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Omega Heaters-Glossary
Absolute Pressure Transducer: A transducer which measures pressure in relation to zero pressure (a vacuum on one side of the diaphragm).
Absolute Pressure: Gage pressure plus atmospheric pressure.
Absolute Zero: Temperature at which thermal energy is at a minimum. Defined as 0 Kelvin, calculated to be -273.15°C or -459.67°F.
ac: Alternating current; an electric current that reverses its direction at regularly recurring intervals.
Acceleration: A change in the velocity of a body or particle with respect to time. The parameter that an accelerometer measures (dv/dt). Units expressed in "g".
Accelerometer: A device which converts the effects of mechanical motion into an electrical signal that is proportional to the acceleration value of the motion. A sensor. A transducer.
Accuracy: The closeness of an indication or reading of a measurement device to the actual value of the quantity being measured. Usually expressed as ± percent of full scale output or reading.
Acoustics: The degree of sound. The nature, cause, and phenomena of the vibrations of elastic bodies; which vibrations create compressional waves or wave fronts which are transmitted through various media, such as air, water, wood, steel, etc.
Activity (ai): A thermodynamic term for the apparent or active concentration of a free ion in solution. It is related to concentration by the activity coefficient.
Activity Coefficient (fi): A ratio of the activity of species i(ai) to its molality (C). It is a correction factor which makes the thermodynamic calculations correct. This factor is dependent on ionic strength, temperature, and other parameters.
Individual ionic activity coefficients, f+ for cation and f- for an anion, cannot be derived thermodynamically. They can be calculated only by using the Debye-Huckel law for low concentration solutions in which the interionic forces depend primarily on charge, radius, and distribution of the ions and on the dielectric constant of the medium rather than on the chemical properties of the ions.
Mean ionic activity coefficient (f±) or the activity of a salt, on the other hand, can be measured by a variety of techniques such as freezing point depression and vapor pressure as well as paired sensing electrodes. It is the geometric mean of the individual ionic activity coefficients: f± = (f+n+f-n-)1/n
Adapter: A mechanism or device for attaching non-mating parts.
ADC: Analog-to-Digital Converter: an electronic device which converts analog signals to an equivalent digital form, in either a binary code or a binary-coded-decimal code. When used for dynamic waveforms, the sampling rate must be high to prevent aliasing errors from occurring.
Address: The label or number identifying the memory location where a unit of information is stored.
Aliasing: If the sample rate of a function (fs) is less than two times the highest frequency value of the function, the frequency is ambiguously presented. The frequencies above (fs/2) will be folded back into the lower frequencies producing erroneous data.
Alloy 11: A compensating alloy used in conjunction with pure copper as the negative leg to form extension wire for platinum-platinum rhodium thermocouples Types R and S.
Alloy 200/226: The combination of compensating alloys used with tungsten vs. tungsten 26% rhenium thermocouples as extension cable for applications under 200°C.
Alloy 203/225: The combination of compensating alloys used with tungsten 3% rhenium vs. tungsten 150 rhenium thermocouples as extension cable for applications under 200°C.
Alloy 405/426: The combination of compensating alloys used with tungsten 5% rhenium vs. tungsten 26% rhenium thermocouples as extension cable for applications under 870°C.
ALOMEGA® An aluminum nickel alloy used in the negative leg of a type K thermocouple (registered trademarks of OMEGA ENGINEERING, INC.).
Alphanumeric: A character set that contains both letters and digits.
ALU: Arithmetic Logic Unit. The part of a CPU where binary data is acted upon with mathematical operations.
Alumel: An aluminum nickel alloy used in the negative leg of a Type K thermocouple (Trade name of Hoskins Manufacturing Company).
Ambient Compensation: The design of an instrument such that changes in ambient temperature do not affect the readings of the instrument.
Ambient Conditions: The conditions around the transducer (pressure, temperature, etc.).
