WO2017041987A1

WO2017041987A1 - Electronic circuit for automatically supplying a first and a second module of a field device, field device, and corresponding method

Info

Publication number: WO2017041987A1
Application number: PCT/EP2016/069197
Authority: WO
Inventors: Bernd Strütt; Gerd BECHTEL; Christian Seiler
Original assignee: Endress+Hauser Gmbh+Co. Kg
Priority date: 2015-09-10
Filing date: 2016-08-12
Publication date: 2017-03-16
Also published as: DE102015115273A1

Abstract

The invention relates to an electronic circuit (2) for automatically supplying a first module (M) and a second module (BT) of a process automation field device (FG) with energy from a two-wire bus (4), comprising a first branch (Z1) with at least one first diode (D1) which is connected to the two-wire bus (4) in the forward direction, a first energy storage device (C1) which can be charged with energy by the two-wire bus (4), wherein the first energy storage device (C1) is connected downstream of the first diode (D1), and the first module (M), said first module (M) being supplied with energy from the energy storage device (C1); and a second branch (Z2) which is connected parallel to the first branch (Z1) and comprises at least the second module (BT), said second module (BT) being supplied with energy solely by the two-wire bus (4). The invention further relates to a field device comprising such a circuit (2) and to a corresponding method.

Description

Electronic circuit for self-sufficient supply of a first and second module of a field device, field device and corresponding method

The invention relates to an electronic circuit for autonomously supplying a first module and a second module of a field device of process automation with energy from a two-conductor bus. The invention further relates to a field device comprising such a circuit. The invention further relates to a corresponding method.

In process automation technology, field devices are often used to detect and / or influence process variables. As field devices are in the

Principle designates all devices that are used close to the process and that supply or process process-relevant information. In addition to sensors and actuators, field devices generally also refer to those units which are connected directly to a field bus and serve for communication with a control station, such as a control system, such as a control system. Remote I / Os, Gateways, Linking Devices and Wireless Adapters.

A large number of such field devices are manufactured and distributed by the Endress + Hauser Group. The omission of wired data transmission for the connection of a field device has the potential in the industrial sector to reduce costs for wiring, the

Improve usability and thus generate benefits for the user.

Frequently, field devices are connected to a control center using two-wire technology. In two-wire technology, or else two-wire technology, power is sent to the power supply and communication signals are sent via the same line: a wire for the way out, a wire for the way back. In other words, power and signal use the same line; there is no separate energy supply. This current or the corresponding power must be managed by the field devices and shared among the individual components of the field device. For example, the sensor element, the communication and the control have to work together with the existing power budget.

Depending on the type of field device, one or more capacitors are required to buffer the energy from the two-wire field bus in order to make measuring and sending the data with the limited power budget possible in the first place. The

US 7,262,693 discloses the use of a capacitor to latch the energy from the bus to then provide it to a wireless module. If the capacitor is chosen too small, the measurement may need to be interrupted. On the other hand, capacitors which are too large are disadvantageous for use in the Ex area. In addition, space for large capacitors may not be available. The above-mentioned wireless module disclosed in US 7,262,693 is generally a module that temporarily requires a large power. The invention has for its object to provide an alternative circuit that provides energy from a two-bus for different connection modules.

The object is achieved by a circuit comprising: a first branch, comprising at least one first diode, which is connected in the forward direction to the two-line bus, and one, the two-wire bus with energy chargeable, first energy storage, wherein the first energy storage of the first diode downstream is, and the first module, wherein the first module is powered by the first energy storage; and a second branch connected in parallel with the first branch, comprising at least the second module, wherein the second module is powered solely by the two-conductor bus.

By the electronic circuit can be prevented that the second module accesses the energy storage. This is achieved by the first diode. Thus, no energy is provided by the energy store in the first branch for the second module in the second branch and no energy is shared between the two branches. It is prevented that energy is taken from the first branch. In other words, a flow of energy from the first branch to the second branch is prevented.

As noted, the wireless module of US 7,262,693 is generally a module that temporarily requires high power. This type of module is intended in the sense of this

Thus, in one embodiment, the first module is generally a module with a temporarily increased power consumption

Two-conductor bus to be delivered. By contrast, in a further embodiment, the "second module" is a module that consumes relatively little energy or power, but at least only as much as the two-conductor bus can deliver continuously.

In a further preferred development, the first module comprises a sensor element for detecting a measured variable, wherein the sensor element forwards values to a wireless module, and wherein the second module comprises the wireless module for wireless transmission of the values to a higher-level unit. The sensor element is fed by the first energy store.

