one substance in an other substance, usually from an area of high concentration to an area of low concen tration. Diffussion of a substance into the outer layer of a metal object, especially of carbon in the surface of steel, was previously known as cementation. 2. A process used in the production of semiconductors which introduces minute amounts of impurities into a substrate material such as silicon or germanium and permits the impurity to spread into the substrate. The process is very dependent on temperature and time.
diffusion firing furnace Systems designed for en- closed elevated temperature processing of solid-state devices and systems in gaseous atmospheres. Diffusi on furnaces are operated at temperatures from 1 000 to 1 300°C to achieve doping of semiconductor sub strates, by one of a number or processes.
diffusion transistor A transistor in which current depends on the diffusion of carriers, donors, or accep tors, as in a junction resistor.
digested sludge Sewage sludge which has been sta bilized by the action of micro-organisms in either the presence or absence of oxygen.
digester A pressure vessel for the cooking of fiber raw material.
digester house The departmet in the pulp mill in which the digesters are housed.
digestion The stabilization, by biological processes, of organic matter in sludge, normally by an anaerobic process.
digit, numeric character 120 digital output digit, numeric character A symbol that represents
one of the nonnegative integers smaller than the radix, for example, in decimal notation, a digit is one of the characters from 0 to 9.
digit place, digit position In a positional represen tation, each site that may be occupied by a character and that may be identified by an ordinal number or by an equivalent identifier.
digit position See digit place.
digital Pertaining to data that consist of digits. Cont rast with analog.
digital amplifier Amplifier the output of which varies in discrete steps related to the control signal.
digital-analog converter See digital-to-analog con verter.
digital back-up An alternate method of digital pro cess control initiated by use of special purpose digital logic in the event of a failure in the computer system.
digital circuit A circuit which has only two stable states, operating in the manner of a switch, that is, it is either “on” or “off” or “high” or “low”.
digital clock A series of synchronized pulses that de termine the bit times (data rate) of a digital pattern.
digital communication 1. The transmission of in
telligence by the use of encoded numbers – usually uses binary rather than decimal number system. 2. A system of telecommunications employing a nominally descontinuous signal that changes in frequency, amp litude, or polarity.
digital communications interface equipment
Line interface equipment include modems (adapters, data sets).
digital computer 1. A computer in which discrete
representation of data is mainly used. 2. A computer that operates on discrete data by performing arithme tic and logic processes on these data. Contrast with analog computer.
digital controller (data processing) A controller that accepts an input sequence of numbers and proces ses them to produce an output sequence of numbers.
digital converter, code translator A device, or group of devices, that converts an input numerical sig nal or code of one type into an output numerical sig nal or code of another type.
digital data 1. Data consisting only of characters. 2. Data represented by digits, perhaps with special
characters and the space character. 3. Data represen ted in discrete, discontinuous form, as contrasted with analog data represented in continuous form. Digital data is usually represented by means of coded charac ters, for example, numbers, signs, symbols, etc.
digital data-handling system The electronic equipment which receives digital data, operates on it in a suitable manner, records it in a suitable manner on a suitable medium, and presents it directly to a computer or a display.
digital delay generator An electronic instrument which can be programmed digitally to delay a signal by a specific interval-time delay generator.
digital device 1. Typically, an IC that switches bet-
ween two exclusive states or levels, usually represen ted by logical 1 or 0. 2. An electronic device that pro cesses electrical signals that have only two states, such as “on” or “off”, “high” or “low” voltages, or “positive” or “negative” voltages. In electronics “digi tal” normally means binary or two-state.
digital differential analyzer, DDA 1. An incremen
tal computer in which the principal type of computing unit is a digital integrator whose operation is similar to the operation of an integrating mechanism. 2. A
differential analyzer that uses digital representations for the analog quantities.
digital encoding Use of a digital code to encode an analog or digital signal.
digital filter 1. An algorithm which reduces undesira
ble frequencies in the signal. 2. A software technique used to eliminate undesired or irrelevant data. Refers to Honeywell TDC 3000 control systems.
digital filtering A computational process or algo rithm by which a sampled signal or sequence of num bers, acting as input, is transformed into a second se quence of numbers called the output. The com putational process may correspond to high-pass, low- pass, bandpass, or bandstop filtering, integration, dif ferentiation, or something else. The second sequence can be used for further processing, as in a fast-Fourier transform analyzer, or it can be converted to an analog signal, producing a filtered version of the original analog signal.
