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 international (metric) system of units.
SAWTOOTH SHOCK PULSE (Terminal Peak)
An ideal shock pulse for which the acceleration-time curve has the shape of a triangular wave wherein the acceleration increases linearly to a maximum value and then drops instantaneously to zero.
SEALED (or SEALED GAGE) PRESSURE
Pressure measured with reference to the pressure in a sealed container; the container is usually within the sensor.
Internal heating resulting from electrical energy dissipated within a current-carrying element.
The part of the transducer which reacts directly in response to the measurand.
The ratio of the change in transducer output to a change in the value of the measurand (e.g., mV/g).
A wave in an elastic medium that causes an element to change its shape without a change in volume, a result of shear stresses. Normally a transverse wave.
SHOCK (Mechanical Shock)
The application of a sudden change in force, position, velocity, or acceleration that excites transient disturbances in a system. Change is normally considered sudden if it takes place in a time that is short compared with natural periods of concern.
A form of shock excitation characterized by a rise and decay of acceleration in a relatively short period of time.
SHOCK RESPONSE SPECTRUM
A plot (amplitude vs. frequency) of the response of a number of single-degree-of-freedom systems to an applied shock.
SHOCK SPECTRUM, PRIMARY (INITIAL)
A shock spectrum derived from response measurement within the duration of a simple shock pulse.
SHOCK SPECTRUM, RESIDUAL
A shock spectrum derived from response measurements after a shock has ended.
The change in electrical output caused by placing a fixed resistor between the appropriate transducer terminals. Used “in the field” for quick calibration.
SHUNT CALIBRATION RESISTOR
A shunt resistor which, when placed across a specified element of the electrical circuit of a transducer, will electrically simulate a specified percentage of the transducer full-scale output at room conditions.
SHUNTING RESISTANCE (Transducer Resistance) (Leakage Resistance)
The electrical resistance observed between the two terminals of a piezoelectric transducer or its integral cable.
SIMPLE HARMONIC MOTION
Periodic vibration that is a sinusoidal function of time.
A system requiring but one coordinate to completely define its configuration at any instant.
An input circuit configured such that one of the input lines is electrically and directly connected to signal ground.
The terminal slope of attenuation of the frequency response of a filter, usually expressed at 6 n dB/octave, where n is the order of the filter.
The maximum rate at which the output voltage of an instrument can be made to change understated load conditions.
The total external capacitance shunting the input terminals of an amplifier. Includes transducer and cable capacitance.
The total of all dc resistive leakage paths shunting the input terminals of an amplifier.
The algebraic difference between the limits of the Range.
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.
STANDARD DEVIATION (sigma)
A statistical term: the square root of the variance, i.e., the square root of the mean of the squares of the deviations from the mean value. If the mean is zero, standard deviation is equal to RMS.
The pressure of a fluid, exerted normal to the direction along which the fluid flows.
An ensemble of time-histories such that their statistical properties are invariant with respect to translations in time.
STEADY STATE VIBRATION
Periodic vibration for which the statistical measurement properties (such as the peak, average, RMS and mean values) are constant.
The ratio of change of force (or torque) to the corresponding change in translational (or rotational) displacement of an elastic element. Usually expressed as: k = F/d = W/δ.
A measuring element for converting mechanical strain into an electrical signal.