Kevin Lavelle at right, Northeast Regional Sales Manager for our meeting host Endress+Hauser, served as tour guide to explain the whys and wherefores of the company’s new demonstration and training facility featuring flow and level instrumentation.
Joe Kurcon of E+H provided the program content for the meeting. He started with a surprising item of trivia: the relationship between wireless networks and the late actress Hedy Lamarr. Mathematically talented, she and composer George Antheil are co-holders of the earliest patent for spread spectrum communications and frequency hopping–the basis of industrial wireless. (Music, when you think of it, is a series of hopping audio frequencies). They presented the idea to the U.S. Navy during WW II to deal with torpedo guidance to overcome enemy counter-measures, but the Navy ignored the idea (not invented here).
Kurcon explained the difference between two types of spread spectrum technology: FHSS and DSSS radio systems. FHSS signals quickly hop through multiple frequency channels. The transmitters and receivers are synchronized. DHSS radio systems spread a narrow frequency source by integrating it with a pseudo-random noise signal that widens it throughout a band.The receiver knows how to eliminate the noise.
He said that FCC rules permit use in three bands: nominally 900, 2400, and 5800 MHz. The highest band reaches the smallest distance so is infrequently used. The rules permit up to one watt of power without end-user licences. Kurcon went on to discuss network wireless topologies, such as point to point, star, and mesh.
He continued with a discussion of WirelessHART, which evolved out of the HART protocol in which digital information is superimposed on a 4-20 ma analog signal. WirelessHART enables users to quickly and easily gain the benefits of wireless technology while maintaining compatibility with existing devices such as flow, temperature, and pressure transmitters.
Usually a WirelessHART adapter connects to the existing HART instruments, forming a mesh network. Data can flow from any adapter to any other, avoiding interference from obstacles that come and go. The signals connect to a gateway that routes them via a wired fieldbus to control computers.
Kurcon concluded with some practical applications from his experience at Endress+Hauser. He said the office has a full-time person who deals with industrial wireless systems, but he happened to be in Germany at the time of this meeting.
Link to more meeting photos.