JAOMAD Glossary S:

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Intro

S—Symbol of ANSI thermocouple type for Platinum 10% Rhodium vs. Platinum; also: means "Speed" or "Frequency" when used in first alpha character position of ISA instrument function tag, means "Safety" as a modifier, means "Switch" when used in succeeding position [see ANSI/ISA S5.1-1984 (R1992)]; also: Solenoid actuator; also: Standard deviation (S) in SPC, a mathematical measure of the variability or spread of a sample of data (is square root of the average of squared deviations of each point from the mean).

S-Glass—In construction of glass bulb type pH sensors, this is a low ohmic glass used for membranes of electrodes for processes where measurements are to be made in acid media and lower temperatures; at higher pH values alkaline error may be significant; see E-, G-, L-Glass.

S-Video—In video development, a way of dividing the signal so luminance is on one wire or signal while red-green-blue (RGB) mix on another and is of higher quality than composite; is also called Y/C Video for Luminance/Chrominance (Lumination/Color); compare with Composite Video and Component Video); used in prosumer equipment, but available on some consumer-grade video products.

S/W—Software.

S(numeral)—ISA standard when released, such as S88, S5.1, S72, which originated with the designation SP(numeral); see SP50, etc.

SA—(Standards Australia); Australian certification laboratory for testing equipment of different vendors to some common standard.

SAA—System Application Architecture; set of standards developed by IBM® providing identical user interfaces for applications running on PCs, minicomputers, and mainframes; also: (Standards Association of Australia), a member of IEC.

SaaS—Software as a Service; see definition.

Safety Instrumented System (SIS)—Instrumentation such as all sensors, processors and final elements that have an impact upon process safety, and which are designed to protect people, process & equipment; commonly called safety or emergency shutdown systems (ESDs), interlock systems, safety systems, protection or protective systems, etc.; standards such as ISA S84, IEC61508 are generally performance-based, that is, they define requirements to be achieved, but do not this to be achieved in any specific way.

Safety Lifecycle—Practical methodology that defines steps necessary to ensure overall plant safety for process plants

Safety Requirements Specification (SRS)—In a Safety Instrumented System, consists of the functional requirement specification or what the system does, and the integrity requirement specification or how well the system needs to do it.

SAM—Sensor Actuator Manager, see definition; also: Sequential Access Method, see definition; also: Security Accounts Manager, see definition; also: Symantec Antivirus for Macintosh, see definition

SAMA—(Scientific Apparatus Makers Association); trade organization that among other things developed standards for industrial process instrumentation and control once widely used in the U.S. power generation industry; now being provided by Measurement and Control Automation Association (MCAA).

SAML—Security Assertion Markup Language; XML-based standard that defines real-time authentication and authorization transactions, used in process of granting and shutting off user access to systems and applications in websites on Internet, Extranets, or Intranets.

Sample & Hold—In instrumentation, electrical circuit that acquires and stores analog voltage on capacitor for subsequent conversion.

Sample Rate—In digital signal processing (DSP), frequency that an analog signal is sampled by a digital system.

Sampling—Measuring at regular intervals the output or variable(s) of a process to estimate characteristics of that process.

SAN—Storage Area Network; see definition.

Sanders 3-D Plotting—Form of Rapid Prototyping, see RP.

Sans Serif—In typographical composition of screen displays and printing, typeface without finishing strokes (serifs).

SAP—Service Access Point; ISO model; also: Systems, Applications, Products; software used in Enterprise Information Systems to link databases from all parts of corporation to develop business solutions, initially developed by SAP Aktiengesellschaft AG.

SAR—Successive Approximation Register; type A/D converters found on board single chip microprocessors provide better speed but less accuracy than "dual slope" technique.

SARA—Superfund Amendments and Reauthorization Act; U.S. federal law passed in 1986 reauthorizing and expanding Comprehensive Environmental Response, Compensation and Liability Act.

Sarbanes-Oxley Act of 2002 (SOx, S-O) [US]—Series of very high profile scandals, such as Enron, caused significant legislative changes to financial practice and corporate governance regulation; introduced stringent new rules with stated objective: "to protect investors by improving the accuracy and reliability of corporate disclosures made pursuant to the securities laws;" defines type of records that must be made and for how long kept, deals with falsification of data (requiring audits), affecting data storage capacities and planning;  with security such a strong theme, many organizations are addressing this using ISO1799 international standard, which impacts network security.

SASE—Specific Application Service Element; protocol of MMS.

SAT—Site Acceptance Testing (of control systems after they arrive at user’s plant from supplier’s factory); see FAT.

Saturable Core Reactor—Inductive "valve" to provide modulating control to a heavy inductive load such as heating elements in furnaces.

SAW—Surface Acoustical Wave type of touchscreen, which confines most of acoustical energy to surface of screen; compare with GAW.

SaW—Safety at Work; system that allows networking of safety devices using standard Actuator Sensor Interface (AS-i) networks.

SBC—Single Board Computer (also ...Controller); see definition.

SBE—Scan By Exception; way to rapidly report information in large process control communication systems by having the host poll all devices, but devices will only communicate data that changed, or indicate anomalies, rather than report everything; when there is nothing to report, device will send a brief "all's well" signal.

SBM—Super Bit Mapping.

SBPC—Single Board Personal Computer.

SBS—Silicon Bilateral Switch.

SC—Signal Common; common ground for a cluster of signals which may not be at either chassis ground or earth ground electrical potential; also: SemiConductor.

SCA—Single Connector Attachment; SCSI technology combines drive signal line with power lines in same connector, allowing ability to change out circuit boards and modules under power (called “Hot-swap”); also: Single Connector Architecture; also: Sneak Circuit Analysis; see SPA; also: Supply Chain Alliance; also: Sensor Chip Assembly; also: Software Communications Architecture; also: Software Configuration Architecture; also: SubChannel Adapter; also: Surface Charge Analyzer; also: Synchronous Clock Adjustment; also: System Communication Architecture; also: Society for Creative Acronyms (really!)  J

SCADA—Supervisory Control And Data Acquisition; generic name for computerized system capable of gathering and processing data and applying operational controls over long distances between Remote Termination Units and Master Termination Units, such as used with power transmission and distribution and pipeline systems; designed for unique communication challenges (delays, data integrity, etc.) due to various media that must be used, such as phone lines, microwave, satellite, etc. usually shared rather than dedicated; its design must assume that communication will often disconnect, Remote Termination Units should be capable of operating unattended;
NOTE: since about middle 1990s some suppliers of systems made up of industrial PCs and PLCs (& some who supplied only industrial grade PCs as HMIs) used in factory automation and connected by simple (usually Ethernet) networks, have referred to these as SCADA systems when that architecture had been originally called (variously) DACs, DASs, DAQs… the differences are they do not deal with the complexities of communication over large distances.

SCADA/DMS—Supervisory Control and Data Acquisition/ Distribution Management System; supervises, controls, optimizes and manages power distribution networks; enables utilities to collect, store and analyze data from hundreds of thousands of data points in national or regional networks, perform network modeling, simulate power operation, pinpoint faults, preempt outages, and participate in energy trading markets.

SCADA/EMS—Supervisory Control and Data Acquisition/Energy Management System; supervises, controls, optimizes and manages generation and transmission systems; enables utilities to collect, store and analyze data from hundreds of thousands of data points in national or regional networks, perform network modeling, simulate power operation, pinpoint faults, preempt outages, and participate in energy trading markets.

Scale-ability, Scalability—Ability to vary information content of program by changing amount of data that is stored, transmitted, or displayed; in a video image, this translates into creating larger or smaller windows of video on screens; also: in terms of system, ability to readily increase capacity and/or functions (sometimes by ability to add more devices to a network).

Scan—In process control, to examine data from process sensors for use in calculations, alarms, etc., intermittently sampling in predetermined manner, each of a number of variables; a single sweep of applications program in some computer, such as all functions of process controller or PLC, based upon input status at the time so that functions can create new set of outputs, or place into historical database.

Scan Table—In digital communication, predetermined list of regularly requested data between two devices that can be transmitted in a single transaction rather than requiring significant overhead of separate individual transactions.

Scan Time—Time it takes to perform all appropriate functions of a (microprocessor based) device, or set of specific functions within that device, such as “I/O scan time.”

Scanner—Electronic device used in making color and tone-corrected separations of images, usually to copy a photo or printed image into a computer for use in a video screen image.

SCE—Supply Chain Execution.

SCC—(Standards Council of Canada); member of IEC.

SCCM—Standard Cubic Centimeters per Minute.

SCCR—Short-Circuit Current Rating; see definition.

SCFH—Standard Cubic Feet per Hour.

SCFM—Standard Cubic Feet per Minute.

Scheduled Release Date—Carefully calculated date determined by estimating actual shipping date and subtracting six months from it. J

Schedules—In FOUNDATION Fieldbus technology, define when Function Blocks (FBs) execute and when data and status is published on the bus.

