| Ŵ (%) | = | 61% |
Central uniformity
In some cases it is convenient to define a the central uniformity. In this case, the reference amplitude (in the denominator of equation 1) is the amplitude at the center of the chosen face, regardless if this is the largest average amplitude:
| 2) Ŵcentral (%) | = | Ūmin or Ūmax | 100 | ||
| Ūcentral |
Note that the stud centerline amplitude is not necessarily used for the numerator.
This definition is normally used only when all of the surface amplitudes are either larger or smaller than the centerline amplitude. If all of the amplitudes are larger than the centerline amplitude, then the uniformity will be greater than 1.0 and the surface is said to have amplitude rise. Conversely, if all of the amplitudes are smaller than the centerline amplitude, then the uniformity will be less than 1.0 and the surface is said to have amplitude droop.
This definition is especially useful for plotting graphs of uniformity versus another parameter (e.g., an altered horn dimension). See zzz for an example of this type of graph.
Contact uniformity
Some applications are welded only along in certain areas of the horn face (i.e., where the horn contacts the plastic part). Then the overall face uniformity is not important; only the uniformity over the contact area matters.
Peripheral uniformity
For a horn that contacts only around the periphery of the face, the peripheral uniformity is —
| 3) Ŵperiphery (%) | = | Ūmin (periphery) | 100 | ||
| Ūmax (periphery) |