"Values" in the sense of this invention are to be understood in a first advantageous embodiment as "values dependent on the measured variable". That is, the sensor element leads from the Measured variable dependent values to the wireless module, and the wireless module wirelessly transmits the values dependent on the measured value to a higher-level unit.

In a second advantageous embodiment, "values" are to be understood as parameters, whereby "parameters" here are to be understood as an actuating or influencing variable which acts on the sensor element and thus changes the behavior of the sensor element or

Provides information about the state of the sensor element. That is, the sensor element forwards parameters to the wireless module, the wireless module wirelessly transmitting these parameters to a higher-level unit. In a further advantageous embodiment, parameters are transmitted in the opposite direction, i. a higher-level unit wirelessly transmits parameters to the wireless module, which sends the parameters to the wireless module

Forwards sensor element.

In a first embodiment, the first module thus comprises a sensor element, for example for detecting the fill level, for example according to the radar principle. In another

Embodiment, the first module comprises a sensor element for determining a

Analysis parameters, in particular for measuring pH, redox potential, also ISFET, conductivity, or oxygen. Further advantageous embodiments comprise sensor elements for detecting the flow according to the principles of Coriolis, magnetic induction, vortex and ultrasound. Further advantageous embodiments include sensor elements for

Detection of the level according to the principles of guided and free radar radar (as already mentioned), as well as ultrasound, also for the detection of a level limit, which can also be used to detect the limit level and capacitive methods. In a further embodiment, the first module comprises a wireless module with increased energy consumption, that is to say a WLAN module, in particular according to the standard IEEE 802.1 1.

The electronic circuit can thus be prevented that also

Wireless module accesses the energy storage. This is achieved by the first diode. It is thus provided by the energy store in the first branch no energy for the wireless module in the second branch. The only connection between the wireless module and the sensor element are the communication links for sending measurement data. However, no energy is shared between the two branches. Another aspect of the electronic circuit is the self-controlling power management of the circuit. The capacity of the energy storage is designed so that enough energy is available for a complete measurement cycle. Therefore, a measurement will always be able to be completed, a current measurement will be delivered and forwarded to the wireless module accordingly. If the wireless module is power for communication needs, which is taken directly from the two-conductor bus, then the energy storage for the measurement is not loaded. In an advantageous embodiment, the state of charge of the energy storage is monitored by a measuring circuit and a measurement is only allowed if enough energy is available. For this reason, get one

Wireless communication always enough energy directly from the two-way bus. The measurement is delayed until the energy store is full. A measurement will be started afterwards.

In a further preferred development, the second branch further comprises: a second diode, which is connected in the forward direction to the two-line bus, and one, from

Zweileiterbus with energy chargeable, second energy storage, the second

Energy storage of the second diode is connected downstream.

It is thus also prevented that energy is taken from the second branch. In other words, a flow of energy from the second branch to the first branch is prevented. The two branches are thus self-sufficient in terms of energy. They can work without the energy of each other. A synchronization of the two branches is not necessary.

In a preferred embodiment, the first and / or the second branch comprise a DC-DC converter for converting the voltage from the two-wire bus into a voltage value that can be used by the wireless module or the sensor element. The DC-DC converter is the first energy storage and / or the second

Energy storage downstream.

Advantageously, the wireless module is a Bluetooth module, in particular the Bluetooth module is sufficient for the protocol stack Low Energy. As mentioned, the second module comprises a module which can be continuously fed by the two-conductor bus. A Bluetooth module with the protocol stack low energy meets this requirement. In an alternative embodiment, the second module comprises a

Sensor element that consumes little energy, at least only as much as the two-conductor bus can deliver continuously. An example of this is a temperature or pressure sensor.

In an advantageous embodiment, the circuit comprises a bus module, which connects the circuit to the two-wire bus, wherein the bus module is configured to support at least one of the FOUNDATION Fieldbus, PROFIBUS PA or HART protocols, and the two-wire bus is a corresponding bus. Thus, the circuit can be connected to a process automation bus. Preferably, the circuit includes a 4..20 mA current output when the bus module supports the HART protocol. Thus, an analog communication can be ensured. The object is further achieved by field device of process automation, comprising a circuit described above.

In a first advantageous embodiment, the field device is a

Level gauge, in particular according to the radar principle, i. as guided and free radar. Alternatively, the field device is used as a measuring device for detecting the

Point level, in particular according to the ultrasound principle or by means of capacitive methods configured.

In a second advantageous embodiment, the field device is an analysis measuring device, in particular the sensor element is for measuring pH,

Redox potential, also designed by means of an ISFET, conductivity, turbidity or oxygen.

As a third advantageous embodiment, the field device is a

Flow sensor, in particular according to the principles Coriolis, magnetic induction, vortex and ultrasound.

