Data Acquisition & Logging Glossary - Complete List

Absolute Pressure Gauge pressure plus atmospheric pressure...
Absolute Pressure Transducer A transducer which measures pressure in relation to zero pressure (a vacuum on one side of the diaph..
Absolute Zero Temperature at which thermal energy is at a minimum. Defined as 0 Kelvin, calculated to be -273.15°C..
Accelerometer A sensor or a transducer which converts the effects of mechanical motion into an electrical signal t..
Accuracy The closeness of an indication or reading of a measurement device to the actual value of the quantit..
Acoustics The degree of sound. The nature, cause, and phenomena of the vibrations of elastic bodies; which vib..
Activity (ai) A thermodynamic term for the apparent or active concentration of a free ion in solution. It is relat..
Activity Coefficient (fi) A ratio of the activity of species i(ai) to its molality (C). It is a correction factor which makes ..
Adapter A mechanism or device for attaching non-mating parts...
Aliasing If the sample rate of a function (fs) is less than two times the highest frequency value of the func..
Alloy 11 A compensating alloy used in conjunction with pure copper as the negative leg to form extension wire..
Alloy 200-226 The combination of compensating alloys used with tungsten vs. tungsten 26% rhenium thermocouples as ..
Alloy 405/426 The combination of compensating alloys used with tungsten 5% rhenium vs. tungsten 26% rhenium thermo..
ALOMEGA An aluminum nickel alloy used in the negative leg of a type K thermocouple (registered trademarks of..
Alternating Current (ac) Electric current whose flow alternates in direction. The number of times the current changes directi..
ALUMEL Alumel is a registered trademark of Hoskins Manufacturing Company. It is an alloy of nickel with up ..
Ambient Compensation The design of an instrument such that changes in ambient temperature do not affect the readings of t..
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..
Ammeter An instrument used to measure current...
Ampere (A) SI unit of electric current. A unit used to define the rate of flow of electricity (current) in a ci..
Amplifier A device or circuit that produces a larger output power, voltage or current than was applied at its ..
Amplitude A measurement of the distance from the highest to the lowest excursion of motion, as in the case of ..
Analogue-to-Digital (A-D) Converter An electronic device or circuit that converts an analogue signal (such as a voltage signal from a te..
Anemometer An instrument for measuring and/or indicating the velocity of air flow...
Angular Frequency The motion of a body or a point moving circularly, referred to as the circular frequency O which is ..
Anti-Alias Filter An anti-alias (or anti-aliasing) filter allows through the lower frequency components of a signal bu..
Anti-reset Windup This is a feature in a three-mode PID controller which prevents the integral (auto reset) circuit fr..
ASCII American Standard Code for Information Interchange. Normally defined as text files...
Asymmetry Potential The potential developed across the glass membrane with identical solutions on both sides. Also a ter..
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 temp..
Backbone The major multi-channel link in a network, from which smaller links branch...
Background Noise Extraneous signals that might be confused with the required measurement. Filters are normally used t..
Backup A system, device, file or facility that can be used as an alternative in case of a malfunction or lo..
Basic Transportation Reference The basic transportation section of the U.S. Government Test Specification MIL-STD-810D, Method 514...
Batch Process Any process on which operations are carried out on a limited number of articles, as opposed to conti..
Bathymetry Measurement of the depths of features at the bottom of the sea, especially by echo-sounding...
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 line..
BCD Serial A digital data output format where every decimal digit is represented by binary signals on four line..
BCD Three-State An implementation of parallel BCD, which has 0, 1 and high-impedance output states. The high-impedan..
Beat Frequency Beat frequencies are periodic vibrations that result from the addition and subtraction of two or mor..
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 curren..
Binary Coded Decimal (BCD) The representation of a decimal number (base 10, 0 through 9) by means of a 4 bit binary nibble...
Bipolar The ability of a panel meter to display both positive and negative readings...
Blackbody A theoretical object that radiates the maximum amount of energy at a given temperature, and absorbs ..
Boiling Point The temperature at which a substance in the liquid phase transforms to the gaseous phase; commonly r..
