The vibration monitoring industry has specialized jargon that is commonly used when talking about vibration sensors, accelerometers and associated applications. It's important that you understand common terminology to communicate effectively with vibration monitoring, reliability, condition monitoring and process automation professionals. We hope you find our glossary useful to find specialized terms and definitions used across vibration, condition monitoring and predictive maintenance.
The pressure measured relative to a perfect vacuum.
ABSOLUTE PRESSURE TRANSDUCER
A transducer that has an internal reference chamber sealed at or close to 0 psia (full vacuum).
The ratio of the error to the output or to the full scale output, as specified, expressed in percent.
The pressure caused by the weight of the earth’s atmosphere; varies with geographic location, altitude, and weather.
See ATMOSPHERIC PRESSURE.
BEST STRAIGHT LINE
The line parallel to, and centered between, two parallel straight lines enclosing all calibration data points.
A Wheatstone bridge configuration utilizing four resistive elements.
See INPUT IMPEDANCE and OUTPUT IMPEDANCE.
The comparison of transducer voltage outputs against the outputs of a reference standard.
COMMON MODE PRESSURE
See LINE PRESSURE.
Electric current independent of either voltage or resistances and fixed at a specific value. A constant current power supply varies its output voltage, up to its maximum compliance voltage, to maintain the fixed current into the load.
The reduction of response at the resonance frequency through the use of a damping medium such as oil. Usually specified as the ratio to the critical damping.
The volume inside the pressure port of a transducer at room temperature and barometric pressure.
The change in length along the primary axis or the distance a diaphragm moves at the center between no-load and rated-load conditions.
The sensing membrane which is deformed when pressure is applied.
The difference in pressure between two measurement points.
An acronym for ENgineering DEVelopment COmpany. A leader in developing instrumentation for the sensing of physical phenomena.
The voltage or current applied to the input terminals of the transducer.
Sensing element is located on the very tip of the transducer (No pressure port).
The range of frequencies over which the transducer voltage output will follow a sinusoidally varying mechanical input within specified limits.
The maximum measurand that a transducer is designed to measure within its specification.
FULL SCALE OUTPUT
The algebraic difference between the output with zero input and output with full scale input (range) applied.
The pressure above (or below) atmospheric. Represents positive difference between measured pressure and existing atmospheric pressure. Can be converted to absolute by adding actual atmospheric pressure value.
The maximum difference between output readings for the same measurand point, one point obtained while increasing from zero and the other while decreasing from full scale. The points are taken on the same continuous cycle. The deviation is expressed as a percent of full scale.
The pressure in a moving fluid which is exerted parallel to the direction of flow, caused by the inertial effects of the mass of the fluid. Also called DYNAMIC PRESSURE or VELOCITY PRESSURE.
Maximum deviation from the linear regression line (least squares fit) for all measured points, expressed as percent of full scale output.
The resistance measured across the excitation terminals of a transducer at room temperature.
INSULATION (ISOLATION) RESISTANCE
The DC resistance, expressed in ohms, measured between any electrical connector pin or lead wire and the transducer body or case. Normally measured at 50 Vdc.
The maximum deviation of the calibration curve from a specified straight line expressed as a percent of full scale output and only measured on increasing measurand.
The maximum pressure in the pressure vessel or pipe for differential pressure measurement. Also called COMMON MODE PRESSURE.
The physical quantity, property, or condition which is measured. (e.g.: pressure, load, weight, acceleration).
The fluid(s) in contact with the diaphragm, the pressure of which is being measured.
Used interchangeably with “linearity.”
Used interchangeably with “repeatability.”
The electrical signal measured at the output terminals which is produced by an applied input to a transducer.
The resistance as measured on the output terminals of a transducer at standard temperature, with no measurand applied, and with the excitation terminals open-circuited.
The maximum pressure or load which may be applied to the transducer without causing a permanent change in the performance specifications.
The pressure which would be exerted by one constituent of a mixture of gases, if it alone were to occupy the same volume as the mixture. See also TOTAL PRESSURE.
Pressure of one Newton (force) per square meter.
The phase angle between the output and the applied signal.
The height of a liquid column at the base of which a given pressure would be developed due to gravity acting on the fluid mass.
Pounds per square inch.
Pounds per square inch absolute.
Pounds per square inch differential.
Pounds per square inch gage.
The measurand values, over which a transducer is intended to measure, specified by their upper and lower limits.
The total pressure that results at the interface when a shock wave traveling in a medium encounters a discontinuity such as a rigid surface or another shock wave.
The ability of a transducer to reproduce output readings when the same measurand value is applied to it consecutively, under the same conditions, and in the same direction. Repeatability is expressed as the maximum difference between output readings as a percent of full scale.
A measure of ability to delineate, detail, or distinguish between nearly equal values of quantity. Also referred to as “threshold” – lowest level of valid measurement.
The time required for the output of a transducer to increase from zero to some specified percentage of its final value when excited by a step change in measurand.
The time required for the output of a transducer to rise from 10% to 90% of its final value as a result of a step change of measurand.
SEALED (or SEALED GAGE) PRESSURE
Pressure measured with reference to the pressure in a sealed container; the container is usually within the sensor.
The part of the transducer which reacts directly in response to the measurand.
The ratio of change in transducer output to a change in the value of the measurand. Specified sensitivity is usually averaged over the full scale range of the measurand.
The change in electrical output caused by placing a fixed resistor between the appropriate transducer terminals. Used “in the field” for quick calibration.
The international (metric) system of units.
The algebraic difference between the limits of the range from zero to full scale.
The group of error limits within which each device will operate.
The sum of the static pressure and the impact pressure. It can be measured at a point where the velocity of the fluid is zero.
The pressure of a fluid, exerted normal to the direction along which the fluid flows.
A measuring element for converting mechanical strain into an electrical signal.
The range of temperature over which a transducer can operate up to full scale and still meet all specifications. Meggitt’s Endevco pressure transducers incorporate temperature compensation.
The utilization of supplementary devices, materials, or components with the transducer to minimize sources of error caused by changing temperature.
The range of temperature over which a transducer may be safely operated up to full scale without causing failure; but specifications may not be met.
THERMAL SENSITIVITY SHIFT
The change in sensitivity due to a change in ambient temperature. Usually expressed as the maximum percentage change in sensitivity.
THERMAL ZERO SHIFT
The change in zero balance due to a change in ambient temperature. Usually expressed as the maximum percentage change of FSO over the compensated temperature range.
The sum of the pressures (partial pressures) which each gas (in a mixture of gases) would exert were it to occupy the containing vessel alone.
A device (or medium) that converts energy from one form to another. The term is generally applied to devices that take a physical phenomenon (pressure, temperature, humidity, flow, etc.) and convert it to an electrical signal.
Pressure measured below atmospheric pressure and with reference to atmospheric pressure (Negative gage pressure).
See IMPACT PRESSURE.
Used when “setting up” a transducer to adjust the output signal to zero when zero load/pressure is applied.
The output signal of the transducer with rated excitation and with no-load applied, usually expressed in millivolts. Also called ZMO and zero pressure output.
The difference in zero balance measured immediately before rated load application of specified duration and measured after removal of the load, and when the output has stabilized.