The invention is further achieved by a method comprising the steps of supplying a sensor element with energy from an energy store, the energy store being charged with energy from a two-conductor bus, supplying a wireless module with energy exclusively from the two-conductor bus, detecting the measured variable by the sensor element, forwarding the value dependent on the measured value to a wireless module, and wireless transmission of the values dependent on the measured value to a higher-level unit by a wireless module.

In a preferred embodiment, the state of charge of the energy store is monitored and a detection of the measured variable only takes place if sufficient energy is available for a measuring cycle. For this reason, a wireless communication always gets enough energy directly from the two-way bus. The measurement is delayed until the energy store is full. A measurement will be started afterwards.

In a further advantageous embodiment, parameters are forwarded from the sensor element to the wireless module, which then wirelessly from the wireless module to a

parent unit. In a further advantageous embodiment Parameters are sent to the wireless module by the parent unit and forwarded by the wireless module to the sensor element.

The invention will be explained in more detail with reference to the following figures. Show it

1 shows the field device according to the invention,

Fig. 2a / b, the circuit according to the invention in a schematic overview in a first (Fig. 2a) and second (Fig. 2b) embodiment, and

Fig. 3 shows the circuit according to the invention in a further embodiment.

In the figures, the same features are identified by the same reference numerals. 1 shows a field device FG of the process automation technology, for example a

Sensor. More specifically, two field devices FG1 and FG2 are shown. The sensor is a pH, redox potential, ISFET, conductivity, turbidity or oxygen sensor. Further possible sensors are flow sensors according to the principles of Coriolis, magnetic induction, vortex and ultrasound. Other possible sensors are sensors for measuring the level according to the principles of guided and free-radiant

Radar as well as ultrasound, also for the detection of a limit level, whereby capacitive methods can also be used to detect the limit level.

Shown is a pH sensor on the left and a fill level sensor on the right according to the radar principle. The field device FG determines a measured variable of a medium 1, in the example in a cup as shown on the left side. However, other containers such as pipes, basins (as shown on the right side), container, boiler, pipe, pipe or similar. possible. The field device FG communicates with a control station, such as directly with a control system 5 or with an intermediate transmitter. Also, the transmitter may be part of the field device, such as in the case of the level sensor. The communication to the

Control system 5 takes place via a two-conductor bus 4, for example via HART, PROFIBUS PA or FOUNDATION Fieldbus. It is also possible to design the interface 6 to the bus additionally or alternatively as a wireless interface, such as the WirelessHART standard (not shown), via WirelessHART a connection directly to a control system via a gateway. In addition, a 4..20 mA interface is optionally or additionally provided in the case of the HART protocol (not shown). Is this done?

Communication additionally or alternatively to a transmitter instead of directly to the control system. 5 Either the abovementioned bus systems can be used for communication, or a proprietary protocol, for example of the "Memosens" type, is used, Field devices described above are marketed by the Applicant As mentioned, an interface 6 is at the bus end of the field device FG The interface 6 connects the field device FG to the bus 4, the field device comprises a corresponding bus module In the wired variant, the interface 6 is configured, for example in the case of the pH sensor, as a galvanically isolating, in particular as inductive, interface then two parts with a first part on the field device side and a second part on the bus side These can be coupled to each other by means of a mechanical plug-in connection via the interface 6 data (bidirectional) and energy (unidirectional, ie in the direction of the control unit 5 for Field device FG) Alternatively, a suitable cable with or without galvanic isolation is used. Possible versions include a cable with an M12 or 7/8 "plug.

The field device FG further comprises an electronic circuit 2 comprising a

Wireless module BT for wireless communication 3. The wireless module BT is configured approximately as a Bluetooth module. In particular, the Bluetooth module satisfies the low energy protocol stack as "Bluetooth Low Energy" (also known as BTLE, BLE, or Bluetooth Smart).

Components. The field device FG thus satisfies at least the standard "Bluetooth 4.0." The communication 3 is performed by the field device FG to a higher-level unit H. The

Higher-level unit H is, for example, a mobile unit such as a mobile phone, a tablet, a notebook, or the like. Alternatively, the higher-level unit H can also be designed as a non-portable device, such as a computer. Alternatively, the higher-level unit is a display with a corresponding interface.

Fig. 2a and Fig. 2b show the electronic circuit 2 in more detail.

The field device FG is connected as mentioned via the interface 6 with the Zweileiterbus 4. The electronic circuit 2 comprises a first branch Z1 and a second branch Z2 parallel to the first branch Z1. The first branch Z1 comprises a first diode D1 in the forward direction to the two-wire bus 4. Shown is the connection of the diode D1 with the anode at the positive pole of the two-wire bus 4. However, without inventive step, a correspondingly opposite configuration is possible.

