4-62
Axis 3
Axis 2
Axis 1
g
10.000 MHz oscillator’s tipover test
             (f(max) - f(min))/2 = 1.889x10-09 (ccw)
             (f(max) - f(min))/2 = 1.863x10-09 (cw)
               delta q = 106.0 deg.
              (f(max) - f(min))/2 = 6.841x10-10 (ccw)
              (f(max) - f(min))/2 = 6.896x10-10 (cw)
              delta q = 150.0 deg.
               (f(max) - f(min))/2 = 1.882x10-09 (ccw)
               (f(max) - f(min))/2 = 1.859x10-09 (cw)
               delta q = 16.0 deg.
Axis 1
Axis 2
4
-2
-4
2
0
Text Box: 45
45
Text Box: 90
90
Text Box: 135
135
Text Box: 180
180
Text Box: 225
225
Text Box: 270
270
Text Box: 315
315
Text Box: 360
360
2
0
Text Box: 45
45
Text Box: 90
90
Text Box: 135
135
Text Box: 180
180
Text Box: 225
225
Text Box: 270
270
Text Box: 315
315
Text Box: 360
360
2
0
Text Box: 45
45
Text Box: 90
90
Text Box: 135
135
Text Box: 180
180
Text Box: 225
225
Text Box: 270
270
Text Box: 315
315
Text Box: 360
360
4
-2
-4
-2
-4
4
2-g Tipover Test
(Df vs. attitude about three axes)
   When an oscillator is rotated 1800 about a horizontal axis, the scalar product of the gravitational field and the unit vector normal to the initial “top” of the oscillator changes from       -1g to +1g, i.e., by 2g.  A simple “2g tipover” test is sometimes used to test an oscillator’s acceleration sensitivity.  Above is actual data of the fractional frequency shifts of an oscillator when the oscillator was rotated about three mutually perpendicular axes in the earth’s gravitational field.  For each curve, the axis of rotation was horizontal.  The sinusoidal shape of each curve is a consequence of the scalar product being proportional to the cosine of the angle between the acceleration-sensitivity vector (see later) and the acceleration due to gravity.
   The 2g tipover test must not be used indiscriminately because many oscillators exhibit irregular variations of frequency with attitude when tested in small increments of angle rather than with just simple 180o rotations.  Irregularities can be caused by, for example, temperature changes due to air convection in the oscillator, and tiny movements of components, circuit boards and wires.  When the frequency vs. attitude behavior is nonsinusoidal, the results of a simple 2g tipover test can be highly misleading.
--------------------------
   R. L. Filler, "The Acceleration Sensitivity of Quartz Crystal Oscillators:  A Review," IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 35, No. 3, pp. 297-305, May 1988.
   J. R. Vig, C. Audoin, L. S. Cutler, M. M. Driscoll, E. P. EerNisse, R. L. Filler, R. M. Garvey, W. L. Riley, R. C. Smythe, and R. D. Weglein, "Acceleration, Vibration and Shock Effects - IEEE Standards Project P1193," Proc. 1992 IEEE Frequency Control Symposium, 763-781, 1992; also, The Effects of Acceleration on Precision Frequency Sources, U. S. Army Laboratory Command Research and Development Technical Report SLCET-TR-91-3, March 1991, AD-A235470.
   IEEE Standard 1193-1994, “IEEE Guide for Measurement of Environmental Sensitivities of Standard Frequency Generators”.