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Since 2004 engineers work because the data transmission in networks in the industrial sector also wirelessly to enable so that the requirements of the relevant standards and different environments are met. Now has Hirschmann Belden with the "Open BAT" platform completed the latest generation of Wireless LAN, which not only provides a faster version of the transmission standard, but for the first time includes a radio interface that was developed specifically for use in automation.

Should be a stable, reliable wireless network will be developed that could previously always find hardware that snugly, was waterproof and very durable. In addition, the necessary standards are met, allowing the use of the devices in your environment as the only EN50155 for trains. Also, the antennas and cables and accessories are of special quality. Nevertheless, it happened again and again that a wireless LAN (WLAN) network did not work so, as you'd hoped.

Data transmission with interruption Port of Hamburg

belden20212One example is an installation at the Port of Hamburg. There it was the task of building wireless connections from bank to bank as well as to the investing ships. It reigned almost ideal conditions. This allowed the installation locations are chosen so that the antennas and access points see each other without barriers' could. In addition, the track was from transmitter to receiver is not very far. In the planning of the network has been taken correctly and initially examined whether there was already existing competing WLAN networks. Then, the best free channels were selected. The antennas used were sized so that the route could be bypassed with high-bandwidth design calculation formulas well. Similar installations have been installed hundreds of times between buildings, as DSL over-the-air connection of communities or mountains - always without problems. First in Hamburg saw everything looks good. The devices showed a physically secure connection. And the received signal was strong enough to achieve the desired bandwidth.

And yet, it was found that the actual data transmission functioned poorly and with many interruptions. Because on the line lost a lot of packages or broken. Especially when a ship should be tied short term, in the time available could not provide the desired amount of data being transferred. Experienced installers were at their wits' end. Finally, everything was planned to have been built and configured as specified by the manufacturer.

belden30212Troubleshooting a complete, complex frequency analysis was performed, which not only investigated the frequency range within which there is the wireless LAN (the so-called ISM band 2,4 GHz range). But it was taken the entire frequency spectrum under the microscope, in which, inter alia, radar, mobile phone networks and radio stations broadcast. It quickly became clear that it was the port of Hamburg but is a rather challenging environment.

Wi-Fi is in 2,4 GHz band is limited to a maximum power of 100 mW and 5 GHz band for a performance of 1000 mW. So that it is compared to the sending in the immediate vicinity of the weakest technologies. Since receive WLAN antennas not only the wireless signal but everything is present to electromagnetic waves, the whole mess to the wireless signal receiver is passed. This is then engaged in it to filter out the right signal. For cost reasons and because existing WLAN radio interfaces were not designed for these situations, the integrated into the chipset frequency filter is very weak. WLAN sends only with 1 W while other radio systems send the right and left of the wireless frequency range of up to or even 10 30 kW. Improvements were completed by between access point and antenna, an additional band pass filter was installed, which passes not only the interfering adjacent frequencies in the direction of the receiver. This allowed the noise level significantly reduced and thus the packet reception rate increased to normal levels.

Friction generated discharges in the open pit

belden40212Another practical experience has been gained in an open pit. There WLAN devices were installed along the conveyor belts to build a mobile network connection. Installation and data transfer worked properly after removing the network. But after a few months of operation, the device gradually lost in transmission power and managed to eventually stop, to ensure the required data transfer. The appliances have been tested in the laboratory. A lightning strike or similar damage had not occurred. The devices also were properly installed. Grounding with a high dimension and an upstream between antenna and lightning protection device And yet to establish clearly that there had been a gradual destruction of components in the wireless receiver, which was due to electrical discharges. It turned out that due to the rubbing air mass above the mine have been going small discharges that have been received by the Wi-Fi antennas and forwarded. This passed the lightning protection because they were below the trigger voltage.

Quantum leap in radio communication

belden50212Both the Port of Hamburg as well as in the application in mining, the problems have been fixed by individual solutions that involved an upstream additional component. This was realized in the form of a bandpass filter and an advanced surge protector that works at low voltages and currents. Both solutions, however, increase the installation costs and also need more space. Especially in many industrial applications, space is a very rare commodity, for example, the installation of Wi-Fi devices on trains. In addition to the equipment of the current generation would have up to six such Überspannungssschutze and / or band-pass filter for each access point must be allowed because there are up to six antenna connectors. The cost of these additional components may exceed the price of a single access point quickly.

Therefore Hirschmann has now developed a wireless interface that consistently meets the needs of such industrial applications. It is possible to accommodate the surge protection components and filter frequency band within the access point.

The miniaturization goes so far that the functions have directly detected on the WLAN module slot. Thus constituting a radio interface of each module, of which up to three are used in an Access Point. The integrated overvoltage protection has withstood tests at discharges up to 25 kV. The also integrated bandpass filter works in each 2,4 GHz and 5 GHz band and the free Wi-Fi so of a disturbing noise.

The new patented "open BAT" platform is the latest generation of wireless devices, representing a new level of wireless technology and come up with an increase in network speed by up to 50% compared to the previous generation. In addition, this platform allows the customer to meet its needs from a virtually unlimited selection of interfaces, power supplies, housing types and specific certifications.

In addition, Open BAT added flexibility by being able to configure a wireless network using either the open BAT devices as stand-alone access point or centrally manage a BAT controllers. In short, the new platform allows it to implement wireless solutions in areas where this was not possible. In addition, customers can choose the right product variant for their own individual solutions, so that it only pays for the features he really needs.

In the development of open BAT emphasis was placed on maximum flexibility value. Therefore, this platform is suitable for applications in a range of industries. It usually involves the factory and process automation, power transmission and distribution, mining, and renewable energy generation.

A particularly important part of this new development is the patented Wi-Fi wireless module. It is not only equipped with integrated bandpass filter and ESD protection, but is also characterized by very low power consumption and an ultra-wide Temperature range. In addition, this module is equipped with particularly robust antenna connectors with low signal attenuation and can be mounted very snugly. For the first time, stable wireless connections are realisieret reliably even in harsh environments.

The author Olaf Schilperoort MBA, Product Manager at Hirschmann Automation and Control, Neckartenzlingen

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