Ambient Pressure: Pressure of the air surrounding a transducer.
Ambient Temperature: The average or mean temperature of the surrounding air which comes in contact with the equipment and instruments under test.
Ammeter: An instrument used to measure current.
Ampere (amp): A unit used to define the rate of flow of electricity (current) in a circuit; units are one coulomb (6.28 x 1018 electronics) per second.
Amplifier: A device which draws power from a source other than the input signal and which produces as an output an enlarged reproduction of the essential features of its input.
Amplitude Span: The Y-axis range of a graphic display of data in either the time or frequency domain. Usually a log display (dB) but can also be linear.
Amplitude: A measurement of the distance from the highest to the lowest excursion of motion, as in the case of mechanical body in oscillation or the peak-to-peak swing of an electrical waveform.
Analog Output: A voltage or current signal that is a continuous function of the measured parameter.
Analog-to-Digital Converter (A/D or ADC): A device or circuit that outputs a binary number corresponding to an analog signal level at the input.
Anemometer: An instrument for measuring and/or indicating the velocity of air flow.
Angstrom: Ten to the minus tenth meters (10-10) or one millimicron, a unit used to define the wave length of light. Designated by the symbol ‰.
Angular Frequency: The motion of a body or a point moving circularly, referred to as the circular frequency O which is the frequency in cycles per second (cps) multiplied by the term (2) and expressed in radians per second (2pf).
Anion: A negatively charged ion (Cl-, NO3-, S2- etc.)
ANSI: American National Standards Institute.
Anti-reset Windup: This is a feature in a three-mode PID controller which prevents the integral (auto reset) circuit from functioning when the temperature is outside the proportional band.
Application Program: A computer program that accomplishes specific tasks, such as word processing.
ASCII: American Standard Code for Information Interchange. A seven or eight bit code used to represent alphanumeric characters. It is the standard code used for communications between data processing systems and associated equipment.
ASME: American Society of Mechanical Engineers.
Assembler: A program that translates assembly language instructions into machine language instructions.
Assembly Language: A machine oriented language in which mnemonics are used to represent each machine language instruction. Each CPU has its own specific assembly language.
ASTM: American Society for Testing and Materials.
Asymmetry Potential: The potential developed across the glass membrane with identical solutions on both sides. Also a term used when comparing glass electrode potential in pH 7 buffer.
Asynchronous: A communication method where data is sent when it is ready without being referenced to a timing clock, rather than waiting until the receiver signals that it is ready to receive.
ATC: Automatic temperature compensation.
Auto-Zero: An automatic internal correction for offsets and/or drift at zero voltage input.
Automatic Reset: 1. A feature on a limit controller that automatically resets the controller when the controlled temperature returns to within the limit bandwidth set. 2. The integral function on a PID controller which adjusts the proportional bandwidth with respect to the set point to compensate for droop in the circuit, i.e., adjusts the controlled temperature to a set point after the system stabilizes.
AWG: American Wire Gage.
Axis of Rotation (Spin Axis): The axis of rotation (spin axis) is that straight line about which a body rotates.
Background Noise: The total noise floor from all sources of interference in a measurement system, independent of the presence of a data signal.
Backup: A system, device, file or facility that can be used as an alternative in case of a malfunction or loss of data.
Bandwidth: A symmetrical region around the set point in which proportional control occurs.
Basic Transportation Reference: The basic transportation section of the U.S. Government Test Specification MIL-STD-810D, Method 514.3, Paragraph I-3.2.1, Page 514.3-5. Basic transportation defines the test profiles that have been defined for equipment that is shipped as secured cargo; by land, by sea or by air. The test levels are based upon land transport stress levels because these are higher than stresses imposed by air or sea transportation environments.
Basic: A high-level programming language designed at Dartmouth College as a learning tool. Acronym for Beginner's All-purpose Symbolic Instruction Code.
Baud: A unit of data transmission speed equal to the number of bits (or signal events) per second; 300 baud = 300 bits per second.
