Acceleration sensitivity of BVA resonators

Acceleration sensitivity of a quartz resonator is usually attributed to the design of the unit. BVA technologies have largely participated to g-sensitivity reduction since 1977. At that time it was claimed that symmetry of the unit structure was fundamental. More recently it has been demonstrated by Tiersten that g-sensitivity could vanish to zero for perfect symmetry (including blank geometry, mounting, etc...). Under those conditions BVA technologies have to be considered in a general discussion on g-sensitivity reduction, because they may help to draw interesting conclusions. In this paper we show that BVA technology is adequate for very low g-sensitivity and why. By very low g-sensitivity we understand largely under 1/spl times/10/sup -10//g in industrial production. Furthermore the influence of some construction parameters and/or lack of symmetry due to manufacturing have been studied through finite element analysis. Results are shown and commented on (orientation of mounting, off centering of contour, off centering of grooves). We then compare these theoretical values to experimental ones. Experimental data are obtained by two methods: measurements under random vibrations and/or sinusoidal vibrations; measurements of frequency deviation in 2g tip over tests. Finally practical design in view of state of the art units is commented on together with production statistics.