Metrnomos modern Of the controlled arrival of the AC voltage (AC), one had taken control possible to have clocks, patients electrically and that did not vary a second by every month or more. This made the invention possible of metrnomo electrical Franz (1938). In this metrnomo, a synchronous motor, like the used ones in the electric clocks, moves synchronously a hammer through a mechanical, adjustable reduction from 40 to 208. These electromechanical units were much successful and were produced until 1994. In 1977, metrnomo of pendulum of Franz introduced the first significant improvements in the mechanism ” Maelzel”. The movable pieces were suspended in the box in such a way that they allow them to autonivelar itself when the box was placed in an inclined surface.
A mechanism to avoid accidental blockades was introduced in the model as well as an adjustment to compensate any failure due to the manufacture variations. These devices took place until 1990. From 1950 to the present time numerous versions of metrnomo electronic have been introduced, adapting to the age and fashion of the moment. The first models of electronic metrnomos they were Metronoma” and Stamford. Later Seth Thomas , Sabine and Metone in the United States. Metrnomos were introduced that operate in this general principle like Cadenzia in Switzerland, England Metrotone or Wittner in Germany.
The precision of these models suffers of the difficulty to compensate the non-linearity of this type of circuit in the complete time interval. The obtaining of a good precision is quite difficult to obtain. At the end of 1970 the electronic digital techniques are habian developed until the point that became economically viable to apply them to the design of metrnomo. The precision was improved in a factor of 10 or more in comparison with the best model available analogical. The capacity and low cost of the microprocessors have done possible to add other functions besides beating to the correct tempo. Marked pulses and other functions are possible to a reasonable cost. These instruments have been introduced by the Wittner manufacturers in Germany, Seiko in Japan and Franz in the EE.UU., among others.