PC Test: Networking and Shared Applications Spur Future of Test

Like other enterprise operations, production test now is influenced by multiple departments that use test data for different purposes. Production operations may use the data for inspection and parts binning. Quality Assurance collects the same information to build statistical process control databases.

The accounting and manufacturing engineering departments may analyze the data to find ways of reducing scrap costs. Test engineers could analyze the same data to look for ways of increasing test-system throughput. In all cases, the goals are higher productivity and lower costs.

As database and networking capabilities expand, test instruments must keep pace by allowing broad access to their functionality and data. This calls for instruments connected to enterprise networks that operate with software understood by all who program or use the instruments and the data. As a result, the need for networking and shared applications is shaping the way test and measurement instruments are designed, including application programs that run them.

Current PC standards include data buses and communications interfaces that allow faster data rates and easier networking than ever before. Now, instrument manufacturers are working on ways to make it easier to adopt the new standards in product test and data acquisition applications. Here are the objectives:

Reduce manufacturing interruptions when switching over to new hardware.

Allow new hardware to be used with existing software.

Avoid nonstandard, add-on communications interfaces that use arcane programming languages.

Minimize overall engineering and programming requirements for new systems.

To reach these objectives, two preliminary steps are being taken by instrument manufacturers:

Development of hardware interfaces for instrumentation networking and data acquisition; for example, IEEE 1394 interfaces. Development of drivers and other software that simplifies the connection of instruments to newer PC hardware.

Hardware Outlook

Use of Platforms and Operating Systems

Several changes are occurring that should overcome these objections. On the user side, Windows NT is rapidly becoming the operating system of choice for instrumentation and control.

To improve compatibility with this de facto standard, instrumentation manufacturers will make wider use of Windows CE as an embedded computing platform. This will allow efficient use of common software standards such as ActiveX controls and other object-oriented programming tools. These embedded tools also make it easier to add web functionality to instruments, allowing wider availability of networked systems and databases.

While interest is growing in the Linux operating system for measurement and control applications, it still needs more development to provide the application ease that most test-system designers demand. Linux??s reputation for stability in these applications seems to be its greatest attraction. Whether it makes significant inroads will depend somewhat on the stability of future Windows NT releases.

Internal PC Data Buses

Designers of systems based on PC plug-in boards will face a different hardware environment—one in which parallel data-bus plug-in slots begin to disappear over the next few years as the universal serial bus (USB) and IEEE 1394 (Firewire) become standard. Current plans by Intel and computer manufacturers will lead to slotless PCs as they eliminate the parallel communications bus to reduce size and increase data rates.

External connection probably will be some form of internal bus extension for USB, Firewire, Ethernet, or other high bandwidth interface. This means that test and data acquisition hardware eventually will be housed in an external box or card rack.

A shift to slotless computers probably will occur very slowly in production facilities. Even though faster PCs and data communications can increase throughput, when production is going smoothly, there often is an attitude of “If it ain??t broke, don??t fix it.” This is evidenced by a lively market in ISA plug-in cards to duplicate existing test-system designs, even though PCI cards have been widely available for the past two or more years. Nevertheless, slotless computers are something both users and suppliers eventually will face.

Networking Protocols for Instrumentation

Before these PC hardware changes become reality, you will see simpler, less expensive network interface adapters that provide greater flexibility in terms of protocols available to instrumentation and test-system designers. This will be facilitated by system-on-a-chip ICs, such as a recently introduced USB-to-Ethernet controller. These ICs are Windows NT-compatible, provide on-board RISC processing, and are capable of 12-Mb/s transfer rates along with guaranteed service latency and bandwidth allocation.

Products like this one will lower the barrier that now deters developers from using networking options not contained on existing platforms. For example, adapting a PC-controlled test system for Ethernet can be an agonizing experience of wrestling with arcane commands and PC interrupts to avoid hardware conflicts.

USB-compatible instruments that will help solve this problem are just beginning to appear. However, within the next year or so, look for more types of instrumentation interfaces and adapters that are truly plug and play.

