Glossary

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.

 






ABSOLUTE PRESSURE

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).

ACCELERATION

A vector that specifies the time rate of change (derivative) of velocity.

ACCELERATION LIMIT (Environmental)

The maximum acceleration level specified for an instrument to which it can be subjected without physical damage. The maximum vibration or shock acceleration to which an instrument can be subjected without permanent damage.

ACCELERATION OF GRAVITY

Standard, by international agreement, g = 9.80665 m/s2 = 386.088 in/s2 = 32.174 ft/s2. Actual acceleration of gravity varies depending on altitude and latitude of location of measurement. Variation is less than +/- 0.5% in industrialized areas of the world, and less than 0.3% in the 48 contiguous states of the USA.

ACCELEROMETER

A transducer which converts input accelerations into outputs (usually electrical) which are proportional to the input acceleration values.

ACCURACY

The ratio of the error to the full-scale Output or the ratio of the Error to the Output, as specified, expressed in percent. More correctly: “Uncertainty”. Note: Accuracy may be expressed in terms of units of Measurand, or as with +/- percent of Full Scale Output.

ACOUSTIC SENSITIVITY

The output of a transducer, not due to rigid body motions, in response to a specified acoustical environment. Usually expressed as equivalent RMS measurand induced by a specified sound pressure level spectrum having an overall value of 140 dB referred to 0.0002 μbar (20 μPa) RMS.

AMBIENT CONDITIONS

The conditions (pressure, temperature, etc.) of the medium surrounding the case of the instrument.

AMPLITUDE LINEARITY

The closeness of the calibration curve of sensitivity to a straight line over a stated range of measurand amplitudes, at a stated fixed frequency.

ANGULAR FREQUENCY

Angular frequency (also known as circular frequency (omega)) is the torsional vibration frequency in radians per second. Multiply by 2π and express in cycles per second (cps) or hertz (Hz).

ANTIRESONANCE

A condition that exists in a system when with a constant applied excitation where any change in frequency causes an increase in system response.

ATMOSPHERIC PRESSURE

The pressure caused by the weight of the earth’s atmosphere; varies with geographic location, altitude, and weather.