WO2018050422A1

WO2018050422A1 - Adaptation of the transmission and/or reception power in a field device

Info

Publication number: WO2018050422A1
Application number: PCT/EP2017/071343
Authority: WO
Inventors: Christian Seiler
Original assignee: Endress+Hauser Gmbh+Co. Kg
Priority date: 2016-09-19
Filing date: 2017-08-24
Publication date: 2018-03-22
Also published as: DE102016117624A1

Abstract

The invention relates to a method for improving the measuring performance of a process automation field device (FG), wherein the field device (FG) comprises at least one wireless module (BT) and at least one functional module (M) for capturing a measurement variable, and wherein the field device (FG) is supplied with energy by means of a two-wire bus (4), and wherein the transmission and/or reception power of the wireless module (BT) is adapted on the basis of environmental parameters. The invention also relates to a field device (FG) for carrying out such a method.

Description

ADJUSTING THE TRANSMIT AND / OR RECEIVING POWER IN A FIELD DEVICE

The invention relates to a method for improving the measurement performance of a field device of process automation and such a field device.

In process automation technology, field devices are often used to detect and / or influence process variables. A large number of such field devices are manufactured and distributed by the Endress + Hauser Group.

Often, field devices are connected to a control center using two-wire technology

connected. 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 power or the corresponding power must be managed by the field devices and under the individual components of the

Field device to be shared. For example, the sensor element for detecting the process variable, the communication with other units and the controller have to get along with the existing power budget.

The renunciation of wired data transmission for the connection of a

Field device has the potential in the industrial sector to reduce costs for wiring, to improve the usability and thus benefit for the

Generate users.

There are measuring methods which do not manage without an energy storage device in the form of an energy storage capacitor, since the available power is not sufficient for the measurement and initially between the measurements

Energy must be collected. An example of this is a level measurement according to the radar principle. Is a corresponding meter a

energy-saving wireless interface added, is not another

Energy storage required in the system when the measuring system fed exclusively from the already existing energy storage capacitor. In this case, the measurement is only performed when the

Energy storage capacitor has sufficient capacity. The duration of the period between the individual measurements then depends on how much power is required by the wireless interface and further functional modules in the system just out of the two-wire current loop. Excess power is stored in the corresponding energy storage capacitor.

For example, US Pat. No. 7,262,693 discloses the use of a capacitor to latch the energy from the bus and then to it

Wireless module to provide.

Depending on the power consumption of the measuring function, however, an exact simultaneous operation of the measurement and radio transmission is often not possible. Then it is e.g. required to perform the measurement alternately to the radio transmission in order to continue to get along without energy storage in the system.

As mentioned, however, both functions (radio transmission and measurement) can often not be operated simultaneously because then a synchronization of the various units is necessary, so that the power balance of the entire

Device can be maintained or it is often necessary to give priority to one of the functions in terms of energy consumption.

If, for example, priority is given to the radio module, this is at the expense of the measuring performance. If more energy is consumed by the wireless function, less energy is available for the measurement function and thus can be measured less frequently or less intensively, which ultimately leads to a reduction in measurement performance and thus to restrictions for the user. The invention is based on the object, a sufficiently high

To ensure measuring accuracy of a field device.

The object is achieved by a method wherein the field device comprises at least one wireless module and at least one functional module for detecting a measured variable and wherein the field device is supplied with energy by a two-conductor bus is, and wherein depending on environmental parameters, the transmission and / or reception power of the wireless module is adjusted.

Preferably, with decreasing transmission and reception power of the wireless module, the measurement performance of the field device is increased by changing operating parameters, and vice versa.

In an advantageous embodiment, the operating parameters are the measuring rate, measuring power, resolution, mathematical operations, clock rate of participating computing units, activation of additional evaluation units,

Compensation units, etc. In general, it concerns with the

Operating parameters around operations and settings that increased

Energy recordings to improve the accuracy of measurement and

Require measuring speed.

In a further preferred development, the connection quality between the field device and a receiver is measured, and the transmission and / or reception power is reduced to a defined minimum, so that the required measurement performance is still maintained. As a result, the consumed power of the wireless module is reduced and thus more energy is available to the functional module.

