SIC 3823

This category includes establishments primarily engaged in manufacturing industrial instruments and related products for measuring, displaying (indicating and/or recording), transmitting, and controlling process variables in manufacturing, energy conversion, and public service utilities. These instruments operate mechanically, pneumatically, electronically, or electrically to measure process variables such as temperature, humidity, pressure, vacuum, combustion, flow, level, viscosity, density, acidity, alkalinity, specific gravity, gas and liquid concentration, sequence, time interval, mechanical motion, and rotation.

Establishments primarily engaged in manufacturing electrical integrating meters are classified in SIC 3825: Instruments for Measuring and Testing of Electricity and Electrical Signals; those manufacturing residential and commercial comfort controls are classified in SIC 3822: Automatic Controls for Regulating Residential and Commercial Environments and Appliances; those manufacturing all liquid-in-glass and bimetal thermometers and glass hydrometers are classified in SIC 3829: Measuring and Controlling Devices, Not Elsewhere Classified; those manufacturing recorder charts are classified in the Commercial Printing industries; and those manufacturing analytical and optical instruments are classified in SIC 3826: Laboratory Analytical Instruments and SIC 3827: Optical Instruments and Lenses.

NAICS Code(s)

334513 (Instruments and Related Product Manufacturing for Measuring, Displaying, and Controlling Industrial Process Variables)

Industry Snapshot

Nearly 500 U.S. companies manufactured process control instruments (PCIs) in 2001, and the value of all industry shipments that year was nearly $7 billion. Because of the industry's technology-intensive products, variety of product types, and the tendency of end-user industries to continue to invest in process improvements even during recessions, PCI shipment values have remained stable in recent years, averaging $6.8 billion from 1995 to 2001. Small firms ($10 million in sales or less) have dominated the global sensor industry as a whole, including the smaller PCI industry segment. As computerized advanced process control techniques continued to become the norm in U.S. industry, PCI end-users increasingly demanded more accurate sensing devices and process control computers (or "controllers") capable of providing real-time direction of a sophisticated range of manufacturing process operations.

Among the largest segments of the PCI industry in 2001 were electronic systems of a non-unified architecture type, accounting for 20.6 percent of shipment values; industrial multifunction process computers (5.8 percent); transmitters producing standardized electronic analog transmission signals (4.9 percent); and various types of mass flow instruments (4.8 percent). In recent years, intense competition from foreign PCI manufacturers challenged U.S. producers at home; at the same time, growing markets in Asia, Eastern Europe, and the former Soviet Union offered U.S. producers opportunities to expand their leading role in the international PCI marketplace.

Organization and Structure

At the heart of industrial process control is the measurement of certain variables, such as temperature and pressure, used in manufacturing processes to transform raw materials into finished products. Measurements made by sensors, meters, or other measuring instruments on the manufacturing process line are sent by a transmitting device to an indicator or recorder for display and/or to a controller (by the 1990s, to a computer) where the data are compared to a pre-established set of parameters. The controller calculates the difference between the measured data and the programmed "setpoint" values and, if necessary, adjusts the process variables to conform to the desired parameters. This feedback-and-response cycle is called a loop, and continuous, repeating loops are performed during the industrial process to ensure product quality, efficient use of raw materials, and process safety. Processes typically involving control include reacting, heating and cooling, distilling, petroleum refining, and pulp and paper manufacturing.

PCI End-Users. The PCI industry is tightly linked to its end-user industries and to the process or so-called "wet" industries in particular. Capital expenditures by these industries on plant and process improvements have a direct effect on the profits of PCI manufacturers. The process industries use raw materials in fluid or bulk solid form for product manufacture and include the chemical, petroleum, petrochemical, pharmaceutical, pulp and paper, food processing, plastics, and municipal water and waste treatment industries.

Historically, the process industries have accounted for almost two-thirds of all PCI purchases. The chemical industry alone traditionally purchases 25 percent of all PCI shipments, followed by the petroleum (19 percent), pulp and paper (11 percent), and food processing industries (7 percent). Other important purchasers include non-process or discrete-piece manufacturing industries, which manufacture iron, steel, and nonferrous metals (such as aluminum and copper), glass and ceramic products, textiles, and machine tools; mining industries; and electric and gas utilities.

