A/h or ALTERATIONS (or ALTERNANCE) PER HOUR

In a watch movement with a balance wheel, one vibration is a single swing of the balance wheel. A vibration is one-half of an oscillation or a semi-oscillation. So, one swing of the balance wheel in either direction, for example clockwise, is one vibration or semi-oscillation, and two swings, for example clockwise then counter-clockwise, is an oscillation. The frequency of a watch movement can be expressed in Hertz (Hz) or in vibrations per hour (vph), which is also sometimes referred to as A/h. The frequency in Hertz is the number of oscillations per second.

Double the hertz figure to get the number of vibrations or semi-oscillations per second. Multiply that number by 360 (the number of seconds in an hour) to get the vph. The most common frequency for modern mechanical wristwatch movements is 4 Hz, or 28,800 vph. A watch ticking at 4Hz makes 4 oscillations per second or 8 semi-oscillations (or vibrations) per second. There are 60 seconds in a minute, so this watch would tick at 480 semi-oscillations (or vibrations) per minute.

Multiplying the 480 vibrations per minute by the 60 minutes in an hour yields the 28,800 vph figure. Since this watch ticks 8 times per second, a chronograph in a 28,800 vph watch can time events to the nearest 1/8 of a second. Following this formula, a watch with a rate of 2.5 Hz or 18,000 vph can time events to the nearest 1/5 of a second. A rate of 3 Hz or 21,600 vph yields an accuracy of 1/6 of a second. A watch with a rate of 36,000 vph or 5 Hz can time to the nearest 1/10 of a second.

Clock & Watch Encyclopedia

A

A/h or ALTERATIONS (or ALTERNANCE) PER HOUR
AMPLITUDE
ANA-DIGI
ANALOG
ANCHOR ESCAPEMENT
ANGLAGE
ANNUAL CALENDAR
ANTIMAGNETIC
APPLIED INDICES
AUTOMATIC MOVEMENT

B

BALANCE
BREGUET OVERCOIL HAIRSPRING

C

CALENDER
CALIBER
CHAPTER RING
CHARGE INDICATOR
CHRONOGRAPH
CHRONOMETER
COLUMN WHEEL
COMPLICATION
COSC (OR C.O.S.C.)
CROWN
CRYSTAL

D

DIAL
DIGITAL
DISPLAY

E

EIGHT-DAY MOVEMENT
ELECTRONIC
EQUATION OF TIME
ESCAPEMENT

F

FINE ADJUSTMENT
FLYBACK CHRONOGRAPH
FREQUENCY
FUNCTION

G

GENEVA SEAL
GENEVA WAVES
GMT
GRANDE COMPLICATION
GUILLOCHE

H

HACK, HACKING SECONDS
HAIRSPRING
HALLMARK
HAND-WOUND MOVEMENT
HOROLOGY

I

INCABLOC
INDEX

J

JEWELS

K

KARAT

L

LEVER ESCAPEMENT
LIGNE
LIMITED-EDITION WATCH

M

MAINSPRING
MANUAL-WIND MOVEMENT
MANUFACTURE
MECHANICAL WATCH
MICRO-ROTOR
MINUTE REPEATER
MOON-PHASE DISPLAY
MOTION WORK
MOVEMENT

O

OSCILLATION

P

PALLET
PERLAGE
PERPETUAL CALENDAR
PERPETUAL DAY/DATE
PLATE
POWER RESERVE
POWER-RESERVE INDICATOR

Q

QUARTZ WATCH

R

RADIO-CONTROLLED
RATTRAPANTE
REGULATION
REPEATER
RETROGRADE DISPLAY
ROTATING BEZEL
ROTOR

S

SCALE
SCREW-DOWN CROWN
SELF-COMPENSATING HAIRSPRING
SHOCK ABSORPTION
SKELETONIZED MOVEMENT
STOP-SECONDS FUNCTION
SUBSIDIARY DIAL
SWISS MADE

T

TANTALUM
TITANIUM
TACHYMETER
TOURBILLON
TRIPLE DATE
TRITIUM

V

VIBRATION or VPH

W

WATER-RESISTANT
WHEEL TRAIN
WORLD TIME WATCH