**Slew rate** |
The maximum rate at which an instrument’s output can be changed by some stated amount. |

**Standard deviation** |
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. |

**Steady state vibration** |
Periodic vibration for which the statistical measurement properties (such as peak, average, RMS and mean values) are constant. |

**Step Stress Test** |
A test consisting of several stress levels applied sequentially for periods of equal duration to a sample. During each period a stated stress level is
applied and the stress level is increased from one step to the next. |

**Stress screening** |
A modern electronics production tool for precipitating latent defects such as poorly soldered connections. Utilizes random vibration and temperature
shock. |

**Sub harmonic** |
A sinusoidal quantity having a frequency that is an integral sub multiple(X1/2,X1/3) of a fundamental (X1) frequency. |

**Tailoring** |
Selecting or altering test procedures, condition, values, tolerance. etc., to simulate or exaggerate the environmental effects of one or more forcing
functions. |

**Transducer (or pickup or sensor)** |
A device which converts some mechanical quantity into an electrical signal. |

**Transmissibility** |
In steady state vibration, Tr is the non dimensional ratio of response motion/ input motion. two displacements, two velocities or two accelerations.
The maximum Tr value is the mechanical ‘Q’ of a system. At resonance, Tr is maximum. |

**Vibration** |
Mechanical oscillation or motion about a reference point of equilibrium. |

**Vibration machine (or exiter or shaker)** |
One which produces controlled and reproducible mechanical vibration for vibration testing mechanical systems, components, or structures. |

**Vibration meter** |
An apparatus ( usually an electronic amplifier, detector and readout meter) for measuring electrical signals from vibration sensors. May read \
displacement velocity and /or acceleration. |

**Wear-out Failure period** |
That period during which the failure rate of some items is rapidly increasing due to the deterioration processes. |