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Introducing the Piaget – Emperador Coussin XL 700P

Quartz rebooted!

As if the weight of the 1970s crisis has been lifted off their shoulders, Swiss watchmakers are suddenly unleashing their imagination on quartz movements. The most recent example is Piaget’s Emperador Coussin XL 700P with a generator-regulated mechanical movement.

Quartz movements were invented in 1967 at the Centre Electronique Horloger in Neuchâtel and first sold by Japanese company Seiko in 1969. The movements use quartz’s electro-physical properties to split time. By applying pressure to a thin quartz strip, its atomic structure (organised into geometric crystals) is distorted and begins to vibrate on a regular basis – over 32,000 times a second. When you add a battery-powered circuit to maintain the vibrations, it also sends electrical impulses to power the seconds hand.


Piaget has taken things further: there’s no battery to power the system. The brand’s 700P calibre is based on a classic mechanical movement: a barrel, wound by an off-centre mini-rotor, fuels a perfectly conventional wheel train. The designers did replace the traditional balance spring with a miniature generator to control the constant force. As the generator turns, it creates an electrical current to power a quartz. But that isn’t what brings the hands to life: it acts as a counter and comparator to control the generator’s rotation speed. This is what performs as a balance wheel as it spins at exactly 5.33 rotations/second (almost 4Hz): the rotor is therefore in direct contact with the wheel and turns often enough to display the time. If it happened to speed up, the quartz resonator would warn a processor which would activate a brake system.

“It’s a very reliable system”, says Eric Klein, Movement Strategy Director at Piaget. “It isn’t affected by magnetic fields and is highly shock-resistant. On top of that, its chronometer performance is at 1 second per day”. Updated to celebrate the 40th anniversary of Piaget’s first quartz movement, the famous ultra-thin 7P unveiled in 1976, the limited edition (188 available) Emperador Coussin XL 700P is the fruit of two years of R&D and a dozen patents.

The idea behind this sort of hybrid engine is nothing new. As Eric Klein himself says, it is based on an original concept by Jean-Claude Berney that was patented in 1972. The engineer was employed by Ebauches SA at the time and was trying to get rid of batteries as they were cumbersome and had a limited life span. However, he never managed to make his invention reliable.

Price: 70,000 CHF (118 available) piaget.com

By Fabrice Eschmann

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