Breakdown Voltage Rating The dc or ac voltage which can be applied across insulation portions of a transducer without arcing ..
British Thermal Units (BTU) The quantity of thermal energy required to raise one pound of water at its maximum density, 1 degree..
Buffer Capacity (B) A measure of the ability of the solution to resist pH change when a strong acid or base is added...
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 seco..
Calibration The process of adjusting an instrument or compiling a deviation chart so that its reading can be cor..
Calorie The quantity of thermal energy required to raise one gram of water 1°C at 15°C...
Capacitance The ability to store an electrical charge, or, more precisely, the ratio of the total charge on a ca..
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 weig..
Centripetal Force A force exerted on an object moving in a circular path which is exerted inward toward the center of ..
Ceramic Polycrystalline ferroelectric materials which are used as the sensing units in piezoelectric acceler..
Ceramic Insulation High-temperature compositions of metal oxides used to insulate a pair of thermocouple wires The most..
CFM The volumetric flow rate of a liquid or gas in cubic feet per minute...
Charge Sensitivity For accelerometers that are rated in terms of charge sensitivity, the output voltage (V)is proportio..
Chatter The rapid cycling on and off of a relay in a control process due to insufficient bandwidth in the co..
Chromel An alloy of nickel with about 10% chromium, used with Alumel in K-type thermocouples...
Clipping The term applied to the phenomenon which occurs when an output signal is limited in some way by the ..
Closeness of Control Total temperature variation from a desired set point of system. Expressed as "closeness of control" ..
CMOS Short for complementary metal oxide semiconductor. Pronounced see-moss, CMOS is a widely used type o..
CMR (Common-Mode Rejection) The ability of a panel meter to eliminate the effect of AC or DC noise between signal and ground. No..
CMV (Common-Mode Voltage) The AC or DC voltage which is tolerable between signal and ground. One type of CMV is specified betw..
Coherence Function A frequency domain function computed to show the degree of a linear, noise-free relationship between..
Cold Junction The reference junction of a thermocouple which is kept at a constant temperature...
Color Code The ANSI established color code for thermocouple wires in the negative lead is always red. Color Cod..
COM Port Short for communication port. A connection on a computer into which a serial device may be plugged...
Common-Mode Rejection Ratio (cmrr) The ability of the differential amplifier to obtain the difference between the + and - inputs whilst..
Common-Mode Signal A signal applied simultaneously to both inputs of a differential amplifier...
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 t..
Compensating Loop Lead wire resistance compensation for RTD elements where an extra length of wire is run from the ins..
Compensation An addition of specific materials or devices to counteract a known error...
Complex Wave The resultant form of a number of sinusoidal waves that are summed together forming a periodic wave...
Conductance The measure of the ability of a solution to carry an electrical current...
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 tru..
Conformity Error For thermocouples and RTDs, the difference between the actual reading and the temperature shown in p..
Connection Head An enclosure attached to the end of a thermocouple which can be cast iron, aluminum or plastic withi..
Constantan An alloy of 40% nickel and 60% copper, with a high volume resistivity and almost negligible temperat..
Contact Emf Electromotive force which arises at the contact of dissimilar metals at the same temperature, or the..
Contact Rating Refers to the power that can be safely switched with a relay. Quoted for non-reactive load, that is ..
Continuous Process Method of producing an article continuously...
Continuous Spectrum A frequency spectrum that is characterized by non-periodic data The spectrum is continuous in the fr..
Control Mode The output form or type of control action used by a temperature controller to control temperature, i..
Control Point The temperature at which a system is to be maintained...
Coriolis Force A result of centripetal force on a mass moving with a velocity radially outward in a rotating plane...
Counts The number of time intervals counted by the dual-slope A/D converter and displayed as the reading of..
CPS Cycles per second; the rate or number of periodic events in one second, expressed in Hertz (Hz)...
Critical Damping Critical damping is the smallest amount of damping at which a given system is able to respond to a s..
Critical Speed The rotational speed of the rotor or rotating element at which resonance occurs in the system. The s..
Cryogenics Measurement of temperature at extremely low values, i.e., below -200 deg C..
