# GLOSSARY OF TERMS: Pressure Meas.

May 17, 2006

ABSOLUTE: Absolute pressure is referenced to a full vacuum and will not adjust for changes in barometric pressure; the barometric pressure will affect the output signal.BIDIRECTIONAL: Measurement range is

ABSOLUTE: The value of a pressure with respect to zero pressure.

AMBIENT: The pressure surrounding a device, often equal to the prevailing atmospheric pressure.

BAROMETER: An instrument designed to measure atmospheric pressure.

CALIBRATION POINT: One particular measurement in a sequence of measurements aimed at providing calibration.

CORRECTION: The value added algebraically to the uncorrected result of a measurement to compensate for systematic error. (Note: Since the systematic error cannot be known perfectly, the compensation cannot be complete.)

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

ERROR: Result of a measurement minus the true value of the measurand. (Error is numerically equal to correction but opposite in sign.)

FLUID HEAD: Pressure generated by a fluid column under the influence of gravity.

HYSTERESIS: Property of a measuring instrument whereby its response to a given stimulus depends on the sequence of preceding stimuli.

PASCAL: The SI unit of pressure, abbreviated to Pa.

RESPONSE TIME: Time interval between the instant when a stimulus is subjected to a specified abrupt change and the instant when the response reaches and remains within specified limits around its final steady value.

SNUBBER: A component fitted in a pressure system line to restrict the gas flow, typically to damp oscillations in pressure.

STABILITY: Ability of a measuring instrument to maintain constant its metrological characteristics with time.

TRANSDUCER: Device that provides an output quantity having a determined relationship to the pressure. Commonly used in pressure measurement to refer to pressure transducers with voltage outputs.

TURNDOWN RATIO: The ratio of the maximum and minimum full-scale pressures to which a device may be electronically adjusted. Typically applies to pressure transmitters.

ZERO ERROR: Datum error for zero value of the pressure.

The terms and definitions for this issue’s Word Search come from a glossary compiled by the National Physical Laboratory (www.npl.co.uk), the United Kingdom’s national measurement institute.