GAS DETECTION 25
the terminal devices and the control unit of a 4-20 mA interface. It’s a bit like cutting a steak with a Swiss army knife: possible, but definitely not a stylish solution.
The most important reasons not to use HART:
• The Bell 202 standard is no longer state of the art It still works, but it was neither designed for today’s computing power nor today’s transmission capabilities. Your IIoT infrastructure requires and deserves more than just the transmission of a “Caller ID”. The HART protocol is intended for process automation, and many of the performance and cost issues associated with it are due to the necessary (backward) compatibility requirements. What if you could use the digital protocol you’ re using anyway?
• It does not offer the option of integrating information from portable gas detectors into your safety system in the future
In order for transmitters to function as “radio hotspots” for portable gas detection devices, an excess of bandwidth is required on the 4-20 mA line. The next big thing in gas detection technology is to obtain a holistic view of all sensor readings, whether from stationary devices or mobile solutions.
• It’s not exactly cheap! Interoperability has its price: Devices have to be tested and registered, the infrastructure beyond the existing cables is complex and sometimes costly, and it costs time and money to be a member of the FieldComm Group so that the protocol can be developed further.
The undisputed advantage of HART:
The large selection of manufacturers and products as well as the interoperability of components associated with the HART protocol and the fact that HART systems have proven themselves in practice for many years are among the great strengths of HART.
ACDC is therefore not intended to compete with HART, but to complement it. It can easily exist in parallel with HART installations. Whenever the focus is less on process automation and more on fast and cost-effective transmission of safety and/ or cost-relevant information, it covers a longstanding industry requirement.
GMA22 MW
communication via ACDC is digital, including the transmission of measured values, but the analogue current signal used as a carrier is still fully functional and serves as a backup and failover in case of an error in digital transmission.
Advantages: • No need to lay new cables
• A step by step exchange of transmitters is possible • Transfer rates of up to 38,400 Bit/s (HART 1,200 Bit/s) • Suitable for Ex-Zones • Range >1.200 meters
• Using the same protocol as transmitters that communicate via digital bus
• Cost effective solution However, with ACDC we are only at the beginning of the development. We are working hard to integrate ACDC into our equipment series and to develop new service, maintenance and compliance processes as well as enhanced security concepts in cooperation with interested manufacturers and customers from various industries.
Simplicity as a design principle
To make it for our customers and implementation partners as easy as possible, we have decided to stick with the digital protocol that we already use for our digital transmitters: Modbus/RTU. It is widespread and established.
All that remained was the challenge of superimposing the Modbus protocol on the transmitter’s analogue 4-20 mA signal. For its purposes, the HART protocol uses Frequency Shift Keying (FSK). The analogue current signal is modulated with a sinusoidal signal whose frequency changes from 1.2 kHz to 2.2 kHz - depending on whether a logical “1” or “0” is transmitted. It’s a complex and therefore costly procedure. It would be much easier if no signal transformation was required.
ACDC achieves this by superimposing an amplitude modulation on the 4-20 mA current signal to generate a digital data stream. All that is needed are a few discrete components and a serial interface available in almost all microcontrollers. This allows for transmission rates of up to 38,400 bit/s.
The advantages of ACDC
The great advantages of ACDC are hardly visible at first sight. You might think that not much has changed. But it is somehow comparable to a Porsche engine put into a beetle chassis.
As long as the transmitters are not digitally addressed, they behave like normal devices on a 4-20 mA interface. Although you will need to replace the old transmitters with ACDCenabled ones, the system at first looks the same as before. Retrofitting and migration are thus possible without any problems within the scope of normal maintenance cycles.
It all changes the moment you switch to digital communication and the full bandwidth of ACDC becomes available. All
A glimpse into Future
Even when transmitting all the additional information available from smart sensors and ACDC-enabled transmitters, the available bandwidth will rarely be fully used. This allows for a solution in which alarms and even readings from portable gas detectors are fed wirelessly into the stationary gas detection system
GMA200 MT16 and thus become part of the alarm system.
Portable gas detection devices from GfG come with an optional radio module. With the portable TeamLink it is already possible to monitor teams of up to 10 people. However, with regard to the safety of lone workers and small work forces, it would be desirable to integrate all portable devices into the stationary safety infrastructure. This would significantly improve security in the workplace.
To achieve this, transmission by radio signal offers considerable advantages over solutions based on WLAN, mobile or satellite telephony. And ACDC will provide the backbone to do so wherever you only have 4-20 mA interfaces on site.
Be at the forefront of development and join in on this endeavour. Let us know your requirements and expectations on connected gas detection. For more information on ACDC and connected gas detection, please get in touch with your local account manager at GfG or send an email to
integration@gfg-mbh.com and start shaping the future.
Author Contact Details Hans-Jörg Hübner - President and CEO, GfG • Klönnestr. 99, 44143 Dortmund, Germany • Tel +49 231 56400-0 • Email:
info@gfg-mbh.com • Web:
www.gfg.biz
Reliable gas monitoring in new craft beer brewery in Croatia
With increasing numbers of tourists, the demand for cool pale ale is apparently also increasing in Croatia. Craft beer from Croatian breweries is enjoying a high demand both domestically and abroad. “Craft beer” generally means beer that has been manually made by an independent brewery. The Craft Beer movement has its origins in the United States. Besides this definition, in Europe the term also refers to creative beers and brewers who pick up and reinterpret old or foreign beer styles.
The new Varionica Brewery in Pisarovina, south of Zagreb, follows the popularity of craft beer breweries in Croatia and is building a professional, modern plant with a production capacity of 40,000 litres per month. In addition to the latest technology in the brewing industry, Varionica is investing in all necessary safety solutions, including reliable gas detection from MSR-Electronic.
In beer production, the yeast feeds upon the wort during the fermentation process, which leads to the production of CO2
installed by the Croatian partner Aurel d.o.o. In the brewery, for example, fixed CO2 air for carbon dioxide concentrations.
and alcohol. Possible hazards include oxygen (O2 and LPG monitoring sensors from MSR-Electronic. The system is )
displacement, resulting in the danger of suffocation for brewery workers, and the risk of being exposed to high carbon dioxide concentrations over a longer period of time. Other hazards could arise from LPG gas used in the boiler and engine room. Varionica relies on the CO2
warning devices with infrared sensors with a measuring range of 0–5 Vol % are used to continuously monitor the ambient
The infrared measuring method with integrated temperature and drift compensation stands for highest accuracy, selectivity and reliability - despite a calibration interval of 5 years and the long sensor life. The digital infrared sensor has a standard analogue output (0) 4–20 mA or (0) 2–10 V DC and an RS-485 interface. Two relays with adjustable switching thresholds are also possible. Calibration can be performed by simply changing the sensor cartridge or by using the integrated, convenient calibration routine directly at the system.
The heart of the system is the GC-06 Controller. The Gas Controller is used for monitoring and warning of toxic and combustible gases and vapours as well as of Freon refrigerants in a wide range of gas detection applications. The large number of freely configurable parameters and setpoints allows individual adaptation to many applications.
For More Info, email: email:
For More Info, email:
52123pr@reply-direct.com
WWW.ENVIROTECH-ONLINE.COM IET Annual Buyers’ Guide 2020/21
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