Quieting the EMI racket: wireless mesh networks can ensure data arrives uncorrupted.

Author:Wilkinson, Jeff
Position:Inspection solutions
 
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Electronics as a group are some of the most mechanically and performance-fragile systems that live in industrial environments. Within those environments are frequent examples of noise and interference sources that disturb or otherwise impair the reliable functioning of electronics.

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While heavy steel packaging and seal rings keep harmful, volatile, and corrosive liquids and particles out of sensitive electronics, they cannot protect the emissions of radio waves in wireless networks. Wireless sensors and metrology instruments frequently are being deployed in production areas.

The wireless systems deliver their quality or production data to critical operations downstream and are crucial components of the modern production reality. With this said, wireless data transmission of data is critically needed and simultaneously vulnerable to shop-induced interference.

Radio frequency (RF) waves are the carrier for data in a wireless data acquisition system. These waves are simply energy propagated through free space. When free space is cluttered with other energy forms, intentional radio waves are compromised.

RF is highly susceptible to corruption and alteration via a variety of Electromagnetic Interference (EMI). EMI has been defined as the "degradation of the performance of a piece of equipment, transmission channel, or system caused by an electromagnetic disturbance" (ANSI). EMI can occur throughout the EM spectrum from 0 Hz to 20 GHz or higher frequencies.

However, EMI problems are most prevalent in the RF spectrum. Since in many applications the RE carries the data, then good RF handling must be encouraged to keep the data intact.

If there is EMI, RF-based systems must manage their performance relative to interference if they are to be useful. There is no such thing as a 100 percent noise immune radio system. So with that truth, systems designers must develop robust wireless data collection networks and sensors to be less susceptible to EMI.

There are many techniques that designers can use to offset the impact of EMI-generated noise in a wireless network. The mesh network is an option that has some distinctive features. First, it has a single and central "gateway" function where all system wide commands and network management can occur. Data from the network also returns here.

Secondly, the sensor/measurement endpoint radios can be active components of the network. Thirdly, numerous routers or repeaters are present and can...

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