Cure Point The temperature at which a normally magnetic material goes through a magnetic transformation and bec..
Current Current is often used to transmit signals in noisy environments because it is much less affected by ..
Current Proportioning An output form of a temperature controller which provides a current proportional to the amount of co..
Curve Fitting Curve fitting is the process of computing the coefficients of a function to approximate the values o..
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, a..
Data Acquisition The automatic collection of data from sensors, instruments and devices: in a factory, laboratory or ..
DCE DCE stands for Data Circuit-Terminating Equipment or Data Communications Equipment. It is part of th..
Device A peripheral which connects to the computer. Mice, keyboards, printers, data acquisition instruments..
Differential Amplifier One whose output is proportional to the difference between two inputs..
Differential Inputs Using differential inputs can reduce noise picked up by the signal leads. For each input signal ther..
Digital-to-Analogue (D-A) Converter Used to produce analogue output signals. These may be control signals or synthesised waveforms...
Direct Current (dc) Current which flows in one direction...
Drift Slow variation of a performance characteristic such as gain, frequency or power output. May be due t..
DTE DTE stands for Data Terminal Equipment. It is part of the RS232 standard and represents, for example..
E-Type Thermocouple Chromel-constantan thermocouple with a temperature range of 0 to 800 oC...
Electromotive Force (emf) Difference of potential produced by sources of electrical energy which can be used to drive currents..
Endurance Limit In fatigue testing, the number of cycles which may be withstood without failure at a particular leve..
Ethernet A local area network to which you can connect data acquisition devices...
Excitation The voltage or current applied to a transducer...
Fast Fourier Transfer (FFT) An analysis algorithm - given a finite set of data points, the FFT expresses the data in terms of it..
FIFO Buffer A first in, first out, store. The first value placed in the buffer (queue) is the first value subseq..
Filtering Attenuates components of a signal that are undesired: reduces noise errors in a signal...
Frequency Measured in hertz (cycles per second), rate of repetition of changes...
Frequency Counter Counts digital pulses over a defined gate time. A typical gate time is between 0.1 and 10 seconds...
Front Panel The front surface of a unit, generally containing switches and indicator lights...
Full Scale Output The difference between the minimum output (normally zero) of a data acquisition device and the rated..
Gain Amplification of a circuit...
GIS Geographic information system. Where data is assembled, stored, displayed and identified according t..
GPIB General Purpose Interface Bus. Also known as IEEE-488 bus. The GPIB standard was designed to connect..
Ground-Truthed When data is collected by remote sensing techniques, ground-truthing confirms that the information i..
HART Highway Addressable Remote Terminal. Provides digital communication to microprocessor-based (smart) ..
Hertz (Hz) Cycles per second unit of frequency...
Hexadecimal Counting system based on 16...
I Symbol for electric current...
I/O Input/Output. A data acquisition system monitors signals through its inputs, and sends control signa..
IC Integrated Circuit (electronic components fabricated on a semiconductor substrate which cannot be di..
IEEE Institute of Electrical and Electronics Engineers. An American Society that, amongst other things, e..
IML Interface Management Language. A programming language used to communicate with measurement instrumen..
Inductance The magnitude of a magnetic field created by a circuit carrying a current. This can cause higher vol..
Input Data entering a device from the environment. A signal being monitored by a data acquisition system...
Instrument Any item of electrical or electronic equipment which is designed to carry out a specific function or..
Integer A positive or negative whole number, or 0...
Integrated Circuit Electronic components fabricated on a semiconductor substrate. An integrated circuit cannot be divid..
Integration Time The time over which an integrating A-D converter averages the input signal. If chosen appropriately ..
Interface A shared boundary. It might be a piece of hardware used between two pieces of equipment, or a softwa..
Interpreter Software enabling a computer to run programs statement by statement...
Interrupt An external signal causing the execution of a program to be suspended...
Inverter A dc-ac converter...
ISA Industry Standard Architecture. An ISA expansion slot lets you plug data acquisition boards into PCs..
ISO International Organization for Standardization, which is made up of national members. A member is th..
Isolation Two circuits are isolated when there is no direct electrical connection between them...
