HEAD CONTROLLING SYSTEM FOR PRINTER

PURPOSE:To omit an adjusting operation at the time of replacing a printing head and enable troubles or failures in the head to be verified on a circuit by passing a minute current to the printing head to detect the resistance of the head, and varying the width of printing pulses according to the resistance detected. CONSTITUTION:A head resistance detecting circuit 2 comprises a transistor 2a and a fixed resistor 2b for passing a minute current to a head 7 at the time of detection, and an A/D converter 2c for converting a voltage drop across the head 7 to a digital quantity, and is controlled by head resistance detecting pulses 10. An output signal 11 from the converter 2c indicates detection data corresponding to the resistance of the head 7, permitting a CPU 3 to process the data. In a ROM 4, data 8a-8z on the width of printing pulses 8 corresponding to the resistance of the head 7 is stored respectively at addresses 4a-4z. Upon receiving the output signal 11, the CPU 3 reads data from a specified address in the ROM 4 so as to obtain the pulse width data according to the signal 11, and varies the printing pulses 8.