An improved mounting apparatus and method for a piezoelectric tuning fork (10) of the type made from a rectangular plate of quartz or similar material, the fork having a stem portion (12) and a pair of tines (14, 16) extending from the stem and defining between them a crotch (18) where they join the stem. The stem is supported on a pedestal (20-36) in such a way that the forwardmost edge (38) of the pedestal is spaced a distance d (in mils) having a magnitude in the range of 2565n/f to 3135n/f, where n is an integer and f is the fundamental frequency of the tuning fork in kilohertz. Improved suppression of overtone components is achieved during operation in the fundamental mode.
The invention relates to a microbeam oscillator. Tuning of the oscillator is carried out by addition or subtraction of material to an oscillator member in order to change the mass of the oscillator member.
A vibratory angular rate sensing system may have one pair of tines forming an angle of about 60 degrees, resulting from the crystalline orientation of the Z-cut quartz wafer of the system. In one configuration each of the tines is provided with a mass offset from the axis of the associated tine, a pivot extends through the plane of symmetry of the tines and may be connected to a dummy reaction mass. The resonant system is suspended from a mounting frame by a pair of suspension bridges. A second embodiment of the invention features two groups of tines, each group including two pairs of tines arranged in the form of a cross. Again, an offset mass is associated with the free end of each tine and each group of tines is secured to its frame by a suspension bridge.
An angular rate sensor system is disclosed, consisting of a balanced resonant sensor. The sensor consists of a tuning fork of a piezoelectric material, preferably of quartz. The tines of the tuning fork are caused to vibrate electromechanically, for example, by impressing an alternating voltage on a pair of electrodes on each tine. This will cause the tines to vibrate. Any component of angular motion around the axis of the sensor causes a cyclic deflection of the tines at right angles to the normal driven vibration of the tines. If the rotational input to the handle of the sensor is applied through a torsion element, the resulting tine deflection is directed to cyclically rotate the entire sensor along the input/output axis. This deflection can be used for changing the capacitance of a capacitance bridge, or for generating an electric signal, due to the piezoelectric effect resulting from the deflection. Finally, the output signal may consist of a frequency-modulated signal or an optical pick-up may be used. The system may take various forms, including one, two, four, or eight tuning forks forming a unitary system.
A rate of rotation sensor is suggested which is structured out of silicon (silicon compounds or silicon/glass compounds) or other semiconductor materials by means of micromechanical techniques. The rate of rotation sensor has the form of a tuning fork whose prongs are situated in planes in parallel to the surface of the semiconductor wafer. These prongs are exited to carry out vibrations in a plane perpendicular to the wafer plane. By means of a sensor element which registers the torsion of the tuning fork suspension, the angular velocity of a rotation of the sensor about an axis in parallel to the tuning fork suspension is measured.
A resonator assembly comprises a rigid support and a rigid crystal which are rigidly connected along linear segments which have one or more matched thermal characteristics. In a particular embodiment, a thermally matched resonator assembly comprises a Z-cut quartz crystal support, a quartz crystal resonator having an active region and including a crystalline structure oriented relative to X-, Y- and Z-crystallographic axes, which X- and Y-crystallographic axes define an X-Y crystallographic plane; and a rigid connector structure for rigidly connecting the resonator to the support along a segment of a line of a plane parallel to or including the X-Y crystallographic plane, which segment extends across a surface of the resonator and is spaced from the center of the active region of the resonator. A method of mounting a crystal which has the aforementioned crystalline structure to a Z-cut quartz support comprises: selecting a chord on a face of the crystal, which chord is a segment of a line of an X-Y plane intersecting the face of the crystal away from the center of an active region of the crystal; and bonding the crystal of the Z-cut quartz support along the length of the chord.