Wireless OPC

A short overview of wireless technologies in use today with OPC.

Wireless monitoring of instrumentation sensors such as temperature, flow, pressure, voltage, current, levels, weight, speeds, revolutions and others is a common requirement in the control industry. The term 'wireless' is used for any system used to transfer of information over a distance without the use of electrical conductors or 'wires'. The distances involved may be short (a few meters) like with a television remote or long (thousands or millions of kilometers) for radio or satellite communications. Wireless OPC solutions exist to meet all needs.

Short Distance - Wireless Industrial Gateways
Technologies:
  • HART
  • Bluetooth
  • ZigBee
    		•  More information on:
    Long Distance - Wireless-Ready OPC Servers
    Technologies:
  • Cellular based technology (GPRS/CDMA)
  • Satellite (Microwave)
  • Radio
  • Telephony (dialup)
    		•  More information on:

    The Wireless LAN
    Wireless communications is becoming increasingly popular for factory and process control automation systems LANs. Wireless infrastructure reduces installation costs, and provides information for production and maintenance workers wherever it's needed. This growth is a result of emerging reliable radio frequency technologies capable of handling the extreme conditions present in industrial plants.

    WiFi
    The most well known wireless technologies is WiFi or W-LAN. WiFi connections are built on the IEEE 802.11x standards which support a wide range of distances. Architectures using directional antennas can create ranges of several kilometers or more with line-of-sight. Wi-Fi technology within business and industrial sites increasing include Wi-Fi access-points that provide redundancy, support for fast roaming and increased overall network-capacity. Some applications may utilize true mesh topologies. Also these Wi-Fi installations may provide secure computer networking gateways, firewalls, DHCP servers, intrusion detection systems, and other functions, comparable to LAN architectures.

    Personal Area Networks
    The term Personal Area Network or PAN has become popular for describing Wireless connectivity within a very limited distance. An example is Bluetooth, which supports connections within a range of approximately 10 to 100 feet. Bluetooth supports serial communications between devices. To support TCP/IP over Bluetooth, Point-to-Point Protocol (PPP) may be used. With TCP/IP support, OPC connections may be run over Bluetooth.

    OPC and the Wireless Network
    In order to extend OPC connectivity beyond a wired LAN, complementary technology that effectively supports DCOM-style interfaces across wider network connections is needed. All that is required to support such technology is a TCP/IP-capable layer, which extends OPC communications over wireless networks. For many applications there is little difference between communicating over a LAN verses a WLAN. However, when using OPC the following items should be considered:

  • Availability: As wireless communication systems become more common,
        customers are expecting the same level of service, availability, and
        performance from the wireless communication networks as the traditional
        wire-line networks. Products like the Matrikon OPC Tunneller are designed to
        improve the availability of OPC communications and reduce lengthy
        interruptions.
  • Bandwidth: Another consideration is the bandwidth required for DCOM
        communications. Matrikon OPC Tunneller also reduces the communications
        overhead used in standard OPC connectivity.
  • Reliability: The remote nature of wireless networks means that prolonged
        disconnections can occur. Architectures that require guaranteed data delivery
        would use OPC HDA based Hub and Spoke solutions.

    		•