BCD, Buffered: Binary-coded decimal output with output drivers, to increase line-drive capability.
BCD, Parallel: A digital data output format where every decimal digit is represented by binary signals on four lines and all digits are presented in parallel. The total number of lines is 4 times the number of decimal digits.
BCD, Serial: A digital data output format where every decimal digit is represented by binary signals on four lines and up to five decimal digits are presented sequentially. The total number of lines is four data lines plus one strobe line per digit.
BCD, Three-State: An implementation of parallel BCD, which has 0, 1 and high-impedance output states. The high-impedance state is used when the BCD output is not addressed in parallel connect applications.
Bearing: A part which supports a journal and in which a journal revolves.
Beat Frequency: Beat frequencies are periodic vibrations that result from the addition and subtraction of two or more sinusoids. For example, in the case of two turbine aircraft engines that are rotating at nearly the same frequency but not precisely at the same frequency; Four frequencies are generated:(f1) the rotational frequency of turbine one, (f2) the rotational frequency of turbine two, (f1 + f2) the sum of turbine rotational frequencies one and two, and (f1 - f2) which is the difference or "beat" frequency of turbines one and two. The difference of the two frequencies is the lower frequency and is the one that is "felt" as a beat or "wow" in this case.
Beryllia: BeO (Beryllium Oxide) A high-temperature mineral insulation material; toxic when in powder form.
Best Fit Straight Line (BFSL): A line midway between two parallel straight lines enclosing all output vs. pressure values.
Beta Ratio: The ratio of the diameter of a pipeline constriction to the unconstricted pipe diameter.
BIAS Current: A very low-level DC current generated by the panel meter and superimposed on the signal. This current may introduce a measurable offset across a very high source impedance.
Binary Coded Decimal (BCD): The representation of a decimal number (base 10, 0 through 9) by means of a 4 bit binary nibble.
Binary: Refers to base 2 numbering system, in which the only allowable digits are 0 and 1. Pertaining to a condition that has only two possible values or states.
BIOS: Acronym for basic input/output system. The commands used to tell a CPU how it will communicate with the rest of the computer.
Bipolar: The ability of a panel meter to display both positive and negative readings.
Bit: Acronym for binary digit. The smallest unit of computer information, it is either a binary 0 or 1.
Blackbody: A theoretical object that radiates the maximum amount of energy at a given temperature, and absorbs all the energy incident upon it. A blackbody is not necessarily black. (The name blackbody was chosen because the color black is defined as the total absorption of light energy.)
BNC: A quick disconnect electrical connector used to inter-connect and/or terminate coaxial cables.
Boiling Point: The temperature at which a substance in the liquid phase transforms to the gaseous phase; commonly refers to the boiling point of water which is 100°C (212°F) at sea level.
BPS: Bits per second.
Breakdown Voltage Rating: The dc or ac voltage which can be applied across insulation portions of a transducer without arcing or conduction above a specific current value.
Bridge Resistance: See Input impedance and Output impedance.
BTU: British thermal units. The quantity of thermal energy required to raise one pound of water at its maximum density, 1 degree F. One BTU is equivalent to .293 watt hours, or 252 calories. One kilowatt hour is equivalent to 3412 BTU.
Buffer Capacity (B): A measure of the ability of the solution to resist pH change when a strong acid or base is added.
Buffer: 1. A storage area for data that is used to compensate for a speed difference, when transferring data from one device to another. Usually refers to an area reserved for I/O operations, into which data is read, or from which data is written.2. Any substance or combination of substances which, when dissolved in water, produces a solution which resists a change in its hydrogen ion concentration on the addition of an acid or alkali.
Bulb (Liquid-in-Glass Thermometer): The area at the tip of a liquid-in-glass thermometer containing the liquid reservoir.
