Field device adapter for wireless data transfer

Abstract

Disclosed is a field device adapter for wireless data transfer, comprising: an adapter housing having a first and a second end, the first end such that the field device adapter can be mechanically connected to a field device and the second end such that a two-wire cable can be connected to the field device adapter. The adapter housing also having an adapter chamber; a supply electronics unit arranged in the adapter chamber and designed to provide a supply voltage via a voltage tap; an adapter electronics unit; and an adapter connection cable at the first end for connecting the adapter electronics to a field device electronics. The adapter electronics are designed to communicate the two-conductor signals between the field device electronics and the two-conducting-wire cable and also to convert the two-conductor signals into radio signals or vice versa.

Claims

1. A field device adapter for wireless data transfer, comprising: an adapter housing having a first end and a second end, the first end being designed such that the field device adapter can be mechanically connected to a field device, and the second end being designed such that a two-wire line for data transfer can be electrically connected to the field device adapter, wherein the adapter housing also has an adapter chamber between the first and second ends; a voltage reference embodied to provide a supply voltage independently of a current on the two-wire line, at least one diode, or a resistor, wherein the voltage reference, the at least one diode, or the resistor is arranged in the adapter chamber and designed to provide the supply voltage via a voltage tap at the two-wire line that is connectable at the second end, wherein the voltage tapping takes place across the voltage reference, the at least one diode, or the resistor; an adapter electronics unit arranged in the adapter chamber and to which the supply voltage is fed; and an adapter connection cable located at the first end for electrically connecting the adapter electronics unit to a field device electronics unit of the field device that is connectable at the first end, wherein the adapter electronics unit is designed to communicate two-conductor signals between the field device electronics unit electrically connectable at the first end by means of the adapter connection cables and the two-wire line connectable at the second end, and wherein the adapter electronics unit is also designed to convert the two-conductor signals into radio signals, to convert radio signals into the two-conductor signals, and to transmit and receive the radio signals by radio.

2. The field device adapter according to claim 1, wherein the adapter electronics unit is designed to convert digital two-conductor signals based on a HART protocol into radio signals and to convert radio signals into digital two-conductor signals based on the HART protocol.

3. The field device adapter according to claim 2, wherein the adapter electronics unit includes a HART modem which carries out the conversion of the digital two-conductor signals based on the HART protocol into radio signals and the conversion of the radio signals into digital two-conductor signals based on the HART protocol.

4. The field device adapter according to claim 3, wherein the HART modem is designed as a secondary master in accordance with the HART protocol.

5. The field device adapter according to claim 1, wherein the adapter electronics unit further includes a communication resistor arranged between the two-wire line that is connectable at the second end and the adapter connection cable located at the first end, wherein the adapter electronics unit is designed to receive the radio signals and convert the received radio signals into the two-conductor signals with the aid of the communication resistor and to route the converted two-conductor signals to the field device electronics unit that is electrically connectable by the adapter connection cables.

6. The field device adapter according to claim 5, wherein the adapter electronics unit is further designed to convert analog two-conductor signals based on a 4-20 mA standard into radio signals and to convert radio signals into an analog two-conductor signal based on the 4-20 mA standard with the aid of the communication resistor.

7. The field device adapter according to claim 2, wherein the adapter electronics unit is further designed to convert the digital two-conductor signals based on the HART protocol into radio signals in accordance with one of the following radio protocols: a Bluetooth protocol, a 6LoWPAN protocol, a WirelessHART protocol, and a 6TiSCH protocol.

8. The field device adapter according to claim 1, wherein the at least one diode is arranged such that a cathode of the at least one diode is connected to the two-wire line which is connectable at the second end and an anode of the at least one diode is connected to the adapter connection cable located at the first end.

9. The field device adapter according to claim 1, wherein an overvoltage protection resistor for overvoltage protection is connected in parallel with the resistor.

10. The field device adapter according to claim 5, wherein the voltage tapping takes place via the communication resistor.

11. The field device adapter according to claim 1, further comprising: a connection terminal for electrically connecting and/or contacting the two-wire line to the adapter electronics unit, wherein the connection terminal is arranged in the region of the second end in the adapter chamber.

12. The field device adapter according to claim 1, wherein the adapter housing takes the form of a PG cable gland.

13. The field device adapter according to claim 1, wherein the second end of the adapter housing is designed such that the field device adapter is mechanically connectable to a cable gland connection of the field device via an M20 thread.

