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.

 






CALIBRATION

The comparison of transducer voltage outputs against the outputs of a reference standard.

CALIBRATION (As applied to vibration sensors)

An orderly procedure for determining sensitivity as a function of frequency, temperature, amplitude, etc. Yields deviations from correct values used for inferring true magnitudes from indicated magnitudes. Calibration may also refer to adjusting an instrument, lessening deviations from a standard sensitivity.

CASE ISOLATION

The minimum resistance, measured at a specified dc voltage, between the output common of an instrument and the entire metallic enclosure of the instrument.

CENTER OF SEISMIC MASS

The point within an accelerometer where acceleration forces are considered to be summed.

CHARGE AMPLIFIER

An amplifier that presents an output voltage that is proportional to the total electrical charge presented to the input.

COMMON MODE PRESSURE

See LINE PRESSURE.

COMPENSATION

Provision of a supplemental device, circuit, or special materials to counteract known sources of error.

COMPLIANCE

The ratio of change in translational (or rotational) displacement of an elastic element to the corresponding change of force (or torque). Compliance is the reciprocal of stiffness.

COMPLIANCE VOLTAGE

The maximum voltage that a constant current source will go to maintain the selected current.

COMPRESSIONAL WAVE

A wave in an elastic medium causing an element of the medium to change volume, a result of compressive or tensile stresses. It is normally a longitudinal wave.

CONSTANT CURRENT

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.

CREST FACTOR

For an oscillating quantity, the ratio of the peak value to the rms value.

CRITICAL DAMPING

Critical damping (Cc) is the minimum viscous damping that will allow a displaced system to return to its initial position without oscillation or overshoot. Cc=2 √mk

CRITICAL FREQUENCY

A particular resonant frequency (see Resonance) at which damage (or degradation in performance) is likely.

CRITICAL SPEED

A characteristic speed of a rotating system, such that the predominant excitation occurs at resonances of the system.

CROSS TALK

The signal observed in one channel due to a signal in another channel. “Cross talk” is erroneously applied to transverse sensitivity of transducers including shakers.

CUT-OFF FREQUENCY

The frequency above or below the frequency of maximum response of a filter at which the response to a sinusoidal signal is 3 dB below the maximum response.

CYCLE

The complete sequence of values of a periodic quantity that occurs during any one period.