The oscillation frequency of the balance wheel as it rotates back and forth to and fro is referred to in vibrations per hours, vph. Each oscillation to and fro is a semi-oscillation. A full oscillation is back and forth once.

So 18,000 vph is equal to 9,000 vibrations to, and 9,000 vibrations fro, or 18,000 full oscillations.

The frequency of oscillations can also be measured in Hz (Hertz), meaning cycles per second.

So 18,000 vph is equal to 9,000 full oscillations and 9,000 divided by 3,600 seconds equals 2.5Hz.

Converting vph to Hz

7,200 vph (semi-oscillations) = 1Hz

18,000 vph (semi-oscillations) = 2.5Hz

19,800 vph (semi-oscillations) = 2.75Hz

21,600 vph (semi-oscillations) = 3Hz

25,200 vph (semi-oscillations) = 3.5HZ

28,800 vph (semi-oscillations) = 4Hz

36,000 vph (semi-oscillations) = 5Hz

43,200 vph (semi-oscillations) = 6Hz

72,000 vph (semi-oscillations) = 10Hz

86,400 vph (semi-oscillations) = 12Hz

108,000 vph (semi-oscillations) = 15Hz