14. The field device adapter according to claim 1, wherein the adapter electronics unit includes a radio unit which has an antenna for transmitting the radio signals and/or for receiving the radio signals and a radio module for converting the radio signals.

15. An automation field device for capturing and/or controlling a process variable, comprising: a field device housing having at least one housing opening; a field device electronics unit disposed within the field device housing and designed to communicate data in the form of two-conductor signals based on a HART protocol; and a field device adapter, including: an adapter housing having a first end and a second end, the first end being designed such that the field device adapter can be mechanically connected to a field device, and the second end being designed such that a two-wire line for data transfer can be electrically connected to the field device adapter, wherein the adapter housing also has an adapter chamber between the first and second ends; a voltage reference embodied to provide a supply voltage independently of a current on the two-wire line, at least one diode, or a resistor, wherein the voltage reference, the at least one diode, or the resistor is arranged in the adapter chamber and designed to provide the supply voltage via a voltage tap at the two-wire line that is connectable at the second end, wherein the voltage tapping takes place across the voltage reference; an adapter electronics unit arranged in the adapter chamber and to which the supply voltage is fed; and an adapter connection cable located at the first end for electrically connecting the adapter electronics unit to a field device electronics unit of the field device that is connectable at the first end, wherein the adapter electronics unit is designed to communicate two-conductor signals between the field device electronics unit electrically connectable at the first end by means of the adapter connection cables and the two-wire line connectable at the second end, and wherein the adapter electronics unit is also designed to convert the two-conductor signals into radio signals, to convert radio signals into the two-conductor signals, and to transmit and receive the radio signals by radio, wherein the field device adapter is mechanically attached at the first end to the at least one housing opening and the adapter electronics unit is electrically connected to the field device electronics unit via the adapter connection cable so that the two-conductor signals between the field device electronics and a two-wire line which can be connected at the second end are transferred by the adapter electronics unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in more detail based upon the following drawings. The following is shown:

(2) FIG. 1 shows a schematic representation of a two-wire field device, as is currently found in a variety of existing automation systems and with which data can be communicated exclusively by wire via a two-wire line;

(3) FIG. 2 shows a schematic representation of a field device adapter according to the present disclosure; and

(4) FIG. 3 shows a schematic representation of a field device to which a field device adapter is attached.

DETAILED DESCRIPTION

(5) FIG. 1 shows schematically a two-wire field device which comprises a metallic housing 2 within which a field device electronics unit 4 is arranged. The field device electronics unit 4 is designed in such a way as to have connection terminals 13 via which a two-wire line 12 is electrically connected. The field device electronics unit 4 and thus the field device 1 are connected via the two-wire line to a superordinate unit, not shown separately in FIG. 1, in order to communicate data with the superordinate unit by wire. Here the measurement or control values are communicated in analog form as a main process variable via the two-wire line 12 as a 4-20 mA current signal, and all other data are transferred in accordance with the HART standard in the form of a digital two-conductor signal.

(6) To enable the two-wire line coming from outside the housing 2 to be put into electrical contact with the field device electronics unit arranged in the housing 2, the metallic housing 2 has a housing opening 3. A cable gland 5 is introduced into the housing opening 3 so that the two-wire line 12 can be introduced into the housing 2 through the cable gland 5. The cable gland 5 preferably takes the form of a PG cable gland, i.e. a cable gland with a heavy-gauge steel conduit thread, in accordance with the DIN EN 62444 standard published in May 2014. The cable gland 5 can, for example, take the form of an M20 PG cable gland, i.e. having an outer diameter of 20 mm.

(7) FIG. 2 shows a schematic representation of a field device adapter 6 according to the invention. The field device adapter 6 has an adapter housing 7 with an adapter chamber 10. The adapter housing 7 is designed in such a way that the field device adapter 6 can be mechanically fastened at a first end to a cable gland 5, especially a PG cable connection, of a field device 1. The first end of the adapter housing preferably has a M20 thread for this purpose. At a second end 9 opposite the first end 8, the adapter housing 7 is designed in such a way that a two-wire line 12 for data transfer can be electrically connected to the field device adapter 6. For example, a connection terminal 11 located at the second end can be used for this purpose. Furthermore, the field device adapter 6 has an adapter electronics unit 14 and a supply electronics unit 15 which are likewise arranged within the adapter chamber 10. As shown in FIG. 2, the supply electronics unit 15 can be embodied as a part of the adapter electronics unit 14 or be separate from the adapter electronics unit 14.

