Impact printer with print hammer firing compensation circuit.

摘要

The circuit (30) detects variations in the nominal velocity of a character band (11) and adjusts the hammer (22) firing times to compensate for the variations. This circuit (30) measures deviations in band velocity that are either faster or slower than a nominal velocity during each character emitter pulse and makes an appropriate correction in the subscan times that gate the hammer firing signals. A bi-directional counter is counted up at a high frequency to a value representing the emitter period including the velocity deviation and then counted down after the error determination at a selected frequency that is a preselected fraction of the high frequency. This technique corrects for each character emitter pulse and incorporates a timing proportionality to assure correct hammer impact.