Thermistor frequency controlled electronic thermometer

Claim 1

A thermistor thermometer, comprising: a capacitance-resistance oscillator circuit comprising a frequency-determining time constant circuit including a thermistor; signal generating circuit means for producing a plurality of signals including a control signal coupled to said capacitance-resistance oscillator circuit for controlling said capacitance-resistance oscillator circuit such as to operate only during repetitively occurring oscillation time intervals, each of said oscillation time intervals being of fixed duration; variable division ratio frequency divider circuit means capable of being present to a plurality of different frequency division ratios, coupled to receive and perform frequency division of an oscillation signal produced by said capacitance-resistance oscillator circuit during each of said oscillation time intervals, for thereby producing a frequency divided output signal; counter circuit means for counting pulses of said output signal from said variable division ratio frequency divider circuit means, and responsive to said counting for producing signals representing address data and temperature data, said address data being changed to a different value each time the number of pulses output from said vfo circuit means increases by a predetermined fixed amount, and said temperature data being cumulatively increased during said oscillation time interval in accordance with a cumulatively increasing count of the number of output pulses from said variable division ratio frequency divider circuit means; division ratio setting means coupled to control the frequency division ratio of said variable division ratio frequency divider circuit, and responsive to said address data for setting said frequency division ratio to a corresponding one of a plurality of frequency division ratios in accordance with the value of said address data; initial value setting means for setting an initial value for said temperature data into said count circuit means prior to each of said oscillation time intervals, in response to a timing signal from said signal generating circuit means; display means comprising latch circuit means coupled to said counter circuit means and responsive to a sampling signal produced by said signal generating circuit means for storing said temperature data from said counter circuit means at the end of each of said oscillation time intervals, decoder driver circuit means coupled to receive said temperature data from said latch circuit means for thereby producing display drive signals, and electro-optical display means for displaying a value of temperature in response to said display drive signals.