First, the embodiment in Fig. 2a will be discussed. The first branch Z1 further comprises a first energy store C1, which is connected downstream of the first diode D1. at the energy storage C1 is about a capacitor for storing energy. For the purposes of this invention, an energy store is not a filter capacitor, smoothing capacitor, a capacitor for ensuring the electromagnetic compatibility or a capacitor such as in

DC-DC converters is needed. The energy storage C1 is directly from the

Two-conductor bus 4 loadable. Connected downstream of the energy store C1 is a sensor element M for detecting the measured variable, i. the sensor element M is fed by the energy storage C1. Between sensor element M and energy storage C1 is a

DC-DC converter DC (english: DC-DC Converter) connected. Of the

DC converter DC converts the input voltage of about 10-45 V to about 3-5 V. The energy storage device C1 supplies the sensor element M with energy. The Zweileiterbus 4 does not provide enough energy, so that the sensor element M could be continuously supplied from the Zweileiterbus 4 with energy. Therefore, a measurement takes place only when the energy storage C1 is sufficiently filled and a complete measurement cycle can take place. For this purpose, the first branch Z1 also includes a corresponding measuring circuit to the

To monitor the charge state of the energy storage C1. After the measurement, the sensor element M forwards the measurement data or parameters, see below, to the wireless module BT. For this purpose, communication lines Tx and Rx are used. Shown here is in the first branch Z1, a sensor element M, via the

Energy storage C1 is supplied with energy, since the energy requirement is greater than the two-wire bus 4 could deliver continuously. In general, it is in the

Sensor element M to a module that temporarily requires a large power or energy. This energy can not be supplied continuously through the two-conductor bus. As an alternative to the sensor element M, a wireless module with an increased energy requirement can be selected, for example a WLAN module. If a WLAN module is used in the first branch Z1, in the second branch Z2 a sensor element is used which can be supplied continuously from the bus 4, for example a temperature or pressure sensor, see below. The second branch Z2 comprises a wireless module BT for the wireless transmission of the values dependent on the measured value to the higher-level unit H. Before the wireless module BT, a DC-DC converter DC is connected, which converts the voltage of about 10-45 V to 3-5 V. As an alternative to the values dependent on the measured variable, parameters are transmitted, whereby as "parameter", as mentioned, an actuating or influencing quantity is to be understood, which acts on the sensor element and thus changes the behavior of the sensor element or provides information about the state of the sensor element For the sake of completeness it should be mentioned that parameters can also be transmitted in the opposite direction, ie a higher-level unit wirelessly transmits parameters to the wireless module, which forwards the parameters to the sensor element.

The wireless module BT is powered exclusively by the two-conductor bus 4 with energy. The wireless module BT never needs more power than the dual-bus 4 could deliver continuously. For this reason, no further capacitor, generally no further energy storage, is necessary in this branch. As an alternative to the wireless module, it is also possible to use a sensor element which can be supplied with energy continuously from the bus 4, for example a temperature or pressure sensor.

By the electronic circuit 2 can be prevented that also the wireless module BT accesses the energy storage C1. This is achieved in particular by the decoupling diode D1. It is thus provided by the energy storage C1 no energy for the wireless module BT. The only connection between the sensor element M and the

Wireless module BT are the communication links Tx and Rx. However, no energy is shared between the two branches Z1 and Z2.

Another aspect of the electronic circuit 2 is the self-controlling power management of the measurement circuit. The capacity of the energy storage C1 is designed so that enough energy is available for a complete measurement cycle. Therefore, a measurement will always be able to be completed, a current measurement will be delivered and forwarded accordingly to the wireless module BT. If the wireless module BT needs energy for the communication, which - as mentioned - is taken directly from the Zweileiterbus 4, then the energy storage device C1 is not charged for the measurement or can not even be charged. As mentioned, the state of charge of the energy storage C1 is monitored and measurement is only allowed if there is enough energy available. For this reason, the wireless module BT for the wireless communication 3 always gets enough energy directly from the Zweileiterbus 4. The measurement is delayed until the energy storage is full. A measurement will be started afterwards.

