Dynamic Range

The difference between the highest voltage level that will overload the instrument and the lowest level that is detectable. Dynamic range is usually expressed in decibels.

Decibel (dB)

A logarithmic representation of amplitude ratio, defined as 20 times the base ten logarithm of the ratio of the measured amplitude to a reference.

Decay Rate

The rate at which an object stops vibrating after being struck.

Diaphragm coupling (Metallic diaphragm coupling)

A coupling consisting of one or more metallic flexible elements in the form of thin circular plates that are attached to one part of the coupling at their outer diameter and to the other part at their inner diameter.

Disc coupling (Metallic disc coupling)

A coupling consisting of one or more metallic flexible elements that are alternately attached to the two parts of the coupling, the attachment points being substantially at the same distance from the centerline.

Distance between shaft ends (BSE)

The distance from the face of one shaft (including any thread end) to the face of the next shaft. For integral flanges, this measurement shall be from the mating face.

Double-engagement coupling (Double flex coupling)

A coupling with two flexing planes. This type of coupling can accommodate parallel offset, angular misalignment, and axial displacement.

Damping

The absorption or dissipation of oscillatory energy. Damping may be necessary to limit the buildup of transient or steadystate resonant oscillations in a system.

Damping coefficient

The ratio of damping energy during one cycle to the elastic deformation energy.

Damping ratio (Factor of critical damping)

The ratio of the actual damping coefficient (C) to the critical damping coefficient ( Cc). The critical damping coefficient is a measure of the minimum damping that will allow a displaced system to return to its initial position without oscillation.