Errors of the Dial Gauge as an Instrument for Measuring Amplitudes of Vibration

Abstract

When used for measuring amplitudes of vibration, the dial gauge was found to have two major errors, one occurring at low frequencies, the other appearing at high frequencies. The low frequency error is caused by the weakness of the hairspring which takes up backlash in the mechanism. When the critical frequency, at which the inertia of the parts overcomes the hairspring torque is exceeded, a constant error equal to the backlash appears in the gauge reading. The high frequency error is produced by jumping of the gauge finger. By suitable installation of the gauge the jumping can be made audible to indicate the approach to the upper limit of accuracy. As the error is small for a safe range beyond this point, the audible indication provides a convenient warning. The high frequency error is postponed by using a stronger gauge spring, and by increasing the initial compression in the spring.