Apparatus and method for remotely measuring temperature

Apparatus for receiving constant frequency variable duty cycle temperature information from a transmitter arranged to transmit energy burst signals relative to the temperature of a remote body;

• comprising:
• means for detecting burst of energy,
• signal forming means for producing a replica signal having a characteristic with a first magnitude during alternate intervals between said received burst of energy and a second magnitude during remaining intervals between said recceived bursts of energy,
• a clock pulse generator for generating pulses at a constant frequency of said replica signal,
• a first counter,
• means for applying said clock pulses to said first counter only when said replica signal characteristic has said first magnitude and
• means for periodically resetting said first counter, the resetting period being substantially greater than the period of said replica signal whereby the count in said first counter immediately prior to its resetting is proportional to the temperature of said remote body.

Apparatus for remotely measuring temperature comprising

• a transmitter including
• a reference signal source having an output,
• a periodic signal generator having an output,
• a testing circuit having inputs respectively connected to said periodic signal generator output and said reference signal source output, and an output at which there is produced a signal having a characteristic with a first magnitude when the voltage at said periodic signal generator output is greater than the voltage at the output of said reference signal source and a second magnitude when the voltage at said periodic signal generator output is less than the voltage at the output of said reference signal source,
• a temperature sensitive electrical element in thermal connection with a remote body of which temperature is to be measured and connected in circuit with one of said periodic signal generator and reference signal source, said element having a characteristic the magnitude of which varies as a function of its temperature, the voltage at the output of said periodic signal generator or said reference signal source being a function of said characteristic, and
• means connected to said testing circuit output and responsive to said testing circuit output signal for radiating a burst of electromagnetic energy following each transition of said testing circuit output signal characteristic between said first and second magnitude, and
• a receiver including
• means for detecting said bursts of energy,
• signal forming means for producing a replica signal having a characteristic with a first magnitude during alternate intervals between said received burst of energy and a second magnitude during remaining intervals between said received bursts of energy,
• a clock pulse generator for generating pulses at a constant frequency substantially greater than the frequency of said replica signal,
• a first counter,
• means for applying said clock pulses to said first counter only when said replica signal characteristic has said first magnitude, and
• means for periodically resetting said first counter, the resetting period being substantially greater than the period of said replica signal whereby the count in said counter immediately prior to its resetting is proportional to the temperature of said remote body.

A method for remotely measuring temperature comprising steps of applying a temperature sensitive circuit element in close thermal communication with the environment of which temperature is to be measured,

• connecting said temperature sensitive element to a source of reference voltage for varying the reference voltage as a function of sensed temperature;
• comparing the magnitude of said reference voltage with the amplitude of an alternating constant frequency signal,
• transmitting bursts of energy each time the amplitude of said alternating signal exceeds the magnitude of said reference signal,
• receiving said burst of energy, constructing a waveform having a duty cycle corresponding to said received bursts of energy, and
• counting constant high frequency signals over a predetermined period of time only during the "on time" of said duty cycle, said count being proportional to the temperature measure, and further comprising transmitting said bursts of energy as a predetermined number of high-frequency pulses,
• counting the number of pulses in each received burst of energy, and
• enabling the counting of said high-frequency signals only when the number of pulses in the received bursts corresponds to said predetermined number of pulses in said transmitted bursts.