Components of a Quartz Watch

Energy accumulator

Counting, transmission

Distribution

Regulation

Display

Accumulator, Battery, Capacitor

Gear train, Frequency divider circuit

Electro-mechanical Transformer, Stepping motor

Quartz

Dial and hands, Aperture discs, Diodes, Liquid crystals

Analog and Digital Quartz Watches

• Principle design of quartz watches

Identification of Components

1. Battery2. Insulator3. Positive contact4. Negative contact5. Printed circuit6. Integrated circuit7. Quartz8. Trimmer

9. Coil10. Coil protector11. Stator12. Rotor13-15. Train wheel16. Train wheel

bridge17. Setting stem

Oscillation - Vibration Frequency - Isochronism

Frequencies

The higher the frequency of the oscillator the more accurate the timekeeper

Ohm’s Law

The Battery

1. The case – positive pole

2. The cathode – positive electrode

3. The pressure ring

4. The separator

5. The gasket

6. The absorbent material – electrolyte

7. The anode – negative electrode

8. The cover – negative pole

Introduction to Electro-chemical Processes

Volta’s battery

Electro-chemical systems used in watch making

Types of Batteries,Storage and Handling

• Four types commonly used in watches:– Silver oxide (low drain) 1,55 V– Silver oxide (high drain) 1,55 V– Lithium 2 V (Li/CuS)– Lithium 3 V (Li/MnO2)

• Storage:– Store at 20 centigrade or 68 Fahrenheit and max.

50% humidity– Batteries have a limited shelf life (due to self

discharge, which is the result of a change in the internal resistance over time) – avoid storing batteries longer then 12 months

– Manufacturer’s use often a production code – do not use batteries produced more than 6 to 12 ago

– Batteries may leak: check gasket seat before installing into watch

• Handling:– Handle batteries with insulated tweezers to avoid

short circuits. Do not touch with fingers.

Sample Battery Chart

Theoretical Life-time and Testing of Batteries

• Test batteries with a voltmeter (very high internal resistance) preferably installed on the movement

• When applying test resistor follow equipment manufacturer’s recommendations

• Note: There is no efficient way to determine a battery’s remaining capacity. Changing a battery is less costly than a come-back.

The Quartz• The quartz (rock crystal) can be found in

alpine regions and has the chemical formula SiO2 (silicon dioxide)

• They are “grown” synthetically in autoclaves and cut to the proper specifications

• They have three axes, which are set perpendicular to each other:

• The piezo-electric effect was discovered in 1880 by the brothers Curie

• is a quartz crystal mechanically deformed an electrical charge results at given points

• if an electrical charge is applied at certain points the quartz crystal is deformed mechanically.

The Quartz as an Oscillator

• Like any other oscillator (pendulum, balance wheel) quartz oscillators need to be activated

• Quartz has electrical properties which resemble a traditional electrical oscillator consistent of a capacitor and a coil

• Once the quartz is oscillating it maintains a very precise and stable oscillation

• The quartz has a “natural” frequency and if the external oscillator’s frequency is the same the quartz vibrates “in resonance”

The Orientation of the Quartz Cuts

• At which angle the quartz resonator is cut from the raw material determines two critical factors:The frequency of the quartz resonator and their oscillation pattern

X cuts

CD/DT cuts

AT cuts

The temperature/frequency curve

Quartzes used in Watchmaking

• Mainly two “cuts” are being used for application in watchmaking:

• Flexion mode

– in the shape of bars or tuning forks

• Shearing mode

– In the shape of lenses

The Tuning Fork Quartz

• Today the most commonly used quartz resonator in watchmaking

• Very stable frequency due to pre-aging quartzes during manufacturing process

• Temperature does not vary too much in wrist watches

• Good shock resistance (mounting crystal at the base of the tuning fork)

• Good mastery of production process

Determination of the Frequency and the Dividing Chain

• The frequencies are determined by using an exponential factor of the number 2 since binary circuits are used to divide the frequency

The Correction of the Frequency• During the manufacture of quartz resonators

variations occur and not all will oscillate at 32,768 Hz (32 kHz)

• The traditional method is to use a trimmer (an adjustable capacitor) or a fixed capacitor to make corrections to the frequency

• Today more often “Inhibition” systems are being used to correct the output signal of the divider chain (inside the integrated circuit)

The Function of the Integrated Circuit

• The integrated circuit is the “brain” of the quartz watch. It has many different functions:

• maintain the oscillation of the quartz

• divide the frequency

• correct the rate of the watch (inhibition system)

• transmit impulses to the motor

• end of life indicator (battery)

• controlled motor drive (servo control circuit)

The Integrated Circuit • Integrated circuits in watchmaking are usually

manufactured using C-MOS technology (complimentary metal oxide semiconductor)

• They are manufactured on silicon wafers in a step by step photo-lithographical process which requires extreme precision

