Hazardous Area Antennas

Gathering information in hazardous areas is critically important for plants to access. Wireless communications is vital for improved efficiencies, real-time monitoring of machinery and equipment, and the safety and well-being of personnel.

Hazardous area antennas from Analynk Wireless are designed and constructed for very rugged industrial applications. Furthermore, all Analynk hazardous area antennas  are UL  listed for Class 1, Groups C & D and have ATEX/IECEx Certification. Finally, a range of frequencies are available from 900MHz, 2.4GHz, Cellular, GPS, Iridium and dual bands.

Fresnel Zones and Industrial Wireless Connections

Industrial wireless connections established outdoors across
long distances have to consider transmission path geometry.

A Fresnel zone, of which there an infinite theoretical number, is an ellipsoid shaped area extending between radio signal transmission and receiving antennas. Having a basic understanding of their impact on successful implementation of a lengthy wireless process signal connection will prove useful.

Wireless transmission of process signals in industrial settings becomes more prevalent every year, and should continue to do so for quite some time. Many installations are part of networks operating similarly to the wifi you may have in your home, with multiple points communicating via a network control scheme of some sort. The facility is flooded with signal coverage through multiple access points, so there may not be much need to consider signal propagation. This is an oversimplification, but as an operator or implementer, making the actual signal connection is probably not going to be an issue in most cases.

What about the other cases?

Antennas with three Fresnel zones depicted and
obstruction that is outside the primary Fresnel zone
Courtesy Wikipedia

An extended transmission distance across an outdoor area requires more understanding of signal propagation and factors that impede successful delivery of process data from transmitter to receiver. One concept that comes into play is the Fresnel zone.

Let's avoid an overly technical approach to Fresnel zones. The purpose of this post is to provide those with limited radio expertise familiarity with the subject of Fresnel zones at a level enabling visualization of the concept, and also to recognize its potential impact on achieving a successful wireless process connection.

We often consider the transmission path between two points to be the familiar "line of sight", an unobstructed straight line between transmitter and receiver. In practice, radio frequency transmission is more accurately characterized by Fresnel zones. Being aware of the shape of the first, or primary, Fresnel zone for your application is an important element in identifying potential obstructions. A general practice is to keep the primary Fresnel zone at least 60% clear of signal obstructions, in order to maintain high wireless link performance.

There are numerous sources of Fresnel zone calculators online, but a strong recommendation to consult with your selected wireless equipment provider is in order here. Combine their expertise at applying their products with your application knowledge to leverage an effective solution.

Industrial Wireless Application: Remote Equipment Monitoring

The A16000 Expansion Module increases the I/O
capacity of a standard wireless transmitter or receiver
Image Analynk Wireless, LLC

Imagine yourself a newly hired facilities manager, the go-to person responsible for the proper and continuous performance every machine on site. One machine in particular, you are informed, is a large walk-in refrigerator that houses the primary raw material for the production operation. There is a lot riding on that machine because the stored material is useless if not kept cold. Oh, and by the way, the plant site is bisected by a public street and the refrigerator is located across the street from the main building where the facilities office is housed. Your assessment of the equipment reveals that a lone temperature alarm device monitors refrigerator temperature and sounds a loud horn if the refrigerator temperature reaches a high limit setpoint. There are no existing wire pathways between the main building and the walk-in refrigerator that are available for your use.

Clearly, the level of risk associated with the refrigerator is high. It merits implementation of an improved strategy to monitor refrigerator performance. Things under consideration include some the following items.

• A real time display of the current refrigerator temperature in the facilities management office. 
• Analysis of the temperature data for an upward or downward trend that might indicate the beginning of a malfunction of the cooling system or controls.
• Monitoring of refrigeration compressor motor current, which can be related to the temperature data to confirm that the compressor is operating when it should.
• Real time display of refrigerant suction and discharge pressures.
• Analysis of refrigerant suction and discharge pressure to identify trends or conditions that may indicate service is needed or malfunction is imminent.
• Verify the door to the refrigerator is closed.
• Monitor evaporator fan motor current to verify that all fans are operating.

The greatest challenge in this application is not the gathering of the information, nor its analysis. The difficulty, as well as a substantial cost and time constraint, is delivering the information from the point of measurement to the point of use. Analog signals for real time temperature, refrigerant pressure, and motor current can be easily derived through the addition of sensors to the equipment. The only sensors likely to require intrusive work to install are those for refrigerant pressure. Routing the measurement signals to the facilities office across the road may prove difficult.

A wired connection between the measurement location to the facilities office will require either an underground or overhead routing of cable, traversing the public road. Permission from state, county, and/or local jurisdictions may be required and present potential barriers to timely completion of the project. The cost to install the cabling will be substantial. The distance may be long enough for signal attenuation to be a concern.

The best solution, in terms of initial cost and time to completion, is to establish a dedicated wireless connection between the walk-in refrigerator and the facilities office.

