Method for operating a wireless network in an industrial process environment

Abstract

Method for operating a WirelessHART radio network (FN) in an industrial process environment, wherein the WirelessHART radio network (FN) comprises multiple participants (A, B, C, D, E, G), wherein the participants (A, B, C, D, E) of the WirelessHART radio network (FN) are field devices, wherein the participants (A, B, C, D, E, G) are controlled and / or monitored via the WirelessHART radio network (FN), wherein at least one first participant (A) of the WirelessHART radio network (FN) operates in a first operating mode or in a second operating mode, in which first operating mode measured values ​​and / or process-relevant data are sent from the first participant (A) at a first update rate, and in which second operating mode data is sent from the first participant (A) at a second update rate, wherein the second update rate is higher than the first update rate.and wherein at least some of the data transmitted during the second operating mode is received by at least one second participant (B) of the WirelessHART radio network (FN), wherein the data received by the second participant (B) is evaluated and a first indicator of the quality of the data transmission is determined and made available to a user.

Description

The invention relates to a method for operating a radio network in an industrial process environment. Furthermore, the invention relates to the use of the method. Furthermore, the invention relates to a device for use in an industrial process environment. In automation technology, particularly in process automation, field devices are frequently used to detect and / or control process variables. Sensors, such as level gauges, flow meters, pressure and temperature gauges, pH / ORP meters, conductivity meters, etc., are used to detect these process variables, measuring levels, flow rates, pressure, temperature, pH, and conductivity. Actuators, such as valves or pumps, are used to control process variables, changing the flow rate of a liquid in a pipe section or the fill level in a container. In principle, field devices are defined as all devices used close to the process that provide or process process-relevant information.In addition to the sensors and actuators mentioned above, the term "field devices" also generally refers to units that are participants in a fieldbus and are capable of communicating with higher-level units, such as remote I / Os, gateways, linking devices, and radio adapters. A wide variety of such field devices are manufactured and distributed by the Endress+Hauser Group. In modern industrial plants, field devices are typically connected to higher-level units via bus systems such as Profibus®, FOUNDATION Fieldbus®, HART®, etc. These higher-level units are usually control systems or automation units, such as a PLC (programmable logic controller). The higher-level units are used, among other things, for process control, process visualization, process monitoring, and commissioning of the field devices. The measured values ​​acquired by the field devices, particularly their sensors, are transmitted via the respective bus system to one or more higher-level units. Data is also transmitted from the higher-level unit to the field devices via the bus system for configuration, parameterization, diagnostics, and actuator control. In addition to wired data transmission between field devices and the higher-level unit, wireless data transmission, or radio transmission, is becoming increasingly important. Wireless data transmission via radio is specified, particularly in the Profibus®, FOUNDATION Fieldbus®, and HART® bus systems. Furthermore, radio networks for sensors are specified in more detail in the IEEE 802.15.4 standard. To implement wireless data transmission, newer field devices, especially sensors and actuators, are sometimes designed as wireless field devices. These typically have a radio unit and a power source as integral components, with the power source enabling the field device to operate independently. Furthermore, it is possible to upgrade field devices without a radio unit, especially sensors and actuators, into wireless field devices by connecting a wireless adapter that includes a radio unit. A wireless adapter is therefore a unit that transforms a "conventional" field device, designed only for a wired connection to a fieldbus, into a wireless field device. For example, such a wireless adapter is described in publication WO 2005 / 103851 A1. The wireless adapter is connected to a communication interface, in particular a fieldbus communication interface, of the field device, and the connection between the wireless adapter and the field device is generally detachable. Via the fieldbus communication interface, the field device can send the data to be transmitted via the bus system to the wireless adapter, which then transmits it wirelessly to the destination. Conversely, the wireless adapter can also transmit data wirelessly to the field device.The radio adapter receives data wirelessly from the gateway and / or the higher-level control unit and forwards it to the field device via the fieldbus communication interface. The field device is typically powered by a power source assigned to the radio adapter or the field device itself. This power source is usually a battery or rechargeable battery. Wireless networks in automation technology are characterized by low energy consumption. A major advantage of wireless networks over wired bus systems is the elimination of cabling and the associated maintenance. Typically, field devices integrated into a wireless network are powered by a battery—a power supply unit with limited capacity—as already mentioned. Wireless networks for automation technology, such as WirelessHART or ISA 100, are designed as mesh networks with varying configurations. Care is taken to ensure that each field device, or more generally, each node, can communicate with at least two other nodes, thus creating the necessary redundancy. An autonomous node for a mesh network is described in WO2005 / 094312 A2. In wireless networks, communication typically only takes place at specific times. Outside of active operating phases, the field devices are put into a standby mode to conserve energy. During these standby phases, energy consumption is at least approximately