SAMPLED-DATA SERVOS - A NEW ANALYSIS.

When the error signal in a servo loop is of sampled-data form, then at some point before it can be used to drive the plant it has to be converted back to continuous form. The point at which this conversion takes place depends on the type of compensator used. In the case of a compensator designed to work with sampled-data signals e. g. one using digital, charge-coupled device or switched-capacitor techniques, it is done at the compensator output, whereas with compensators designed to work with continuous signals it is done in two stages, a sampled-data stage followed by a continuous-signal stage, in which case conversion is carried out at the interface between the two. A zero-order hold circuit is discussed that performs the reverse sampling by converting a sampled-data signal to a continuous signal.