SCI—Serial Communications Interface.

SCIA—(Steering Committee for Industrial Automation); within ISO/IEC.

SCL—Substation Configuration Language; XML-based description language as part of IEC61850 spec for plug-and-play information flow between equipment from different suppliers of Intelligent Electronic Devices (IEDs), especially in context of maintenance and asset management in power utilities.

SCM—Supply Chain Management; process of all operations from your customer’s customers to you supplier’s suppliers, automated including Internet connections.

SCP—Simple Control Protocol; see definition; also: Supply Chain Planning. see definition; also: Short Circuit Protection.

SCR—Silicon Controlled Rectifier; a three terminal PNPN device that normally blocks current flow in both directions until its gate is pulsed with a timed electrical signal, so that a modulation of a small electrical current can smoothly modulate a much larger one; also: Saturable Core Reactor; an inductive "valve" to provide modulating control to a heavy inductive load such as heating elements in furnaces; also: Selective Catalytic Reduction system.

Screen Scraper—Software that allows PC to intercept character-based data from mainframe (often presented in a green screen) and present it in easier to understand graphical user interface (GUI); newer screen scrapers present information in HTML, so it can be accessed with a browser.

Screensaver Lock /Screen Saver Program—Program that automatically activates when workstation or PC has been inactive for specified length of time; can also provide additional security if password protect option is turned on, so that only person with correct password can unlock screen saver and access that workstation or PC.

Script—In the context of the World Wide Web, a (gateway) script is a program that runs on a server and processes requests based on input from the browser.

Scroll—To move all or part of video screen material up or down, left or right, to allow new information to appear.

Scroll Bars—Bars adjacent to window in workstation screen view which allows user to scroll contents within that window to display more information than can normally be shown within that window.

Scroll Box—Small box within scroll bar to move view by dragging with cursor.

SCS—(Sira Certification Services, Ltd) British certification and testing laboratory for testing equipment of different vendors to some common standard: also: Silicon Controlled Switch.

SCSI—[pronounced: skuzy] Small Computer System Interface; parallel interface standard for attaching peripheral devices to computers, providing faster data transmission rates than standard serial or parallel ports; additionally, many devices can be attached, making this an I/O port, not just an interface; although an ANSI standard, there are many variations, so two SCSI interfaces may be incompatible; also: System Can’t See It J.

SCSI CAM—Small Computer System Interface, Common Access Method extension.

ScTP—Screened Twisted Pair; wiring for signals.

SCTS—Secondary Clear To Send; modem interface control signal (typically EIA RS232/422) indicating readiness for alternate device to accept data from DCE; see CTS.

SD—Super Density; compact disk made by SD Alliance®; now called DVD; see DVD.

SDH—Synchronous Digital Hierarchy; see definition.

SDK—Software Development Kit; software tool kit designed for third party software developers to build add-on functionality or integration between systems.

SDL—Security Development Lifecycle initiative, see definition.

SDLC—Synchronous Data Link Control; bit-oriented standard protocol developed by IBM® superseding bisynchronous transmission; uniform discipline for transfer of data between stations in point-to-point, multipoint, or loop arrangement, using synchronous data transmission techniques.

SDoC—Supplier’s Declaration of Conformity; see definition.

SDR—Software Defined Radio; see definition

SDRAM—Synchronous Dynamic Random Access Memory; used for high performance main memory in computers and workstations; synchronizes itself with the CPU's bus and is capable of running at 100 MHz, about three times faster than conventional FPM RAM, and about twice as fast EDO DRAM and BEDO DRAM.

SDS—Smart Distributed System; a CANbus based I/O communications systems for intelligent sensors and end elements by Honeywell MICROSWITCH®.

SDSL—Symmetric Digital Subscriber Line; technology which allows more data to be sent over existing copper telephone lines by sending digital pulses in the high-frequency area of telephone wires, and since these high frequencies are not used by normal voice communications, can operate simultaneously with voice connections over the same wires; called symmetric because it supports the same data rates for upstream and downstream traffic; see also ADSL; ADSL is more popular in North America, whereas SDSL is being developed primarily in Europe.

SDWA—Safe Drinking Water Act (U.S.).

SE—Single-Ended; in instrumentation, analog input that is measured with respect to common ground.

SEC, SEA—(Swiss Electrotechnical Committee) of the Swiss Electrotechnical Association; member of IEC.

SECAM—Systeme Electronique Couleur Avec Memoire; adopted as a television standard for France, Eastern Europe, Russia, and parts of Middle East on October 1, 1967; variations include SECAM "Vertical: and SECAM "Horizontal;" commonly referred to as "SomEthing Contrary to American Methods" J ; see NTSC, PAL, PAL-M.

Secondary Device—Part of flowmeter, which receives from primary device a signal proportional to flowrate, and then transmits it, displays it, records it, or performs any combination of these.

Secondary Standard—Standard of unit measurement derived from a primary standard; see Primary Standard.

Secondary Station—Station in a communications system that has been selected to receive a transmission from a primary station; assignment of secondary status may be temporary, and continues for duration of a transmission.

SECS—Semiconductor Equipment Communications Standard; designed in early 1980s to be fully dynamic, non-fixed, variable length, self-defining messaging protocol between equipment and host control computer; intent was to allow independent manufacturers of both equipment and host computers to connect to each other without specific knowledge of each other, a goal never achieved; now being replaced by Computer Integrated Manufacturing Application Framework (CIM-AF); see CIM-AF.

SECS-I—early version SECS designed for RS 232 serial communications then available between computers and equipment.

SECS-II—later version SECS designed for TCP/IP communication between computers and equipment.

Secure Sockets Layer (SSL)—Implementation of secure information transmission through Internet developed by Netscape Communications^®; an application-layer protocol, typically used to authenticate and encrypt traffic between Web servers and clients; technology allows SSL-enabled server to authenticate itself to any SSL- enabled client and vice versa, allowing both machines to exchange encrypted information; since SSL appliances connect remote users only to specified applications, entire network is not open to just anyone; requires only a browser and doesn't need client software, so at airport kiosk, for example, user can open Web browser, enter single URL, user name, and password per user, then access whatever applications on intended network their IT managers have Web-enabled; compare IPsec.

Security—In computers, protection of data against unauthorized access; software programs and data can be secured by issuing identification numbers and passwords to authorized users of a computer, nevertheless, systems programmers, or other technically competent individuals, will ultimately have access to these codes; passwords can be checked by operating system to prevent users from logging onto system in first place, or they can be checked in software, such as DBMSs, where each user can be assigned specific individual view (subschema) of database; any application program running in the computer can also be designed to check for passwords; data transmitted over communications networks can be secured by encryption to prevent eavesdropping; although precautions can be taken to detect an unauthorized user, it is extremely difficult to determine if valid user is performing unauthorized tasks so effective security measures are balance of technology and personnel management.

Security Accounts Manager (SAM) —Part of Windows NT that manages database of usernames, passwords and permissions; resides in each server as well as in each domain controller; see PDC & Trust Relationship.

Security Development Lifecycle (SDL)—Computing security initiative by Microsoft’s Trustworthy Computing Security Development Lifecycle to expand boundaries of Active Directory concept to focus on deploying products that require fewer patches and a higher level of reliability.

Security Guideline—In Internet activities, definition of minimum security levels, e.g. for user authentication and access control, as well as encryption, digital signature and intrusion detection.

SED—Surface-conduction Electron-emitter Display; see definition.

Seebeck Coefficient—Derivative (rate of change) of thermal EMF with respect to temperature, normally expressed in millivolts per degree.

Seebeck Effect—When two junctions in two dissimilar metals form a circuit, and each junction is held at different temperatures, a current flows in that circuit which is caused by difference in temperature between those two junctions.

Seebeck EMF—Open circuit voltage caused by difference between hot and cold junctions of a circuit made with two dissimilar metals.

Segment—In FOUNDATION Fieldbus technology, section of H1 fieldbus that is terminated in its characteristic impedance; can be linked by Repeaters to form longer H1 fieldbus; each Segment can include up to 32 H1 devices.

Selecting—In communication, a process of inviting another station or node to receive data, compared to polling.

Selective Heat Sintering (SHS)—A 3D printing technique; see Additive Manufacturing.

Selective Laser Melting (SLM)—A 3D printing technique; sometimes also referred to by the terms Selective Laser Sintering (SLS) or Direct Metal Laser Sintering (DMLS); see Additive Manufacturing.

Selective Laser Sintering (SLS)—A 3D printing technique; sometimes also referred to by the terms Direct Metal Laser Sintering (DMLS) or Selective Laser Melting (SLM); see Additive Manufacturing.

Self-Heating—Internal heating of equipment as a result of power dissipation.

