PLCs, DCSs & Controllers


New generation AS-interface master

July 2004 PLCs, DCSs & Controllers

In addition to its diagnostics (error counters, corrupted slaves lists, peripheral fault lists, etc) the new stainless steel enclosed AS-interface master (from Bihl+Wiedemann) now has a wide range of new, useful features - they include:

Recognition of duplicate addresses

When two AS-interface (ASi) slaves have the same address the master cannot send a request to each slave separately. Until recently, different masters reacted differently to this situation, without actually recognising the problem. As both slaves' responses overlap on the line, it is impossible for the master to recognise a correct response. This results in an unstable network, without any indication to the user. The new master solves this irritating problem. A duplicate address is recognised and a corresponding error message is displayed. The configuration error and duplicate address flags are set and a list of duplicate slaves is updated.

Earth fault detector

Communication on the ASi bus is still possible if one of the ASi lines short-circuits to plant earth. However, the data signals in such a case can be highly influenced by electro-magnetic disturbances. Circuits with a line-to-earth fault are likely to have a high number of communication errors, the cause of which used to be a mystery to the user. The new master's earth fault detector will now immediately raise an alarm in the event of an earth fault, a message is displayed on the master's display and an earth fault flag is set.

Over-voltage detector

The new master detects severe common mode oscillations. ASi is designed as an earth-free system. This design can sometimes cause the potential of both ASi lines to fluctuate with reference to ground. This may not cause communication errors on the bus, but it can influence externally connected sensors. A sensor with inductive characteristics may generate an erroneous signal during such common mode oscillations, causing the master to temporarily receive an incorrect input signal. The new master warns the user of this danger in the form of an over-voltage flag and corresponding error message.

Noise detector

ASi is designed to operate at a high threshold noise level, even if this means that telegrams are repeated occasionally. However, if this threshold is exceeded, an unacceptable number of telegram disturbances is created. The master detects alternating signals produced by neither the master nor the slaves and subsequently sets a noise flag. This helps the user identify the source of these disturbances. The noise flag could for example be raised cyclically upon the cyclic activation of a frequency inverter, thus identifying the source.

Adding short-circuit protection

It is well known that a short-circuit between the communication lines of a fieldbus network will pull down the entire network. This will cause downtime on that section of the plant until the short-circuit is located and corrected, but with the whole network down, where does one begin looking?

Stonel offers a range of drop connectors for the above networks with a protection circuit on each drop, ensuring that a short circuit on a drop will not affect the rest of the bus. A trip current of 240 mA for AS-interface and 40 mA for Profibus PA and FF isolates the drop from the rest of the network, and visibly indicates the short by means of an LED.



Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

EtherCAT Box modules for confined spaces
Beckhoff Automation PLCs, DCSs & Controllers
Users of EtherCAT and EtherCAT P Box modules from Beckhoff’s EP and EPP series benefit from 25 years of IP67 expertise in the I/O sector. The broad product range for decentralised distribution of the I/O level directly at the machine or system has been continuously expanded and further developed during this time.

Read more...
ABB updates distributed control system
ABB South Africa PLCs, DCSs & Controllers
Leveraging 30 years of continuous innovation and reliability, ABB’s updated Freelance 2024 distributed control system (DCS) offers greater plant adaptability, faster and more reliable device communication, improved system security, and seamless data exchange.

Read more...
Four ways modern operations control can boost sustainability and efficiency
PLCs, DCSs & Controllers
With the growing importance of digital transformation, HMIs and scada have evolved from control panels to vast operational hubs. Next-gen HMI/scada can bring together data, personalisation, and advanced insights to successfully achieve organisational goals, it is important to think about HMI/scada holistically within the operations ecosystem.

Read more...
The convergence of intelligence: DCS, SCADA and TLC
Schneider Electric South Africa PLCs, DCSs & Controllers
In the early days of industrialisation, control systems were primarily mechanical, and relied on manual intervention and simple feedback loops to manage processes. Now, in the 21st century, industrial process automation systems are mind-blowingly intelligent, and provide almost unparalleled control and monitoring capabilities, making them integral to modern industrial systems.

Read more...
PC-based control for advanced hydrogen storage technology
Beckhoff Automation Editor's Choice PLCs, DCSs & Controllers
The proportion of renewable energies from solar, wind and water is rising continuously. However, sufficient storage options are of the essence to use these energies as efficiently as possible. GKN Hydrogen offers a particularly compact and safe option, low-pressure metal hydride hydrogen storage systems with PC-based control from Beckhoff.

Read more...
ABB modernises key board mill
ABB South Africa PLCs, DCSs & Controllers
ABB has secured a landmark contract to modernise Smurfit Kappa’s Paper Machine 5 at its corrugated cardboard mill near Mexico City. ABB will provide Smurfit Kappa with DCS, accompanied by a comprehensive paper machine drives system, encompassing some of the market’s most advanced drives and motors meticulously designed to optimise PM5’s performance.

Read more...
The synapses of the distributed control system
Schneider Electric South Africa PLCs, DCSs & Controllers
Industrial operations require a distributed control system (DCS) to coordinate and control their process subsystems in real time. Like the brain, a DCS is a multitasking maestro, controlling and coordinating complex processes in a myriad of industrial setting such as large manufacturing plants, providing valuable top-down control.

Read more...
Modular assembly platform for clean manufacturing
Beckhoff Automation PLCs, DCSs & Controllers
JR Automation delivers custom automated solutions for numerous industries. It has done this through its scalable, modular automation platform, FlexChassis, which speeds up time to market while cutting costs. The company chose the XTS linear transport system from Beckhoff because of its speed, and modular design that allows for multiple configurations.

Read more...
Selecting the best remote access solution for your application
PLCs, DCSs & Controllers
In today’s Internet of Things (IoT) world, remote mobile access is a necessity for many industrial applications. There are several ways of implementing this connectivity with routers and virtual private networks.

Read more...
PLCs and PACs simplify data acquisition
PLCs, DCSs & Controllers
Data acquisition, data logging and data analysis are required functions for most modern industrial control systems. The simplest and lowest cost way to provide these functions is often by using the same platform providing real-time control, namely the PLC or the PAC.

Read more...