In an advantageous embodiment, the connection quality determined by the ambient conditions is determined by the field device and / or the receiver by means of the measurement of the Received Signal Strength Indicator (RSSI) and / or the

Measured packet error rate.

In this case, in a preferred embodiment, the distance from field device to receiver can be determined at least qualitatively on the basis of this measurement.

In an advantageous embodiment, the operation of the wireless module and the functional module is controlled so that the wireless module energy priority over the functional module has priority. It is particularly advantageous that no synchronization takes place between the wireless module and the functional module.

The environmental parameters are preferably at least one of the parameters: distance between the field device and a receiver,

atmospheric attenuation / absorption, attenuation / absorption by persons and objects in the vicinity of the field device and / or the receiver, and / or reflections and extinction by superimposition of radio waves,

electromagnetic interference fields / waves, other sparking systems in the

Environment and weather phenomena, which the connection quality

affect.

The object is likewise achieved by a field device which is set up to carry out a method described above.

The invention will be explained in more detail with reference to the following figure. Fig. 1 shows a field device in which the method according to the invention is applied.

Fig. 1 shows field devices FG of process automation technology. More specifically, two field devices FG1 and FG2 are depicted, these being sensors. 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. Further possible sensors are sensors for measuring the fill level according to the principles of guided and free-radar radar and ultrasound, also for detecting a limit level, which can also be used to detect the limit level and capacitive methods. The sensor comprises a sensor element as a function module M of the field device FG. Also, the sensor element may be part of the electronic circuit 2, see below.

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. Nevertheless, they are other containers such as pipes, tanks (as shown on the right), containers, boilers, pipes, pipes 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 part of the field device, such as in the case of the level sensor. The communication to the control system 5 via a two-conductor bus 4, such as 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 above-mentioned bus systems (HART,

PROFIBUS PA or FOUNDATION Fieldbus), or a proprietary protocol of the "Mennosens" type, for example, is used, and corresponding field devices as described above are marketed by the Applicant.

As mentioned, an interface 6 for connection to the two-wire bus 4 is provided on the bus-side end of the field device FG. Shown is a wired variant for connection to the bus by means of the interface 6. The interface 6 is, for example, as a galvanically isolating, in particular as inductive

Interface designed. This is shown with the pH sensor. The interface 6 then consists of two parts with a first part on the field device side and a second part on the bus side. These are by means of a mechanical

Plug connection can be coupled together. Data (bidirectional) and energy (unidirectional, i.e., in the direction from the control station 5 to the field device FG) are sent via the interface 6. Alternatively, an appropriate cable with or without galvanic isolation is used. Possible versions include a cable with an M12 or 7/8 "plug

Level gauge according to the radar principle shown. The field device FG further comprises an electronic circuit 2 comprising a wireless module BT for wireless communication 3. This wireless

Communication 3 is not the connection to the two-wire bus 4. The wireless module BT is designed as a Bluetooth module. The Bluetooth

In particular, the module complies with the protocol stack Low Energy as "Bluetooth Low Energy" (also known as BTLE, BLE, or Bluetooth Smart.) If necessary, the wireless module BT comprises a corresponding circuit or components The field device FG thus satisfies at least the "Bluetooth 4.0" standard. ,

The communication 3 is performed by the field device FG to a higher-level unit H here or receiver. This is not shown to scale. The higher-level unit H is, for example, a mobile unit such as a

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

In order now to have a sufficiently high measuring accuracy of the field device FG

ensure the transmission and reception performance of the wireless module BT is down to a defined minimum, depending on the connection quality. This reduces the consumed power of the

Wireless module and thus is the function module M more energy

Available. The chipsets available today for the BT wireless module allow adjustment and measurement of various parameters. It may even be possible to put the chip BT in a "whisper mode"

offset to further save energy.

The method according to the invention provides for reducing the transmission and reception power of the wireless module in order thereby to carry out the measuring performance of the field device

Increase change of operating parameters. The operating parameters are, for example, the measuring rate, measuring accuracy, resolution,

mathematical operations, etc. It depends on

Ambient parameters, the transmission and / or reception power of the

Wireless module BT adapted. As "environmental parameters" should be at least one of the parameters distance between field device FG and a receiver H, atmospheric attenuation / absorption, attenuation / absorption by persons and objects in the vicinity of the field device FG and / or the receiver H, and / or reflections and extinction by superimposition of radio waves, electromagnetic interference fields / waves, other sparking systems in the

Environment and weather phenomena, which the connection quality

impair, be understood.