Self-Adaptive Tuning—Technique within controller which watches loop and tunes controller when it thinks it should; does not require process bump in setpoint or controller output to perform, rather it uses normal loop changes; upon startup, may need initial bump or programming of some loop conditions; see Auto-Tuning.

Self-Correcting Memory (code, transmission)—Term sometimes used for Error Detection and Correction; software which looks for specific rules of construction, detects expressions which do not conform, and substitutes an equivalent form.

Self-powered Transmitters―See Type 4 analog (4-20mA) transmitters.

Semantics—In computer programming, actual meaning or use of a parameter, apart from its legitimate method of specification; see Syntax.

SEMI—(Semiconductor Equipment and Materials International); global industry association serving companies that provide equipment, materials and services used to manufacture semiconductors, displays, nano-scaled structures, micro-electromechanical systems (MEMS) and related technologies.

Semiconductor—Basis of all integrated circuits, any of a class of solids which have higher resistivity than a conductor, but lower resistivity than an insulator, so that it will conduct electrical current in different amounts depending upon how it is affected by outside conditions (like strength of external magnetic or electrical fields, pressure, temperature, light, etc.)

Sensitivity—Minimum value of change in a signal to cause a change in receiving device.

Sensitivity Shift—Change in slope of a calibration curve due to a change in sensitivity.

Sensor—(Sensing Element) That part of process measurement device which reacts in direct response to process change, providing some measurable output; also: known as a Detector, and as a Primary element.

Sensor Actuator Manager (SAM)—Simple, powerful, distributed control manager providing connectivity to various sensors, actuators, and host systems thorough a network such as NeSSI-bus, Ethernet, and  FOUNDATION Fieldbus.

Sensorbus Architecture—Control architecture that uses digital, serial, multidrop, two-way communications between and among simple field devices and control/monitoring systems; there are several different “competing” types; generally considered communicating small, “bit level” messages of low function among unsophisticated devices at high speeds over short distances, as defined by Automation Research Corporation (ARC), see also Fieldbus, Devicebus. Sequence Control—Control of a sequence of actions, with the completion of one movement or set of conditions initiating the next.

Sequential Access—Access mode in which records are retrieved in same order in which they were written; each successive access to file refers to next record in that file.

Sequential Access Method (SAM)—Organizing data in prescribed ascending or descending sequence; searching sequential data requires reading and comparing each record, starting from top or bottom of file.

Sequential Function Charts (SFC)—Originally formulated by Telemecanique as GRAFCET and standardized under IEC-848 and NFC-03-190 to graphically represent a control system as flow chart sequence of alternating steps and transitions, to be better understood by all engineering disciplines; generally offers improved organization, modularity, and readability over free-form programming; see Function Block Diagram, Instruction List, Ladder Logic, and Structured Text.

Sequential Manipulation Control—Advanced process control strategy whereby manipulated variables are managed in prescribed order and on "as needed" basis.

SER—Sequence of Events Recorder (SOER), the device.

SERCOS—SErial Real-time COmmunication System; digital interface standard for distributed, multiaxis motion control.

Serial Transmission—Most common transmission mode in which information bits are sent sequentially on a single data channel (wire, radio beam, etc.).

Series (Universal) Motor—Noninduction type motor utilized for small equipment; speed will decrease as load increases.

Serif—In typographical composition of screen displays and printing, the finishing stroke at ends of main strokes of many letters in some typefaces.

Server—Processor that supplies network with specified service, such as routing function, common source of data (database), memory, or functions, to be shared by many devices requesting these.

Service-Oriented Architecture (SOA)—Underlying structure supporting communications between services; defines how two computing entities, such as programs, interact in such a way as to enable one entity to perform a unit of work on behalf of another entity such as the interaction of various computing functions to make a purchase on line and subsequently have it delivered; each interaction is self-contained and loosely coupled, so that each interaction is independent of any other interaction.

Servlet – In computer programs, Java application that runs in Web server or application server and provides server-side processing, typically to access a database or perform e-commerce processing; is Java-based replacement for CGI scripts, Active Server Pages (ASPs) and proprietary plug-ins written in C and C++ for specific Web servers (ISAPI, NSAPI) so are portable between servers and operating systems.

Servo Loop Motor (SLM)—Technology that provides extremely high positioning resolution in digital servo systems for improvement in dynamic response, control bandwidth, and torque variation performance.

Servomechanism—Automatic device for controlling large amounts of power through application of much smaller amounts of power.

Servomotor—Power driven mechanism, which supplements primary control operated by much weaker force, as in a servomechanism.

Session—Connection between two stations that allows them to communicate; in IBM® SNA the logical connection between two network addressable units; also: time period that user engages in dialog with an interactive computer.

Session Layer— In digital communication, layer five of OSI reference model; provides protocols for assembling physical messages into logical messages.

Setpoint (SP)—Value at which controller is set to hold, or drive output signal for control of a process; also: with timers, time or count value from which (or to which) the unit times or counts; it may be manually set, automatically set, or programmed.

Setpoint Control—Control technique in which computer supplies a calculated setpoint value to an analog instrumentation control loop.

Setting Accuracy—Ability of equipment (controllers, timers, etc.) to be set within tolerance of selected value.

SEVA—Sensor Validation/Advanced Diagnostics; monitoring health of transmitters through a fieldbus and plant asset management package.

Seven-Twenty four (7-24)—Seven days per week, twenty-four hours per day; reference to operating around-the-clock every day.

SFA—Sales Force Automation.

SFC—Sequential Function Chart; not a standalone language, but a language which pervades all of the IEC 1131 standard languages, see Function Block Diagram, Instruction List, Ladder Logic, and Structured Text; a way of organizing programs written in these languages to accomplish sequential control by partitioning into sets of steps and transitions interconnected by directed links, see also Sequential Function Charts; also: Shop Floor Control; also: Supercritical Fluid Chromatography.

SFID—(Society for Information Display).

SFM—Scanning Force Microscopy; measures in angstroms, more powerful than scanning electron microscopes in locating defects on integrated circuits; also: Surface Feet per Minute.

SFMS—Shop Floor Management System; provides on-line data capabilities to capture such as product progress, location, scrap, and relevant operator, machine, product, and quality data.

SFS—Suomen Standardisoimisliito r.y.

SG—Signal Ground; electrical potential, usually called signal common (SC), a common baseline for signal reference.

SGC—Solid Ground Curing, form of Rapid Prototyping, see RP.

SGML—Standard Generalized Markup Language; international standard (ISO 8879) to identify structure and content of documents for publication and delivery of these as electronic information; common ancestor of both XML and HTML and can be re-rendered, into print, Braille, XML, HTML, large-print, text-to-speech, or other technologies yet to emerge; see XML, HTML.

SGMP—Simple Gateway Management Protocol; predecessor to SNMP; see SNMP.

SGRAM—Synchronous Graphic Random Access Memory, type of DRAM used increasingly on video adapters and graphics accelerators; can synchronize itself with CPU bus clock up to speeds of 100 MHz, and uses several other techniques, such as masked writes and block writes, to increase bandwidth for graphics-intensive functions

S/H—Sample and Hold; see definition.

Shaded Pole Motor—Low starting torque motor that depends on induced current to create magnetic field necessary to start that motor.

Shape Memory Alloy, Smart Memory Alloy (SMA)—Property possessed by certain alloys that allows them to return, when heated, to their original shape after having been deformed.

Shared Controller—Controller containing preprogrammed algorithms that are usually accessible, configurable, and assignable; it permits a number of process variables, loops, and functions to be controlled by a single device.

Shared Display—Operator interface device, usually a video screen, used by plant operator to display process control information from a number of sources.

Shared Hubs—In Ethernet systems, can transmit messages out all the ports with no filtering; if one node is sending data, all other nodes have to wait until the first is finished before sending their messages; compare Smart Hub; see Hub.

Shared Memory Architecture (SMA)—Refers to a design where the graphics chip does not have its own dedicated memory, and instead shares the main system RAM with the CPU and other components.

Shareware—Programs offered for free (or free for specified period of time), usually downloaded over Internet.

Sharpness—In video displays, crispness of screen displays, like focus; generally due to convergence of red, blue, and green electron beams into single white "dot" on the screen.

Shear Modulus—Ratio of shear stress and angular shear distortion.

Shear Stress—Where normal stress is perpendicular to designated plane, shear stress is parallel to that plane.

Shell—In computer software, program or function created around some central kernel or core program and rely upon it for proper operation.; compare with Kernel.

Shielding—Protective covering that reduces electromagnetic and radio frequency interference or leakage in a cable or device.

Short-Circuit Current Rating—Prospective symmetrical fault current at a nominal voltage to which an apparatus or system is able to be connected without sustaining damage exceeding the defined acceptance criteria; used to determine compliance with NEC 110.10; tested value not to be determined by Over Current Protective Device.

