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| Figure 1. Intelligent Instrumentation's Factory Monitor Web server lets you monitor activities on the plant floor using a Web browser. (Illustration courtesy of Intelligent Instrumentation.) |
In addition to storage and presentation, PC-based DA systems have become easier to use. DA applications fall into several categories: high speed or low speed and high resolution or low resolution. Systems can be categorized as packaged or nonpackaged. Developments in semiconductor electronics, software, and networking have brought new features to these systems, and many of the features have been adopted to make DA systems easier to use.
Recently, vendors have begun to incorporate the Universal Serial Bus (USB) into their DA systems. These companies include Data Translation (the DT98000 Series); DATAQ Instruments (the DI-720 and DI-730); Intelligent Instrumentation (the UDAS Series); IOtech (Personal Daq/56); National Instruments (the DAQpad-4350); and Omega Engineering (the OMB-DAQ-55/56). In spite of what is commonly reported in information technology publications, DA vendors say USB works well, especially with Windows 2000. The benefits? You get connectivity and flexibility, and you can even hot swap without rebooting.
Now you don't have to open the PC to insert boards, configure the software, or "plug-n-pray." Vendors have developed USB interfaces that also provide power to DA peripherals. USB allows up to 127 devices to be connected in a chain. Each time a new USB device is added to the network, the PC will map the device for data collection. According to IOtech, USB-based DA systems avoid the limitations of products based on the PCMCIA interface in terms of power and the number of I/O channels it can handle. Looks like the acceptance of a new technological trend.
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| Photo 1. Thanks to networking, data acquisition is becoming part of enterprisewide information systems. (Photo courtesy of Hewlett-Packard.) |
Perhaps as an acknowledgment of the growth in plant-floor DA systems, Daniels says that Intelligent Instrumentation will keep its focus on Ethernet connections for DA systems. He points to the growing use of Ethernet throughout the enterprise. The network technology has extended its reach to every part of a company's operations. It also adds the benefits of a common networking technology for the enterprise. When looking to the future, Daniels envisions greater use of wireless networks with DA.
Boards Aplenty
Backplanes and PC boards remain a major factor in today's market. With its business focus, National Instruments has taken steps to increase the performance of PC backplanes using the PCI bus.
In a technique called scatter-gather, PCI boards use a DMA bus master to control data transfers on the PCI bus and storage in memory. This method has been used in an earlier incarnation in the ISA 8237 DMA controller. To be effective, both the driver software and DMA bus master must cooperate.
In high-speed DA, the data buffers of many systems overflow when they can't keep up with data transfers, so data must be read from and written to the buffer simultaneously. To address this issue, DA vendors have developed software to work with the PCI bus to improve data transfer. This includes using driver software that implements memory-mapped I/O, not direct I/O addressing, and DA products that use on-the-fly scatter-gather bus mastering.
Remote and Portable
The makers of DA systems know that there are situations in which only a dedicated system will do. In this form, the systems fall into one of three categories: remote, portable, or specialized. These represent areas in which PC-based devices have not gained a very big foothold.
Agilent Technologies (the company recently formed from Hewlett-Packard's measurement and components businesses) offers stand-alone DA systems. The HP 34970A 6 (omega) digital multimeter combines portability, signal conditioning, and high measurement accuracy for collecting test data.
IOtech's PC-based LogBook/360 is a 16-bit 100-kHz system that offers modem-based communications with PCs. It's a good example of how DA connections can be made.
Semiconductor and packaging technology allow DA systems to be ever smaller. Keithley Instruments combines small size and Ethernet connections in its KNM-THM32-Ethra-C thermistor measurement module. Its ability to be mounted next to sensors lets users get error-free temperature readings anywhere in a plant.
Given the trends of microminiaturization and lower power consumption, DA systems are replacing older electromechanical devices. Omega Engineering points to small data collectors, such as the OM Nomad Series of temperature/humidity data loggers. These types of devices (a bit larger than a pager) replace the windup chart recorders used to record the important parameters relating to a food shipment. They eliminate the recording problems associated with vibration, shock, and breakage associated with mechanical devices and moving parts. The Nomad also records data in a computer-readable format, making life easier and validating data less expensively.
Fluke is one company that has decided to span the remote and distributed world of DA with a spread spectrum data logger. The Hydra Series wireless loggers operate on <1 W, require no FCC license, and transmit data up to 1/4 mile without losing the connection.
For high-end features, Nicolet Instrument Technologies offers the DAT/AIT, a portable system that combines a recorder, oscillograph, and oscilloscope in one unit. The DAT/AIT lets you collect and record data on a 2 MB Jaz drive and view and analyze the information on the same system.
