| 摘要 |
Piezoelectric video disc recording cutterheads have small and intricate geometries that make it difficult to compute or measure their mechanical characteristics, especially during the recording process. A monitoring circuit, for use during recording, for monitoring and measuring the mechanical characteristics of a recording cutterhead takes the form of a bridge network. The motional charge or motional current, which are related to the mechanical characteristics of the cutterhead, is measured by means of the bridge network. One branch of the bridge is arranged to include the piezoelectric cutterhead, the other branch comprises a variable capacitor which is adjusted to compensate for the shunt capacitance of the equivalent electrical circuit of the cutterhead. When the variable capacitance is properly adjusted the combination of the currents through the bridge network provides a signal representative of the displacement characteristics of the cutterhead.
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