To determine the determined by the environmental conditions

Connection quality will be two independent measurements either by the

Field device FG, the receiver H or performed by both. On the one hand, the measurement of the Received Signal Strength Indicator (RSSI) should be mentioned. The RSSI is the received broadband power in the frequency channel, including thermal noise and noise generated in the receiver itself. Also, the power components from all other sources, for example, neighboring neighboring cells and adjacent channel interference, are included in the measurement. Second, this is the measurement of the packet error rate, i. how many packets per time unit arrive undisturbed at the receiver. Or in other words, it checks how many repetitions were necessary to transmit the packets / time unit. In order to determine the packet error rate by the field device FG, a feedback of the respective remote station H is necessary. If the measurement is located at the receiver H, an adjustment between transmitter FG and receiver H is necessary only for acyclic data transmission. Based on these two measurements, it is possible to approximate the distance between the measuring device and the evaluation unit.

The wireless module BT always transmits with the lowest possible power and thus provides the measuring function with the highest possible power output from the

Total budget of the two-wire interface 4 available. Thus, the

Measurement performance increased, for example by increasing the measurement rate, measurement accuracy, further calculation such as averaging, clock rate of participating computing units,

Activation of additional evaluation units, compensation units, etc. In general, these are operations and settings that increased Require energy pickups to improve measurement accuracy and measurement speed.

A synchronization of the wireless module BT with the function module M does not take place. In the optimal case, this is not necessary either, since sufficient power is available for both.

As an additional aspect, it should be mentioned that the security is increased if the field device FG does not transmit with maximum possible power, but with minimum required power, since then the "operating radius" of the field device FG is limited to the radio transmission.

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

C energy storage capacitor

FG field device

H Parent unit

M functional module

Claims

claims

1 . Method for improving the measuring performance of a field device (FG) of process automation,

wherein the field device (FG) comprises at least one wireless module (BT) and at least one function module (M) for detecting a measured variable and wherein the field device (FG) is powered by a two-conductor bus (4), and

wherein the transmission and / or reception power of the wireless module (BT) is adjusted as a function of environmental parameters.

2. The method according to claim 1,

wherein with decreasing transmission and reception power of the wireless module (BT), the measurement performance of the field device (FG) by changing

Operating parameters, is increased, and vice versa.

3. The method according to claim 2,

where the operating parameters are the measuring rate, measuring power, resolution, mathematical operations, clock rate involved

Computing units, activation of additional evaluation units,

Compensation units, etc. acts.

4. The method according to at least one of claims 1 to 3,

wherein the connection quality between field device (FG) and a

Receiver (H) is measured, and wherein the transmitting and / or

Receiving power is reduced to a defined minimum, so that the required measurement performance is just kept.

5. The method according to claim 4,

wherein the link quality determined by the environmental conditions is measured by the field device (12) and / or the receiver (12) by means of the Received Signal Strength Indicator (RSSI) measurement and / or the packet error rate.

6. The method according to claim 5,

At least qualitatively the distance from

Field device (FG) to receiver (H) is determined.

7. The method according to at least one of claims 1 to 6,

wherein the operation of the wireless module (BT) and the functional module (M) is controlled so that the wireless module (BT) energy priority over the function module (M) has priority.

8. The method according to at least one of claims 1 to 7,

wherein between wireless module (BT) and functional module (M) no

Synchronization takes place.

9. The method according to at least one of claims 1 to 8,

wherein the environmental parameters are at least one of the following parameters: distance between field device (FG) and a receiver (H), atmospheric damping / absorption,

Attenuation / absorption by persons and objects in the vicinity of the field device (FG) and / or the receiver (H), and / or reflections and extinction by superpositions of radio waves, electromagnetic interference fields / waves, other sparking systems in the environment and

Weather phenomena which impair the connection quality.

10. Field device (FG) for process automation, which is adapted to the method according to at least one of the preceding claims

perform.