The Value Is Software
While boards, PCs, and boxes make up a large part of DA product offerings, software is proving to be the key to product value. Graphical programming--the foundation of many PC development environments--is one of many factors influencing DA system usage. Developed by Hewlett-Packard and licensed by many, HP VEE Lab lets you configure your DA system one graphic element at a time by picking, placing, and connecting icons on screen. ComputerBoards and Data Translation are among the companies supporting VEE Lab.
Laboratory Technologies (Labtech) Corp. designed version 11 of its Labtech Notebook software to be both Windows NT- and Windows 2000-compatible. In addition to being Y2K-compliant, the software offers viewing over the Internet and 32-bit driver support. To save money, you don't have to buy multiple copies of the software for each application. Labtech will let you run multiple versions of the software on the same PC. Because Labtech Notebook supports multiprocessor systems, each version will run efficiently or make applications really fly.
Keithley Instruments has been working in the software driver area. The company offers 32-bit Active X drivers (Xcontrols) optimized for DA applications and 32-bit DriverLINX applications development device drivers. Keithley also offers ExcelLINX, a software package that makes it easy for you to drop DA data into an Excel spreadsheet for data collection, configuration, and display.
With the integration of its DataSocket software in LabView 5.1, National Instruments offers greater connectivity by delivering data over the Internet. The company believes that industry is adapting and adopting Internet technology faster than it embraced the PC in years past. National Instruments talks of even being able to do remote viewing--as in OSHA being able to witness a test in real time over the Internet without having to travel to the site. As with software packages with TCP/IP (transmission control protocol/ Internet protocol) found in an Ethernet link, vendors of other DA packages say they have comparable capability.
Standards
Within the industry, groups are trying to promote interoperability by developing software standards. One such group, the Open Data Acquisition Association, is promoting a protocol called the Open Data Acquisition Standard (ODAS). The standard is designed to provide a consistent data interface so that third-party software can read and understand data collected by a DA system. According to Frederick Putnam, CEO of Labtech, ODAS is similar to OLE for Process Control (OPC). ODAS is designed for PC plug-in devices, and OPC is designed for PLC-type factory-floor devices. ODAS is progressing, albeit slowly. As Putnam points out, standards have a long incubation period. The question remaining: When will enough people want to read DA data with third-party applications?
Another protocol, the Interchangeable Virtual Instruments (IVI), is meant to provide a standard for virtual instruments. IVI has more support and National Instruments' backing. It also has a more immediate payback for its supporters: The standard provides vendors and users with a common configuration for virtual software instruments. IVI strives to reuse code to reduce maintenance and speed development. The goal of IVI is to make DA easier for users and less costly for vendors to support.
Conclusion
By adopting such technologies as networking, DA systems can serve new users in new kinds of environments. As vendors develop new products for these environments and as standards simplify the use of DA technology, DA systems will become even more practical and prominent.
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Agilent Technologies PO Box 4026 Englewood, CO 80155-4026 800-452-4844 fax 303-662-3726 tmo_help@hp-usa-om7.om.hp.com |
Keithley Instruments 28775 Aurora Rd. Cleveland, OH 44139 888-534-8453 fax 440-248-6168 product_info@keithley.com |
| ComputerBoards, Inc. 16 Commerce Blvd. Middleboro, MA 02346 508-946-5100 fax 508-946-9500 info@computerboards.com |
Laboratory Technologies Corp. (Labtech) 2 Dundee Park, Ste. B09 Andover, MA 01810 978-470-0099 fax 978-470-3338 info@labtech.com |
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| Data Translation, Inc. 100 Locke Dr. Marlboro, MA 01752 508-481-3700 fax 508-481-8620 info@datx.com |
Microsoft Corp. 1 Microsoft Way Redmond, WA 98052 425-882-8080 fax 425-936-7329 www.microsoft.com |
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| DATAQ Instruments, Inc. 150 Springside Dr., Ste. B220 Akron, OH 44333 800-553-9006 fax 330-666-5434 info@dataq.com |
National Instruments 11500 N. Mopac Expwy. Austin, TX 78759 800-258-7022 fax 512-683-9300 info@natinst.com |
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| Fluke Corp. PO Box 9090 Everett, WA 98206-9090 800-443-5853 fax 425-356-5116 fluke-info@fluke.com |
Nicolet Technologies 5225 Verona Rd., Bldg. 4 Madison, WI 53711 608-276-5600 fax 608-273-5061 info2@nicolet.com |
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| Intelligent Instrumentation 2425 E. Medina Rd. Tucson, AZ 85706 800-685-9911 fax 520-573-0522 sales@instrument.com |
Omega Engineering 1 Omega Dr. PO Box 4047 Stamford, CT 06907 203-359-1660 fax 203-359-7870 info@omega.com |
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| IOtech, Inc. 25971 Cannon Rd. Cleveland, OH 44146 440-439-4091 fax 440-439-4093 sales@iotech.com |
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