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GLOSSARY
Acceptance Test: An original test of a new device under carefully controlled conditions and with expert operators,
to determine that the device will comply with the accuracy requirements for Weights and Measures approval to be
used as a resale device.
Accessories (Auxiliary Equipment): Items used with a measuring device to facilitate the collection and use of
information obtained from it (register, pulse output device). Also, items furnished to improve or control meter
performance (strainers, air eliminators, valves)
Accumulative: A term applied to indicating elements or recording elements to describe the fact that they are not
resettable to a zero indication in normal use.
Accuracy: Freedom from error, usually expressed in percentage.
Accuracy Curve: A graph or plotted curve showing the performance characteristics of a measuring device. The
information plotted is the amount of error at the rates of flow between the minimum and maximum rated capacity of
the device.
Adjustor: A ratio changing device which is used to obtain agreement between the indicated and/or recorded volume
and the actual volume measured. The ratio may be either continuously variable or variable in increments.
Air Eliminator (also Air Release or Vapor Eliminator): A device installed upstream of the measuring device to
avoid measuring air or vapor. Air or vapor measured with liquid will result in registering a volume larger than the
liquid volume.
Air Separator: A device of the air eliminator type designed to include the capability of separating air or vapor
intimately mixed with the liquid. It may include one or more air eliminator mechanisms and usually incorporates a
greater volume or other means for achieving separation.
Air (Vapor) Control System: An arrangement of various elements intended to assist the air eliminator – or air
separator – by stopping or reducing flow of liquid when air or vapor is detected. These devices may have various
trade names.
Ambient Temperature: Literally, this is the temperature of the surroundings. It is usually used to denote the
temperature of the atmosphere in a given location at a specific time.
Analog Device: A device in which the indicated quantity is a constantly changing amount, which indicates directly
the amount being measured. An example is the pointer on a clock or a continuous motion type indicator. In reading
this for the delivered quantity, it may be necessary to estimate the fractional units.
Back Pressure Valve: A device intended to maintain a desired minimum upstream pressure.
Bubble Point: The conditions of temperature and pressure under which a liquid will begin to form vapor.
Calibration: The procedure of setting or bringing a meter or a prover into agreement with an established standard.
Check Valve (Non-return Valve): A device designed to prevent a reversal of flow of liquid.
Clingage: The liquid film that adheres to the inside surface of a container after it has been emptied.
Coefficient of Expansion: A number usually expressed as a decimal that indicates the change of volume per unit of
volume per degree of temperature change.
Counter (Register): A device which indicates a quantity related to the volume measured by the meter.
