Data Acquisition and Programmable Automation Controller
Data Acquisition and Programmable Automation Controller
Today's open, IP based wired and wireless local and wide area networks are more flexible and often less expensive. Because of this, retrofitting an existing RTU or implementing new applications using outdated RTU technology doesn't make good business or technical sense.
PACs in contrast, provide superior communication capabilities, versatile I/O options, board temperature and shock specifications, and use today leading communication standards. These features make PACs a well-suited alternative to legacy RTUs in the field, especially when older, proprietary networks are retired due to increasing maintenance costs or obsolescence.
A data acquisition (DAQ) system is a PC base device that provides fast signal acquisition, basic signal conditioning, data storage capabilities, and limited networking. The majority of DAQ systems are PC based, limiting their use in challenging physical environments or remote locations. Most DAQ systems thus find their home in the comfort of a laboratory rather than in the field locations.
PACs offer versatile and flexible signal sensing, conditioning and multiplexing. With a PAC powerful processors and large amounts of global memory, acquired raw data can be aggregated, collated or otherwise processed before being sent to a database or other application. Alternately, the data could be archived locally. Because a PAC is not a PC and is not hindered by a PC's high cost of ownership, it can be deployed in field applications with confidence.
The PAC exchanges manufacturing, production, and inventory data with an enterprise SQL database. This database in turn shares data with several key business systems, including an enterprise resource planning (ERP) system, operational equipment effectiveness (OEE) system, and supply chain management (SCM) system. Because data from the factory floor is constantly and automatically updated by the PAC, timely and valuable information is continually available for all business systems.
A Remote Terminal Unit (RTU) is a controller like device that is installed at a remote location to collect sensor and other data. Popular for decades, RTUs are typically used as part of a supervisory control data acquisition (SCADA) network, where a RTU sends data to a SCADA master. The RTU also receives information from the SCADA master to operate field devices at the remote location.
RTUs are primarily deployed in distant geographic areas to monitor, acquire and control remotely disperse assets such as pipelines, wellheads, lift-stations, or telecommunication facilities. Traditional PLCs don't natively posses the communication capabilities needed for use in these types of applications. Also PLC typically don't offer the ruggedness to withstand harsh environmental conditions, nor the flexible I/O configuration required in most RTU applications. In the absences of these capabilities, RTUs were developed specifically with a focus on communication capabilities, suitably for harsh environments, and flexible I/O configuration.
A PAC is notable for its modular design and construction, as well as the use of open architectures to provide expandability and interconnection with other devices and business systems. In particular, PACs are marked both by efficient processing and I/O scanning, and by the variety of ways in which they can integrate with enterprise business systems.
Most agree that industrial analyst ARC Advisory Group originated the term "PAC". ARC coined the term for two reasons: to help automation hardware users better define their application needs, and to give automation hardware vendors a term to more clearly communicate the capabilities of their products.
According to ARC, a programmable automation controller must fulfill the following requirements:
Operate using a single platform in multiple domains, including logic, motion, drives, and process control.
Employ a single development platform using common tagging and a single database for development tasks across a range of disciplines.
Tightly integrate controller hardware and software.
Be programmable using software tools that can design control programs to support a process that "flows" across several machines or units.
Operate on open, modular architectures that mirror industry applications, from machine layouts in factories to unit operation in process plants.
Employ de-facto standard for network interfaces, languages, and protocols, allowing data exchange as part of networked multi-vendor systems. Provide efficient processing and I/O scanning.