A/D: Analog-to digital conversion.

Aberration: An optical phenomenon resulting from the failure of a lens or mirror to produce a good image.

Absolute Pressure: Actual pressure on a confined gas, irrespective of the atmosphere on the outside.

Absolute Temperature: The temperature measured from absolute zero as in the Kelvin and Rankine scales.

Absolute Zero: The lowest temperature theoretically attainable (at which the kinetic energy of atoms and molecules is minimal).

Absorption: (1) Loss of energy traveling through a medium. (2) Internal taking up of one material by another. (3) Transformation of radiant energy into other forms of energy when passing through a material substance.

Acceleration: Rate of change of velocity.

Accommodation: Changes in focus of the crystalline lens to adjust the eye of various object distances.

Accuracy: (1) The closeness of agreement between a test result and the accepted reference value (ISO 5725-1). (2) Closeness of agreement between the result of measurement and a true value of the measurand. Accuracy is a qualitative concept (VIM:1993)

Adjustment (of a measuring instrument): The operation of bringing a measuring instrument into a state of performance suitable for its use.

Adsorption: Adhesion of one substance to the surface of another.

Alpha: The current amplification factor when connected in a common base configuration.

Alternating Current (AC): Current which reverses polarity at a uniform frequency.

Altimeter: An instrument that measures the height above ground.

Ambient Temperature: Temperature of the air in the immediate vicinity.

Ammeter: A meter that measures the flow of electrical current in amperes.

Amperes: The basic unit of electric current adopted under the Systeme International d’Unites.

Amplification: The process by which ionization effects are magnified to a degree suitable for their measurement.

Apparent Power: The power value obtained in an alternating current circuit by multiplying the effective values of voltage and current. The result is expressed in volt-amperes, and must be multiplied by the power factor to secure the average or true power in watts.

Arc: A portion of the circumference of a circle.

Atmospheric Pressure: The force exerted on a unit area by the weight of the atmosphere.

Auditee: The organization being audited

Backlash: A form of mechanical hysterysis (lag) in which there is a lag between the application of a driving force and the response of the driven object.

Barometer: An instrument that measures atmospheric pressure.

Baud Rate: A unit of measure for data transmission speed. It represents the number of signal elements transmitted per second.

Best Fit Straight Line: The equation of a straight line, calculated from a set of measurement results, which attempts to minimize the differences between the line and the measurement results. There is more than one statistical method used, each of which may place the straight li

Beta: The current amplification factor of a transistor when connected in a common-emitter configuration.

B H Curve: A characteristic curve showing the relation between magnetic induction (B) and magnetizing force (H) for a magnetic material. It shows the manner in which the permeability of a material varies with flux density.

Bifilar Winding: A method of winding transformers in which the wires are placed side by side and wound together.

Bimetallic Element: Two strips of dissimilar metal bonded together so that a change in temperature will be reflected in the bending of the element, as a result of differential expansion.

Bleed Valve: A small valve to bleed off small amounts of water from container vessel or bath.

Blowdown: Removal of liquids or solids from a process/storage vessel or a line by the use of pressure.

British Thermal Unit (BTU): A unit of heat equal to the amount of heat required to raise one pound of water one degree Fahrenheit at one atmosphere pressure.

Buffer:  A solution that maintains a set pH value regardless of added acids or bases.

Buoyancy: The power to float or rise in a fluid.

Buoyant Force: The upward force which any fluid exerts on a body placed in it.

Byte: Eight related bits of information processed as a unit. Eight bits equals one byte.

Calibrate: Check or adjust the graduations of a quantitative measuring instrument.

Calibration Point: One particular measurement in a sequence of measurements aimed at providing calibration.

Calibration: A set of operations that establish, under specified conditions, the relationship between the values of quantities indicated by measuring instrument or measuring system and the corresponding values realized by standards.

Capillarity: The characteristic of a liquid to be raised or depressed in a tube of small bore. This action is caused by a combination of cohesive, adhesive, and surface tension forces.

Cavitation: Process in which small bubbles are formed and implode violently. This results in aggressive cleaning action in ultrasonic cleaners.

Celsius Temperature Scale: A temperature scale based on mercury in glass thermometer with the freezing point of water defined at 0 degree C and the boiling point of water defined at 100 degree C, both under conditions of normal atmospheric pressure.

Center of Instrument: The intersect point of the vertical, horizontal, and optical axis of a transit or similar instrument when perfectly calibrated.

Centripetal Force: The inward force on a body moving in a curved path around another body.

Certified Reference Material (CRM): Reference material, by a certificate, one or more of whose property values are certified by a procedure which establishes its traceability to an accurate realization of the unit in which the property values are expressed, and for which each certified valu

Certify: Provide evidence for or authorize officially.