Short Message Service (SMS)—Transmission of short text messages (no longer than 160 alpha-numeric characters) to and from a mobile phone, fax machine, or IP address.

Shot Noise—Noise caused by random current fluctuations arising from the discrete nature of electrons.

SHS—Selective Heat Sintering; a 3D printing technique; see Additive Manufacturing

SHTTP—Secure HyperText Transfer Protocol; implementation of secure information transmission through Internet by Terisa Systems^®.

Shunt—Conductor joining two points in electrical circuit to form parallel path; all or some portion of current may pass through that shunt.

SI—(System Internationale); International System of Units; (Le Systeme International d'Unites); also: System Integrator.

SIC—Standard Industry Classification; system of industry codes which classifies 1004 types, focused primarily in the durable goods manufacturing to track economic progress; in its 60^th year, it was supplanted in 2001by North American Industry Classification System (NAICS) which breaks out services & high technology sectors of businesses in finer detail.

SI/O, SIO—Serial Input/Output.

Siemens—In conductivity measurement, a unit of conductance of a solution, formerly known as mho; reciprocal of electrical measurement called Ohms (W).

Sigma (s)—In quality control, statistical unit of measure which reflects capability. Example:
s of 0.2 = 308,537 defects per million opportunities
s of 3 = 66,807 defects per million opportunities
s of 4 = 6,210 defects per million opportunities
s of 5 = 233 defects per million opportunities
s of 6 = 3.4 defects per million opportunities
With s of 3 to 4, cost of quality is about 10% of sales; moving towards 6s offers significant opportunity for savings in production!

Sigma Scale—In quality control, measure which correlates directly to such characteristics as defects-per-unit (discrete production), parts-per-million defective (process production), or probability of failure/error.

Signal—Electrical, pneumatic, hydraulic, or frequency transmittance (either input or output) that conveys information (analog or digital).

Signal Common—Common ground for a cluster of signals which may not be at either chassis ground or earth ground electrical potential; sometimes called signal ground.

Signal Conditioning—To process the form or mode of a signal to make it intelligible to, or compatible with, a given device, such as pulse shaping, pulse clipping, compensating, digitizing, and linearizing.

Signal to Noise Ratio—Ratio of signal power to noise power, usually measured in decibels.

SIL—Safety Integrity Level; requirements for safety instrumented system (SIS) based upon process hazard analysis and risk assessment; see Safety Instrumented System.

Silicon Controlled Rectifier—Three terminal PNPN device that normally blocks current flow in both directions until its gate is pulsed with a timed electrical signal, so that a modulation of a small electrical current can smoothly modulate a much larger one.

SIM—Subscriber Identity Module, see definition; also: (Society for Information Management), see definition.

SIMD—[pronounced: simdee] Single Instruction Multiple Data stream computing where at every instant all processors carry out same set of instructions on data in its own local memory; see MIMD.

SIMM—Single In-line Memory Module.

Simple Control Protocol (SCP)—Unified home networking software standard intended to increase interoperability with current home networking technologies through compatibility with Microsoft's Universal Plug and Play (UPnP) architecture, as well as devices based on the Internet Protocol (IP); could be applicable to small industrial control systems.

Simple Network Management Protocol (SNMP) —Widely used protocol designed to facilitate management of networked devices from a central location; based on TCP/IP; this protocol runs at transport layer of OSI network model and provides components for vendor-developed network management utilities; designed originally for management of devices such as routers and switches, its usage has grown rapidly to encompass the monitoring of nearly any electronic device one can think of; now  used to monitor and manage television broadcast studios, automated fare collection systems, airborne military platforms, energy distribution systems, emergency radio networks, as well as various SCADA applications.

Simple Object Access Protocol (SOAP)—Allows program running in one kind of operating system (such as Windows) to communicate with a program in the same or another kind of an operating system (such as Unix or MAC) by using the World Wide Web's Hypertext Transfer Protocol (HTTP) and its Extensible Markup Language (XML) as the mechanisms for information exchange; SOAP specifies exactly how to encode an HTTP header and an XML file so that a program in one computer can call a program in another computer and pass it information; similar in purpose to DCOM and CORBA distributed object systems, but lighter weight and less programming intensive (at least initially); also specifies how the called program can return a response.

Simplex Cable—Term sometimes used for a single fiber optical cable.

Simplex Mode—Operation of a channel in one direction only with no capability of reversing.

Simplex Transmission—Transmission in one direction only.

SIMTARS—(Safety in Mines Testing and Research Station) Australian certification and testing laboratory for testing equipment of different vendors to some common standard.

Simulation—In process control, using analog or digital computer to represent dynamics of process itself, responding appropriately to all control signals from instrumentation system to train operators and/or control techniques; also: in Plant Simulation, procedure for predicting behavior of plant by solving the mathematical relationships that describe behavior of  plant's constituent components.

Simulator—In Plant Simulation, computer programmed to mimic input/output behavior of a plant according to plant's model.

Single Board Computer—Printed circuit board that contains complete computer, including processor, memory, I/O and clock; cost-effective answer for systems requiring limited I/O and not to be significantly modified or expanded in future; does not use backplane, but is bolted to mounting surface with I/O connections made directly to board; while not expandable as bus-based systems, most can be customized to some degree with plug-in expansion modules.

Single-Ended (SE)—In instrumentation, analog input that is measured with respect to common ground.

Single-ended Transmitters―See Type 2 or Type 3 analog (4-20mA) transmitters.

Single Mode—Describing optical wave guide designed to propagate light of only a single wavelength and perhaps a single phase; essentially optical fiber that allows for only one light beam or data carrying lightwave channel, and is optimized for that particular frequency.

Single Phase Motor—Any motor energized by a single alternating voltage.

Single Shot—Mode of operation in a timer where control switch (momentary or sustained) initiates timing period during which output is energized; after timing period output is de-energized and timer resets.

SIP—Single In-line Packaging of circuit chips, type of housing for electronic components in which the connecting pins protrude from one side, also called Single In-line Pin Package (SIPP), compare DIP and PGA; also: Sterilize In Place, typically in food/pharmaceutical processing vessels where parts are not removable.

SIPAI—(Shanghai Institute of Process Automation Instrumentation) Chinese certification and testing laboratory for testing equipment of different vendors to some common standard.

SIR—Surface Insulation Resistance.

SIS—(Standardiseringskommissionen i Sverige); Swedish member of IEC; also: Strategic Information System; also: Short-Interval-Scheduling; also: Safety Instrumented System, see definition..

SISO—Single Input Single Output; systems requiring relatively straightforward feedback and/or feedforward control methods. See MIMO, MISO, TITO.

Site—In Internet/Intranet/Extranet activities, general term for a collection of files accessed through a web address, covering a particular theme or subject, and managed by a particular person or organization; opening page is called a "home page;" often resides on servers connected to the web network and is able to format and send information requested by worldwide users 24 hours a day, seven days a week (24/7).

SiTVS—Silicon Transient Voltage Suppresser.

Skil Saw—Portable cutting tool used to make studs too short.  J

SKU—(pronounced "skew") Stock Keeping Unit; a number or string of alpha and numeric characters that uniquely identify a product; may be a universal number such as a UPC code or supplier part number or may be a unique identifier used by a specific vendor.

SLA—StereoLithogrAphy, form of Rapid Prototyping, see RP; and a 3D printing technique; see Additive Manufacturing; also: Service Level Agreement.

Slave—Remote system or terminal whose functions are controlled by central "master" system; it is similar in concept to host system in that it responds to remotely generated requests, but unlike host system is usually capable of performing limited range of operations.

SLC—Subscriber Loop Carrier; also: Single Loop Controller.

SLDC—Single Loop Digital Control.

SLDRAM—SyncLink synchronous Dynamic Random Access Memory; type of memory being developed by consortium of computer manufacturers called SyncLink Consortium; competing with Rambus memory (RDRAM) as the future PC memory architecture.

Slew Rate, Slue Rate—Rate at which output of device can be driven from one limit to other over its dynamic range.

SLIC—Subscriber Line Interface Circuit.

Slide—In video development, a transition where the old scene exits from frame in a particular direction, for example "slide left."

Slider—“Device” adjacent to function within workstation screen view to make analog changes to some application, such as a trend cursor, scaling value, or page selections. 

SLIP—Serial Line Internet Protocol; enables TCP/IP over asynchronous lines, important to UNIX® and Internet communities.

SLM, SLPM—Standard Liters per Minute.

SLM—Servo Loop Motor; see definition; also: Selective Laser Melting; a 3D printing technique; see Additive Manufacturing.

Slope Adjustment—In measurement of pH, correction within pH meter for changes in response of electrode compared to ideal response.

SLS—Selective Laser Sintering, form of Rapid Prototyping, see RP; and a 3D printing technique; see Additive Manufacturing.

SLV—Single Layer Varistor.