digital fluidics That section of fluidics which deals with digital data.
digital frequency monitor A special purpose digi tal counter that permits a train of pulses to pass th rough a gate for a predetermined time interval, counts them and indicates the number counted.
digital IC 1. A switching type integrated circuit. 2. An
IC that processes electrical signals that have only two states, such as “on” or “off”, “high” or “low” voltages, or “positive” or “negative” voltages. In electronics “digital” normally means binary or two-state. 3. Digi tal integrated circuit (SSI, MSI, LSI), a monolithic group of logic elements. May be small-scale integra tion (e.g., SSI gates, flip-flops, latches); medium-scale integration (e.g., MSI decoders, adders, counters); lar ge-scale integration (e.g., LSI memories, micropro cessors).
digital image analysis Technology to measure and standardize the output of a computer-interfaced vidi con system.
digital indication See indicating device.
digital information display The presentation of di gital information in tabular form on the face of a digi tal information display tube.
digital integrator Device for summing or totalizing areas under curves that gives numerical readout. Also see integrator.
digital logic A signal level is represented as a number value with a most significant and least significant bit. Binary digital logic uses numbers consisting of strings of 1’s and 0’s.
digital logic modules Circuits which perform basic logic decisions AND/OR/NOT.
digital measuring instrument A measuring instru ment which provides a digitized output and/or display. Note: This term relates to the form of presentation of the output or display, not to the principle of operation of the instrument. Examples: Digital voltmeter, digital ohmmeter.
digital motor See stepping motor.
digital multiplexer A data selection device that per mits sharing a common information path between multiple groups of digital devices, such as from a computer CPU to any of several groups of digital out- put devices.
digital ohmmeter See digital measuring instrument.
digital optical disk See optical disk.
digital output (electrical transducers) Transdu cer output that represents the magnitude of the measu rand in the form of a series of discrete quantities co ded in a system of notation. Note: Distinguished from analog output.
digital point 121 dilution methods digital point 1. A user-defined process variable that
represents a device that has on/off or open/closed sta tes (e.g., a switch). 2. An individual hardware connec tion to monitor or control the process through pulses or logic levels. Refers to Honeywell TDC 3000 con trol systems.
digital positioner The digital positioner is a single acting, two stage, force balance instrument. It receives a digital electrical signal and positions a pneumatic control valve.
digital position transducer A device that converts motion or position into digital information.
digital readout Pertaining to measuring instruments, presentations of the values of the measured quantity by means of figures appearing discontinuously, for ming a number which directly indicated each of those values. Opposed to analog readout.
digital representation A discrete representation of quantized value of a variable, i.e. the representation of a number, by digits, perhaps with special characters and the space character.
digital resolution The value of the least significant digit in a digitally coded representation; also used to denote that fraction of full scale represented by one quantum.
digital rotary transducer A rotating device utili zing an optical sensor that produces a serial binary output as a result of shaft rotation.
digital signal A signal the information parameter of which may assume any value out of a set of discrete values which are represented by numbers.
digital signature A numerical representation of a set of logic states, typically used to describe the logic-sta te history at one device under test output pin during the complete test program.
digital speech communications Transmission of voice signals in digitized or binary form.
digital speed transducer See digital tachometer.
digital status contact A logical (on/off) input used mainly to sense the status of remote equipment in pro cess control systems.
digital storage oscilloscop In a digital storage os cilloscop, the data is stored in a memory inside the os cilloscope, the data being “read” and displayed on the face of the cathode ray tube as often as necessary to give the impression of a continuous display.
digital switch 1. A means to interconnect two or
more circuits whose information is represented in di gital form, using a time-divided network consisting of nonlinear elements. 2. An automatic switching center capable of switching digital signals. It may be a “cir cuit switch” or a “message switch”.
digital tachometer Any of several instruments de- signed to determine rotational speed and display the indication in digital form.
digital telemetering Telemetering in which a nume rical representation is generated and transmitted; the number being representative of the quantity being me asured.
digital telemeter receiver A device that receivers the numerical signal transmitted by a digital telemeter transmitter and stores it or converts it to a usable form, or both, for such purposes as recording, indication or control.
