With continuous improvements in the performance of personal computers (PCs), operating systems, and software, more and more applications can be effectively and efficiently addressed by PC-based test-system configurations. Each day, you are finding that PC-based test is a better and more cost-effective alternative than the measurement and control methods you used previously.
As a result, companies are working very hard to introduce even more high-performance, easy-to-use test-system products that capitalize on the power and flexibility of the PC. Here are details on six of the most salient trends driving PC-based test-system development.
1. Software
The most important software trend is the emergence of Windows NT®. Because of its superior performance, Windows NT is fast becoming the operating system of choice for PC-based test. It is much more robust than Windows® 3.1/95 and virtually crash-proof, and it fulfills the market’s requirements in terms of operating-system capabilities by providing:
Symmetric multiprocessing which allows the operating-system code to run on any free processor in a multiprocessor computer. This provides higher throughput and greater availability than does asymmetric multiprocessing.
Stability with full-memory protection for 32-bit applications.
Preemptive multitasking making it possible to run multiple applications with better sharing of resources.
Multithreading which provides the capability to execute applications in two or more locations using multiple threads. A thread is an executable entity that belongs to one process.
Real-time performance with latencies of only 5 ms to 10 ms.
Reliability in a multiuser environment.
Compliance with standards, such as Presentation Manager and POSIX applications.
The wider use of ActiveX controls allowing you to easily call up word-processing and spreadsheet applications is the next important trend emerging today. Using ActiveX to provide canned modules for the most common applications dramatically reduces the programmer’s workload. ActiveX controls also are language-independent, which means they can be used with many different programming languages. This flexibility makes ActiveX controls highly desirable software tools.
Another trend unfolding is the development of 64-bit operating systems and microprocessors, which should be available sometime in the next two or three years. These operating systems will continue the evolution from today’s Windows 95 and NT platforms toward greater resolution, accuracy, and faster throughput for PC-based test applications. As a result, we will likely see 64-bit PC-based test hardware that benefits from these faster operating systems.
2. Web Applications
In addition to their other uses, ActiveX controls enable remote control functions over the Internet. For a nominal cost, it now is possible for an entire company to have its information linked in hyperspace, making it easier to monitor and control from remote locations. Companies that adopt this technology soon will be light-years ahead of their competitors.
3. Networking Buses
The trend in PC-based test is moving away from the use of discrete, separate networks connected individually to one or, at most, a few PCs. Today, users requiring access to data from anywhere within the enterprise want to connect their applications into plantwide or enterprise networks.
The capability to provide remote access allows important functions to be conducted by staff at the headquarters, rather than locally. Some of the most exciting new networks or communications standards for PC-based test include Ethernet, the universal serial bus (USB), and Industrial Fieldbus.
Most test and measurement applications today use the serial port, 4-20 mA, and IEEE 488 bus communications protocols, respectively, according to a Keithley study published in 1997 (Table 1). The survey respondents indicated that use of these protocols will decline except for applications that do not require remote access. However, users who also need control capabilities are likely to migrate to faster protocols, such as FireWire, Ethernet, and USB.
Ethernet
To access a PC-based test system from anywhere in the enterprise or the web, users are turning more to Ethernet-based networks. Because such networks have no distance limitations and are common in most enterprises, it is not surprising that Ethernet is evolving into the de facto communications network of choice.
Ethernet’s installed base is enormous. In the study, 72% of the respondents reported that Ethernet was their facility’s data network standard. While the most popular version of Ethernet still is 10Base-T operating at 10 Mb/s, a 100 Mb/s version has been deployed.
USB
Originally designed to simplify peripheral connections for consumer applications, USB also has evolved for PC-based test systems. For those not requiring enterprise access but needing a localized network that is simple, fast, and easy to connect, USB can be a viable alternative.
Connecting to peripherals today often is difficult, requiring switch settings and hardware drivers. Yet, connecting into a USB port can be as easy as plugging in a toaster. A connecting cable plugs into the USB port of the PC and the peripheral’s USB port.
PCs equipped with Windows operating systems easily recognize and accommodate USB. Plug-and-play, hot swapping, and speeds up to 12 Mb/s are some of the features that make USB so attractive.
Industrial Fieldbus
The Industrial Fieldbus is a network communications standard that allows products from different manufacturers to talk with one another over a communications bus using a common protocol. Compared to what is available with proprietary networks, a fieldbus capability provides a wider range of equipment choices. Today, many fieldbus standards—such as those from ISA-SP50, Profibus, CAN, and DeviceNet—compete for viability.
It may be some time before a common fieldbus standard evolves. Eventually, users may become frustrated with the myriad of fieldbus choices and revert to a de facto standard such as Ethernet.