Competitive Structure. In spite of historically strong growth performance and high technology product groups, the PCI industry has traditionally been undervalued by the financial community. This sometimes prevented PCI companies from attracting the capital necessary to maintain growth and made firms in the industry ideal targets for acquisition by foreign and domestic companies. Although changes in the PCI industry's structure challenged the traditional hold of the largest companies in the 1990s, the major producers still dominated the industry and were the leaders in sales and employment by the end of the decade. Due to advances in digital technology, however, PCI system integration capabilities and product compatibility increased considerably. As a result, manufacturers who formerly dominated the industry faced competition from firms whose products could be tied into larger manufacturers' systems, thereby allowing these smaller firms to penetrate closed markets.

An increasing number of end-user manufacturers sought out PCI vendors who could provide them with complete integrated systems for their process control applications. Instrument manufacturers who formerly produced only components were thus forced to broaden their product lines. Despite increasing system compatibility, PCI vendors still competed in the areas of price, quality, added features, delivery, reputation, reliability, and service.

Legislation. Antipollution regulations by the Environ-mental Protection Agency (EPA)—the largest single regulatory influence on the PCI industry—required manufacturers to purchase instruments to monitor and control their industrial waste levels. Mandated spending to comply with Occupational Safety and Health Administration (OSHA) plant safety regulations was the next largest regulatory action affecting PCI purchases. PCI producers were also affected by Food and Drug Administration (FDA) policies regulating the manufacture of pharmaceuticals. While government regulation stimulated the sale of antipollution-related PCI products, it also reduced the capital available for new projects that would increase sales of PCIs.

Product Groups. The products of the PCI industry can be divided into several broad groups: general-purpose control system instruments; flow and level instruments; pressure instruments; temperature and primary temperature instruments; gas and liquid analyzers; humidity instruments; instruments for process variables such as speed, weight, density, and specific gravity; and other PCI instruments and spare parts, supplies, accessories, and related products.

General Purpose Control System Instruments. The biggest-selling PCIs, general purpose control system instruments, included multifunction computer control systems as well as general instruments for measuring, displaying, transmitting, and controlling process variables. General-purpose measuring instruments operate electronically or pneumatically to register and quantify process variable conditions in the manufacturing process. During the 1990s sensor products were available for measuring more than 40 different physical properties, from wind to acceleration, and roughly 75 different sensing technologies (for example, acoustic or zirconium oxide) were in use worldwide. The sensor's measurement or reading is transformed into a signal that is displayed or sent to the controller for comparison with process variable set points.

Indicators receive the data gathered by the measuring sensor and present them to the operator in digital or analog form. Digital indicators represent process variable data in discrete numerical or alphanumerical form on a liquid crystal or light-emitting diode display or through a computer screen. Recorders are used for graphing or permanently storing process variable measurements. Early recorders used pen-and-ink mechanisms to mark rolled strips of paper or circular charts. Computer technology has enabled measurements to be recorded digitally in computer memory for later display in printed form or on computer graphics programs. Controllers receive data signals remotely or directly from measuring or transmitting instruments and send instructions or error signals to actuating valves or other components on the process line if the signals indicate that the process variables are diverging from desired conditions.

Flow and Level Instruments. Flow meters have historically constituted one of the largest sources of industry revenue. Although there are more than 100 types of meters, the most common are differential-pressure, turbine, mass-flow, variable-area, magnetic, and positive-displacement meters. Flow meters are used to measure the rates of flow of fluid chemicals, gases, liquids containing particulate matter (slurries), water, sewage, and gas, among other applications. Level instruments can be used to determine the amount of raw materials available for production purposes or the number of items manufactured by the process. They are typically installed in tanks, bins, hoppers, or other storage devices to monitor levels of materials such as gasoline, milk, solvents, plastic granules, coal, or oil.

Pressure Instruments. The vast majority of products manufactured by industry firms are the result of processes that use pressure to perform work. Punch presses and boilers are typical pressure-based industrial process machines. Pressure measuring instruments such as gauges and pressure transmitters operate hydraulically, pneumatically, or electronically to measure pressure, absolute pressure, vacuum pressure, or draft pressure. The two most common types of pressure gauges are liquid-filled columns or tubes (similar to household barometers) and elastic pressure elements, which operate on spring-action, diaphragm, or bellows principles.

Temperature and Primary Temperature Instruments. More than half of all measured process variables undergo some form of temperature measurement during the manufacturing process. Accurate temperature measurements are important in many industrial processes but are critical in processes like rubber curing, food processing, and medical sterilization, where slight temperature variances can destroy final product quality. The four basic temperature-measuring instrument types are thermocouples, resistance thermometers, thermal radiation meters, and non-glass filled systems, such as industrial mercury-filled thermometers. Primary temperature instruments are the sensors that receive and measure the initial temperature data in the process control loop.