Isolation Between Inputs A transient at an input can also propagate to other equipment connected to that input. This is preve..
Isolation to Earth or System A high transient voltage at one input may damage not only the input circuit, but the rest of the dat..
J-Type Thermocouple Iron-constantan thermocouple with a temperature range of 0 to 750 oC...
k A symbol for a thousand, from kilo...
K A unit of stored data. 1K = 1024. Also stands for a degree on the Kelvin temperature scale...
K-Type Thermocouple Chromel-Alumel thermocouple with a temperature range of -200 to 1200 deg C...
LAN Local area network. A data communication system connecting devices in the same vicinity. Data is tra..
LIFO Last in first out. Describes a stack method of data storage...
LIMS Laboratory information management system...
Linearity Ideally an A-D or D-A converter converts the input or output range into equal steps. In practice the..
Mains Source of electrical power, normally the electricity supply system...
Mains Frequency Electricity ac supply frequency; 50 Hz in UK, 60 Hz in US...
MES Manufacturing Execution System...
Metre The SI fundamental unit of length, equal to 1.093 yards. (Meter in US.)..
MIS Manufacturing Information System...
MMI Man Machine Interface. Also known as human machine interface. The communication between the computer..
Modbus An industrial networking system that uses peer-to-peer communications...
Modular Form of construction in which hardware or software units, often with differing functions, are quickl..
Multiplexing Where each signal is switched in turn to a single analogue-to-digital converter. As opposed to where..
N-Type Thermocouple Nicrosil-Nisil thermocouple with a temperature range of -200 to 1200 oC...
Network The physical interconnection of devices sharing a communications protocol...
Node A device with a direct point of access to a network...
Noise Any unwanted electrical signals contaminating the signal to be measured. This noise may be electroni..
Non-Conforming A product outside manufacturing limits but not necessarily defective...
Non-Destructive Testing (NDT) Method of inspecting materials and products without affecting their subsequent properties and perfor..
Nyquist Theorem The Nyquist theorem demands that a signal be sampled at at least twice its maximum frequency. To get..
OEM Original Equipment Manufacturer. A company which makes basic computer hardware for other manufacture..
Offset Error If you get a reading other than zero for a zero condition then you have an offset error: every readi..
Ohm SI unit of resistance, such that one ampere through it produces a potential difference of one voltag..
On-Off Control A simple control system which is either on or off...
Output Information leaving a device...
PC Personal computer. Generally applied to computers conforming to the IBM designed architecture...
PCI Peripheral Component Interconnect A local bus standard developed by in 1992. PCI cards plug into you..
PCMCIA Personal Computer Memory Card International Association Industry group that developed the specificat..
Peer-to-Peer Communication A communication between networked devices in which any device can initiate data transfer...
PI&D Piping and instrumentation diagram...
PID Proportional gain, integral action time and derivative action time. PID software, for example, compa..
PLC Programmable Logic Controller...
Pole A relay contact...
Positive Temperature Coefficient An increase in resistance due to an increase in temperature...
Protocol A set of rules used in data communications...
Pulse A temporary change in voltage of any length...
QA Quality assurance...
Ramp Voltage A steadily rising voltage...
Range The maximum and minimum allowable full-scale signal (input or output)..
Reed Relay Consists of two thin magnetic strips (reeds). When a coil close to the reeds is energised, they are ..
Relay Electromechanical device that opens or closes contacts when a current is passed through a coil...
Repeatability The ability of an instrument to give the same reading under repeated identical conditions...
Resistance Temperature Device (RTD) Resistance temperature devices (or detectors) rely on the principle that the resistance of a metal i..
Resolution A measure of the smallest change that can be detected...
rms Root mean square. The square root of the sum of the squares of a set of quantities divided by the to..
RS232 An EIA (Electronic Industries Association) standard that defines a protocol for serial data communic..
RS485 Another EIA protocol for serial communications. Allows several devices to be connected to a single c..
Sample and Hold A component of a type of analogue-to-digital converter. The analogue signal is frozen in a sample an..
SCADA Acronym for supervisory control and data acquisition, a computer system for gathering and analyzing ..