FIG. 2b shows a development in which the second branch Z2 likewise comprises a diode, which is designated by the reference symbol D2. This is connected in the same configuration as the diode D1. The second branch Z2 also includes an energy store, here referred to as C2. The above applies analogously to C2. It is thus also prevented that energy is taken from the second branch Z2 and it is also a

Energy flow from the second branch Z2 to the first branch Z2 prevented. The two branches Z1, Z2 are thus self-sufficient in terms of energy. They can work without the energy of each other. A synchronization of the branches Z1, Z2 is not necessary (for energy-technical reasons). Fig. 3 shows an embodiment in which the DC-DC converter DC to the first

Energy storage C1 is not downstream. Instead, the DC-DC converter DC is connected upstream of the energy store C1 and the diode D1. The above applies analogously to this type of circuit. Optionally, an additional linear regulator L between DC-DC converter DC and wireless module BT can be switched. Alternatively, another DC-DC converter DC is possible. Not shown, but without inventive step, it is possible that a similar circuit as in Fig. 2b, ie with additional components diode D2 and second energy storage C2 in the second branch Z2, is constructed.

LIST OF REFERENCE NUMBERS

1 container with medium to be measured

2 electronic circuit

3 wireless connection

4 two-conductor bus

5 control point

6 interface

BT wireless module

C1 energy storage

C2 energy storage

D1 diode

D2 diode

DC DC-DC converter

FG field device

H superior unit

L linear controller

M sensor element

Tx sending values

Rx receiving values

Z1 First branch

Z2 Second branch

Claims

claims

Electronic circuit (2) for self-sufficient supply of a first module (M) and a second module (BT) of a field device (FG) of the process automation with energy from a Zweileiterbus (4), comprising

- a first branch (Z1) comprising at least

^■ a first diode (D1), which in the forward direction to the two-conductor bus (4)

is switched, and

^■ one from the two-wire bus (4) loadable with energy, the first energy storage (C1), wherein the first energy store (C1) of the first diode (D1) is connected downstream, and

^■ the first module (M), wherein the first module (M) from the first energy storage (C1) is powered, and

- One, the first branch (Z1) connected in parallel, second branch (Z2), comprising at least

^■ the second module (BT), the second module (BT) being used exclusively by

Two-conductor bus (4) is powered.

Electronic circuit (2) according to claim 1,

wherein the first module comprises a sensor element (M) for detecting a measured variable, wherein the sensor element (M) forwards values to a wireless module (BT), and wherein the second module transmits the wireless module (BT) to a higher-level unit (BT). H).

Electronic circuit (2) according to claim 1 or 2,

wherein the second branch (Z2) further comprises:

- A second diode (D2), which is connected in the forward direction to the Zweileiterbus (4), and

- One, the Zweileiterbus (4) loadable with energy, the second energy storage device (C2), wherein the second energy storage device (C2) of the second diode (D1) is connected downstream.

Electronic circuit (2) according to at least one of claims 1 to 3,

wherein the first and / or the second branch (Z1, Z2) a

DC converter (DC) comprise, and wherein the DC-DC converter (DC) is connected downstream of the first energy store (C1) and / or the second energy store (C2).

5. Electronic circuit (2) according to at least one of claims 2 to 4,

wherein the wireless module (BT) is a Bluetooth module, in particular the Bluetooth module meets the protocol stack Low Energy.

6. Electronic circuit (2) according to at least one of claims 1 to 5,

wherein the circuit comprises a bus module connecting the circuit to the

Two-bus (4) binds, wherein the bus module is designed to support at least one of the FOUNDATION Fieldbus, PROFIBUS PA or HART protocols, and it is the Zweileiterbus (4) is a corresponding bus.

7. Electronic circuit (2) according to at least one of claims 1 to 6,

wherein the circuit (2) comprises a 4..20 mA current output if the bus module supports the HART protocol.

8. Field device (FG) of process automation, comprising a circuit (2) according to

at least one of claims 1 to 7.

9. field device (FG) according to claim 8,

wherein the field device (FG) is a fill level measuring device, in particular according to the radar principle.

10. Field device (FG) according to claim 8,

wherein the field device (FG) is an analysis measuring device, in particular the sensor element (M) for measuring pH, redox potential, is also ISFET,

Conductivity, turbidity or oxygen designed.

1 1. Method for detecting a process automation process variable and for

wireless transmission of a value dependent on the measured value to a

higher-level unit (H), comprising the steps

Supplying a sensor element (M) with energy from an energy store (C1), the energy store (C1) being charged with energy from a two-line bus (4),

- Supplying a wireless module (BT) with energy exclusively from the

Two-conductor bus (4),

- detecting the measured variable,

- Forward the values dependent on the measured value to a wireless module (BT), and

- Wireless transmission of the values dependent on the measurand to one

superior unit (H) through the wireless module (BT). Method according to claim 1 1,

wherein the state of charge of the energy store (C) is monitored and a detection of the measured variable takes place only when sufficient energy is available for a measuring cycle.