Gas and Liquid Analyzers. Analyzers of gas and liquid in continuous on-stream industrial processes are often classified according to the nature of the interaction between the gas and liquid to be measured and an external source of energy. Analyzers allow molecular-level measurement of process materials without interruption of the process for sample extraction. Analyzers are used to measure industrial effluents and waste products, viscosity of liquids used in mixing processes and food processing, the acidity or alkalinity of process materials, and the octane number in petroleum refining, among other applications. In addition to gas and liquid analyzers, the most common instrument types are oxygen, chromatographic, infrared, and pH analyzers.

Humidity Instruments. Instruments such as hygrometers and psychrometers measure the water vapor content of air in such industrial applications as test chambers, pharmaceutical and food packaging, heat treating, and industrial drying. Wet-bulb/dry-bulb humidity, relative humidity, vapor pressure, and dew point are the most common types of measurements performed by industrial humidity instruments.

Other Process Control Instruments. This category includes instruments for measuring such process variables as specific gravity, density, viscosity, weight, or force. Instruments in this category are used in such specialized applications as determining the "freeness" of pulp and paper products, the size of particulate solids in slurries, or the boiling point in petroleum refining.

Background and Development

The modern process controls industry grew out of three historical developments: the emergence of mass production technology, the evolution of instruments for measuring and analyzing process variables, and the development of computer technology in process control applications.

Eli Whitney's invention of the interchangeable part in 1800 represented an important early milestone in the evolution of mass production manufacturing techniques. In the early 1800s, Oliver Evans developed the principle of the automatic manufacturing sequence, which was followed later in the century by advances in machine tooling and the gradual transition from rudimentary assembly line manufacturing methods to true industrial mechanization.

In the nineteenth century there was fundamental progress in the measurement of properties like temperature, pressure, and fluid flow. In 1822, Thomas J. Seebeck's development of the principle of continuous electrical current flow across metals of differing temperatures laid the foundation for the modern industrial thermocouple. Contemporary thermistor technology grew out of Michael Faraday's discovery of the principles of temperature resistance in the 1830s. E. Bourdon's invention in 1852 of a method for measuring pressure based on the effect of internal pressure variations on the closed end of a curved tube remains a common pressure instrument technology, and the production of the first commercial venture tube flow meter in 1887 marked a major advance in fluid meter technology that was still in wide use in the 1990s.

The first commercial industrial controller using newly developed computational procedures, or algorithms, for regulating processes was marketed in 1936. The earliest form of process control was performed solely by the operator who read data from a measuring gauge on the process line, determined whether the measurement varied from some desired set point value, and turned a valve if the process variable required adjusting. Later controllers were pneumatically or electrically powered devices designed to maintain constant, hard-wired set points that sometimes contained both the component for measuring process variables and the component for actuating the regulating valves.

The earliest computer-based control systems appeared in the mid-1950s. Computer technology allowed controllers to communicate with other PCIs (such as measuring sensors) as well as a central control room computer. These controllers contained a computer-driven version of a control algorithm for indicating, controlling, and actuating control components. In addition to allowing process set points to be altered remotely and automatically through a computer terminal, computerized controllers offered lower cost, greater control speed, and increased reliability in comparison to earlier analog systems.

The first automated industrial process plants were constructed in the 1950s, and by 1965 over 1,000 industrial plants worldwide were computer controlled to some extent. The evolution of computer operation—from vacuum tubes to transistors and from integrated circuits to microchips—led to the introduction of faster and smaller microprocessing computers in the 1970s and 1980s. Identical microprocessor-based controllers located at different points on the process line—so-called distributed control systems—quickly began to replace centralized stand-alone control computers. This generation of highpowered, reprogrammable controllers gave operators direct control over more process loops and also enabled them to reconfigure control programs for new processes or applications.

Current Conditions

In the early 2000s, so-called "virtual manufacturing" was an increasingly important tool for players in the U.S. PCI industry, helping them to increase quality levels, lower costs, and be more responsive in a business climate where changes unfolded very rapidly. This approach, in which computers are used to simulate and test manufacturing processes before they are actually designed and implemented, provided companies with a number of advantages.

According to an article by Vivek Bapat in the November 1, 2002 issue of InTech , a publication of the Instrumentation, Systems, and Automation Society (ISA), "Since virtual manufacturing allows engineers to view a computer-simulated version of how the finished machine or processes should operate on the plant floor, they can eliminate process design flaws in the early stages of development to yield significant savings. Engineers can monitor and implement product changes while simultaneous development of the production machinery moves ahead. It also allows engineers to implement technology enhancements prior to production, further reducing development costs. In addition, operator training can occur in a virtual environment, minimizing risk to the operation."

