Omega folder

The following text is a slightly revised transcript of Omega
'Folder 0 - 1510, which seems to be a slightly more in-depth
description of the workings of the Omega Marine Chronometer.

The line drawings are photographs of the originals.

This document was probably part of a press release.

OMEGA Folder 0 -1510

Description and performances

The quartz watch, Megaquartz 2400 is the first watch whose
oscillator is equipped with a high frequency quartz (2.4 million
oscillations per second = 2.4 Mhz).

This ensures great accuracy - less than one second variation per
month. The watch is fitted with a calendar, a pusher for
correcting the second, as well as a rapid hour corrector which
enables it to be adapted to the time zone without loss of
accuracy in minute and second.

1. Description of Quartz crystal

The high frequency (HF) quartz gives better results than other
types of quartz in all respects : shock resistance, low
temperature coefficient, slow aging. Both surfaces of the
lenticular shaped crystal are metalized so as to permit electrical
contact. Vibrations is of the shearing type : the upper part of the
crystal moves in opposite direction to the lower part. Thus,
there is no vibration in the neutral area

and the quartz disk can therefore be fixed securely and with
great shock resistance.

The influence of temperature on performance is shown by a
shallow S shaped graph whose trace crosses the Y axis on or
around the 28 degree Centigrade point. One may conclude that it
is a straight line between + 10 and + 50 degree C. By

judicious cutting of the crystal, the inclination of this straight
line may be altered in order to obtain a thermal coefficient
approaching 0 around 28 deg. C. The watch will be adjusted to
a zero rate at the average temperature of wear (28 deg. C).

Any variation around this temperature will thus incur a slight
loss or gain.

(Indeed, Omega were later forced to issue a press release to
clearly make the point that while the watch will give less than
one second a month rates, to do this it must be worn on the
wrist. Perhaps in display cases and shop windows, < 1 sec /
month rates were embarrassingly not being observed.)

2. Description of electronics

The quartz resonator (1) is maintained at its resonant frequency
(2, 359,296 Hz) by the oscillator driver circuit (2).

The trimmer (3) allows adjustment of the quartz oscillator
within approximate limits of +- 2 secs. per day. This frequency
of approximately 2.4 Mhz is then divided by 6 by the analogue
divider (4) which comprises a transformer (5), namely to
393,216 Hz.

(On the drawing this section has been struck through and the
comment 'not now used' added. One assumes that in production
[1510 / 1516 movements ?] frequency division was done
completely digitally by a revised chip.)

18 logical division stages (6) (17 dividers by 2 and 1 divider
by 3) lower the frequency to 1 Hz. The energy is supplied by the
power cell (10). After setting-up, the control circuit (7) feeds
the motor (8) each second with an impulse lasting 6 ms.

The motor, of the electro-dynamic type, converts

the electrical data into mechanical data for the time

display module (9).

2. Description of movement

The watch consists of 3 modules :

1. The electronic module comprising the quartz

resonator with its trimmer, the integrated circuit,

the transformer, the connecting point with the

motor, the phasing contacts for the second and for

correction of the second.

2. [Sadly this section is missed from the copies in the Science
Museum, but seems to refer to the electro-dynamic motor
module.]

3. The time display module comprising the reduction wheel-
train, the date and the hour corrector.

Electronic Module

This miniature printed circuit (6) forms the support of the
module. It is fixed to the plate by 3 screws (2) one of which
ensures electrical contact on the plate.

The module consists of the following :

- The quartz (3) and the trimmer (4) constituting the time base.

- The transformer (5) serving for a first analogue division.

- The integrated circuit (1) which comprises :

- the quartz driving circuitry EQ

- one analogue division stage DA

- one logical division stage DL

[Also on the electronics module are : ]

- the circuit forming the appropriate impulse for the motor CM

- two capacitors

- the power cell contact blade (8) that connects directly to the
module.

(Sadly three further pages are missing from the copies held at
the Science Museum, but they do have page 8 : )