Inhibition System• The accuracy of the quartz watch depends

largely on the frequency of the quartz• The frequency of quartzes vary due to

manufacturing tolerances • These variations can be corrected outside

the IC by either using a trimmer or fixed capacitor

• Another system is using a special IC which corrects the frequency inside the divider chain

• Watches with inhibition system will always indicate a large gain when the rate is tested using acoustical and capacitive pick-up modes

• This gain is corrected every so often (commonly every 60 seconds) by eliminating a set number of impulses at the 16 kHz level of the divider chain

• These type of watches must be tested by using the motor (inductive) pick-up and preset the integration time (measurement interval) to 60 seconds

The IC of a Digital Quartz Watch

• This type of IC’s may contain additional functions such as:

• Multiplex circuit

• Segment driver circuit for LCD (64Hz)

• Alarm

• Chronograph

Introduction to Electro-magnetism

When an electric current flows through a coil the coil becomes a magnet. By adding

a soft-iron core this effect can be “directed” and increased.

The Motor

• Early on watch manufacturers used various designs of electro-mechanical transformers in quartz wrist watches

• Balance wheel

• Tuning fork

• Micro motor (compact)

The Lavet Motor

• Today most commonly used in quartz analog watches

• Introduced during the second part of the 1970’s due to the availability of small and very powerful magnets (samarium kobalt alloy)

• Principle components:

Evolution of the Lavet Motor

• Early design with open stator

• Current design with closed stator

• Rotor “floats” inside stator opening

The Function of the Lavet Motor

• The motor impulse

• The rotor at rest

• The positive motor impulse

The Function of the Lavet Motor

• The negative motor impulse

• The rotor at rest (after 180 degrees)

• The rotor has completed one revolution (two impulses needed)

The Display

• Train wheel and display of an analog quartz watch

The Electronic Display• Digital quartz watches use a seven digit

display matrix for numbers

• In LED quartz watches each segment is made out of several light emitting diodes (gallium arsenide or gallium phosphate). These displays required a lot of energy and two hands to read the time.

The Liquid Crystal Display• Liquid crystals are organic substances that have

different physical properties depending on the temperature

• Liquid crystals can vary by their molecular structure (smectic, nematic, cholesteric or dichroic). Today mainly nematic substances are used for watches

The Design of the LCD• Design principle

• Side view

1. Upper glass2. Upper polarization filter3. Individual electrodes4. Common electrode5. Frame6. Liquid crystals

7. Lower glass8. Lower polarization filter9. Reflector10. Common electrode contact11. Fill hole / Solder point

1

1

2

2

3

3

4

410

5

5

6 7

7

8

8

9

9

11

Function of a LCD

1

2

7

3

6

54

8 9

1. Reflector2. Polarization filters3. Liquid crystal molecules in normal state4. Incoming light5. No contrast6. Electrical field applied (electrodes not shown)7. Liquid crystal molecules arranged8. Incoming light9. Contrast

Diagnosis of Quartz Analog Watches

1

3

5

4

1. Checking the rate (quartz frequency)

Acoustic or capacitive pick-up (Inhibition system)

2. Checking the rate (magnetic field of motor during impulse)

Inductive pick-up (Inhibition system)

3. Testing the battery

4. Checking the motor impulse

5. Checking the coil resistance

6. Checking the insulation of circuit and coil

7. Checking the consumption

8. Checking the lower working voltage

2

Diagnosis ETA 955.112

Checking the Rate(Acoustic Pick-up)

Checking the rate with case closed

Checking the Rate(Inductive Pick-up)

Testing the Voltage(Battery Installed)

Checking the Motor Impulse(Battery Installed)

Coil Resistance(Battery Removed)

Checking the Average Consumption(Battery removed)

Checking the Base Consumption

(Battery removed)

Controlled Motor Drive

Testing the Controlled Motor Drive

End of Life Indication(Battery removed)

• Certain movements with seconds hand have an indicator to signal the need for a battery replacement

• This function is activated when the battery voltage drops below 1,4 V

• When replacing the battery the movement may continue to operate in the EOL mode for up to one minute

• Pulling out and pushing back in the stem will reset the EOL function

Lower Working Voltage(Battery Removed)

Lower Working Voltage(Battery Removed – Fast Action Mode)

The Thermo-compensation System (ETA 255.511/561)

• In the mid-1980’s the first quartz watches with thermo-compensation systems were introduced in the quest for high-precision watches (deviation of +/- 10sec/year) as alternative to utilizing mega-hertz quartzes.

• The design is based on using a twin-quartz solution where the temperature variance of a standard 32 kHz quartz is electronically stabilized by comparing its accuracy to a 262 kHz quartz and (with the help of a sophisticated electronic circuit) introduce a correction every eight minutes via an inhibition system.

• To make corrections to the regulation a specified procedure needs to be followed and a timing machine with a 480 seconds integration time is required.

Thermo-compensation circuit and Temperature-Frequency Curve

Rate in sec/day

Regular quartz

Thermo-compensated quartz

Temperature-Frequency Coefficients