News and New Products

Rugged wireless-sensor networks suit harsh industrial environments

By Margery Conner, Technical Editor -- EDN, 6/7/2006

Industrial environments are usually harsh, with hazards that can range from strong mechanical vibrations, high temperatures, noisy electrical environments, and even explosive gases. It’s difficult and expensive to install wiring in these environments, which range from oil rigs to refineries. Thus, these applications are primary targets for ultralow-power wireless-sensor networks.

Targeting this market, Dust Networks has released SmartMesh-XT, an enhancement of its mesh-networking platform. The system offers a rugged design for Class 1 Division 1 environments, including vibration resistance and an industrial-temperature range of –40 to +85°C. The company claims that the network, which relies on the company’s TSMP (Time Synchronized Mesh Protocol), achieves reliability greater than 99% in such electrically noisy environments. TSMP, a media-access and networking protocol, operates on standard, off-the-shelf radio chips and allows every node in the mesh network to act as a router.

This product targets use in applications employing the HART (Highway Addressable Remote Transducer) Protocol, which the HART Communication Foundation supports. The protocol, an industrial standard for device communication, calibration, and maintenance, comprises an analog 4- to 20-mA line and a digital signal on the analog line. Rob Conant, Dust’s co-founder and vice-president of marketing, says, “Most HART devices today don’t enable the digital-calibration data because you have to superimpose the digital data on the analog line and go through the distributed-control system.” He claims that, by using a separate wireless network to handle the digital diagnostic and calibration data, HART enables you to handle data in parallel rather than intermingling with mission-critical control signals. He says that 25 million HART devices are in use and that most don’t enable digital-calibration data.

The family of products comprises network nodes and managers in both the 900- MHz and the 2.4-GHz bands. The 900-MHz products include the M1030 mote, or node, and the PM1230 embedded-system manager. The 2.4-GHz products, which use IEEE 802.15.4 radios, include the M2135 mote and the PM2130 embedded-system manager. The communication distances for the networks range from 75 to 300.