As the industry moved toward the mid-2000s, the outlook was positive. According to Manufacturing USA , shipment values were expected to reach projected levels of $8.8 billion in 2002, and then rise to $9.1 billion in 2003 and $9.3 billion in 2004. During this same time period, capital investment also was expected to increase, rising from a projected $262.7 million in 2002 to $270.1 million in 2003 and $277.5 million in 2004.

Industry Leaders

Among the U.S. PCI industry's largest firms in the early 2000s were Thermo Electron Corporation ($2.1 billion in sales, 10,900 employees) and Rosemount, Inc., which was part of Emerson Electric Co. ABB, Inc., a subsidiary of the $23.7 billion Swiss conglomerate. ABB Ltd. was another major industry player, along with Milwaukee, Wisconsin-based Rockwell Automation, Inc. Invensys Foxboro, part of Invensys plc's Production Management Division, also was a leading contender.

Thermo Electron was founded in 1956 in Massachusetts by a professor of mechanical engineering who envisioned creating a "technology-driven" company that produced new technologies to meet emerging social needs. Since its inception, Thermo Electron has spun off no fewer than 18 publicly traded companies. Among its PCI-related operations, the company's Thermo Instrument Controls division manufactured PCIs and systems, from gas analysis to flow automation, for the chemical, petrochemical, refining, oil and gas, and mining industries.

Like Thermo Electron, Rosemount was founded in 1956 and initially built up its business through government aerospace contracts until it diversified into PCIs in the mid-1960s. After gaining a reputation for manufacturing reliable pressure and temperature transmitters, Rosemount merged with Emerson Electric in 1976 and, in 1993, acquired Fisher Controls International to form Fisher-Rosemount, one of the world's largest manufacturers of PCI equipment.


The size of the PCI industry's workforce has declined since its peak in 1989. In 1997, the industry employed approximately 48,000 people, with an average hourly wage slightly above $13. By 2000, this total had declined to 44,147 workers, who earned an average of more than $16.50.

Production positions accounted for more than half of the industry's employment in 1996. By 2000, this percentage had declined to about 44 percent. The production positions most representative of the industry included machinists, precision electrical and electronic assemblers, and instrument makers. Workers in these categories built and integrated the components that constituted the industry's product groups and, in some applications, fabricated instruments requiring accuracies of one ten-millionth of an inch. Engineers—from electrical and electronics engineers to mechanical and computer engineers—comprised another significant segment of the industry's employment. Only electrical and electronics engineers and computer engineers were expected to see significant employment growth to 2005.

America and the World

U.S. companies have played a leading role in the worldwide PCI marketplace. Nonetheless, foreign PCI industries—led by Germany, Japan, and the United Kingdom—have made significant inroads into the U.S. domestic and overseas markets. Between 1989 and 1995, for example, PCI imports more than doubled, fueled by comparatively lower foreign labor costs, foreign government subsidies of overseas PCI manufacturers, and the ability of some foreign manufacturers to bring research breakthroughs to commercial use sooner than U.S. firms. Moreover, some foreign PCI manufacturers responded to the focus placed by many U.S. companies on quarter-to-quarter profits by adopting longterm market penetration strategies, which allowed them to absorb short-term losses. Import values within the industry increased during the late 1990s, rising more than 8 percent from 1998 to 1999, and almost 18 percent from 1999 to 2000. However, values declined slightly from 2000 to 2001, falling from $4.3 billion to $4.2 billion.

Although the United States continued to lead the world in new PCI technology in the 1990s, American engineers focused on revolutionary breakthroughs in technology, while foreign research concentrated on gradual, evolutionary innovation. At the same time, foreign manufacturers' readiness to embrace new technologies enabled them to market PCI innovations sooner than more cautious U.S. producers. While U.S. funding of industrial research and development has focused on product development almost twice as much as improvements in industrial processes, the emphasis of Japanese funding has been the reverse, thus contributing in part to Japan's competitiveness in new PCI technology. Foreign firms looking for acquisition targets have been drawn to PCI industry firms because of the industry's history of continual growth, its high technology base, and its generally undervalued stocks and book value.

Exports and Free Trade. Despite the success of foreign companies in penetrating the U.S. market, the United States continued to show a trade surplus in PCIs, aided by continuing U.S. advances in new technology and the weakness of the dollar overseas. Historically, one-fifth to one-fourth of U.S. PCI shipments have gone to the export market, with the highest concentrations in high technology products like computer controllers and process analyzers. PCI export values increased during the late 1990s, rising more than 6 percent from 1998 to 1999 and almost 16 percent from 1999 to 2000. However, values declined slightly from 2000 to 2001, falling from $4.6 billion to $4.4 billion.