CGS System: The common metric system of units (centimeter-gram-second).

Characteristic: A property that helps to differentiate between items of a given population.  Note: The differentiation may be either quantitative (by variables) or qualitative (by attributes).

Clinometer: An instrument used by surveyors in order to measure an angle of inclination or elevation.

Coefficient of Linear Expansion: The change in unit length in a solid when its temperature is changed 1 degree.

Coefficient of Volume Expansion: The change in unit volume of a solid when its temperature is changed 1 degree.

Cohesion: The intermolecular force that holds together the molecules in a solid or liquid.

Collimation: The process of aligning the optical axis of optical systems to the reference mechanical axes or surfaces of an instrument, or the adjustment of two or more optical axes with respect to each other.

Collimator: An instrument designed to produce collimated (parallel) rays of light usually equipped with displacement and tilt graticules.

Comparator: An instrument for comparing some measurement with a fixed standard.

Complex Vibration: The combination of two or more sinusoidal vibrations existing simultaneously.

Compound: Two or more substances combined in definite proportions by weight and united chemically.

Condensate: Steam which rises and cools to a liquid.

Conductivity: The transmission of heat or electricity or sound.

Conformity: Fulfillment of specified requirements.

Contacts: Elements used to mechanically make or break an electric circuit.

Continuous Duty: A device able to operate continuously with no off or rest period.

Contract Review: Systematic activities carried out by the supplier before signing the contract to ensure that requirements for quality are adequately defined, free from ambiguity, documented, and can be realized by the supplier.

Contractor: Supplier in a contractual situation

Convection: Transmission of energy or mass in a medium by movement of the medium itself.

Conversion Chart: Must be used to convert a parts per million reading to micromho or vice versa because the ppm scales are non linear and the micromho scales are linear. Because of the curve, there is no set ratio so one must refer to the chart.

Correction: The value added algebraically to the uncorrected result of a measurement to compensate for systematic error.

Corrective Action: Action taken to eliminate the causes of an existing nonconformity defect or other undesirable situation in order to prevent recurrence.

Creep: The long term change in dimensional characteristics of a body under load, in an elastic force measurement device. This term refers to the change in reading which occurs when a constant load is applied for a period of time.

Critical Angle: The angle between and at which there is neither refraction or internal reflection.

Critical Size: For fissionable material, the minimum amount of a material which will support a chain reaction.

Cryogenic: The science of refrigeration pertaining to the methods for producing and measuring very low temperatures.

Damping: (1) The prevention of free swinging or vibration by some means, usually friction or resistance. (2) The dissipation of energy with motion or time.

Decay Time: The time required for the trailing edge of a pulse to decrease from 90 percent to 10 percent of its maximum amplitude.

Defect: Nonfulfillment of an intended usage requirement of reasonable expectation, including one concerned with safety.

Degree of Documentation: Extent to which evidence is produced to provide confidence that specified requirements are fulfilled.

Deionization: Removal of ionized minerals and salts from a solution by a two phase ion exchange procedure.

Demineralization: Removal of mineral constituents from water.

Density: The mass per unit volume. CGS unit: gm/cm

DI Water: Deionized water.

Dial Indicator: This is a mechanical lever system used for amplifying small displacements and measuring it be means of a pointer which transverses a graduated dial.

Dialysate Meter: Verifies the total concentration of ionized salts in dialysate solutions used in hemodialysis or kidney equipment.

Differential Voltmeter: A voltmeter that operates on the potentiometric principle. The unknown voltage is compared to an adjustable calibrated voltage developed within the differential voltmeter.

Differentiating Circuit: A circuit in which the output voltage is proportional to the rate of change of the input voltage.

Diffraction: When light passes sharp edges or goes through narrow slits the rays are deflected and produce fringes of light and dark bands.

Digital Voltmeter: An electronic voltmeter that gives readings in digits.

Diopter: A unit of measurement of the refractive power of a lens which is equal to the reciprocal of the focal length measured in meters.

Direct Current (DC): A current with a constant polarity.

Disposition of Nonconformity: Action to be taken to deal with an existing nonconforming entity in order to resolve the nonconformity.

Distortion: Any deviation from the desired waveform.

Double Pole Double Throw (DPDT): A term used to describe a switch or relay output contact form. Two separate switches that operate simultaneously each with a normally open and normally closed contact and a common connector.

Drift: Slow change of a metrological characteristic of a measuring instrument.

Dyne: The unit of force which, when acting upon a mass of 1 gm, will produce an acceleration of 1 cm/sec/sec.