 A multi-input transmitter is installed at the walk-in refrigerator. The transmitter converts digital (switch) and analog input signals into encrypted digital data and transmits in the 900 MHz band to the receiver installed in the facilities office. The receiver decrypts the received data and mirrors the original analog and digital signals at its output terminals. Wireless overcomes the barriers presented by a wired installation, allowing completion in a timely manner at substantially reduced cost.

If you can operate a walkie-talkie, you can establish industrial wireless connections between remotely located, or mobile, equipment and central monitoring locations. Share your ideas and challenges with industrial wireless experts, leveraging your own knowledge and experience with their application expertise.

Wireless Communications for Industrial Automation Continues to Expand Because It Performs

Wireless communications capabilities for process control
extend beyond WiFi

Wireless connection between a sensor and control or monitoring station is not new anymore. Products have matured, familiarity with the technology is widespread. Certainly, there are still large swaths of industrial installations that do not utilize the technology. This can be for any number or reasons, but new industrial technology tends to follow a predictable course throughout its adoption. There will be innovators and early adopters that can justify higher risks with the prospect of great returns. Many industries and companies will wait until perceived technological difficulties with implementation are overcome and products become more mainstream and easy to apply. That is where industrial wireless is today. Assembling complete working systems is a straight forward operation. Costs are comparatively modest. It's easier to visualize a payback.

Let's review some of the benefits a wireless installation can bring.

• Safety: Wireless connections can reduce personnel exposure to hazardous environments or situations that previously required human intervention or a manual gauge or instrument reading.
• Easy Scale-up: Adding points on a network is generally a simple incremental process.
• Operational Advantage: When deployed to replace manual instrument or gauge readings, real time data for diagnostics and efficiency measurements are now available. Information that is more accurate, timely, and consistent will produce better results.
• Installation Savings: Installation of wireless connected assets has been reported to be up to 10 times less expensive than wired installation. The reduced space and planning for cables and conduit can make what were once complex and time consuming operations much quicker and easier.
• Mobility: Wireless technology allows for real time connections to mobile platforms. Whether within a plant, on the road, or on the high seas, there are wireless products that can make the connection.
• Distance: Don't just think WiFi, think radio, think satellite, think cellular. Connections can be established across very long distances using standard products from the industry.
• Conversion of Legacy Devices: Many existing in-place devices can have their wired connections replaced with a wireless version. This accommodates a staged transition from wired to wireless in facility.

Analynk Wireless manufactures a broad range of wireless communications equipment for industrial process control and automation. Share your wireless connection challenges and ideas with the experts at Analynk and start benefiting from the technology. It's not new anymore. It's mainstream.

Understanding Telecommunications Terminology

Industrial wireless communications can include satellites

If you are delving into wireless communications for process control operations and expect to go beyond the use of industrial Wi-Fi, you are likely to encounter some concepts and lexicon that may be unfamiliar. A source of recognized standard definitions for industry specific terms will serve as a useful tool for understanding the specifics of radio communications.

Federal Standard 1037C, entitled Telecommunications: Glossary of Telecommunication Terms was issued by the General Services Administration late in the last century. It was superseded in 2001 by American National Standard T1.523-2001, Telecom Glossary 2000, published by Alliance for Telecommunications Industry Solutions commonly known as ATIS). The current version of the ATIS Telecom Glossary is available for use by the public. Find the glossary website, with its search engine, and either type a term to search for in the box or browse the extensive listings in alphabetical order. It's easy to use and can help you sort out the meanings of some industry specific terms.

Analynk Wireless is a wireless communications equipment provider to the industrial process control sector. Contact the application specialists at Analynk and share your wireless communication challenges.

Screen shot of the glossary, showing search box in upper left area

Understand Fresnel Zones and Their Potential Impact On Your Process Signal Radio Transmission

Rendition of an ellipsoid, the representative shape
of a Fresnel zone

Most of us have been touched by wireless communications in the industrial process control setting. The majority of the installations are likely to be networks that operate similarly to the wireless network you may have in your home. Multiple points communicate through a network controller of some sort. The facility is flooded with signal coverage through multiple access points, so there may not be much need to consider signal propagation. Of course, this is an oversimplification. The point to be made is that, as an operator or implementer, making the actual signal connection is probably not going to be an issue in most cases.

How would you approach an application with a one mile transmission distance?

Antennas with three Fresnel zones depicted and
obstruction that is outside the primary Fresnel zone
Courtesy Wikipedia

An extended transmission distance across an outdoor area requires more understanding of signal propagation and the factors that can impede the successful delivery of your
process data from transmitter to receiver. One concept that may come into play is the Fresnel zone.

I shall avoid any deep or technical approach to Fresnel zones, as my purpose is to provide the designer, technician, or implementer, who may have limited radio expertise, familiarity with the subject at a level empowering visualization of the concept to recognize the potential for its impact upon achieving a successful project. That said, a Fresnel zone, of which there an infinite theoretical number, is an ellipsoid shaped area extending between transmission and receiving antennas.  While we often consider the transmission path between two points as the popular "line of sight", an unobstructed straight line, radio frequency transmission is more accurately characterized by Fresnel zones. Being aware of the shape of the first, or primary, Fresnel zone for your application is an important element in identifying potential obstructions. A general practice is to keep the primary Fresnel zone at least 60% clear of signal obstructions, in order to maintain high wireless link performance.