Burn-In: A long term screening test (either vibration, temperature or combined test) that is effective in weeding out infant mortalities because it simulates actual or worst case operation of the device, accelerated through a time, power, and temperature relationship.
Burst Pressure: The maximum pressure applied to a transducer sensing element or case without causing leakage.
Burst Proportioning: A fast-cycling output form on a time proportioning controller (typically adjustable from 2 to 4 seconds) used in conjunction with a solid state relay to prolong the life of heaters by minimizing thermal stress.
Bus: Parallel lines used to transfer signals between devices or components. Computers are often described by their bus structure (i.e., S-100, IBM PC).
Byte: The representation of a character in binary. Eight bits.
Calender-van Dusen Equation: An equation that defines the resistance-temperature value of any pure metal that takes the form of RT = RO(1 + AT + BT2) for values between the ice point (0°C) and the freezing point of antimony (630.7°C) and the form RT = RO[1 + AT + BT2 + C(T-100)T2] between the oxygen point (-183.0°C) and the ice point (0°C).
Calibration: The process of adjusting an instrument or compiling a deviation chart so that its reading can be correlated to the actual value being measured.
Calorie: The quantity of thermal energy required to raise one gram of water 1°C at 15°C.
Cation: A positively charged ion (Na+, H+).
Cavitation: The boiling of a liquid caused by a decrease in pressure rather than an increase in temperature.
Celsius (centrigrade): A temperature scale defined by 0°C at the ice point and 100°C at boiling point of water at sea level.
Center of Gravity (Mass Center): The center of gravity of a body is that point in the body through which passes the resultant of weights of its component particles for all orientations of the body with respect to a uniform gravitational field.
Centripetal Force: A force exerted on an object moving in a circular path which is exerted inward toward the center of rotation.
Ceramic Insulation: High-temperature compositions of metal oxides used to insulate a pair of thermocouple wires The most common are Alumina (Al2O3), Beryllia (BeO), and Magnesia (MgO). Their application depends upon temperature and type of thermocouple. High-purity alumina is required for platinum alloy thermocouples. Ceramic insulators are available as single and multihole tubes or as beads.
Ceramic: Polycrystalline ferroelectric materials which are used as the sensing units in piezoelectric accelerometers. There are many different grades, all of which can be made in various configurations to satisfy different design requirements.
CFM: The volumetric flow rate of a liquid or gas in cubic feet per minute.
Character: A letter, digit or other symbol that is used as the representation of data. A connected sequence of characters is called a character string.
Charge Sensitivity: For accelerometers that are rated in terms of charge sensitivity, the output voltage (V)is proportional to the charge (Q) divided by the shunt capacitance (C). This type of accelerometer is characterized by a high output impedance. The sensitivity is given in terms of charge; picocoulombs per unit of acceleration (g).
Chatter: The rapid cycling on and off of a relay in a control process due to insufficient bandwidth in the controller.
CHROMEGA®: A chromium-nickel alloy which makes up the positive leg of type K and type E thermocouples (registered trademarks of OMEGA ENGINEERING, INC.).
Clear: To restore a device to a prescribed initial state, usually the zero state.
Clipping: The term applied to the phenomenon which occurs when an output signal is limited in some way by the full range of an amplifier, ADC or other device. When this occurs, the signal is flattened at the peak values, the signal approaches the shape of a square wave, and high frequency components are introduced. Clipping may be hard, as is the case when the signal is strictly limited at some level; or it may be soft, in which case the clipping signal continues to follow the input at some reduced gain.
Clock: The device that generates periodic signals for synchronization.
Closeness of Control: Total temperature variation from a desired set point of system. Expressed as "closeness of control" is ±2°C or a system bandwidth with 4°C, also referred to as amplitude of deviation.
CMR (Common-Mode Rejection): The ability of a panel meter to eliminate the effect of AC or DC noise between signal and ground. Normally expressed in dB at dc to 60 Hz. One type of CMR is specified between SIG LO and PWR GND. In differential meters, a second type of CMR is specified between SIG LO and ANA GND (METER GND).
