Piezo-crystal's temperature-dependent stress-less length variation irreversibility determining method, involves determining whether variation is irreversible when determined temperature gradient is less than comparison temperature gradient

摘要

The method involves determining a temperature gradient in a surrounding area of a piezo-crystal (2) related to a preset length of time. A comparison temperature gradient is provided relative to the preset length of time. The determined temperature gradient is compared with the comparison temperature gradient. A determination is made whether temperature-dependent stress-less length variation of the piezo-crystal is irreversible, when the determined temperature gradient is smaller than the comparison temperature gradient. An independent claim is also included for a device for operating a piezo-crystal.