Temperature measuring device and thermal head device having the same

Claim 1

A thermal head device comprising: a thermal head including a plurality of thermal elements; a temperature-sensitive element positioned in the vicinity of said thermal head to measure a temperature thereof, said temperature-sensitive element changing its resistance with a temperature variation; a reference resistor having a reference resistance corresponding to an average resistance value of said temperature-sensitive element; switching mans for selecting one of said temperature-sensitive element and said reference resistor; control means for generating a start pulse signal to initiate a measurement of the temperature of said thermal head; pulse generating means, coupled to said switching means and said control means, for separately generating a first one-shot pulse and a second one-shot pulse in response to said start pulse signal supplied from said control means, said first one-shot pulse having a first pulse width indicative of said reference resistance and said second one-shot pulse having a second pulse width dependent on the resistance of said selectively connected temperature-sensitive element; pulse width measuring means, connected to said pulse generating means, for measuring said first pulse width and said second pulse width, said first pulse width being obtained when said switching means selects said reference resistor, and said second pulse width being obtained when said switching means selects said temperature-sensitive element; temperature signal generating means for generating a temperature signal indicative of the temperature of said thermal head from said first and second pulse widths supplied from said pulse width measuring means so that an error contained in said second pulse width is canceled by said first pulse width; and driving means for generating a driving signal to be supplied to said plurality of thermal elements from said temperature signal.