SCADA Supervisory control and data acquisition - a large scale software package usually used to monitor an..
Scan Normal channel scanning in a data acquisition system involves stepping round and reading each input ..
Seebeck Effect The principle that describes how a thermocouple works. In a circuit in which there are junctions bet..
Self-Calibrating A data acquisition card or module with a stable on-board reference voltage that software can use for..
Sensitivity A measure of the minimum change in an input signal that an instrument can detect...
Sensor A device that can detect a change in a physical quantity (light or pressure for example) and produce..
Serial Communication Where data is transferred one bit at a time...
Set Point Value of a controlled variable, departure from which causes a controller to operate to reduce the er..
Settling Time When a change in signal occurs, the time taken for the input or output channel to settle to its new ..
SI International system of units. Abbreviation for Systeme International (d'Unites)...
Signal General term referring to a conveyor of information...
Signal Conditioning Makes a signal suitable for input to an analogue-to-digital converter. For example, a signal may be ..
Simultaneous Sampling When all analogue signals are read simultaneously. This is achieved by providing each input with its..
Sine Wave Waveform of a single frequency, indefinitely repeated in time. In practice there must be a transient..
Single-Ended Input An analogue input that is measured with respect to a common earth. Single ended inputs are only suit..
Slew Rate The maximum rate of change of an output signal...
Software Trigger A programmed event, such as a specific key press or mouse click, that triggers data capture...
Spike Short pulse of voltage or current - usually undesirable...
Square Wave Wave that alternates between two fixed values. Has very rapid (theoretically zero) rise and fall tim..
Stability The ability of an instrument or sensor to maintain a constant output when a constant input is applie..
Strain When a material is distorted by forces acting on it, it is said to be strained. Strain is the ratio ..
Strain Gauge A sensor that experiences a change in resistance when it is stretched or strained. It is attached to..
Successive Approximation A technique used in A-D converters to measure an analogue signal. It compares the signal with progre..
Surge A large, momentary, increase in the voltage on a power line...
T-Type Thermocouple Copper-constantan thermocouple with a temperature range of -200 to 400 oC..
Talker A device on the GPIB (general purpose interface bus) that sends information to a Listener on the bus..
Thermal Coefficient of Resistance The change in resistance of a semiconductor per unit change in temperature..
Thermal Conductivity A measure of the rate of flow of thermal energy through a material in the presence of a temperature ..
Thermistor A temperature sensor. The name comes from thermal resistor. It is a semiconductor that exhibits a la..
Thermocouple Popular temperature sensor because of its low cost, wide operating range and ruggedness. Consists of..
Throughput Number of results produced per unit time...
Time Stamp Information added to data to indicate the time at which it was collected...
Transducer A device which converts a physical quantity into an electrical signal. Examples include thermocouple..
Transient A short surge of current or voltage, often occurring before steady-state conditions have become esta..
Truncation Rejection of the final digits in a number, thus lessening the precision but not necessarily the accu..
TTL Abbreviation for transistor-transistor logic. Referring to logic circuits consisting of two or more ..
TTL-Compatible For digital input circuits, a logic 1 is obtained for inputs of 2.0 to 5.5 V which can source 40 mic..
Twisted Pair Cable that consists of individual wires wrapped around each other for carrying telephone or computer..
Unipolar A signal range that is always positive or always negative, for example 0 to +10 V..
UPS Uninterruptible Power Supply. Used to keep critical equipment, including computers, running in the e..
USB Universal Serial Bus A serial bus gradually replacing RS232 on PCs because of its higher speed. Gene..
VAC AC Voltage..
Volt SI unit of potential difference such that the potential difference across a conductor is 1 volt when..
Voltage The value of an electromotive force or potential difference expressed in volts...
Voltage-to-Frequency Converter A device that converts an analogue input voltage into a sequence of digital pulses with a frequency ..
WAN Abbreviation for wide area network. A network of circuits spanning a large region which is used to t..
Wheatstone Bridge A network of four resistances, an emf (voltage) source, and an indicator connected such that when th..
Zero Balance With transducers like strain gauges, the output is large compared to the changes caused by the strai..

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