TEMPERATURE TRANSDUCER AND TELEMETRY SYSTEM

• US 3,582,921 A
• Filed: 08/06/1968
• Issued: 06/01/1971
• Est. Priority Date: 08/06/1968
• Status: Expired due to Term

• Current Assignee: Charles R. Krieger
• Original Assignee: Charles R. Krieger
• Inventors: Krieger, Charles R.
• Application Number:
  US04/750,541
• Time in Patent Office: 1,029 Days
• US Class Current: 340/870.09
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G01K 2207/06 for preparation purposes
• CPC Class Codes: G01K 7/22 the element being a non-linear resistance, e.g. thermistor G01K7/26 takes precedence
• CPC Class Codes: G08C 15/04 the signals being modulated on carrier frequencies

Abstract

A temperature transducer having a small battery powered oscillator circuit packaged in a portable housing with a relatively slender probe projecting from the housing for insertion into food products or the like. A temperature responsive element is mounted at the tip of the probe and is coupled to a modulation switching circuit inside the housing for periodically activating the oscillator for a time duration which is proportional to the temperature of the temperature responsive element. A plurality of such transducers are used in the telemetry system, each having a different frequency of oscillation, and each being inserted into a food product to be processed, e.g. into a ham to be smoke. The output signal of the individual transducers are picked up by a multichannel receiver outside the smokehouse, and the time duration modulation signals are translated into analog signal levels by a digital-to-analog converter. These analog signal levers are analyzed in an output circuit to produce output signals for controlling various functions, such as, the temperature of the smokehouse, the sounding of an alarm if any of the hams exceed a predetermined inner temperature, and the indicating of the inner temperature of any given ham without opening the smokehouse or interrupting the smoking process.

Claims

1. A temperature transducer comprising a housing member, a relatively slender probe attached to said housing member and projecting therefrom, a temperature responsive element attached to said probe, an oscillator circuit within said housing member for generating and transmitting a uniform carrier wave, a battery within said housing member for activating said oscillator circuit, and a modulator circuit coupled between said temperature-responsive element of said oscillator circuit for controlling the output signal thereof in accordance with the temperature of said temperature-responsive element, said modulator circuit comprising a modulator switching circuit for periodically activating said oscillator circuit to transmit a uniform carrier wave for a time period which is proportional to the temperature of said temperature-responsive element.

2. A temperature transducer as defined in claim 1 wherein said modulator switching circuit comprises a multivibrator circuit coupled to said oscillator circuit for periodically activating the oscillator during one of the two multivibrator states and for periodically deactivating the oscillator during the other of the two multivibrator states, said temperature-responsive element being coupled to said multivibrator circuit for controlling the time duration of at least one of the two multivibrator states in accordance with the temperature of said temperature-responsive element.

3. A temperature transducer as defined in claim 2 and further comprising an electrical connector attached to said housing member for receiving electrical power input to recharge said battery, and switch means attached to said housing member for automatically deactivating said oscillator and multivibrator circuit when said battery is being recharged.

4. A temPerature transducer as defined in claim 1 and further comprising an electrical connector attached to said housing member for receiving electrical power input to recharge said battery, and switch means attached to said housing member for automatically deactivating said oscillator and modulator switching circuit when said battery is being recharged.

5. A temperature telemetry system comprising a plurality of temperature transducers each including a temperature-responsive element, an oscillator circuit for generating and transmitting a uniform carrier wave, a battery for activating said oscillator circuit, and a modulation switching circuit coupled between said temperature responsive element and said oscillator circuit for periodically activating the oscillator circuit to transmit a uniform carrier wave for a time period which is proportional to the temperature of said temperature-responsive element;

a receiver circuit for receiving the output signals of said oscillator circuits; and

an output circuit coupled to the output of said receiver circuit for producing signals relating to the temperatures of the temperature-responsive elements in said plurality of temperature transducers.

6. A temperature telemetry system as defined in claim 5 wherein each of said temperature transducers includes a housing member, an electrical connector attached to said housing member for receiving electrical power input to recharge said battery, and switch means attached to said housing member for automatically deactivating said oscillator and modulator switching circuits when said battery is being recharged, and further comprising a transducer storage unit containing a plurality of receptacles for receiving and storing said plurality of transducers, and electrical connector means in each of said receptacles for applying power to the corresponding transducer to recharge the battery thereof.

7. A temperature telemetry system as defined in claim 5 and further comprising a digital to analog converter circuit coupled between said receiver circuit and said output circuit for converting the time duration signals from said oscillator circuits into analog signal levels.

8. A temperature telemetry system as defined in claim 7 wherein each of said oscillators transmits a different frequency when activated, and wherein said receiver circuit contains a multiple channel input for simultaneously receiving the output signals of all of said oscillators on different channels.

9. A temperature telemetry system as defined in claim 7 wherein said output circuit contains a comparison circuit coupled to the output of said digital to analog converter circuit for comparing said analog signal levels to predetermined signal levels and for producing signals as a function of the difference between said analog signal levels and said predetermined signal levels.

10. A temperature telemetry system as defined in claim 9 wherein each of said transducers includes a housing member, a relatively slender probe attached to said housing member for insertion into food products, each of said temperature-responsive elements being attached to the corresponding probe, and wherein said predetermined signal levels are proportional to temperature levels relating to the processing of said food products.

11. A temperature telemetry system as defined in claim 7 wherein said output circuit includes a meter for indicating the numerical value of said analog signal levels and switch means for selectively coupling each of said analog signals to said meter to provide a visual indication of the temperature of the corresponding temperature-responsive elements.

12. A temperature telemetry system as defined in claim 11 wherein said output circuit includes means for producing an alarm signal when the difference between any one of said analog signal levels and a predetermined signal level exceeds a predetermined value.

13. A temperature telemetry system as defined in claim 11 wherein each of said transducers has a visible mark on the exterioR thereof for uniquely identifying the transducer.

14. A temperature telemetry system as defined in claim 13 and further comprising a food processing chamber having a plurality of spatially separated areas for receiving food products to be processed, each of said spatially separated areas having a visible mark corresponding to the mark on the exterior of one and only one of said transducers.