| 摘要 |
<p>479,637. Piezo - electric crystals. STANDARD TELEPHONES & CABLES, Ltd. Feb. 12, 1937, No. 4298. Convention date, May 1, 1936. Drawings to Specifleation. [Class 40 (v)] A piezo-electric crystal has its temperature coefficient of frequency adjusted by thinning at the edges so as to vary slightly the angle # between the major surface and the Z-axis. This has little effect on frequency which may, however, be adjusted by concaving the surfaces or by thinning the crystal as a whole. The angle # is selected within a range +36À5‹ to +39‹ or - 51‹ to - 53‹ according to the working temperature of the crystal, Figs. 12, 13 (not shown). The thickness is then selected to give the required frequency. One electrode is preferably convex, making contact with the crystal at a node, and the other electrode is preferably spaced 0À002" from the crystal to prevent arcing. The crystal preferably vibrates in a face shear mode. Specification 471,465 is referred to.</p> |