zero. As mentioned previously, in mesh networks, it is common for two nodes or two field devices to communicate with each other in a narrow frequency band during the relatively short period of a so-called time slot. Examples of such mesh networks have also become known from the publications DE 10 2005 022 989 A1 , GB 24 27 797 A , US 2004 / 02 46 935 A1 and US 2009 / 00 59 814 A1. From US patent 5467083 A1, a wireless electromagnetic data transmission system and method for boreholes has become known. The publication WO 2009022967 A2 discloses a procedure for managing the neighborhood list for a user terminal. If the field devices are, for example, measuring instruments, they are only activated when a measurement is actually requested or retrieved from the measuring point because it needs to be updated. However, in some systems, the measurement may only be requested once or twice a day. Consequently, measurement values ​​are transmitted over the wireless network infrequently. Due to these periods of inactivity, the field devices have a low workload. The update rate of the measurement values ​​in the aforementioned case is then only 1 to 2 times per 24 hours. Therefore, it is only possible to determine the signal quality of the wireless connection between such a device and its neighbors in the wireless network to a limited extent. The invention is therefore based on the objective of determining the quality of a radio connection between a participant in a radio network and his neighbors as quickly as possible. With regard to the method, the problem is solved according to the invention in that the radio network comprises several participants, wherein the participants are controlled and / or monitored via the radio network, wherein at least one first participant of the radio network is operated in a first operating mode or in a second operating mode, in which first operating mode data is sent from the first participant with a first update rate, in which second operating mode data is sent from the first participant with a second update rate, wherein the second update rate is higher than the first update rate, and wherein at least some of the data sent during the second operating mode is received by at least one second participant of the radio network.The data received from the second participant is evaluated, an initial indicator of the data transmission quality is determined and made available to a user. Wireless networks, such as WirelessHART, can now support up to 255 devices. Such a network can be used to monitor and / or control these devices remotely, for example, from a control room. The devices in such a network can be field devices like sensors and / or actuators, which in turn control and / or monitor processes in an industrial environment. Other devices can include remote I / Os, gateways, linking devices, and wireless adapters. According to the invention, a participant in the radio network is operated in a first operating mode or a second operating mode. The first operating mode can, for example, be a measurement mode for acquiring a measured quantity. However, the first operating mode can be interrupted by idle phases, as described above. A participant in a radio network in an industrial process environment, such as a measuring device, may therefore only transmit measurement data or other process-relevant information a few times a day via the radio network to, for example, a control unit. To keep energy consumption low, the participant, especially if it is powered by a battery, will be inactive as often as possible and will transmit as few bits as possible when active. The update rate at which data, especially data packets, are sent is correspondingly low. To determine the quality orA low workload, i.e., a low update rate of the data transmitted by the participant, is a disadvantageous characteristic of the quality of the connection to the radio network. Therefore, according to the invention, a second operating mode is provided, which has a higher update rate than the first operating mode, allowing data to be transmitted. Of course, in addition to the first and second operating modes, other operating modes, such as those for diagnostics and / or maintenance, etc., can also be provided, in which the participants of the radio network, in particular the first and / or second participant, can be operated. The second update rate can be chosen to be sufficiently high for this purpose to enable the timely detection of changes in the quality of the radio connection, especially data transmission. Determining the quality of the radio connection can be used for the alignment of the antenna or...The positioning of the participant is used. The update rate can refer, for example, to the number of data updates sent within a given time period. The data can be sent in the form of data packets or telegrams. These telegrams contain at least one destination address. The update rate therefore indicates, for example, how often data is sent from one participant to another, or more generally, to the wireless network. Each transmitted data packet or telegram can represent an update. The information contained in the data, data packet, or telegram can vary from update to update, for example, in the case of measurements of a changing quantity. Alternatively, the data can also contain the same standard message repeatedly. Specifically for communication in industrial process environments, communication standards have become established where a participant only sends data upon request. Examples of such standards are Foundation Fieldbus, Profibus, and HART. Corresponding field devices may then transmit data infrequently over the wireless network. A so-called burst mode has emerged from the state of the art. In this burst mode, data is sent by the participant without a specific request from a higher-level unit. The update rate in burst mode can be up to 10 / s or as low as 1 / s – this depends on the wireless network used. The update rate in normal, i.e., primary, operating mode is, for example, less than 1 / min or less than 1 / h, and especially less than 1 / d. Burst mode can therefore be used, for example, as a secondary operating mode. The update rate at which data is sent must be distinguished from the baud rate and the transmission rate. For example, the baud rate indicates how many symbols are transmitted