digital telemeter transmitter A device that con verts its input signal to a numerical form for transmis sion to a digital telemeter receiver over an intercon necting channel.
digital thermometer Electronic temperature mea suring device that reads and/or prints out numerically.
digital-to-analog conversion The transformation of a digital representation of a quantity into the analog value of that quantity.
digital-to-analog converter, D/A or DAC A con verter which changes a digital input signal into an analog output signal.
digital-to-analog multiplier, DAM A device which provides the means of obtaining the continuous mul tiplication of a specific digital value with a changing analog variable. The product is represented by a vary ing analog voltage. Syn: Multiplying – digital-to-ana log converter (MDAC).
digital transmission 1. A mode of transmission in
which all information to be transmitted over the facili ty is first converted into digital form and then sent down the line as a stream of pulses. (Such trasmission may imply a serial bit stream, but parallel forms are also possible). When noise and distorsion threaten to destroy the integrity of the pulse stream, the pulses are detected and generated. 2. The transmission of a sig nal in which information is represented by a code of discrete elements. Compare with analog transmission.
digital valves With digital valves, the final control element in a closed loop control system may be more readily interfaced with a computer. One design con sists of a series of on-off valve elements installed in a common body. These elements are a computer opera ted relay system. When open, each element offers a different orifice area, thus, by a binary bit code (on- off) the combination of orifice areas is made to give the desired flow.
digital voltmeter See digital measuring instrument.
digit compression Any of a number of techniques used to pack digits.
(to) digitize To convert an analog measurement of a physical variable into a numerical value, thereby ex- pressing the quantity in digital form. See analog-to-di gital converter.
digitized signal Representation of information by a set of discrete values, in accordance with a prescribed law. Every discrete value represents a definite range of the original undigitized signal. See analog-to-digital converter.
digitized speech A numerical representation of speech in which the amplitude of the speech wave- form as been recorded at regular intervals. Speech is typically sampled from 8,000 to 12,500 times per se cond.
digitizer A device which converts an analog measure ment into a digital form.
digitizers A purely graphical input device (i.e. a CAD/CAM/CAE) system digitizer for convening lo- cations into storable electronic impulses) with a surfa ce on which a location or a point is selected and then automatically converted into a digital x y coordinate suitable for transmission to a computer.
digitizing The process of converting an analog signal to a digital signal.
digitron display A type of display in which all digits appear in the same plane.
digit-transfer bus The main wire or wires used to transfer information (but not control signals) among the various registers in a digital computer.
dilatometer An apparatus for accurately measuring thermal expansion of materials.
dilution Adding solvent to a solution to lower its con centration.
dilution methods Methods in which the discharge is deduced from the determination of the ratio of the concentration of the tracer injected to that of the tracer
dilution ratio 122 direct-arc heating
at the samling cross-section. See also dilution ratio. Pertains to liquid flow measurement in open channels.
dilution ratio 1. The ratio of the concentration of tra
cer in the injected solution to that at the downstream sampling section. Pertains to liquid flow measurement in open channels. 2. The ratio of the concentration of tracer in the injected solution to that in the sampling cross-section. Pertains to measurement of fluid flow in closed conduits.
dimensional stability (of paper or board) The ability (of paper or board) to maintain its size and sha pe when exposed to changes in moisture content or to mechanical stresses.
dimensionless quantity A quantity in the expressi on of which the exponents of the base quantities, in a given system, are zero. Examples: Linear strain, coef ficient of friction, refractive index are dimensionless quantities in the system of quantities, l, m, t.
dimensionless velocity (relative velocity) The ratio of the flow velocity at a given point to a referen ce velocity measured at the same time which may be the velocity at a particular point (for example the cen tre-line velocity) or the discharge velocity.
dimension of a quantity An expression which re- presents a quantity of a system of quantities as the product of powers of the base quantities of the system.
diminished radix complement, radix-minus- one complement A complement obtained by sub tracting each digit of the given number from the num ber that is one less than the radix of that digit place.
DIN Abbreviation for Deutches Institut für Normung. Determines the standards for electrical and other equipment in Germany.
DIN jack A system of multipin jacks and plugs allo wing several connections to be made at once. named after the German Institute for Standards (DIN).