KineticSystems ::. Data Acquisition (DAQ)

Technical Notes

System-level Standards - Are They for You?

Why did the Department of Defense
move to commercial-off-the-shelf products?
How did a major automaker eliminate test
stand incompatibility?

Data acquisition systems and other instrumentation have included standards for many years. However, these generally were not system-level standards. Typical standards covered the mounting of hardware on 19" racks, RS-232 serial protocol, the nominal AC supply voltage and so forth. We at KineticSystem s have been supplying data acquisition systems built to recognized internationalstandards for 25 years. However, in the last 5 to 7 years, there has been a significantly increasing demand from customers for standards-based systems. Prior to that time, customers primarily were interested in how our "black box" compared to someone else's "black box." They were not very concerned about the components of our systems, as long as they were reliable and performed the desired function.

The Value of Sys tem-level Standards

Increasingly, customers are demanding that the instrumentation they purchase conform to one or more system-level standards that are supported by a number of suppliers. In fact, they often specify which standards are required. Large companies and the U.S. Government are leading this charge. There are many advantages to using standards-based products and systems. Some of these are:

A multivendor supply: The customers are not "locked in" to a single vendor. They can "mix and match" products from multiple vendors to achieve the best system.
Improved system operation and maintenance, particularly for customers with more than one system, operator training and system maintenance are simplified because of the high level of standardization.
Better price-performance: Competition and higher manufacturing volumes cause suppliers to give more value at lower prices.

Hardware Standards

The PC backp lane has become the bus of choice to meet many of the less sophisticated instrumentation requirements. VMEbus, while developed as a backplane for Motorola processors, has become a standard for many data acquisition and control applications. Because of many limitations in the VME specifications, particularly for analog conversion, the major instrumentation manufactures developed the specifications for VXIbus (VME eXtensions for Instrumentation), now an Institute of Electrical and Electronic Engineers (IEE E) Standard. The VXI plug&play Systems Alliance was formed to make multivendor systems easier to install, use and maintain. The popularity of VXIbus is growing at a very high rate. An increasing number of VXI-based data acquisition and instrumentation projects for the U.S. Government as well as for private industry are being specified.

Software Standards

The choice of computer operating system (OS), the basic system-level interface to the user, is split into two major camps, UNIX and non-UNIX. Because of the sheer number of PCs, Microsoft Windows is the non-UNIX operating system of choice for many instrumentation systems. Windows 95 eliminates many of the limitations of Windows 3.1. One limitation of Windows 3.1 and Windows 95 is that they only run on Intel and Intel-compatible processors. Windows NT operates on a variety of processors, making it more general in its application, but less popular today. With the expected convergence of Windows 95 and Windows NT into a sing le OS in the future, the resulting operating system should play an increased role in instrumentation. Because of the number copies in use, Windows already has become a one-company "standard."

In 1968, AT&T developed the UNIX operating system. It allowed a single OS to run on multiple hardware platforms from multiple vendors. UNIX is often specified as the required operating system for a wide variety of applications. However, there are many flavors of UNIX available, based on AT&T Sys tem V, Berkeley, Xenix, and so forth. To avoid these incompatibilities, a set of truly portable UNIX standards, called POSIX, is being developed by the International Standards Organization (ISO) and the IEEE. The major suppliers of UNIX operating systems are committed to making their software POSIX-compliant. Much progress has been made in this direction. IEEE Std 1003.4, Real-time Extensions to POSIX, plays an important role in time-critical systems. POSIX compliance is being specified for many appli cations. However, the large number of computers running a version of Windows, makes it a major contender for the foreseeable future.

Replacing the $300 Hammer

We all remember the media blitz several years ago about defense spare-parts procurement, including the $300 hammer and the $1200 ash tray. Certainly, there have been abuses in the procurement of goods for defense applications. However, the high cost of most items can be attributed to the fact that they are produced in low volu me and manufactured to detailed military specifications. As defense budgets shrink, the Department of Defense (DoD) must find ways to get "more bang for their buck." In order to enhance operational readiness while reducing the planning, procurement and maintenance costs for test systems, DoD is directing that COTS (commercial-off-the-shelf) products, based on recognized international standards, be used whenever possible.

The Common Test System (CTS) is an example of the new DoD procurement polic y. This system will test the major types of missiles in the U.S. arsenal at sites throughout the world. Each of these systems will contain 5 to 7 VXIbus chassis with modules being supplied from a number of vendors. These systems will replace incompatible proprietary systems supplied by the manufactures of the various missiles such as the Patriot, the Tomahawk and the Phoenix. The use of commercial standards in these new systems also should help to meet the requirement for a 20-year system life.

Test Stand Incompatibilities

A major automaker has a component test lab with 60 computer-controlled test stands. From the operator's standpoint, most of these systems are different from each other. As each requirement came about, an integrator was requested to build a "box." The type of computer, the operating system and application software, and the instrumentation hardware were not specified by the customer. Extensive operator and technician training are the most significant problems cause d by these incompatible systems. With a downsized workforce, each worker can deal only with some of the systems. When workers are on vacation or when there is any turnover, it is extremely difficult to keep all of the test stands operating. The next-generation systems will be VXI-based with one VXI chassis for each pair of test stands. Each VXI chassis will be hosted by a computer with a UNIX operating system and an application program that is common to all test stands. The reduction in lifecycle co st and increase in productivity are expected to be substantial.

The Commitment to Standardization

Based on the foregoing discussion, one would believe that, like the flag, motherhood and apple pie, everyone would require that all future instrumentation be based on recognized standards. However, standardization can have its cost. If a user has a number of proprietary instrumentation systems, and additional systems are needed, the best choice may be to purchase additional syste ms of the same type. This avoids the added training needed for a new type of system. However a number of questions need to be asked when making the decision to stay with proprietary systems or to make the move to standards-based systems:

Do my present proprietary systems have the flexibility to meet my current and future needs?
What is the true cost of being "locked in" to a single supplier?
As new software is developed in the industry, will I be "loc ket out" of its use?

The answers to these and other questions often lead to a choice of standards-based systems.

Biography

Bob Cleary co-founded KineticSystems Corporation in 1970 and is its Chief Executive Officer. He has developed many of the high performance CAMAC and VXIbus data acquisition and control products in the KineticSystems product line. He is a co-author of the book, "High Performance Data Acquisition and Control," has given many seminars on VXIbus and has presented numerous technical papers. Mr. Cleary has been granted 18 U.S. and 24 foreign patents.