per unit of time. These symbols can be encoded using bits. The transmission rate, i.e., the amount of data transmitted per unit of time, can then be determined based on the encoding used and the baud rate. The second participant can be located at a different location within the system than the first, but reachable via the wireless network. To receive data transmitted by the first participant, the second participant must be within range of the first participant's wireless connection. At least some of the data received by the second participant can then be used to determine an initial indicator of the data transmission quality over the wireless connection. This initial indicator can then be provided to a user. The user, who could be, for example, the system's operating personnel, can therefore quickly obtain information about the quality of the wireless connection or data transmission within the wireless network. Based on this information, a user can then, for example, adjust the antenna of the first or, if applicable, the second participant, or take other necessary steps.Move the radio adapter away from the first or second participant, i.e., place the radio adapter in a different location than, for example, the field device itself. In industrial environments, reflections of the radio signal, i.e., multipath propagation, can also occur due to the geometric arrangement of equipment in the plant, such as tanks or pipelines, etc., which impairs the connection of a participant to the radio network or to spatially neighboring participants. In one embodiment of the method, the second participant is therefore also operated in a first or a second operating mode, wherein in the first operating mode data is sent by the second participant at a third update rate, and wherein in the second operating mode data is sent by the second participant at a fourth update rate, the fourth update rate being higher than the third update rate, wherein at least some of the data sent by the second participant during the second operating mode is received by the first participant, wherein the data received by the first participant is evaluated and a second indicator of the quality of the data transmission is determined and made available to a user. As mentioned above, multipath propagation can, for example, lead to interference with the radio link. It has been observed that when exchanging data between two participants via a radio link, an asymmetry can occur between the two transmission directions. This can result in the first participant receiving data sent by the second participant with higher quality than the second participant receiving data sent by the first participant. The second participant, in its second operating mode, can, for example, send data at essentially the same second refresh rate as the first participant. Of course, instead of the second refresh rate used by the first participant in its second operating mode, the second participant can also send data at the fourth refresh rate, which does not necessarily correspond to the second refresh rate of the first participant.However, this fourth update rate should be at least higher than the third update rate so that a measure of the data transmission quality can be determined with sufficient accuracy and as quickly as possible. The first and second participants can also be in the second operating mode simultaneously, at least temporarily. The determination of the quality of the radio connection, in particular the first and / or the second parameter, must be carried out as simultaneously as possible with a change in the position of one of the participants, among other things in order to be able to draw conclusions about the correct positioning and orientation of the antenna or the participant. In a further embodiment of the method, the first indicator value is sent back to the first participant, and the second indicator value to the second participant. This allows the quality, or the indicator value representing the quality, of the data transmission from the first to the second participant, or from the second to the first participant, to be made available to a user at the location of the first or second participant in the wireless network, for example, via a local display unit. Alternatively, it is also possible to send only the first indicator value back to the first participant. Based on the first and second indicator values, the quality of the signal path, for example, between neighboring participants, can then be determined. From the first and second parameters, a third parameter can be determined, indicating the quality of the data transmission between the first and second participants. The first, second, and / or third parameter can then be displayed locally at the first and / or second participant, on a display of a connected field device, or on a handheld device. The amplitude of the received radio signal transmitting the data can serve as the first, second, or third parameter. Alternatively, the ratio of received data to transmitted data—i.e., the loss rate—can be used as a parameter for data transmission quality. In a further embodiment of the method, the data received by the second participant is data transmitted directly by the first participant. The data received by the second participant can originate directly from the first participant without being forwarded via an intermediate station, for example. This allows the identification of the participants in the wireless network that are spatially close, and especially those closest to the first participant, and who are still capable of receiving the data transmitted by the first participant. Furthermore, the quality of the data transmission to at least one of these neighboring participants can be determined. In one variant of the procedure, the data received by the first participant may be data sent directly by the second participant. In one embodiment of the method, several participants in the radio network, particularly spatially adjacent participants, are switched to the second operating mode. This allows the quality or quality indicator of a radio connection, or a common quality indicator of several radio connections, to be monitored and / or determined, particularly within a specific cell or spatial area of ​​the radio network or within a specific area of ​​the system. Since data