Condition Monitoring Glossary

Glossary of terms for Condition Monitoring

Accelerometer: An accelerometer is a sensor or transducer where the output is directly proportional to acceleration. They are used to convert mechanical movement into an electrical signal.

Accuracy: Accuracy is an instruments capability of indicating the true value.
Ambient Environment / Ambient Conditions: They are the conditions which characterize the air or other medium which surrounds material.

Auto Ranging: Auto Ranging is an instruments capability of switching among ranges automatically. They are usually in decade steps.

Axial: Axial is in the same direction as the shaft centre line.

Baseline Spectrum: A baseline spectrum is the vibration spectrum which is taken when a machine is in good working condition. It is then used as a reference for future monitoring or analysis.

Compliance: Compliance is the reciprocal of stiffness.

Condition Monitoring: Condition Monitoring is the measurement, recording and analysis of machinery parameters which can determine the machinery’s health. The current machine condition or signature, is compared with earlier condition or fingerprint, usually taken when a machine was new. It can then be used as an indicator when detecting potential failure before it occurs.

Constant Bandwidth Filter: Constant bandwidth filter is a band-pass filter whose bandwidth is independent of centre frequency. The filters are simulated digitally by an FFT process are constant bandwidth.

Damped Natural Frequency: Damped Natural Frequency is the frequency where the damped system will oscillate in a free vibration situation.

Digital Tachometer: A digital tachometer is a panel mounted meter with LED display and is programmable for any engineering rate.

Displacement: Displacement is the change in position or distance of an object relative to a reference. It specifies the change of distance or position and is usually measured from the mean position or position of rest. This usually applies to axial and is less often to angular motion.

Displacement Transducer: A displacement transducer is a transducer whose output is proportional to the distance between it and the measured object (usually the shaft).

Dynamic Range: Dynamic range is the ratio of a specified maximum level of a parameter, such as current, frequency, power and voltage, to the minimum detectable value of that parameter. It is the ratio of the largest to smallest signal level a circuit can handle and is normally expressed in dB.

Electromotive Force: Electromotive Force is force that causes the movement of electricity, such as potential difference of voltage. It is a measure of voltage in an electrical circuit.

Frequency Analyser: A frequency analyser can be used to examine the spectral composition of some acoustic, electrical or optical waveform. It often measures the power spectrum.

Hand-Held Tachometer: A hand-held tachometer is a hand held device which is used to measure rates such as inches per minute, feet per minute or revolutions per minute.

High-Pass Filter: A high pass filter is a filter with a transmission band starting at a lower cut-off frequency and extending to infinite frequency.
Hysteresis: Hysteresis is also called deadband. It is the portion of a measuring system’s response where a change in input doesn’t produce a change in output.

Low-Pass Filter: A low-pass filter is a filter where the transmission band extends from dc to an upper cut-off frequency. It is a filter which passes signals with less than 3 dB attenuation up to its cut-off frequency, and attenuates the signal above that frequency.

Oscillation: Oscillation is the variation with time of a quantity such as acceleration, force, jerk, pressure, stress, velocity. It usually implies some regularity.

Parameter: A parameter is a measured quantity.

Peak: Peak is an extreme value of varying quantity, it is measured from the zero or mean value. It is also a maximum spectral value.

Range: Range is a statement of the upper and lower limits over which an instrument works satisfactorily. It is the region between the limits within which a quantity is measured, transmitted or received. It is expressed by stating the lower and upper range values in engineering units.

Self-Induced Vibration: It is the results from the conversion of non-oscillatory energy into vibration, as wind exciting telephone wires into mechanical vibration.

Sensitivity: Sensitivity is the minimum change in a physical variable which an instrument can respond, it is the ration of the change in output magnitude to the change of the input which causes it after the steady-state has been reached.

Stability: Stability is the ability of an instrument or sensor to maintain a consistent output when a constant input is applied.

Transient Vibration: Transient vibration is temporarily sustained vibration of a mechanical system. It could consist of a forced or free vibration or both.