Efforts to ease international trade barriers and open foreign markets—such as the General Agreement on Tariffs and Trade (GATT)—helped to offer U.S. PCI producers potential new opportunities overseas in the 1990s. The North American Free Trade Agreement (NAFTA) in particular was projected to substantially expand the markets for U.S. PCIs in Mexico and Canada. Other leading foreign markets for U.S. PCIs are the European Community nations, Eastern Europe (especially Poland), Asia (especially China), and South America.

Research and Technology

The major developments in PCI technology involve advances in the power and usefulness of the computers used in process control applications, the continued evolution of artificial intelligence software applications for process control, and the development of an international standard for communicating between components in process control systems. In the mid-1990s, the rapid emergence of the World Wide Web as a source of industry information and a medium for commercial marketing also allowed small PCI firms to overcome their limited marketing budgets and to sell their products globally.

PCI Computer Hardware. The PCI industry is the most computer-automated segment of the combined measuring and control industry. As was true throughout U.S. industry in general, the computers used in industrial process control continued to fall in price and increase in power, speed, and memory. Advances in microchip technology allowed PCI producers to offer a wider range of functions in smaller, lighter, and cheaper instrument packages. Personal computers were increasingly used as process monitors, as workstations for configuring control systems, and as a means for gathering process data and coordinating controllers. Microchip technology also resulted in microprocessor-based "smart" instruments with self-learning and self-tuning capabilities.

PCI Computer Software. Many of the research advances benefiting the PCI industry involve artificial intelligence software used in experimentation, analysis, design, and prototyping of process control systems. Computer graphics modeling or simulation software programs allowed designers of process control systems to simulate complex manufacturing processes before they were actually created. Because they could also predict the final properties of raw material mixtures, these systems could also be used in the formulation of new products. Some programs also permitted simulated process system models to be tested through online interaction with the sensors and actuators that measure and control the variables in the manufacturing process. Self-diagnosing systems are capable of analyzing their own operation, anticipating future conditions, and making changes before problems arise.

Knowledge-based or expert systems used alogical, inductive reasoning and pattern recognition techniques to simulate the imprecise and unpredictable nature of manufacturing processes. These and related "fuzzy logic" programs learn from process events, make qualitative instead of purely logical adjustments to process conditions, and can evaluate and compensate for faults in the process design. In addition to optimizing efficient use of process variables, such software programs allow endusers to more accurately predict the final properties of process mixtures. Because expert systems are programmed to learn and "think" independently, they are able to make instantaneous changes in the quantity and quality of the raw materials introduced into the process without the intervention of human operators.

Communication Standards. Although long delayed, so-called fieldbus communications, an international protocol for linking all data communications between process control components regardless of design or manufacturer, was expected to eventually have a profound effect on the structure of the process controls industry. Fieldbus would allow the immediate conversion of data from traditionally analog-operating process sensors into digital signals, thus greatly expanding the integratibility or interoperability of PCIs. It represented a trend toward open or "transparent" system architectures that would allow end-users to mix and match system components, resulting in less expensive system expansion, improved performance, and enhanced reliability.

Further Reading

Bapat, Vivek. "Explaining the Virtues of Virtual Manufacturing." InTech , 1 November 2002. Available from .

Darnay, Arsen J. Manufacturing USA. Farmington Hills, MI: The Gale Group, Inc., 2003.

Industrial Computing. Instrument Society of America. Available from . Accessed 2003.

Instrument Society of America. Available from . Accessed 2003.

InTech: The International Journal of Measurement and Control. Instrument Society of America. Available from . Accessed 2003.

International Trade Administration. "U.S. Aggregate Foreign Trade Data." U.S. Foreign Trade Highlights . Available from . Accessed 2003.

Motion Control. Instrument Society of America. Available from . Accessed 2003.

U.S. Census Bureau. Annual Survey of Manufactures. Washington, DC: U.S. Department of Commerce, Economics and Statistics Administration, U.S. Census Bureau, February 2002. Available from .

——. "Selected Instruments and Related Products: 2001.". Current Industrial Reports. Washington, DC: U.S. Department of Commerce, Economics and Statistics Administration, U.S. Census Bureau. September 2002. Available from .

U.S. Department of Commerce. International Trade Administration. "Industry Sector Data." 14 March 2003. Available from .

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