transmission and data reception can be essentially independent of each other, in an advantageous embodiment several, particularly spatially adjacent, participants in the radio network can be in the second operating mode simultaneously, at least temporarily. In one embodiment of the method, the participants in the radio network, between whom a radio connection is possible, communicate with each other via a peer-to-peer connection in the second operating mode, with the data being transmitted between the participants via this peer-to-peer connection. The peer-to-peer connection used here is a so-called direct connection, in which the participants are connected to each other via the radio network without communicating through an intermediate station, particularly a hierarchically superior one, such as a gateway. The data transmitted by the first participant in the second operating mode is addressed to the second participant, or, in the case of several spatially adjacent participants, to these participants.In the event that at least one second participant is also in the second operating mode, the data sent by the at least one second participant will be addressed to the at least one first participant, e.g. in the form of telegrams. In a further embodiment of the method, if the determined first and / or second characteristic value, or a third characteristic value derived from the first and / or second characteristic value, exceeds or falls below a predetermined threshold, measures are taken to improve the quality of the data transmission, or a corresponding signal is output. For example, it may occur that communication via the radio network is still possible under certain operating and / or environmental conditions, but this communication breaks down with even a slight deterioration of these conditions. Therefore, a threshold value can be provided that specifies the required minimum quality of the connection. If the characteristic value exceeds or falls below this threshold, a corresponding signal can be output, for example, by the first subscriber, to a user who is, for instance, located on-site. This signal could, for example, be...This involves the flashing of a display that may be present on the first participant or the display of a corresponding message on the screen. In another embodiment of the method, the participants in the radio network are field devices. As already mentioned, the location of field devices in an industrial plant can only be changed to a limited extent. It is therefore necessary to ensure the connection of the field devices to the radio network accordingly. In another embodiment of the method, measured values ​​and / or process-relevant data are transmitted during the first operating mode. The field devices are usually actuators or sensors that transmit process-relevant data via the wireless network. Furthermore, the use of the method according to one of the above configurations for the commissioning and / or optimization of a radio network in an industrial process environment is proposed. With regard to the device, the problem is solved by the device having a communication interface for data transmission via a radio network, wherein the communication interface serves as a transmitter and / or receiver for sending or receiving data, wherein the communication interface in a first operating mode serves to send data with a first update rate, wherein the communication interface in a second operating mode serves to send data with a second update rate, wherein the second update rate is higher than the first update rate, and / or wherein the communication interface, in particular in the second operating mode, serves to evaluate received data and to determine a characteristic value for the quality of the data transmission and to make the characteristic value available to a user. In one embodiment of the device, the wireless network is a WirelessHART network. In one embodiment of the device, the second operating mode serves to send data to the nearest participants in the WirelessHART network, particularly those who are directly reachable. Burst mode is an operating mode in which a participant repeatedly sends data without being prompted by a higher-level unit. In burst mode, for example, the current measurement data can be sent at the highest possible update rate, e.g., 2 to 4 times per second. Alternatively, a standard message can be sent instead of the measurement data. In one embodiment of the invention, the first, the second, and / or a specific group of participants in the radio network can be put into burst mode. The invention is explained in more detail with reference to the following drawings. Figure 1 shows a schematic representation of a radio network in an industrial process environment, and Figure 2 shows a schematic representation of multipath propagation between two participants in the radio network. Fig. 1 shows a schematic representation of a radio network FN in an industrial process environment, such as a process automation system. The radio network FN comprises several participants A, B, C, D, and E (in this case, field devices, each configured as a radio field device) and a gateway G. The gateway G allows access to participants A, B, C, D, and E of the radio network FN via one of the fieldbuses commonly used in automation technology. In this example, the gateway G functions as both a protocol converter and a network manager. Furthermore, the gateway G itself acts as a participant A, B, C, D, E, and G within the radio network FN, as it, like the other participants A, B, C, D, and E, has its own address within the network. Participants A, B, C, D, and E are in radio communication (FV) with each other and with gateway G, as shown by the dashed lines in Fig. 1. Since participants A, B, C, D, and E, as well as gateway G, can communicate with each other via multiple redundant radio links (FV), communication is maintained even if one of the radio links fails. Known technologies can be used for the radio links (FV), such as Frequency Hopping Spread Spectrum (FHSS) or Direct Sequence Spread Spectrum (DSSS). Gateway G can be a configuration / management system, such as the Endress+Hauser Group's 'Fieldgate' product. Gateway G communicates with the higher-level unit (SE) via the radio network (FN) or the fieldbus.The connection to the higher-level unit SE can be established