SM—System Management; in FOUNDATION Fieldbus context, see definition

SMA—SNA (System Network Architecture) Management Architecture; also: Storage Management Appliance; also: Shape Memory Alloy also: Software Maintenance Agreement; also: Shared Memory Architecture also: Surface Mount Assembly; also: Smart Memory Alloy; also: System Management Architecture; also: Service Management Automation.

Small Caps—In typographical composition of screen displays and printing, an alphabet of small capital letters available in most roman type faces approximately the size of lower case letters, used in combination with Larger Capital Letters.

Smart Hub—In Ethernet systems also called intelligent hub, managed hub, or switched hub; has built-in programmed firmware for network management facilities to allow connection of more than two networks by looking at destination address and forwarding the message to proper network segment; thus, by limiting the number of signals along each leg, reduces traffic on each, which reduces potential of collisions, and improves performance; one user’s experience changed a 50% collision rate to only 1% by using smart hubs in a large system; used on ARCNET® networks as well; see Switched Ethernet.

Smart Memory Alloy, Shape Memory Alloy (SMA)—Property possessed by certain alloys that allows them to return, when heated, to their original shape after having been deformed.

Smart Transducer—Processor-based transducer which connects sensor or actuator with digital network to communicate peer-to-peer with other devices on that network (typically one of the fieldbusses); performs data management within and may do computations and even control algorithms.

SMB—Server Message Block; protocol to divide tasks between DOS based PCs and UNIX® systems; also: Small & Medium Business (market).

SMD—Surface Mounted Device.

SMDS—Switched Multimegabit Data Service; high speed data transfer standard developed by BellCore® for public carriers.

SME—(Society of Mechanical Engineers).

SMIS—(Standards and Metrology Institute of Slovenia).

SMS—Short Message Service; see definition.

Smokescreens—Vendor named category of control system specifications written by users & system consultants which describe in disguise a one-and-only vendor-specific item in great detail but ask several vendors for quotations (many are called but only one can be chosen); see also Dowatchados, Druthers, Expectifications, Gotchas, Ropushers, Stickits, Stonecutters, Wannagirls. J

Smoke Test—Test of new or repaired hardware by turning it on and watch if smoke emerges showing it doesn't work; test of newly developed software or revised software for the first time just to see if it runs.

SMOP—Simply a Matter Of Programming (usually preceded by the phrase, "There's nothing to it, it's..."). J

SMP—Symmetric MultiProcessing; type of computing architecture which allows large number of users and transactions which can be supported in parallel.

SMPTE—(Society of Motion Picture and Television Engineers); society for motion picture and television industries with 10,000 members and 250 Sustaining (corporate) members worldwide; for advancing theory and application in motion imaging, including film, television, video, computer imaging, and telecommunications; generates standards, engineering guidelines, and recommended practices to be followed by respective field professionals.

SMPTE Time Code—In video development, a system of giving each frame of video a unique number to allow indexing and precise tape control for synchronous timing.

SMRs—Small Modular Reactors; being touted by some with passive and seismic safety features as safer, cheaper, and more scalable alternatives to large-scale nuclear power plants; can bury a small reactor in a shallow layer of bedrock, perhaps 30-50 meters underground;, if things at the plant go south for any reason, the granite will provide natural containment; simply cement in any access tunnels going down to the facility and walk away.

SMT—Simultaneous Multi-Threading; ability of modern processors to interleave multiple instruction streams; also: Software Metrics Tracking; also: Spill Management Team; also: Standard Measurement Technique; also: Surface Mount Toroid; also: System Maintenance Test also: Surface Mount Technology; method of mounting elements on a printed circuit boards; see THT.

SMTP—Simple Mail Transfer Protocol; part of TCP/IP suite.

SMU—Source Measure Unit; four instruments in one: a voltage source, a voltmeter, a current source, and a current meter.

SNA—Systems Network Architecture; developed by IBM in the mid-1970s using SDLC protocol as key element for communication among IBM® and other devices.

SNAcP—Sub-Network Access Protocol.

SNADS—System Network Architecture Distributed System; developed by IBM®.

SNAP—Specifications for Nonheat Advertising Printing; standard for printing industry used by some color printers.

SNDCP—Sub-Network Dependent Convergence Protocol.

Sneakernet—Informal term describing the transfer of electronic information, especially computer files, by physically moving removable media such as magnetic tape, floppy disks, compact discs, USB flash drives, or external hard drives from one computer to another;. Usually done in lieu of transferring the information over a computer network; the name is a tongue-in-cheek sound-alike to Ethernet, and refers to the use of someone wearing sneakers as the transport mechanism for the data. J

SNICP—Sub-Network Independent Convergence Protocol.

SNMP—Simple Network Management Protocol; see definition.

SNOBOL—StriNg Oriented symBOlic Language; computer language developed at Bell Labs and still used for text applications including databases and editors.

Snoopware—Software that tracks user's activity on a computer; can run in undetectable stealth mode to record keystrokes and screen snapshots; Some programs can send routine e-mails to the eavesdropper for remote review; see Key Logger and Spyware.

SNPA—Sub-Network Point of Attachment.

SNR—Signal to Noise Ratio; ratio of signal power to noise power, usually measured in decibels.

Snubber—Mechanical or hydraulic device for restraining motion, in instrumentation, device installed between instrument and process used to protect instrument from rapid pressure fluctuations;  also: device which is used to damp the motion of the valve stem, usually by oil filled cylinder/piston assembly where valve stem is attached to piston and flow of hydraulic fluid from one side of piston to the other is restricted.

SNV—(Schweizerische Normen-Vereinigung); standards group in Switzerland.

S-O—Usually SOx; Sarbanes-Oxley; see definition.

SOA—Service-Oriented Architecture; see definition.

SOAP—Simple Object Access Protocol; message-based protocol based on XML for accessing services on the web initiated by Microsoft, IBM and others, employing XML syntax to send text commands across Internet using HTTP; similar in purpose to DCOM and CORBA distributed object systems, but lighter weight and less programming intensive (at least initially).

SOC, SoC—System On Chip; Component designed with millions of electronic gates on single chip with gate-based designs are replacing transistor-based ASIC designs; includes all the electronics for complete, working product contained on a single chip; while computer on a chip (CoC) includes all hardware components required to process, SoC includes computer and all required auxiliary electronics.

Society for Information Management (SIM)—Founded in 1968 as the Society for MIS, it is a membership organization comprised of corporate and division heads of IT organizations; provides a forum for exchange of technical information and offers educational and research programs, competitions and awards.

SOCMA—(Society of Chemical Manufacturing & Affiliates) U.S. based trade association dedicated solely to the batch, custom and specialty chemical industry.

SOE—Sequence Of Events, the function; also: Spatial Operating Environment; see definition.

SOER—Sequence Of Events Recorder, the device.

Softcontrol—PC-based process controller; see below.

SoftLogic—PC-based logic controller; controller is software which can run on variety of personal-computer form factors; most useful in applications requiring high data collection and processing as well as communications to other networks.

Software—Non-hardware portion of computer which causes that computer to perform specific functions, depending how it was programmed; often defined as entire set of programs, procedures, and related documentation associated with a computer; see Hardware; Firmware; Wetware.

Software as a Service (SaaS)—(pronounced 'sass');one of three main categories of cloud computing service; software distribution model in which applications are hosted by a vendor or service provider and made available to customers over a network, typically the Internet; closely related to the ASP (application service provider) and On Demand Computing software delivery models. IDC identifies two slightly different delivery models for SaaS: hosted application management (hosted AM) model is similar to ASP: a provider hosts commercially available software for customers and delivers it over the Web; in software on demand model, the provider gives customers network-based access to a single copy of an application created specifically for SaaS distribution; main purpose is to reduce total cost of hardware & software development, maintenance, and operations; security provisions are carried out mainly by the cloud provider; compare: Platform-as-a-Service, Infrastructure-as-a-Service.

Software-defined Radio (SDR) —Radios that provide software control of a variety of modulation techniques, wide-band or narrow-band operation, communications security functions such as hopping, and waveform requirements of current and evolving standards over a broad frequency range; enables wide range of applications within wireless and broadband industries that potentially can provide efficient and comparatively inexpensive methods for overcoming many of technical constraints that currently limit existing telecommunication systems; overcomes current incompatibility radio issues, and significantly increases data transmission speeds.

Software Sensor—In analytical measurements, analyzer that replaces or supplements hardware analyzer or laboratory measurement for closed loop process control; using neural network computing, includes prediction net and sensor validation net.

Softwiring—Interconnection of software function blocks to create a system, control strategy, or some operation; implemented within DCS in a way analogous to wiring physical hardware components as part of system configuration.

SOIC—Small-Outline Integrated Circuit; small-dimension, plastic, rectangular, surface mount chip package that uses gull-wing pins extending outward.

