It’s a widening horizon for wireless
14 September 2012
Les Hunt reviews the wireless device market to update readers on what’s new in this fast-moving data gathering, data monitoring and control sector.
According to Intelligent Distributed Controls' Kevin Buckley, continuing developments in low-power wireless technology has effectively addressed issues that have been worrying potential users, such as security and robustness. Products now meet the market need for cost-effective, standards-based wireless networks that connect sensors in remote control and monitoring applications, even in electrically noisy industrial environments.
Based on the licence-free IEEE802.15, 2.4GHz frequency band, wireless systems such as ZigBee are full-blown telemetry systems in their own right, providing wireless personal area networking (WPAN) and digital wireless connections between computers and related devices, such as sensors.
This type of network eliminates the use of physical data buses such as wired Ethernet; it also now offers some key security features, including acknowledgement that data has been received at its destination; retransmission in the event of failure due to radio collisions or reflections (rather like TCP/IP network); validation of message content using data sequence numbering (Frame Check Sequence); network redundancy, such that a failure of a node on the network will enable messages to be re-routed via other nodes; and network protocol security encryption.
Remotely located wireless sensors and data acquisition systems can be powered via battery or, better still, from an energy harvesting device (see panel story), the latter converting a local source of energy (heat, mechanical vibration, etc) into an electrical supply that is sufficient to power them. Devices can be positioned anywhere within a plant, gathering data such as energy readings, temperature/flow levels pressures, fault diagnostics and so on.
Indeed, one of Frost & Sullivan's 'big three' predictions for the industrial automation and process control market foresees a greater uptake of mobile and wireless communication technologies. The market researcher says the need for higher productivity and greater efficiency will drive organisations to implement greater interaction between the factory floor and the enterprise level; it is likely that wireless will have a major role to play in achieving this.
Developing new products to realise these greater efficiencies in the industrial sector, Mantracourt has just released its T24-RDC wireless remote data collector, a remote data acquisition system that can utilise the existing GPRS network to enable remote monitoring of sensors and instrumentation. Using a Quad band GPRS modem, the wireless data collector allows users to log and report data to multiple destinations, including servers, email addresses and mobile phones via text messaging.
The T24-RDC accepts data from multiple inputs including: mV/V strain measurement, 4-20mA, 0-10V, temperature, pulse and potentiometer. All data is time and date stamped and sent to destinations at regular intervals. Measurements are also compared with user-defined limits that can trigger alert messages, allowing real time monitoring of an entire system.
According to Mantracourt's Kelly Voysey, a number of working systems were tested in field trials during the product’s development stages. One example was used to monitor the performance of the loads exerted on hydraulic struts shoring up construction pits, with the data being collated on a website for viewing. The T24-RDC has also been used to help monitor vibration levels during a construction project, enabling the sending of text messages to the phones of key personnel when vibration levels rose above set limits.
This product joins another recent introduction to Mantracourt's T24 series - the T24-TA Pt 100 temperature measurement and wireless unit that records temperature and periodically transmits the data to a remote receiver. Between transmissions the device is optionally put in a power saving sleep mode to conserve its battery power. The module can transmit to a range of receivers, including handheld indicators or fixed displays. The T24-TA is available for immediate plant use or as a PCB version that OEMs can integrate into their own equipment.
White space M2M
Beyond the immediate confines of industry, there are countless applications in the wider world that are ripe for wireless adaptation. Offering much promise is the recently released ‘white space’ – a huge and relatively unused part of the radio spectrum freed up by the digital TV switchover.
Weightless, the body behind the Weightless machine-to-machine (M2M) communications standard for white space spectrum, added its voice to Ofcom's recent call for a ‘kick start’ of rapid regulatory turnaround, the rapid occupation of the spectrum, and deployment of M2M white space standards and technology in order to demonstrate its many applications. Ofcom CEO, Ed Richards, outlined his views on white space at an EU Policy debate in Brussels last March.
In May, Weightless held its first plenary session in Cambridge, the purpose of which was to discuss the evolution of its M2M communications standard for white space. At that event, CEO William Webb said: "It’s wonderful to see the movers and shakers of the wireless industry meeting to establish a standard for the common good, as well as for the networking necessary to put together the complex value-chains in this space." He indicated that the standard was on schedule for completion early in 2013.
In 2011, IMS Research projected that the volume of SIM cards shipped into cellular modules used for M2M communications would be more that 350 million per year by the end of the decade; however, the market researcher now concedes that white space radio could present a threat to this nascent market. Although it will take a number of years for the market to develop, IMS senior analyst, Alex Green believes white space radio does look well positioned to fill some of the gaps between WAN cellular M2M communications and LAN short range wireless (such as ZigBee, Bluetooth Smart) M2M communications.
At present, white space radio is being presented, among other things, as a viable means of delivering broadband to remote areas, as a wireless based backbone for smart meter reading and that sleeping giant, the ‘Internet of Things’.
A question of range
With perhaps the exception of white space, range can be an issue when it comes to mainstream industrial or building management wireless implementation; however, there are exceptions. Moore Industries' wireless network module (WNM), for example, can be used to send process signals between remote field sites, a single unit capable of transmitting for up to 30 miles (direct line-of-sight) or, when configured as a repeater, for a virtually unlimited transmission range.
The bi-directional WNM makes use of Spread Spectrum Frequency Hopping technology to avoid interference problems caused by crowded radio spectrums, allowing multiple radio networks to use the same band while in close proximity. Operating at standard operating frequencies of 902-928MHz (30 mile range) or 2.4-2.4835GHz (15 mile range), the WNM does not require a regulatory license and can typically be installed without performing costly RF site surveys.
When it is set in the Smart Switch Ethernet (SSE) mode, the WNM enhances the speed and reliability of data packet transmission by determining the most efficient path of broadcast (including direct to a single radio or to some or all radios in a network) on a packet-by-packet basis. The WNM can be used with Moore Industries' NCS NET Concentrator System, as well as other SCADA and distributed I/O systems.
WNM models are available for data communications networks that use Ethernet and serial (RS-485) communications. In each WNM network, one module is set as a master, communicating with a single WNM remote unit in a point-to-point architecture, or multiple WNM remote units in a point-to-multi-point architecture.
EnOcean's ECO 200 third generation mechanical energy converter, when combined with the company’s PTM 330 transmitter module, provides a complete battery-less wireless based switching unit for building and industrial automation. This battery-less, wireless technology harvests energy entirely from its surroundings – from light, differences in temperature or motion.
Mechanical energy converters, for instance, can produce the energy needed to transmit a wireless signal just from the press of a button. The magnetic flux is suddenly reversed by a coil as soon as a spring mechanism reaches a snap-over point. ECO 200 energy converter is the latest advancement of these mechanical energy generators.
It comes with even more efficient energy conversion, less noise emission plus higher load capability. A further benefit of the new-generation converter is its simple installation. The PTM 330 wireless module, which can be connected to the energy converter by spring contacts, features four digital inputs to map up to four switching states. Additionally, an interface allows configuration of the content of the wireless telegrams during manufacture of a user device
Like every EnOcean wireless module, the PTM 330 also has a unique 32-bit identification number to eliminate any overlap with other wireless sensors. Wireless range is up to 30m inside buildings and 300m in the open, with versions for both 868MHz and 315MHz operation.