Today, programmable automation controllers (PACs), such as NI Compact FieldPoint, provide a new option for implementing industrial data acquisition systems. PACs combine the best features of the PC, including the processor, RAM, and powerful software, with the reliability, ruggedness, and distributed nature of the PLC.
Specifically, Compact FieldPoint provides easy-to-use PC-based features, such as a floating-point processor for custom calculations, an embedded interactive Web server for easy control and monitoring, removable CompactFlash for data logging, and Ethernet connectivity to share data across the network easily. It couples this PC functionality with rugged PLC packaging to deliver a CE heavy industrial electromagnetic compatibility rating for electrically noisy environments, a -25 to 60°C temperature range, and 50 g shock and 5 g vibration ratings for mobile and vibrating environments. Compact FieldPoint is a suitable platform to perform control or data logging with acquisition rates at 300 Hz or lower in a rugged or distributed environment.
Achieving high-accuracy analog I/O
From their PC heritage, PACs, such as Compact FieldPoint, feature high-accuracy analog I/O with built-in signal conditioning, NIST-traceable calibration, and up to 16-bit resolution. With Compact FieldPoint, users can accurately interface with digital I/O, perform analog output, and input calibrated analog values from sensors, including thermocouples, RTDs, current sources, and high-voltage sources. Once analog signals are measured, the user may need to use the signals as a variable in a control algorithm or as inputs for analysis calculations. Because Compact FieldPoint runs LabVIEW Real-Time, users may rapidly build their applications using the built-in functions, or easily implement their own custom calculations.
Methods for logging and sharing data
Once data is acquired and analysed there is often a need to log the data or share it over a network. The Ethernet may be used to share logged or realtime data from Compact FieldPoint across the user's network. With Compact FieldPoint, users can distribute process information, share reports, and remotely control embedded LabVIEW applications.
For logging, Compact FieldPoint uses non-volatile internal Flash and removable CompactFlash for storage, so more than 1 GB of data may be stored in standard DOS-compatible files. Compact FieldPoint can log data in two ways:
* It may be used as a standalone data logger by logging data in a standard tab or comma-delimited file, standard Excel spreadsheet formats, or more advanced formats, such as XML. To retrieve the data, the user can use a built-in FTP server, transmit the data over a phone line, or simply remove the CompactFlash and physically transport it to a PC for further analysis.
* It may be used as a redundant logger on a networked system with a distributed control system (DCS) or PC-based control system that logs the information to a database. If communication is interrupted, Compact FieldPoint automatically logs the data locally. Then, once the connection is restored, Compact FieldPoint can transmit the data over the network, where the user can easily insert it into the database for loss-free logging.
With Compact FieldPoint, users can program with LabVIEW for easy analog manipulation, data logging, and networking, while providing ruggedness formerly limited to PLCs.
Ten questions that National Instruments recommends one asks before settling on a programmable controller:
* Does the controller have an open architecture designed for customisation?
* Does the controller have adequate shock, vibration, and temperature specifications?
* Does it offer the flexibility to choose the ideal control scheme?
* Does the automation platform include accurate analog I/O?
* Is there a need for advanced or custom calculations requiring a floating-point processor?
* Are the automation system's software tools easy-to-use and productive?
* Is it possible to interact with the controller via the Web?
* Will the controller perform custom communication with third party devices?
* Can the controller reliably log data?
* Can other parts of the system, such as motion, vision, test, and scada, use the same software as the controller?
(Find out the answers by going to www.ni.com/info and enter code zagrkw)
For more information contact National Instruments SA, 011 805 8197, [email protected]
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