CMV (Common-Mode Voltage): The AC or DC voltage which is tolerable between signal and ground. One type of CMV is specified between SIG LO and PWR GND. In differential meters, a second type of CMV is specified between SIG HI or LO and ANA GND (METER GND).
Coherence Function.: A frequency domain function computed to show the degree of a linear, noise-free relationship between a system's input and output. The value of the coherence function ranges between zero and one, where a value of zero indicates there is no causal relationship between the input and the output. A value of one indicates the existence of linear noise-free frequency response between the input and the output.
Color Code: The ANSI established color code for thermocouple wires in the negative lead is always red. Color Code for base metal thermocouples is yellow for Type K, black for Type J, purple for Type E and blue for Type T.
Common Mode Rejection Ratio: The ability of an instrument to reject interference from a common voltage at its input terminals with relation to ground. Usually expressed in db (decibels).
Common Mode: The output form or type of control action used by a temperature controller to control temperature, i.e. on/off, time proportioning, PID.
Communication: Transmission and reception of data among data processing equipment and related peripherals.
Compensated Connector: A connector made of thermocouple alloys used to connect thermocouple probes and wires.
Compensating Alloys: Alloys used to connect thermocouples to instrumentation. These alloys are selected to have similar thermal electric properties as the thermocouple alloys (however, only over a very limited temperature range).
Compensating Loop: Lead wire resistance compensation for RTD elements where an extra length of wire is run from the instrument to the RTD and back to the instrument, with no connection to the RTD.
Compensation: An addition of specific materials or devices to counteract a known error.
Compiler: A program that translates a high-level language, such as Basic, into machine language.
Complex Function: Any mathematically defined relationship given by the following expression:
y(x) = a(x) + ib(x)
Where: x = the real variable
a(x) = the real part of y(x)
b(x) = the imaginary part of y(x)
Complex functions are usually expressed in terms of both their amplitude and phase.
Complex Wave: The resultant form of a number of sinusoidal waves that are summed together forming a periodic wave. Such waves may be analyzed in the frequency domain to readily determine their component parts.
Conductance: The measure of the ability of a solution to carry an electrical current. (See Equivalent Conductance)
Conduction: The conveying of electrical energy or heat through or by means of a conductor.
Confidence Level: The range (with a specified value of uncertainty, usually expressed in percent) within which the true value of a measured quantity exists.
Conformity Error: For thermocouples and RTDs, the difference between the actual reading and the temperature shown in published tables for a specific voltage input.
Connection Head: An enclosure attached to the end of a thermocouple which can be cast iron, aluminum or plastic within which the electrical connections are made.
Constantan: A copper-nickel alloy used as the negative lead in Type E, Type J, and Type T thermocouples.
Continuous Spectrum: A frequency spectrum that is characterized by non-periodic data The spectrum is continuous in the frequency domain and is characterized by an infinite number of frequency components.
Control Character: A character whose occurrence in a particular context starts, modifies or stops an operation that effects the recording, processing, transmission or interpretation of data.
Control Mode: The output form or type of control action used by a temperature controller to control temperature, i.e., on/off, time proportioning, PID.
Control Point: The temperature at which a system is to be maintained.
Convection: 1. The circulatory motion that occurs in a fluid at a non-uniform temperature owing to the variation of its density and the action of gravity. 2. The transfer of heat by this automatic circulation of fluid.
Coriolis Force: A result of centripetal force on a mass moving with a velocity radially outward in a rotating plane.
Correction (Balancing) Plane: A plane perpendicular to the shaft axis of a rotor in which correction for unbalance is made.
Coulomb Sensitivity: Charge/unit acceleration, expressed in Pc/g (charge sensitivity).
Coulomb: A measurement of the quantity of electrical charge, usually expressed as pico coulomb (10-12 coulombs).