via a wired or wireless connection. Preferably, a high-speed protocol, such as the Ethernet protocol, is used at the control level LE, where the higher-level control unit SE is located, for example, in a control room. At the field level, where participants A, B, C, D, E and the gateway G are located, one of the standard fieldbuses is used. The participants A, B, C, D, E, and G in the depicted cell of the system can be operated in both a first and a second operating mode. The first operating mode primarily serves the transmission of measured values ​​or other process-relevant information. The second operating mode can be used for commissioning the FN radio network or for its optimization. In the first operating mode, participants A, B, C, D, E, and G can communicate with each other either via a peer-to-peer connection or via a hierarchically superior entity, such as the gateway. If all packets first pass through the network's central node, in this case the gateway, this is primarily for network organizational reasons. Routing is simplified in complex, synchronized networks this way. Alternatively, participants A, B, C, D, E, and G can also communicate with each other via a wired connection (not shown), i.e., exchange data. In the first operating mode, it is also possible for a participant, e.g., participant A, to communicate with another participant, e.g., participant E, or with gateway G via at least one other participant (in Fig. 1, this is participant B). Data sent by participants A, B, C, D, and E can be forwarded via such an intermediary station. To determine the signal quality of a data transmission in the radio network FN, at least the participants A, B, C, D, E of the radio network FN, between which the quality of the signal transmission is to be determined, are put into the second operating mode. For example, if only the quality of the data transmission between participants A and B is to be determined, it may be sufficient to put only these two participants A and B into the second operating mode. If only one-way data transmission, i.e., from a first participant A to a second participant B, is to be determined, it is sufficient to simply put the first participant A into the second operating mode, so that it sends data with a higher update rate compared to the first operating mode. The data sent by the first participant A can then be received, at least partially, by the second participant B. Based on, for example, the signal amplitude of the data or the loss rate of the transmitted data, the second participant B can determine the quality of the data transmission. Using this characteristic value, the availability of the first participant A under different environmental conditions, e.g., different weather conditions, can be estimated. The first determined characteristic value can also be sent back to the first participant A, so that it is available at the first participant A's location, i.e., on-site, and can be made available to a user. Alternatively, the data received from the second participant B can also be sent to the first participant A. The first participant can then use this returned data to determine a characteristic value for the data transmission. The data sent by the first participant A can be explicitly addressed to the second participant B. To determine the connection quality bidirectionally, the second participant B can also be put into the second operating mode, so that the second participant also sends data with an update rate that is higher than in the first operating mode. Instead of participant B from Fig. 1, another participant within the range of the radio link of the first participant A can also be used to determine the quality of the connection. In Fig. 1, this is, for example, the fourth participant D. From the fifth participant E, for example, the quality of the radio connection to the gateway G, the second participant B and / or the third participant C could be determined. As mentioned, more than two participants A, B, namely a specific group of participants A, B, C, D, E, can also be switched to the second operating mode. This allows the quality parameters, i.e., key performance indicators, to be determined in the specific area of ​​the system. The determined key performance indicators can then, for example, be made available to a user on-site in the field or transmitted to the control unit SE at the management level LE. The data transmitted by the first participant A in the second operating mode can be received, for example, by other participants B and D who are within range of the radio link of the first participant A. This allows the characteristics of the respective radio link FV to be determined. Based on these parameters, a user can then take measures to improve the connection quality. This includes, for example, adjusting an antenna (if present) belonging to one of the participants A, B, or D, adding another transmission node, or relocating the radio unit / antenna. This improves the stability and reliability of the wireless network. Furthermore, the network architecture can be simplified during the initial setup phase. Figure 2 shows a schematic representation of multipath propagation of a radio signal between two radio network participants F1 and F2. If the participants are field devices F1 and F2, relocating them within a system is often not possible, as the field devices F1 and F2 control and / or monitor the process at a predetermined measuring point. Obstacles such as tanks T1 and T2 may also be present along the radio link, for example, between the two participants shown in Figure 2. These obstacles can reflect the transmitted radio signals or interfere with their propagation. The radio signals are indicated by dashed lines in Figure 2. Due to the reflection of the radio signals, the transmission quality can therefore depend on whether the radio signals are transmitted from the first field device to the second field device or vice versa. An asymmetrical radio connection between two participants in a wireless network can also simply be due to the quality of the transmitting and receiving equipment of each participant. It can also be due to different transmit signal strengths; for example, participant A might transmit at 0 dB and participant B at 10 dB. Participant A might hear participant B, but participant B might not hear participant A.

