / or to modulate the second communication signal.

8. Field device according to one of claims 6 to 8, wherein the demodulation unit (7) consists of the capacitance (8).

9. Field device according to one of claims 6 to 8, wherein the field device (2) is adapted to transmit a process variable via a loop current, in particular a 4 to 20mA loop current, wherein a means for current regulation (10),

in particular, a current regulator that sets loop current according to the process variable, and the current regulating means (10) is part of the modulation unit (9) and is further configured to modulate the second communication signal (6) to the loop current such that the loop current is the second communication signal (6).

10. Field device according to one of claims 6 to 8, wherein the field device (2) is adapted to a process variable via a voltage signal, in particular a 0 to 10 V voltage signal to transmit, wherein the modulation unit (9) is designed such that a first Connection with a second connection for the two-wire line via a means for current regulation, which in particular has a controllable resistance, is connected and the means modulates the second communication signal to an own current of the field device as output current.

1 1. Communication box for data transmission with a field device (2) of

Automation technology, wherein the communication box (4) via a two-wire line (3) with the field device (2) is connectable, comprising:

a modulation unit (1 1) which is adapted to perform a voltage modulation of a voltage signal of the two-wire line (3), so that the Voltage signal of the two-wire line (3) has a first communication signal (5) for data transmission;

a demodulation unit (12) which is adapted to demodulate a current signal of the two-wire line (3), so that a second communication signal (6) of the communication box (4) is available.

12. System of automation technology comprising at least one field device (2) according to one of claims 6 to 10, a communication box (4) according to claim 1 1 and a two-wire line (3) which connects the field device (2) with the communication box (4) and via the field device (2) can be supplied with energy.

13. The system of claim 12, wherein the communication box (4) has at least one further functionality to equip the field device (2) also with this functionality, wherein the communication box with the field device according to the method of claim 1 data related to the further functionality exchange

14. The system of claim 13, wherein the communication box is formed on the at least one further functionality to allow a connection of the communication box via a radio protocol or a wired protocol and the

Communication box with the field device exchanges data relating to the radio protocol or the wired protocol.