Firewire has not yet become widely available on PCs, and there still are protocol issues to be resolved before it is used on industrial instrumentation and control systems. To correct the latter, the Instrumentation and Industrial Control Working Group of the 1394 Trade Association probably will approve a data communications protocol draft before the end of this year.

The association also has drafted a protocol for using the IEEE 1394 bus to communicate IEEE 488.1 and 488.2 messages and command/control sequences, which could be approved at the same time. Along with increasing availability on PCs, this should accelerate Firewire??s industrial usage. It ought to be very attractive because of plug-and-play simplicity, high bandwidth, and its shared communications bus.

Another development that promises improved network connectivity is the availability of higher-performance, lower-cost microprocessors. The architectures of these digital signal processors and RISC processors allow very fast data exchanges and floating-point throughput. They also provide a powerful software development environment with visual and open application programming interfaces for adding third-party, high-level language (HLL) tools.

In some cases, a web server or thin client with internet protocols is included in the microprocessor. These features should encourage wide usage among instrumentation manufacturers.

Software Developments

Web Protocols

With built-in web servers, the File Transfer Protocol (FTP) and Hypertext Text Transfer Protocol (HTTP) can reduce the difficulty and cost of adding instrumentation to an existing plant network. With these protocols, a platform-independent web browser can be used to install an instrument on the network, configure it, monitor status, and collect data.

For example, FTP allows system developers to link a web page to a database that uses off-the-shelf software, such as Access, Filemaker, or Oracle. HTTP permits authorized personnel to view instrumentation outputs, read and write memory locations, and reset configurations. Security tools such as passwords, encryption, and firewalls can be used to prevent unauthorized data access. While there is limited availability today, the appearance of commercial instruments with these features should begin to accelerate in the year 2000.

Test-Program Development and Portability

To take advantage of this new hardware, you may have to modify old programs or write new ones. According to recent studies, 80% of all test-system software is developed using open-system HLL tools such as C++, Delphi, and Visual Basic. The other 20% is developed with off-the-shelf packages such as HP VEE, LabVIEW, SnapMaster, and TestPoint.

To minimize the need to write or rewrite code, HLL tools make heavy use of application libraries and vendor-specific device drivers. The availability of these tools from instrumentation vendors should continue to expand, but changes now underway could minimize the need for new test software when moving to newer-generation hardware or from one type of network to another.

Two software giants, Microsoft and Sun, have created methods of near universal network connectivity to minimize hardware and software changes. The term universal may be a bit strong since a developer typically must choose one camp or the other for a completely compatible set of hardware and software.

Microsoft??s common object model, in the form of DCOM, also allows networking of heterogeneous equipment and software. Still, programming and operations tend to be less complex when the hardware, operating system, and software all use the Microsoft model.

Similarly, maximum compatibility, speed, and ease of use in the Sun model are achieved with Java in silicon because interpretation and compiling are not required. For applications written in Java code, microprocessors that execute the Java Virtual Machine Instruction Set provide high performance with minimal memory.

For networking such hardware and object-oriented software, there is Sun??s Jini connectivity technology. This allows any object with a computer chip and network connection to exist as a service on a Jini-type network. Object-based information, such as measurement data and equipment status, may be directly passed from one device to another, which can act on the information without having it pass through a central control program.

Although instrumentation manufacturers may gravitate to one camp, it shouldn??t make any difference whether the network is based on Ethernet, Firewire, or USB. An object-oriented model allows easy application sharing and network support for database access and distributed computing. This will become the norm in future instrumentation design, allowing binary compatibility across operating systems and hardware platforms.

About the Author

John Kraizel is the manager of engineering for test and measurement business at Keithley Instruments. Since joining Keithley in 1989, he has held positions including senior design engineer, project manager, and engineering manager. Mr. Kraizel earned a B.S.E.E. from Case Western Reserve University and an M.B.A. from Weatherhead School of Management at CWRU. Keithley Instruments, 28775 Aurora Rd., Cleveland, OH 44139, (440) 498-2806.