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P Bulova Thermatron

Bulova went into financial despair over the development of this unique and promising system, causing Bulova to market its watch prematurely. The watch reached the market at a stage when it was still too expensive, unreliable and not commercially viable.

1980Presentation of the prototypes of the Thermatron, the first watch in the world which uses the heat of the body to charge a battery in order to let the quartz movement run.
1982The commercial production starts in Bienne, Switzerland. Two slightly different calibers 2467.10 and 2467.20 are introduced and marketed in six differently designed cases.

The physicist Seebeck discovered that the difference in voltage between two metals that are brought into contact with each other, is proportional to the temperature difference between the two metals depending on the kind of metal. Bulova chose the following metals to be combined in a thermic couple: antimon, bismut and tellurium. The small difference in temperature of 1.5 degrees Celsius between the skin or the back of the watch and the isolated upper side of the watch, causes each thermic couple made of these metals to produce a voltage of about 0.25 millivolts. The seven hundred thermic couples brought together in the edges of the 'Thermatron' and arranged in four groups of 175 couples each, produce about 175 mV. This voltage, however, is still insufficient to drive the watch. Therefore, an IC is used to change the direct current to an alternating current using the modified coil of the stepping motor to transform the 100 mV to 1.4 Volts; enough for the stepping motor (Lavet) to run. The radiation of the skin to the watch case is about 50 milli- watts. The efficiency of the thermogenerator is so low that it produces only 10 microwatts.

Nevertheless it is more than sufficient to enable the watch to work, since it only needs 2 microwatts. The CEH in Neuchâtel performed the research for this very ingenious new technique.

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Copyright © by Pieter Doensen

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