SOJ—Small-Outline J-lead; type of microprocessor chip module that uses J-shaped pins that extend inwards; unlike DIPs, which plug into holes on circuit board, SOJ chip attaches directly to circuit board's surface.

Solenoid Valve—ON/OFF (shut-off) valve whose position is determined by current flow to a coil.

Solid Leading—In typographical composition of screen displays and printing, no additional white space is added between lines of type.

Solid Modeling—Three dimensional modeling in which solid characteristics of an object are built into database so that complex internal structures can be realistically represented.

Solid State (Device)—Any element that controls current without moving parts, heated filaments, or vacuum gaps.

Solid-State Lighting (SSL)—Refers to a type of lighting that uses semiconductor light-emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination rather than electrical filaments, plasma (used in arc lamps such as fluorescent lamps), or gas.

Solid State Output—Output signals from triacs, transistors, field effect transistors, and other semiconductors.

SONET—Synchronous Optical NETwork; send signals over optical fiber and complement ATM by providing standardized interfaces, high rates of data transmission, and high reliability.

SOP—Standard Operating Procedure; procedure which has been predefined and which should be referenced during a specific phase of operations.

SOS—Silicone On Sapphire.

Source—Light emitter, either LED or laser diode, in a fiber optic link.

Source Code—Non-executable program written in a high level language; a compiler or assembler must translate source code into object code (machine language) that computer can understand and process.

SOx (SOX)—Sarbanes-Oxley; see definition;  also: Schema for Object-oriented XML; XML software schema developed by Veo Systems and Muzino Communications  based on DTD, but adds data typing and reuse mechanisms; also: Supercritical Oxygen; also: Sulfur Oxides.

SP—Set Point; of process control loop determining desired value at which process will operate.

SP50—Standards & Practices group 50 of ISA, which originally formed in 1950 to develop the 4-20mA standard I/O signal, and has been developing a fieldbus standard since about 1985; Fieldbus Foundation, a not-for-profit organization dedicated to developing single, worldwide, interoperable fieldbus... formed from merger of WorldFIP North America and ISP Foundation in 1994.

SP72.01—Standards & Practices group 72 of ISA, PROWAY-LAN industrial data highway, link control (ANSI/ISA).

SP72.02—Standards & Practices group 72 of ISA, Process Messaging Service, MMS companion std. for process control.

SP72.03—Standards & Practices group 72 of ISA, Process Communication Architecture standard to enable digital transmission of voice and data via standard telephone lines.

SP88—Standards & Practices group 88 of ISA, which has been developing a batch standard since about 1988; uses object-oriented concepts to define terminology and models for batch control processes.

SP95—Standards & Practices group 95 of ISA, formed in October, 1996 to develop standard for boundary between corporate (Enterprise) business plan and plant floor, especially dynamic, real-time process control systems.

SP99—Standards & Practices group 99 of ISA for Manufacturing and Control Systems (Cyber) Security.

SP100—Standards & Practices group 100 of ISA, for wireless standards; see WINA.

SPA—Sneak Path Analysis, also called sneak circuit analysis (SCA), is to identify unexpected and unrecognized electrical paths or logic flows in electronics systems, called sneak circuits or paths that under certain conditions produce undesired results or prevent systems from operating as intended; paths come about in various way; designers do not always have a complete view of the relationship between functions and components in complex systems, particularly those with many interfaces; historically, users discovered sneak paths when they observed an unintended effect during system operation; also: Single Point of Access (AT&T); also: Sampling Probe Algorithm; also: Scalable Processing Architecture; also: SCSI Peripheral Adapter; also: Secure Password Authentication; also: Secure Platform Architecture (HP-Compaq); also: Sensor Performance Analysis; also: Simple Power Analysis; also: Single Piece Anode; also: Single Purpose Application; also: Smart Pixel Array; also: Special Protection Area; also: Special Purpose Access.

Space—Absence of a signal, an open condition, no current flowing; in transmission, a space impulse is equivalent to a binary "0."

SPAG—(Standards Promotion and Applications Group).

Span—Algebraic difference between limits of the range of a measuring or controlling device (between upper and lower range values).

Spanning Tree Protocol (STP)— Part of IEEE 802.1 standard employing an algorithm used in transparent bridges that dynamically determines best path from source to destination, avoiding bridge loops (two or more paths linking one segment to another), which can cause bridges to misinterpret results; algorithm creates hierarchical "tree" that "spans" entire network including all switches and determines all redundant paths, making only one of them active at any given time.

SPARC—Scale-able Processor ARChitecture (Sun Microsystems®); also: Scale-able Processor Architecture Reduced instruction set Computer, a very powerful workstation using RISC technology.

SPARCL—Smart Pixel Array Cellular Logic; pixel arrays through which two-dimensional frames of data are moved optically to perform digital operations on those incoming data frames and/or data frames stored within that pixel array; multiple pipelined optical processors constructed as SIMD to speed image processing from optical sensors.

Spatial Operating Environment (SOE)—Causing operations by user combining physical gestures and spatial location to interact with video on screen objects.

SPC—Statistical Process Control; quality control method employing on-line (continuous) statistical procedures for immediate analysis to improve management of continuous processes, often by using patterns of alarms and other discrete events; usually open loop form of control: SPC often follows SQC analysis for quality control.

SPDS—Safety Parameter Display System.

SPDT—Single Pole Double Throw; electrical switch action on a wire which can be used to select one of two paths for flow of signal or power.

Specific Gravity—Comparison of mass (or weight) of a substance to that of an equal volume of water.

Specific Heat—Ratio of thermal energy required to raise temperature of a body 1° to thermal energy required to raise an equal mass of water 1°.

Specialization—In object oriented software, allowsa subclass to differ from its superclass; see Subclass, Superclass.

SPI—System Programming Interface; also: Serial Parallel Interface.

SPICE—Simulation Program, Integrated Circuit Emphasis.

Splash Screen—On Internet, main menu screen, or opening graphic to Web page; in computer systems, same idea, but may also be point of security code entry, show copyright and revision level information, etc.; usually used only upon initial start-up.

SPLD—Simple Programmable Logic Device that provides an array of logic blocks that can be programmed. See ASIC, PLD, CPLD.

Splice—In FOUNDATION Fieldbus technology, H1 Spur measuring less than 1 m (3.28 ft.) in length.

Spline—Term used to describe irregular curve concept in conventional drafting, often performed with a French curve tool to assure curve passes through a series of defined points.

Split Phase Motor—Inexpensive ac motor generally used for easy starting loads; it features two sets of windings, one for startup and one for running motor; once motor has attained full speed, current to starting windings is switched OFF.

SPOOL—Simultaneous Peripheral Operation On Line; program or piece of hardware that controls data going to an output device.

Spooler—See Buffer Memory.

Spreadsheet—Computer program which arranges data and formulas in matrix of cells; provides user with quick and easy access to wide variety of highly detailed reports based on highly inaccurate assumptions.  J

Spread Spectrum Radio Technology—Digital communication technique where signal is created by modulating the radio frequency signal with a spreading sequence code or by “hopping” the frequency of the carrier signal; developed for US military to prevent jamming.

Sprite—In digital graphic displays, individual component of animation, such as a character, icon, or graphic that moves independently.

SPST—Single Pole Single Throw; electrical switch action used to interrupt flow through a wire; (ON/OFF).

Spur—In FOUNDATION Fieldbus technology, H1 branch line connecting to the Trunk that is a final circuit. A Spur can vary in length from 1 m (3.28 ft.) to 120 m (394 ft.).

Spurious Error—Random or erratic malfunction.

SPX—Sequenced Packet Exchange; an operating system by Novell, Inc.

Spyware—Software that in background sends information about computer user’s Web surfing habits to another Web site; usually self-installed in user’s computer with some free download selected from Web, or even by merely visiting a Web site; other names include "parasite software," "scumware," "junkware" and "thiefware;” see Key Logger & Snoopware.

SQC—Statistical Quality Control; employing laws of probability and statistical procedures for off-line analysis to maintain acceptable level of product quality, often by using predetermined discrete samples over period of time in order to specify aims, goals, and quality parameters.

SQE—Signal Quality Error; in CSMA/CD communication media access method, test between transceiver/MAU and DTE to ensure collision detection circuit in the transceiver/MAU is working, also known as "heartbeat."

SQL—[pronounced: see-quill] Structured Query Language; ISO database access standard for communicating (querying, updating, and managing) with various relational data bases; allows client to access only that data required to satisfy a specific request, reducing network traffic and improving performance; derived from an IBM^® research project that created Structured English Query Language (SEQueL) in the 1970s; now accepted standard in database products.

SRAM—Static Random Access Memory; type of memory that is faster and more reliable than the more common DRAM (Dynamic RAM); term static means it doesn't need to be refreshed like Dynamic RAM, but requires more space; used mainly for cashe for quick access; see DRAM, MRAM, RAM.