Counter Weight: A weight added to a body so as to reduce a calculated unbalance at a desired place.
Counts: The number of time intervals counted by the dual-slope A/D converter and displayed as the reading of the panel meter, before addition of the decimal point.
CPS: Cycles per second; the rate or number of periodic events in one second, expressed in Hertz (Hz).
CPU: Central processing unit. The part of the computer that contains the circuits that control and perform the execution of computer instructions.
Critical Damping: Critical damping is the smallest amount of damping at which a given system is able to respond to a step function without overshoot.
Critical Speed: The rotational speed of the rotor or rotating element at which resonance occurs in the system. The shaft speed at which at least one of the "critical" or natural frequencies of a shaft is excited.
Cryogenics: Measurement of temperature at extremely low values, i.e., below -200°C.
CSA: Canadian Standards Administration.
Cure Point: The temperature at which a normally magnetic material goes through a magnetic transformation and becomes non-magnetic.
Current Proportioning: An output form of a temperature controller which provides a current proportional to the amount of control required. Normally is a 4 to 20 milliamp current proportioning band.
Current: The rate of flow of electricity. The unit of the ampere (A) defined as 1 ampere = 1 coulomb per second.
Curve Fitting: Curve fitting is the process of computing the coefficients of a function to approximate the values of a given data set within that function. The approximation is called a "fit". A mathematical function, such as a least squares regression, is used to judge the accuracy of the fit.
Cycle Time: The time usually expressed in seconds for a controller to complete one on/off cycle.
Damping: The reduction of vibratory movement through dissipation of energy. Types include viscous, coulomb, and solid.
Data Base: A large amount of data stored in a well-organized manner. A data base management system (DBMS) is a program that allows access to the information.
dB (Decibel): 20 times the log to the base 10 of the ratio of two voltages. Every 20 dBs correspond to a voltage ratio of 10, every 10 dBs to a voltage ratio of 3.162. For instance, a CMR of 120 dB provides voltage noise rejection of 1,000,000/1. An NMR of 70 dB provides voltage noise rejection of 3,162/1.
DC: Direct current; an electric current flowing in one direction only and substantially constant in value.
Dead Band: 1. For chart records: the minimum change of input signal required to cause a deflection in the pen position. 2. For temperature controllers: the temperature band where heat is turned off upon rising temperature and turned on upon falling temperature expressed in degrees. The area where no heating (or cooling) takes place.
Dead Volume: The volume of the pressure port of a transducer at room temperature and ambient barometric pressure.
Debug: To find and correct mistakes in a program.
Debye-H¸ckel Equation: Used in relating the activity coefficient (fi) to ion strength (see Activity coefficient):where I is the ionic strength, A and B the temperature-dependent constants (see Table A.5), Zi the valence of the ion (i), and  the ion-size parameter in angstroms.
Decimal: Refers to a base ten number system using the characters 0 through 9 to represent values.
Default: The value(s) or option(s) that are assumed during operation when not specified.
Degree: An incremental value in the temperature scale, i.e., there are 100 degrees between the ice point and the boiling point of water in the Celsius scale and 180°F between the same two points in the Fahrenheit scale.
Density: Mass per unit of volume of a substance. I.E.: grams/cu.cm. or pounds/cu.ft.
Derivative: The derivative function senses the rate of rise or fall of the system temperature and automatically adjusts the cycle time of the controller to minimize overshoot or undershoot.
Deviation: The difference between the value of the controlled variable and the value at which it is being controlled.
Diaphragm: The sensing element consisting of a membrane which is deformed by the pressure differential applied across it.
Dielectric Constant: Related to the force of attraction between two opposite charges separated by a distance in a uniform medium.
Differential Input: A signal-input circuit where SIG LO and SIG HI are electrically floating with respect to ANALOG GND (METER GND, which is normally tied to DIG GND). This allows the measurement of the voltage difference between two signals tied to the same ground and provides superior common-mode noise rejection.
