Patent US 4,125,023

A temperature-measuring apparatus which comprises a first series circuit formed of first and second resistor elements connected between first and second power supply terminals; a second series circuit including a third resistor element connected to the first power supply terminal, a thermosensitive resistor which is connected to the second power supply terminal and whose resistance varies with temperature, a standard resistor having an equal resistance to that which the thermo-sensitive resistor indicates at a referential temperature, and a switching element for connecting the third resistor element selectively to the thermo-sensitive resistor or standard resistor; and analog-digital converter which is impressed with voltage occurring between the junction of the first and second resistor elements and the junction of the third resistor and thermo-sensitive resistor or standard resistor and makes counts corresponding to the measured resistance of the thermo-sensitive resistor and that of the standard resistor; first and second registers for storing counts delivered from the analog-digital converter which corresponds to the measured resistance of the thermo-sensitive resistor and that of the standard resistor; a third register for storing a count corresponding to the referential temperature; a subtractor for subtracting the contents of the second register from those of the first register; and an adder for adding together an output count from the subtractor and a count denoting the contents of the third register.