SRP—Source Routing Protocol; routing specification by IBM®.

SRS—Safety Requirements Specification; see definition.

SS—Steam Supply; also: Stainless Steel; also: Simultaneous Sampling; system in which all input or output channels are updated (or digitalized) at the same time.

SSC—Single Station Controller.

SSFDC—Solid State Floppy Disk Card; flash memory media made by Toshiba®.

SSH—Secure Shell; software from SSH Communications Security, Inc., Palo Alto, CA that provides secure logon for Windows and Unix clients and servers, replacing telnet, ftp and other remote logon utilities with encrypted alternative.

SSI—Small Scale Integration; multifunction semiconductor, such as a microprocessor, with fewer than 12 equivalent gates.

SSID—Service Set Identifier; name assigned to wireless Wi-Fi network where all devices must use this case-sensitive name, a text string up to 32 bytes long, in order to communicate; typically set to equipment vendor's name, it can be manually changed.

SSL—Solid-State Lighting; see definition; also: Secure Sockets Layer; see definition.

SSOLR—Solid State OverLoad Relay; used in motor protection technology.

SSOP—Shrink Small Outline Package.

SSR—Solid State Relay.

SSU—Saybolt Seconds Universal.

ST—Structured Text; see definition.

Stability—Ability of equipment or system to retain all of its performance specifications throughout its life span; also: in power supplies, the change in dc output as function of time at constant line voltage, load, and ambient temperature, and normally specified for an 8-hour period after a 30 minute warm-up; also: in SPC, when only normal variation is present (called statistical control).

Stagnation Pressure—Sum of static and dynamic pressures.

Standard Function Block (FB)—In FOUNDATION Fieldbus technology, built into fieldbus devices as needed to achieve desired control functionality; automation functions provided by Standard FBs include Analog Input (AI), Analog Output (AO) and Proportional/Integral/Derivative (PID) control; there can be many types of FBs in a device; order and definition of Standard FB parameters are fixed and defined by specification.

Standardization—In pH measurement, method of compensating for inaccuracy of pH electrode where meter is "standardized" or adjusted to give ideal response to standardizing solution (buffer) so that pH of other solutions can then be more accurately measured.

Star—In LAN topology, a configuration of computing devices in which each user is connected by communication links radiating out of a central hub that handles all communications.

State Logic—Alternative to Ladder Logic as an implementation format, developed by Adatek, Inc., Sand Point, Idaho; it is gaining popularity and may be more efficient for process control because it is event or time driven, rather than sequence driven or rule based, advantages include expedited program development, ability to implement multiple tasks simultaneously, and virtually automatic program documentation.

Stateful Inspection—Method of authenticating and securing computer data transmission through a firewall.

Statement—Expression of instruction within some computer language.

Static Calibration—Calibration of equipment or system at fixed points in ambient conditions.

Static Error Band—Error band in ambient conditions.

Static Pressure—Pressure of fluid whether in motion or at rest.

Station—"Drop" on communication system to process data, such as input/output signals to and from the plant, information interface with an operator, history collection, etc.

Statistical Multiplexor—Device that allows single channel to carry information from multiple devices simultaneously.

Statistical Process Control (SPC)—Employing on-line (continuous) statistical procedures for immediate analysis to improve management of continuous processes, often by using patterns of alarms and other discrete events; usually an open loop form of control: SPC often follows an SQC analysis for quality control.

Statistical Quality Control—Employing laws of probability and statistical procedures for off-line analysis to maintain acceptable level of product quality, often by using predetermined discrete samples over period of time in order to specify aims, goals, and quality parameters.

STC—Self Tuning Controller; allows automatic retuning of PID controllers in changing environments, for slowly changing process conditions, and during the dynamics of startups.

Steady Flow—Flowrate in measuring section of a flow line that does not vary significantly with time.

Steady State—A system in equilibrium, when all potential opposing forces are at rest or balanced; in fiber optics, equilibrium mode distribution.

Steganography—Hidden word cryptography for confidentiality and authentication.

STEP—STandard for Exchange of Product model data; European version of PDES by ANSI which enables companies to digitally represent product information between departments and manufacturing partners.

Step Index—Type of optical fiber with uniform refractive index at its core and a sharp decrease in refractive index at its core/cladding interface.

StereoLithogrAphy (SLA)—A 3D printing technique; see Additive Manufacturing.

Stickits—Control System Specifications which say user mistakes will be repaired by vendor for free but stated in much finer language; see also Dowatchados, Druthers, Expectifications, Gotchas, Ropushers, Smokescreens, Stonecutters, Wannagirls. J

STIM— Smart Transducer Interface Module, defined by IEEE-P1451 to perform its own control or data manipulation task within a processor-based (smart) transducer, located closest to actuator or sensor (not adjacent to network but has defined interface through NCAP); generally includes transducer electronic data sheet (TEDS); see NCAP, TEDS.

STL—Standard Template Library; emerging international ANSI/ISO standard for C++ programming language, originally designed by Alexander Stepanov and Meng Lee of Hewlett-Packard Company.

STN, STNLCD—SuperTwisted-Nematic; passive color liquid crystal display (LCD) technology, less expensive than active color TFT displays, but improving in contrast and brightness; reference PMLCD & AMLCD.

STO—Seriplex™ Technology Organization; formed to advance Seriplex™ control bus technology, broaden its applications and acceptance, and promote additional product development; purchased by Square D® and its parent company Groupe Schneider in 1995, supported by more than 50 companies, and being offered as an open system, low-level distributed I/O control bus.

Stochastic Screening—In electronic publishing and video screen displays, a digital screening process that converts images into very small dots (14-40 microns) of equal size and variable spacing; second order screened images have variable size dots and variable spacing; also called Frequency Modulated (FM) screening.

Stonecutters—Vendor named category of control system specifications written by users & system consultants which change date on that 1952 specification, but not always on drawings, or possibly they really want vacuum tubes; see also Dowatchados, Druthers, Expectifications, Gotchas, Ropushers, Smokescreens, Stickits, Wannagirls. J

Stop Band—In digital signal processing (DSP), frequency band in filters which is attenuated more than a certain amount; see Pass Band.

Stop Bit—Signal following character or block that prepares receiving device to receive next character or block.

Storage—In computing, device into which data can be entered, in which it can be held, and from which it can be later retrieved; usually considered kept magnetically or optically on disks, rather than electronically on chips (in RAM or ROM) which is usually referred to as memory.

Storage Area Network (SAN)—High-speed special-purpose network (or subnetwork) that interconnects different kinds of data storage devices with associated data servers on behalf of a larger network of users; typically, this is part of the overall network of computing resources for an enterprise.

Storage Specifications—Environmental conditions over which equipment or a system can be stored without degrading ultimate operating performance or life span; see Extreme and Operating.

Storyboard—In video and other presentation media development, a visualization of the order of a piece, using representative frames from each shot or sequence to show a visual skeleton or outline of that piece; useful concept in developing operator screen sequences for various process actions.

STP—Spanning Tree Protocol; routing specification for IEEE 802.1, see definition; also: Standard Text Programming; also: Shielded Twisted Pair, wiring for signals with at least two conductors twisted together six twists per inch to minimize effects of electromagnetic radiation between them, and covered with metal-backed mylar, plastic, PVC, or metal woven sleeve for protection from external EMI and RFI (compare with UTP).

STR—Self Tuning Regulator; generally refers to class of self-adaptive control systems, forerunner (1970s) of self tuning controller (STC).

Straight Screwdriver—Tool for opening paint cans; sometimes used to convert common slotted screws into non-removable screws.   J

Strain Gauge—Measuring element for converting force, pressure, tension, etc., into output signal.

Strength Member—That part of fiber optic cable composed of Kevlar™ aramid yarn, steel strands, or fiberglass filaments that increase tensile strength of that cable; also: anchor person on tug of war team. J

Stress Puppies—People who seems to thrive on being stressed out and whiny.    J

STRI—Technological Institute of Iceland.

String—In computing, sequence of characters or bits treated as single item.

Strouhal Number—Nondimensional parameter important in vortex meter design; equals frequency times reference length divided by velocity.

Structural Testing—In process validation, examining internal structure of source code; includes low-level and high level code review, path analysis, auditing of programming procedures and standards actually used, inspection for extraneous dead code, boundary analysis, and other techniques; generally requires specific computer science and programming expertise to perform.

Structured Query Language (SQL)—ISO database access standard for communicating (querying, updating, and managing ) with various relational data bases; allows client to access only that data required to satisfy a specific request, reducing network traffic and improving performance; derived from an IBM^® research project that created Structured English Query Language in the 1970s; now accepted standard in database products.

Structured Text (ST)—High level, block structure language of programmable controllers which has syntax that resembles Pascal; used to express complex statements involving variables representing a wide range of different types of data, including analog and discrete values, as well as management of time, dates, and durations; one of five languages accepted under IEC 1131 standard for PLCs; see Function Block Diagram, Instruction List, Ladder Logic, and SFC.