There are numerous sources of Fresnel zone calculators online, but a strong recommendation to consult with your selected wireless equipment provider is in order here. Combine their expertise at applying their products with your application knowledge to reach the best outcome.

Practical Considerations for Wireless Transmission of Industrial Process Control Signals

Industrial process signal transmitter

Rigging up the proper gear to establish wireless transmission of process measurement signals is generally a straight forward task. There are, however, a vastly different set of considerations than those for a wired transmission of the same signal. In order to select the right equipment for the job, some general comprehension of radio signals can be useful.

Radio wave frequencies are below the infrared range on the electromagnetic spectrum, thus their wavelengths are comparatively long. Three things can happen to electromagnetic radiation (radio waves) when encountering a barrier. 

• Reflectance: The wave bounces off the barrier.
• Transmittance: The wave passes through the barrier.
• Absorbance: The wave is stopped.

Which of the three possibilities will occur depends upon a number of factors relating to the signal and the barrier, some of which include:

• The wavelength of the radiation
• The intensity of the radiation hitting the barrier
• The chemical composition of the barrier
• The physical microstructure of the barrier
• The thickness of the barrier

Here is a conglomeration of knowledge items pulled together from a number of public sources that can be applied when considering a wireless installation.

Milliwatts (mW) are the common measurement unit of radio frequency (RF) power. A logarithmic scale of decibels, referencing 1 mW as the zero point, provides a useful way to express the comparative strength of RF signals. Using decibels, a signal strength of 1 mW is registered as 0 dBm. RF power attenuates according to a logarithmic function, so the dBm method of expressing RF power enjoys widespread use.

Industrial wireless communications applications in North America predominantly operate in either the 2.4 GHz or 900 MHz frequency range. Higher frequency will provide more bandwidth, but at the cost of reduced transmission distance and obstacle penetration. Lower frequency can require a larger antenna to attain the same signal gain.

Transmission power is not the only solution for delivering a signal. Low power signals can be successfully received by sensitive radio equipment. Reducing the data transmission rate can increase the functional sensitivity of the receiving equipment, too.

Be mindful of the existence or potential for RF background noise in your communications environment. A higher level of background noise can hamper the effectiveness of your equipment. The "noise floor" varies throughout the frequency spectrum and is generally below the sensitivity level of most equipment. Industrial environments can sometimes provide unusual conditions which may warrant a site survey to determine the actual noise floor throughout the communications area.

Weather conditions can impact signal transmission

Radio transmission is susceptible to environmental elements on a variable basis. Since the environment can change without notice, it is useful to know the fade margin of a wireless installation. Fade margin expresses the difference between the current signal strength and the level at which the installation no longer provides adequate performance. One recommendation is to configure the installation to provide a minimum of 10dB of fade margin in good weather conditions. This level can provide sufficient excess signal strength to overcome the diminishing effects of most weather, solar, and interference conditions.

There are a number of simple methods to determine whether an installation has at least a 10 dB fade margin. Temporarily installing a 10dB attenuator on the system antenna, or installing a length of antenna cable that yields 10dB of attenuation will allow you to determine if the installation can accommodate 10dB of environmental impact on the signal. If the system operates suitably with the attenuation installed, you have at least that much fade margin.

RF signals attenuate with the square of the distance traveled, so if transmission distance is to be doubled, then the signal power must increase fourfold. 

True “line of sight” signal paths are found in a limited number of installations. The number, type, and location of obstacles in the signal path can have a significant impact on the signal and contribute to what is referred to as path loss. Probably the simplest way to reduce the impact of obstacles is to elevate the antennas above them.  Obstacles, in almost every case, are affixed to the earth, so their interference is reduced by elevating antennas to “see” over the obstacles.  

Wooded areas can be a significant barrier

When the signal path extends through an outdoor area, weather conditions have an impact on the path loss, with higher moisture levels increasing the loss. Large plants, most notably heavily wooded areas, can impose substantial reduction on RF signals and may require elevating antennas above the trees or using repeaters to route the signal around a forested area.

Industrial installations routinely present many reflective obstacles in the signal path. The transmitted signal may reflect off several obstacles and still reach the receiving antenna. The received signal strength will be the vector sum of all the paths reaching the antenna. The phase of each signal reaching the antenna can impact the total signal strength in a positive or negative way. Sometimes relocating the antenna by even a small amount can significantly change the strength of the received signal.

Antenna cable 

Antenna cable contributes to signal attenuation. Use high quality cable of the shortest length possible to minimize the impact on performance.

Analynk Wireless has the equipment and expertise to help you deliver wireless process signals across the room, across the street, or across the globe.