| 摘要 |
PROBLEM TO BE SOLVED: To correct the print density of a thermal head automatically. SOLUTION: Data is transmitted from a control circuit 203 to one heater in a thermal head 101 and a driver 202 is activated to conduct the thermal head 101 thus outputting a pulse from a pulse output circuit 205. Voltage between a voltage detection resistor 212 and the heater of the thermal head 101 is amplified by an amplifier 207, subjected to A/D conversion by an A/D conversion circuit 204 and then stored in a nonvolatile memory 206. Resistance of the heater under initial state of the thermal head 101 and resistance of the heater under use are measured and stored in the nonvolatile memory 206. Resistances of all heaters under use are averaged and the output value of an appropriate pulse is set in the pulse output circuit 205. Furthermore, abnormality of heater resistance is detected based on the difference from the initial value thereof.
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