Differential Pressure: The difference in static pressure between two identical pressure taps at the same elevation located in two different locations in a primary device.
Differential: For an on/off controller, it refers to the temperature difference between the temperature at which the controller turns heat off and the temperature at which the heat is turned back on. It is expressed in degrees.
Digit: A measure of the display span of a panel meter. By convention, a full digit can assume any value from 0 through 9, a 1/2-digit will display a 1 and overload at 2, a 3/4-digit will display digits up to 3 and overload at 4, etc. For example, a meter with a display span of ±3999 counts is said to be a 3-3/4 digit meter.
Digital Output: An output signal which represents the size of an input in the form of a series of discrete quantities.
Digital-to-Analog Converter (D/A or DAC): A device or circuit to convert a digital value to an analog signal level.
DIN (Deutsche Industrial Norm): A set of German standards recognized throughout the world. The 1/8 DIN standard for panel meters specifies an outer bezel dimension of 96 x 48 mm and a panel cutout of 92 x 45 mm.
DIN 43760: The standard that defines the characteristics of a 100 ohm platinum RTD having a resistance vs. temperature curve specified by a = 0.00385 ohms per degree.
Discharge Time Constant: The time required for the output-voltage from a sensor or system to discharge 37% of its original value in response to a zero rise time step function input. This parameter determines a low frequency response.
Disk Operating System (DOS): Program used to control the transfer of information to and from a disk, such as MS DOS.
Displacement: The measured distance traveled by a point from its position at rest. Peak to peak displacement is the total measured movement of a vibrating point between its positive and negative extremes. Measurement units expressed as inches or millinches.
Dissipation Constant: The ratio for a thermistor which relates a change in internal power dissipation to a resultant change of body temperature.
Dissociation Constant (K): A value which quantitatively expresses the extent to which a substance dissociates in solution. The smaller the value of K, the less dissociation of the species in solution. This value varies with temperature, ionic strength, and the nature of the solvent.
DMA: Acronym direct memory access. A high speed data storage mode of the IBM PC.
Double Precision: The degree of accuracy that requires two computer words to represent a number. Numbers are stored with 17 digits of accuracy and printed with up to 16 digits.
Drift: A change of a reading or a set point value over long periods due to several factors including change in ambient temperature, time, and line voltage.
Droop: A common occurrence in time-proportional controllers. It refers to the difference in temperature between the set point and where the system temperature actually stabilizes due to the time-proportioning action of the controller.
Dual Element Sensor: A sensor assembly with two independent sensing elements.
Dual-slope A/D Converter: An analog-to-digital converter which integrates the signal for a specific time, then counts time intervals for a reference voltage to bring the integrated signal back to zero. Such converters provide high resolution at low cost, excellent normal-mode noise rejection, and minimal dependence on circuit elements.
Duplex Wire: A pair of wires insulated from each other and with an outer jacket of insulation around the inner insulated pair.
Duplex: Pertaining to simultaneous two-way independent data communication transmission in both direction. Same as "full duplex".
Duty Cycle: The total time to one on/off cycle. Usually refers to the on/off cycle time of a temperature controller.
Dynamic (Two-Plane) Balancing Machine: A dynamic balancing machine is a centrifugal balancing machine that furnishes information for performing two-plane balancing.
Dynamic Calibration: Calibration in which the input varies over a specific length of time and the output is recorded vs. time.
Dynamic Pressure: The difference in pressure levels from static pressure to stagnation pressure caused by an increase in velocity. Dynamic pressure increases by the square of the velocity.
Dynamic Unbalance: Dynamic unbalance is that condition in which the central principal axis is not coincident with the shaft axis.
Echo: To reflect received data to the sender. For example, keys depressed on a keyboard are usually echoed as characters displayed on the screen.
Electrical Interference: Electrical noise induced upon the signal wires that obscures the wanted information signal.
