- A quartz-movement relies on a series of electronic pulses.electrical signals image by Albert Lozano from Fotolia.com
The quartz crystal creates a constant set of pulses, typically at a rate of 32,768 oscillations per second (Hz). An electronic circuit monitors this stream of pulses and outputs one pulse for every 32,768 input pulses it receives. This output pulse is now at a frequency of one pulse per second and is the time reference for the watch. The display updates once each second. - A quartz crystal is commonly used to generate a time base.quartz image by Alex from Fotolia.com
A quartz crystal is a small piece of either fabricated or naturally occurring silicon dioxide. This crystal is a specific size and orientation and has well-defined physical properties. Silicon dioxide has a piezoelectric property, meaning that it will oscillate when exposed to an electric voltage. This oscillation is dependent upon the cut of the crystal, but does not vary over temperature. - When connected to a quartz crystal, an oscillator circuit will generate a constant stream of pulses based upon the characteristic frequency of the crystal. For a watch, a crystal of 32.768 kHz is common. A battery powers the oscillator circuit that provides a constant frequency output independent of temperature, voltage fluctuations or movement of the watch.
- A divide-by circuit converts from high to low frequencies.circuit image by veroji from Fotolia.com
The output of the oscillator feeds into a circuit called a counter. This circuit counts the number of input pulses it receives, and issues a single output pulse when it reaches a pre-determined value. For the 32.768 kHz example, a 15-bit counter is used. A 15-bit counter issues one output pulse for every 32,768 input pulses it receives, and therefore outputs one pulse per second. - A quartz movement watch may have a digital or analog displayBlue digital wrist watch image by GenerImageN from Fotolia.com
The time display of a quartz-movement watch may be analog or digital. For an analog display, a small stepper motor will move the second hand 1/60th of the watch's circumference for each pulse. A digital display will update the display's seconds digits by one for each pulse.