4. Form Factor
A key movement is toward smaller, smarter, and less expensive PC boards. Capabilities are increasing as size is decreasing. Correspondingly, interest is renewed in PCMCIA cards for PC-based test. The portability of notebook PCs allows users to bring this test technology to any field location.
The new 32-bit CardBus standard for notebook PCs is gaining attention because it permits data transmission over the PCMCIA bus at PCI rates (132 MB/s throughput). The evolution from the PCMCIA bus to CardBus seems likely to follow a path similar to that of the migration from the ISA bus to the PCI bus.
In addition to notebook PCs, palmtop PCs have entered the market, making field PC-based test applications even easier to perform. The palmtop PC enables users to download data in field locations for later analysis.
The move toward smaller and smarter boards is forcing an evolution beyond the board as a form factor itself. Many vendors now promote small devices that can be located anywhere, as close to the signal sensors as possible.
This distributed I/O, as implemented in external I/O devices, is becoming a reality for several reasons. Locating the measurement device as close as possible to the sensor or signal source eliminates major sources of noise and results in more accurate measurements. Rack-mounted, chassis-based, distributed plug-and-play I/O boards also are gaining popularity because of the great number of points that can be measured remotely.
5. Cost and Throughput
In addition to providing better performance and a smaller form factor, technological advancements are being provided at a lower cost per unit. For example, for digital and analog I/O, product costs on a per-channel basis are expected to drop 25% to 30% over the next five years.
Despite falling prices, throughput is increasing with all types of PC-based test systems. For example, CardBus enables portable applications to run at higher speeds, permitting portable PCs to operate at the same data rate as PCI bus-equipped desktop PCs.
Many manufacturers have introduced boards containing their own digital signal processors (DSPs). DSP-based boards typically operate at much greater speeds than non-DSP boards.
Switching from an ISA bus to a PCI bus provides a tremendous increase in throughput. For example, the theoretical peak throughput of the ISA bus is 2 MB/s to 3 MB/s, while the PCI bus throughput is 132 MB/s. The growth of the PCI bus allows the use of PCI plug-in boards that handle a new class of higher-speed applications. That means systems will be able to collect greater quantities of data at higher speeds.
6. Market Streamlining
Substantial shifts in both technology and standards are melding the previously distinctive data acquisition, test and measurement, and process-control markets, significantly changing the alternatives available. The convergence of data acquisition, test and measurement, and control applications ultimately will result in broader-based systems and software, as compared to the more narrowly focused systems and software available today. Eventually, products no longer will be aimed at particular markets, but rather will be applicable across a wide range of markets and customers.
Summary
Technological developments in PC-based test systems are converging with the rising expectations for more demanding measurement capabilities. Both hardware and software innovations and capabilities are increasing rapidly. The cost and size of products are falling while throughput is increasing.
Windows NT is becoming the operating system of choice for PC-based test. Users requiring access to data for PC-based test are connecting their applications into plantwide or enterprise networks, such as Ethernet, USB, and Industrial Fieldbus. With the emergence of ActiveX controls, the Worldwide Web will become a key communications medium that provides a platform for networked information and addresses the needs of the individual buyer.
About the Authors
Fred Glow is the strategic marketing manager for the Keithley MetraByte product
line. Previously, he held a senior management position with Analog Devices and other positions at Automation Research and Foxboro. Mr. Glow has a B.S. degree in engineering from Lehigh University and an M.S. degree in engineering management from Northeastern University.
Jim Borton, the marketing manager for the Keithley MetraByte data acquisition
product line, formerly held marketing and engineering positions at Reliance
Electric and Allen-Bradley. Mr. Borton earned a degree in electrical engineering technology from Youngstown State University.
Keithley Instruments, 28775 Aurora Rd., Cleveland, OH 44139-1891, (440) 248-0400.
|
Type of Protocol
|
1996 Percent |
1997 Percent |
Future Percent |
|
Serial Port |
72.5 |
71.1 |
46.3 |
|
4-20 mA |
64.5 |
51.9 |
35.4 |
|
IEEE 488 |
38.4 |
48.1 |
34.3 |
|
Ethernet |
39.9 |
36.8 |
42.9 |
|
HART |
9.4 |
6.7 |
5.1 |
|
USB |
— |
6.7 |
20.0 |
|
DeviceNet |
2.2 |
5.0 |
12.0 |
|
Interbus S |
— |
2.9 |
1.7 |
|
Field Bus H1 |
10.1 |
2.9 |
6.3 |
|
IEEE 1394—FireWire |
— |
1.3 |
8.0 |
|
Profibus |
1.4 |
0.8 |
5.7 |
Table 1.
Copyright 1998 Nelson Publishing Inc.
June 1998