Claims

Method for operating a WirelessHART radio network (FN) in an industrial process environment, wherein the WirelessHART radio network (FN) comprises multiple participants (A, B, C, D, E, G), wherein the participants (A, B, C, D, E) of the WirelessHART radio network (FN) are field devices, wherein the participants (A, B, C, D, E, G) are controlled and / or monitored via the WirelessHART radio network (FN), wherein at least one first participant (A) of the WirelessHART radio network (FN) operates in a first operating mode or in a second operating mode, in which first operating mode measured values ​​and / or process-relevant data are sent from the first participant (A) at a first update rate, and in which second operating mode data is sent from the first participant (A) at a second update rate, wherein the second update rate is higher than the first update rate.and wherein at least some of the data transmitted during the second operating mode is received by at least one second participant (B) of the WirelessHART radio network (FN), wherein the data received by the second participant (B) is evaluated and a first indicator of the quality of the data transmission is determined and made available to a user. The method according to claim 1, wherein the second participant (B) is also operated in a first or second operating mode, wherein in the first operating mode data is sent by the second participant (B) at a third update rate, and wherein in the second operating mode data is sent by the second participant (B) at a fourth update rate, wherein the fourth update rate is higher than the third update rate, wherein at least a part of the data sent by the second participant (B) during the second operating mode is received by the first participant (A), wherein the data received by the first participant (A) is evaluated and a second characteristic of the quality of the data transmission is determined and made available to the user. Method according to one of claims 1 or 2, wherein the first characteristic value is sent back to the first participant (A) or the second characteristic value is sent back to the second participant (B). Method according to at least one of claims 1, 2 or 3, wherein the data received by the second participant (B) is data sent directly by the first participant (A). Method according to at least one of claims 1 to 4, wherein several participants (A, B, C, D, E, G) of the WirelessHART radio network (FN), in particular spatially adjacent participants (A, B, C, D, E, G), are put into the second operating mode. Method according to at least one of claims 1 to 5, wherein the participants (A, B, C, D, E, G) of the WirelessHART radio network (FN) are connected to each other via a peer-to-peer connection in the second operating mode, between which a radio connection (FV) is possible, and wherein the data is transmitted between the participants (A, B, C, D, E, G) via the peer-to-peer connection in the second operating mode. Method according to at least one of claims 1 to 6, wherein, in the event that the determined first and / or second characteristic value or a third characteristic value derived from the first and / or second characteristic value exceeds or falls below a predetermined threshold, measures are taken to improve the quality of the data transmission or a corresponding signal is output. Use of the method according to one of the preceding claims for commissioning and / or optimizing a WirelessHART radio network (FN) in an industrial process environment. Field device for use in an industrial process environment, with a communication interface for data transmission via a WirelessHART radio network (FN); wherein the communication interface serves as a transmitter and receiver for sending and receiving data; wherein in a first operating mode, the communication interface serves to transmit measured values ​​and / or process-relevant data at a first update rate; wherein in a second operating mode, the communication interface serves to transmit data at a second update rate, which second update rate is higher than the first update rate; and / or wherein the communication interface serves to evaluate received data and determine a characteristic value for the quality of the data transmission and make the characteristic value available to a user. Field device according to claim 9, characterized in that the second operating mode serves to send data to the nearest participant (A, B, C, D, E, G) in the wireless HART radio network.

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