Ultrasonic temperature telemetry system

• US 3,878,502 A
• Filed: 06/26/1973
• Issued: 04/15/1975
• Est. Priority Date: 06/26/1973
• Status: Expired due to Term

• Current Assignee: James M. Rochelle
• Original Assignee: James M. Rochelle
• Inventors: Rochelle, James M.
• Primary Examiner(s): Farley, Richard A.
• Application Number:
  US05/373,712
• Time in Patent Office: 658 Days
• Field of Search: 340/5R,206 73/362AR,339A,362R,362SC
• US Class Current: 367/134
• CPC Class Codes: A01K 61/95 specially adapted for fish
• CPC Class Codes: A61B 5/0008 Temperature signals
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G08C 23/02 using infrasonic, sonic or ultrasonic waves

Abstract

A temperature-sensitive implantable fish tag has been provided which employs a sensing thermistor located at the end of a flexible appendage which varies the repetition rate of an acoustic transmitter in proportion to the measured temperature to provide a pulse interval modulated signal transmission. The transmitter circuit includes a class B stage to function as both the oscillator and an acoustic projector driver. The transmitted signal is easily decoded using a commercially available ultrasonic receiver whose output is demodulated by a 50 msec oneshot having a preset trigger threshold which controls a digital time intervalometer and provides echo pulse rejection. With the transmitter implanted in a freely swimming fish, the behavioral responses of the fish to environment temperature may be studied.

Claims

1. An acoustic temperature telemetering transmitter, comprising:

a sensor for monitoring the temperature to be telemetered, said sensor being located in heat transfer relation with the temperature to be monitored and having a resistance proportional to temperature;

a modulating circuit means for producing fixed period modulating pulses at intervals responsive to the resistance of said sensor, said modulating pulses having a period substantially less than said intervals;

an acoustic projector;

a gateable oscillator circuit connected to said projector and operable at a carrier frequency when gated '"'"''"'"''"'"''"'"'On'"'"''"'"''"'"''"'"' sufficient to project acoustic energy from said projector when gated '"'"''"'"''"'"''"'"'On'"'"''"'"''"'"''"'"'; and

a gating circuit means connected between said modulating circuit and said oscillator for gating said oscillator '"'"''"'"''"'"''"'"'On'"'"''"'"''"'"''"'"' for a fixed period equal to the period of said modulating pulses and '"'"''"'"''"'"''"'"'Off'"'"''"'"''"'"''"'"' for the remaining period of each of said intervals so that said transmitter projects pulses of acoustic energy from said projector at intervals related to said temperature being monitored.

2. An acoustic temperature telemetering transmitter as set forth in claim 1 wherein said gateable oscillator circuit includes a power source, a transformer tank circuit means connected to said projector, an output stage transistor having a base, emitter and collector electrodes, said collector of said output stage being connected in series with a primary winding of said transformer to said power source, said emitter of said output stage transistor being connected to ground potential and said base of said output stage transistor connected to the output of said gating circuit means, and a base resistor connected between said tank circuit and the base of said output stage transistor.

3. An acoustic temperature telemetering transmitter as set forth in claim 2 wherein said tank circuit means further includes a tuning capacitor connected in parallel with a secondary winding of said transformer having one end connected to said power source and the other end connected to said base resistors and wherein said acoustic projector is connected between said power source and an appropriate voltage tap of the secondary winding of said transformer.

4. An acoustic temperature telemetry transmitter as set fOrth in claim 3 for transmitting acoustic signals through a liquid medium wherein said acoustic projector is a piezoelectric acoustic projector.

5. An acoustic temperature telemetering transmitter as set forth in claim 4 wherein said modulating circuit means includes a complementary multivibrator which switches states in response to the resistance of said sensor.

6. An acoustic temperature telemetering transmitter as set forth in claim 5 wherein said sensor is a thermistor.

7. An underwater acoustic temperature telemetering system, comprising:

a transmitter located within a temperature varying medium whose temperature is to be monitored, including a sensor for monitoring the temperature to be telemetered, said sensor being located in heat transfer relation with the temperature to be monitored and having a resistance proportional to temperature, a modulating circuit means for producing fixed period modulating pulses at intervals responsive to the resistance of said sensor, said modulating pulses having a period substantially less than said intervals;

an acoustic projector, a gateable oscillator circuit connected to said projector and operable at a carrier frequency when gated '"'"''"'"''"'"''"'"'On'"'"''"'"''"'"''"'"' sufficient to project acoustic energy from said projector when gated '"'"''"'"''"'"''"'"'On,'"'"''"'"''"'"''"'"' and a gating circuit means connected between said modulating circuit and said oscillator for gating said oscillator '"'"''"'"''"'"''"'"'On'"'"''"'"''"'"''"'"' for a fixed period equal to the period of said modulating pulses and '"'"''"'"''"'"''"'"'Off'"'"''"'"''"'"''"'"' for the remaining period of each of said intervals so that said transmitter projects pulses of acoustic energy from said projector at intervals related to said temperature being monitored; and

a receiver located at a position remote from said temperature varying medium, including a detector means for providing an electrical output in response to the detection of said pulses of acoustic energy from said transmitter, a tuner connected to the output of said detector means and tuned to receive signals at said carrier frequency, a one-shot multivibrator connected to the output of said tuner, said multivibrator having a threshold trigger level set so that said multivibrator triggers corresponding with a selected maximum signal level of each of said pulses of acoustic energy, and a time intervalometer for measuring the time elapsed between each triggering of said multivibrator, said time interval measurement corresponding to the temperature of said medium being monitored.

8. The underwater acoustic temperature telemetering system as set forth in claim 7 wherein said detector means is a hydrophone.

9. The underwater acoustic temperature telemetering system as set forth in claim 8 wherein said time intervalometer is a digital intervalometer and further including a digital recording means connected to said digital intervalometer for recording said time interval measurements.

10. The underwater acoustic temperature telemetering system as set forth in claim 9 wherein said one-shot multivibrator has a preselected switching period less than said timing interval during which said receiver is nonresponsive to acoustic signals, thereby rejecting echo signals following a transmitter pulse.