(8) The supply electronics unit 15 may comprise a voltage reference, at least one diode, preferably a z diode, or a resistor, and may be designed to provide a supply voltage for voltage supply to the adapter electronics unit 14 via a voltage tap.

(9) In the simplest case, the supply voltage is provided via a voltage tap via the voltage reference, the at least one diode, preferably z diode, or the resistor. The diode is arranged such that a cathode is connected to the two-wire line 12 which can be connected at the second end 9 and an anode is connected to the adapter connection cable 16 located at the first end 8. A plurality of corresponding series-connected diodes is also conceivable. In the case whereby the supply electronics unit 15 has a resistor via which the voltage tapping takes place, a further resistor parallel to the resistor can be provided for overvoltage protection.

(10) The adapter electronics unit 14, which is fed by the supply voltage provided by the supply electronics unit 15, is connected at the first end 8 to the adapter connection cable 16 and at the second end 9 to the two-wire line 12 by the connection terminals 11. The adapter electronics unit 14 is designed such that two-conductor signals, that is to say the 4-20 mA-based analog two-wire current signal as well as the two-wire digital signal formed according to the HART standard, communicate in both directions between the two-wire line 12 and the adapter connecting cables 16. In other words, the adapter electronics unit forwards the two-conductor signals in both directions. Furthermore, the adapter electronics unit 14 is designed to tap off the two-conductor signals, especially the digital two-conductor signals which are transferred according to the HART standard, and to convert them into radio signals and transmit the same by radio. The adapter electronics unit 14 can, however, not only be designed for transmitting the radio signals, but also for receiving radio signals and converting the radio signals into digital two-conductor signals which are then fed via the connection cable 16 to a field device electronics unit 4. The conversion and transmission or reception is effected via a radio unit 19 which for this purpose has a radio module for the conversion and an antenna for transmitting or receiving. In this way, for example, a field device can be wirelessly parametrized via radio signals.

(11) For converting the digital two-conductor signals into signals suitable for transmission by means of the radio unit and vice versa, the adapter electronics unit 14 comprises a HART modem which is connected for communication with the radio unit 19, for example by means of a serial interface 21, such as UART. In order for the adapter electronics unit 14 to be able to communicate two-wire digital signals to the field device 1, the HART modem is designed as a secondary master and the adapter electronics unit 14 also has a communication resistor 18. A voltage modulation corresponding to the digital two-conductor signal to be transmitted is implemented via the communication resistor 18.

(12) The adapter electronics unit 14 and the radio unit 19 can furthermore be designed such that the analog current signal or two-conductor signal is also captured or tapped by the adapter electronics unit 14 via the communication resistor 18 and converted into radio signals by the radio unit 19 so that even the analog two-conductor signals are transferable by radio.

(13) The radio unit 19 is designed in such a way that in particular radio signals may be in accordance with a Bluetooth protocol or variant derived therefrom, a 6LoWPAN protocol, a WirelessHART protocol, and/or a 6TiSCH protocol.

(14) FIG. 3 shows a schematic representation of a field device 1 to which a field device adapter 6 as described above is attached. As shown in FIG. 3, the field device adapter 6 can be arranged in such a way that it is located between the housing opening 3 of the field device 1 and the cable connection 5. In this case, the second end 9 of the adapter housing 7 is designed in such a way that the cable gland 5 can be fastened in place. For example, the second end 9 can also take the form of a PG cable gland with an M20 thread in accordance with the DIN EN 62444 standard published in May 2014.

(15) Alternatively, the field device adapter 6 can also be designed in such a way that it itself serves as a cable gland and thus when it is fitted to the field device no separate cable connection is required. It goes without saying that in this case the second end 9 does not necessarily have to take the form of a PG cable gland. 1 Automation field device 2 Field device housing 3 Housing opening 4 Field device electronics unit 5 Cable gland 6 Field device adapter 7 Adapter housing 8 First end of the adapter housing 9 Second end of the adapter housing 10 Adapter chamber 11 Connection terminals of the field device adapter 12 Two-wire line 13 Connection terminals of the field device 14 Adapter electronics unit 15 Supply electronics unit 16 Adapter connection cable 17 HART modem 18 Communication resistor 19 Radio unit 20 M20 thread for mechanically connecting the adapter to a cable gland of a field device 21 Serial interface 22 Lines for the power supply