A number of trends are affecting how much control you can get for your instrumentation dollar. Here's what to look for when purchasing temperature and process controls.

Serial interface communication is built into DIN-rail-mountable controllers so they can be wired to a PLC or computer.

Reduction in controller size is due to advances in semiconductor technology, which require a reduced number of components to build the devices.

Like most things in life, process control has long been a case of "get what you pay for." In those applications that required tight temperature control, processors were willing to pay for sophisticated controls. For most processes, however, stringent control was not necessary, so process equipment was outfitted with relatively simple controls capable of monitoring relatively few process variables. While adequate, this control scheme did not always allow the process engineer to know all he would like to know about his process.

Changes affecting process and temperature controls development have widened the capabilities of the devices while, in general, lowering prices. It is now possible to achieve a high degree of control with a relatively small investment. These 10 trends in temperature and process controls will continue to impact the choices available to you. Keeping abreast of control technology trends will put you in the driver's seat when it is time to make a purchasing decision.

With software support, controller setup can be accomplished via a PC.

TIP 1: Purchase Costs Shrink
Due to the development of semiconductor technology, which allows controllers to be built with fewer components, temperature and process controllers cost less. In addition, they are smaller in size and have increased reliability. So, you may be able to satisfy your process' needs for less than previously possible.

TIP 2: Devices DIN-Rail Mountable
As the trend continues toward building temperature controllers inside of machines and control panels, a slim-width, DIN-rail-mountable controller has emerged. Often, serial interface communication such as RS485 is built in so the controller can be wired to a PLC or computer and performance can be monitored. These small temperature controllers inside machines and control panels may provide you with networking capability without the need to select the components.

TIP 3: Controller Size Reduced
The trend toward the miniaturization of controllers has been ongoing for the last several years. Recently, manufacturers have introduced the smallest version yet seen on the marketplace: a 1? DIN controller with a front-panel measurement of only 1.9 x 0.9" (48 x 24 mm). Currently, the most popular controller size is the 1? DIN, which measures 1.9 x 1.9" (48 x 48 mm), but this is expected to shift toward the 1? DIN size. The 1? DIN miniaturized size allows more efficient use of panel space. The reduction in size is due to advances in semiconductor technology, which allow a smaller number of components to be required to build controllers while increasing the reliability.

The trend toward continually improving the features and functionality of these smaller-sized controllers will undoubtedly continue. However, it is improbable that the controllers will go any smaller in the future. Anything smaller than this size would prove difficult for a user to program and wire.

TIP 4: Software Support Included
Most control manufacturers already have designed software to support their controllers. Software can help set up, control and monitor controllers, thus ensuring a more controlled process. Setup can now be completed on a PC in a Windows environment instead of using the controller's front-panel keypad. Data parameters can be saved on a PC and copied to multiple controllers, providing a significant time savings for OEMs. Process values also can be monitored remotely. Each benefit helps reduce labor costs and increase productivity. Be sure that your controller provides software support to aid in setup and ease control and monitoring problems.

TIP 5: Datalogging and Trending Possible
Data recording and analysis have become standard protocol in most processes. Datalogging allows a user to review and analyze any potential causes for a product's or process' failure or subpar performance. The data also can be used to predict future process trends, help maintain quality control and reduce scrap rates by allowing users to predict future problems.

Recording and analyzing data can help predict future process trends and maintain quality control.

TIP 6: Fuzzy Logic More Widely Available
Fuzzy logic is an approach to computing that brings reason to the vagueness found in human experiences or the unclear boundaries in physical processes. Traditional Boo-lean logic is based on a series of "yes" or "no" answers, but fuzzy logic tries to bring degrees of partial truth to the equation for a more human approach. Fuzzy logic was first initiated by the University of California, Berkeley, in the 1960s, so it is not a new concept. But, fuzzy logic's use in the process and temperature control industry is increasing. While fuzzy logic is not needed for every application, it can prove helpful in hard-to-control processes that may be susceptible to sudden upsets or disturbances. When purchasing new controls, determine if your process is difficult to control or if it would benefit from fuzzy logic.

TIP 7: Multiloop Control Made Affordable
The measurement and control of various temperature points is a common application, especially in the rubber and plastics industry. Many times, there is a need for cascade control, where the control of one point is dependent upon the successful control of another point. Using a single controller for multiple inputs and outputs is becoming increasingly popular. A single controller reduces the complexity and bulkiness of wiring that normally would be required between multiple single-loop controllers. Determining whether or not your process could benefit from a single controller managing several inputs and outputs could provide cost and space savings over multiple single-loop controllers.

TIP 8: PLC Control of Temperature
The trend toward increasing the functionality of PLCs has reached a point where PLCs can be used to control temperature. Traditionally, they were used to control digital signals. However, recent advances in semiconductor technology have allowed PLCs to monitor analog signals such as those from a thermocouple. PLCs also offer multiple inputs and outputs, which may satisfy your process control requirements.

TIP 9: PCs Employed In Factory Automation
Considering the commonality of PCs in the home and workplace, it seems inevitable that they eventually will have an influence in the industrial automation market. One benefit of a PC-based automation system is that it is a leading-edge technology. Any new technological advances or developments such as the Internet can be quickly passed on. PCs also offer efficient communication between different applications.

At least for the foreseeable future, a PC will have difficulty competing against low-end, cost-effective temperature and process controllers. But, PCs will continue to be strong when used for data acquisition, reporting and controller programming.

Using a single controller for multiple inputs and outputs reduces the complexity of wiring that is required between multiple single-loop controllers.

TIP 10: Communication Networked
Communication networking is the single most important trend in the temperature and process controller market. Typically, this area has been behind other factory automation equipment in terms of the use of network communication protocols. Sim-ply put, device-level networks are the communication link between industrial components, such as sensors and pushbuttons, to central controllers, such as PLCs or stand-alone temperature controllers. Although the standardization of a single network type offers the advantage of information being exchanged between multiple vendors' hardware, it is unlikely that this will occur any time soon. Rather, there will be a reduction in the number of available networks.

For example, in the United States, DeviceNet is emerging as a prevalent platform. Some other examples include Profibus, Modbus, Fast E-net and Ethernet. Because different network buses are better at supporting different applications, a single industry device-level network is improbable. What does appear to be occurring is that different applications using different network languages are being connected by common bridges, which are used to translate the different languages, thus allowing communication.

The trends occurring in the temperature and process control industry continue to significantly change the marketplace. Take each trend into consideration before purchasing new controls and determine which, if any, may affect your process and therefore your purchasing decision.