Tracking trends: Predictions for instrumentation, data acquisition, sensors, and networking
New implementations of industrial temperature control loops by electronic temperature controllers are expected to decline through 2005, according to a study by Venture Development Corp. (VDC), Natick, MA. The study indicated that a growing number of users intend to implement temperature control loops in PLCs, distributed control systems (DCSs), and PCs.
The evolution of industrial temperature control progressed from manual control to mechanical and electromechanical thermostats, to electronic controllers, to process controls using PLCs, DCSs, and PCs. This evolution is driven by users wanting more features as well as better integration of controls.
According to the survey, PLCs are expected to gain the largest share of new temperature control loop implementations through 2005. However, this is not true for all industries. Electronic temperature controller implementations are expected to decline in all industries. The largest decline is expected among users in the pulp and paper industries; the least decline is expected among users in the food and beverage industries.
DAQ gaining ground
Another VDC study found that users of external chassis and module data acquisition (DAQ) products plan to make greater use of Universal Serial Bus (USB), Ethernet, Firewire (IEEE-1394), and wireless networks for data communication.
The survey polled DAQ users regarding current requirements, as well as requirements by 2007. Products identified in the survey were external chassis and modules, which includes data loggers, distributed/remote I/O, paperless chart recorders, PC front ends, and standalone systems as well as plug-in analog I/O boards classified by bus architecture, which includes compact PCI, ISA, PC/104, PCI, PCMCIA (PC cards), PXI, VME, and VXI.
Among external chassis and module users, significant shifts are expected in the communication networks they will use. Performance requirements will drive most of this shift. Higher data rates will be necessary because of increasing sample data rates, the number of parameters being monitored, and increasing resolution requirements. Ease of installation and use, and price will affect the market as well.
Transducer and transmitter trends shift
A recent study, also by VDC, evaluates and forecasts the U.S. market for various technologies used in process transmitters, nonprocess transducers and transmitters, and component-level pressure sensors, which include solid-state devices that are supplied as silicon chips or with limited packaging that allows them to be incorporated into transducers and transmitters.
In 2002, shipments of pressure transducers and transmitters in dollar volumes totaled $1.230 billion. Transducers and transmitters with pressure output only amounted to 93.5% of this volume, whereas multivariable types equaled 6.5%.
However, in 2007, shipments of pressure transducers and transmitters in dollar volumes are expected to total $1.443 billion. Pressure output types will fall to 85.3% of this volume, whereas multivariable types will amount to 14.7%
The survey stated that the reasons for this growth are cost savings, higher reliability, space savings, easier calibration, and reduction in process intrusion or penetration.
Multivariable pressure-sensing devices combine pressure output with one or more other types of sensing output — usually temperature — into a single unit.
Industrial control networking outlook
The largest percentage of smart process transmitters are shipped with the Highway Addressable Remote Transducer (HART) communication interface. HART is expected to continue to account for a large number of shipments during the next 5 yr because of the large installed base of instrumentation using this technology and products for maintenance or repair. However, for new and retrofit applications other fieldbuses are gaining ground.
HART was developed by Rosemount in the late 1980s, and became an open standard in 1990. HART provides bidirectional digital communication simultaneously with the 4%%MDASSML%%20 mA standard used by traditional instrumentation.
ODVA adopts time synchronization standard
The Open Device Vendors Association (ODVA) announced its plans to add time synchronization services for real-time control applications to its Common Industrial Protocol (CIP). Users will benefit from expanded application coverage of current fieldbuses, such as DeviceNet and Ethernet/IP.
This coverage includes sequence-of-events recording, distributed motion control, and other distributed applications that require increased coordination of control. The CIPsync system will be based on the recent IEEE-1588 standard.
Timing requirements placed on measurement and control systems are becoming more demanding. Also, distributed control and networking are becoming more prevalent. In the past, users had to rely on programming combined with communication technologies to accommodate timing constraints.
These constraints necessitated an alternate means of enforcing the timing requirements of these measurement and control systems. One way to accomplish this is for system components to have built-in real-time clocks that can synchronize with each other.
Measurement and control systems have certain specific requirements for implementing clock synchronization technology. These requirements include:
Timing accuracy must be in the submicrosecond range
The technology must be available on multiple industrial networking protocols, including Ethernet
Administration should be minimal
The technology must be capable of implementation on low-cost and low-end devices
The network resources should be minimal.
IEEE-1588 addresses the clock synchronization requirements of measurement and control systems. It defines a protocol that enables precise synchronization of clocks with network communication, local computing, and distributed objects.
The protocol will enable systems that include clocks of various inherent precisions, resolutions, and stabilities to synchronize. The default behavior of the protocol will allow simple systems to be installed and operated without requiring administrative attention of users.