Stud—Threaded machine-type bolt or screw used for attachment of wire or cable connectors.

Stuxnet—Very advanced computer worm that took many man-years to create; discovered in June 2010 by a Belarus-based company doing business in Iran; designed to jump from computer to computer using human and network pathways until it found the specific, well-protected control system it was designed to destroy (most likely Iran’s nuclear enrichment program).  Once it penetrated the facilities in Iran, it targeted Siemens programmable logic controllers (PLCs) and human machine interfaces (HMIs). From there, it modified commands and data going to the frequency converters that regulate the speed at which centrifuges spin to enrich nuclear fuel. The worm made the centrifuges turn very quickly so they were damaged, but not destroyed. The worm also masked the changes in speed or PLC logic from being discovered at the operator’s control panel. At its height, Stuxnet infected an estimated 100,000 computers and 50 to 60 industrial control systems around the world.

Subclass—In object oriented software, class of objects created from another class; inheritance provides the subclass with all attributes and methods of its parent, or superclass; subclasses may define their own methods and may override those similar methods in their superclass; see superclass, inheritance, method.

Subdirectory—In computer programming, directories located within directories as convenient structure for organizing files into easily found groups; like having address showing where files are located.

Subhead—In typographical composition of screen displays and printing, usually located beneath headline as secondary information or as summarizing phrases between sections of text.

Sublayer—Subdivision of an OSI layer, for example, Data Link Layer is subdivided into LLC and MAC sub-layers.

Subroutine—In computing, set of software instructions executed by a single line of codethat may or may not have input and/or output parameters.

Subscriber Identity Module (SIM)—Smart card inserted into GSM phones that contains that telephone account information; allowing a borrowed or rented GSM phone as if it were your own; SIM cards can also be programmed to display custom menus on the phone's readout.

Subsystem—Group of hardware and/or software components which perform distinct function or operation as part of some overall system.

Subtractive Primaries—In color reproduction, yellow, magenta, and cyan ...hues used for process color printing inks.

Successive-approximation ADC—Analog to digital conversition that sequentially compares series of binary-weighted values with analog input to produce output digital in a given set of steps which are the same number of bits in the resolution of A/D converter.

Suitcase Connector—Another name for Insulation Displacement Connector (IDC) due to how it functions; plastic connectors can be used to connect two different diameter wires (such as a 14ga bus and a 20ga feeder) together without the need for soldering.

Superclass—In object oriented software, class of objects from which a subclass is created, the subclass inheriting all attributes and methods of that superclass; see Subclass, Inheritance, Attributes, Methods.

SuperTwisted-Nematic (STN)—Passive color liquid crystal display (LCD) technology, less expensive than active color TFT displays, but improving in contrast and brightness; reference PMLCD & AMLCD.

Supervisory Control Action—Control action in which control loops operate independently, but are subject to intermittent corrective action, such as through setpoint adjustment, from a computer or similar external source; generally used for come degree of coordinating overall production of a plant.

Supervisory Programs—Computer programs that have primary function of scheduling, allocating, and controlling system resources rather than processing data to produce results.

Supplier’s Declaration of Conformity (SDoC)—Method of conformity whereby manufacturer states that product meets requirements of appropriate standard, such as in context of CE mark; compare with Third-Party Certification.

Supply Chain Planning (SCP)—Applications using sophisticated algorithms to determine constraints, define capacity, and generate optimal and feasible solutions, such as Manufacturing Planning, Replenishment and Distribution Planning, Supply/Demand Balancing, Order Promising, and Demand Planning.

Support—The mailing of advertising literature to customers who have returned a registration card.  J

Suppressed-zero Range—In measuring systems, range in which zero value of measured variable is less than lower-range value; compare Elevated Zero Range.

Surface Acoustical Wave (SAW)—Type of touchscreen which confine most of acoustical energy to surface of screen; compare with GAW.

Surface-condustion Electron-emitter Display (SED)— flat panel display technology from Canon and Toshiba in 2002 and based on field emission technology (FED), using low voltage surface-conduction electron-emitters for each pixel on the cathode plate and regular CRT-like phosphors on the glass anode plate; expected to require one third the power of a plasma display; see FED.

Surfaces—In CAD systems, wireframe models with "skin;" can cast shadows or exhibit shades.

Surfing—Term used to describe activity of searching Internet or other computer networks for specific or random information.

Surge Current—Current of short duration that occurs when power is first applied to capacitive loads or temperature dependent resistive loads; exceeds steady state current for a short time duration, normally described by its peak amplitude and time duration.

SUS—Silicon Unilateral Switch.

SV—Secondary Variable (of a transmitter); may mean in some applications, a level measurement in depth has associated secondary variable of volume or weight.

SVC—Switched Virtual Circuit; in digital communications, network connection that is established at time transmission is required and disconnected when session is completed; normally implemented in connection-oriented systems such as analog telephone network and ATM networks, contrast with PVC; also: SuperVisor Call; mainframe computer instruction that passes control to operating system; also: Static Var Compensation; used to continuously provide the reactive power required to control dynamic voltage swings under various system conditions and thereby improve the power system transmission and distribution performance; also: Single Variable Control; also: Safety Verification Condition(s); also: Smart Virtual Circuit.

SVGA—Super Video Graphics Adapter (Array); introduced in 1988 as a refinement of VGA which offers higher resolution of at least 800 x 600 pixels, & greater color compatibility of at least 16 colors compared with VGA; see CGA, EGA, PGA, UXGA, VGA, XGA.

SVID—System V Interface Definition; in AT&T® UNIX®.

Switch—Device that connects, disconnects, selects, or transfer one or more circuits and is not designated as controller, relay, or control valve.

Switched Hub— See Smart Hub, Hub.

Switched Ethernet—In Ethernet systems uses an intelligent switch (hub) that directs messages to a specific destination, allowing other devices to send their messages without waiting; full-duplex switched Ethernet adds a feature that provides separate transmission and reception channels so that a device can send and receive signals simultaneously; see Smart Hub, Hub.

Switched Line—In communications, link for which physical path may vary with each use such as telephone networks.

Switching Regulated Supply—Power supply which uses on of several duty cycle control formats to maintain constant output voltages instead of linear control; duty cycle control can be achieved by pulse width or pulse frequency modulation; typically more expensive because of their circuit complexity and component quality, but offer greater efficiencies, good size, weight, and cooling characteristics.

SWOP—Specifications Web Offset Publications; color standard for the printing industry used in some electronic printers.

Symantec AntiVirus for Macintosh (SAM)—Popular Macintosh anti-virus program from Symantec Corporation, Cupertino, CA.

Symmetrical Compression—System that requires equal processing capability for compression and decompression of an image; this form of compression is used where both compression and decompression is used frequently.

Synchronous—Logic or communications in which all operations are controlled by clock pulses; synchronous transmission eliminates need for "start" and "stop" bits, all is sent at a fixed rate.

Synchronous Data Link Control (SDLC)—IBM® standard protocol superseding bisynchronous transmission; uniform discipline for transfer of data between stations in point-to-point, multipoint, or loop arrangement, using synchronous data transmission techniques.

Synchronous Digital Hierarchy (SDH)—International standard for high speed telecommunication over optical/electrical networks which can transport digital signals in variable capacities; this synchronous system provides a more flexible , yet simple network infrastructure often used in SCADA systems.

Syntax—Rules governing structure of a language; also: in computers, grammatical rules for software programming that specify how instructions can be written; also: in computers, legitimate manner of specifying something apart from its actual meaning, see Semantics.

Synthetic Instruments—Instrumentation functions implemented purely in software that runs on general purpose, non-specific measurement hardware with a high speed A/D and D/A at its core; software is specific whereas hardware is generic, so "personality" of a synthetic instrument can be changed in an instant; example: A voltmeter may be a spectrum analyzer a few seconds later, and then become a power meter, or network analyzer, or oscilloscope, thus totally different instruments are implemented on the same hardware and can be switched back and forth in the blink of an eye.

System Chip—Component designed with millions of electronic gates on single chip; gate-based designs are replacing transistor-based ASIC designs.

System Management (SM)—In FOUNDATION Fieldbus technology, provides basic level of integrated operation access devices by synchronizing execution of Function Blocks (FBs) and communicating Function Block (FB) parameters on fieldbus; handles publication of time of day to all devices, automatic assignment of device addresses, and searching for parameter names or "tags" on fieldbus.

System Software—Software designed for specific computer system or family of computer systems to facilitate operation and maintenance of that system and associated programs, e.g., operating systems, compilers, utilities, etc.

System Specifications—Formally describe how system will meet functional requirements.

Systems Integration—Ability of computers, instrumentation, and equipment to share data or applications with other components in the same and other functional areas.

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