PURPOSE: To effectively lower the resistance value of a heat generating resistor, by mounting a pulse generation circuit for applying a voltage pulse having a peak value equal to or more than a predetermined value to the heat generating resistor of a thermal head and a resistance meter for measuring the resistance value of the above mentioned heat generating resistor.
CONSTITUTION: The initial setting of a peak value Vs and the number (n) of pulses is performed by a calculation part 12 and a voltage pulse is applied to a heat generating resistor, of which the resistance value is larger than an objective value R0, from a pulse generation circuit 10. Next, a switch 9 is changed over to measure the resistance value of the above mentioned heat generating resistor by a resistance meter 11. This measured value is evaluated by the calculation part 12 and, when said value is larger than R0 and lower than the preceding measured value, in order to further lower the resistance value of the heat generating resistor to set the same to R0 or less, the peak value Vs is set so as to be made high by ΔV. The pulse generation circuit 10 output a high peak value corresponding to said setting. Therefore, the resistance value of the heat generating resistor is effectively lowered so as to be set to the objective value R0 or less and irregularity can be reduced.
YAMASHITA HIROMI
ENDO TAKAFUMI
KATAYAMA KOHEI
MURATA YUKIO
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