Frequency perturbations in vibrating quartz crystals, caused by externally applied forces, have been investigated for some time. The parameters affecting the force-frequency sensitivity were recently established and evaluated, making possible the derivation of a normalized coefficient K f . An empirical chart, showing the coefficient K f for all singly rotated crystals, (yxl)θ, is presented for all directions of force in the azimuth angle ψ. The maximum force-frequency coefficient is found to be |K f | ≅ 30 × 10 ⁻¹⁵ (msN ⁻¹ ) for angles θ = +17°, +26.5° and +64°. A crystal cut (yxl) − 18.5° shows a constant coefficient K f = +5.3 × 10 ⁻¹⁵ (msN ⁻¹ ) for all angles of ψ. Coefficients K f (ψ) for BT-, Y- and AT-cut crystals are also shown on separate graphs. The force-frequency behavior of every crystal cut in the singly rotated Y-cut group can be determined from the chart. The chart is a useful tool for the design of frequency standards and precise force-sensing elements. More significantly, the chart provides normalized experimental data to form a basis for a theoretical treatment of the force-frequency effect.

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