Thermocouple system having a PN junction for cold junction compensation
First Claim
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1. A solid state thermocouple actuated electronic switch circuit with solid state cold junction compensation, said circuit comprising:
- a thermocouple having a junction of two dissimilar metals with each metal being a current conducting member;
a first amplifier having its input terminals electrically connected respectively to said current conducting members of said thermocouple forming a cold junction and responsive to the voltage signal generated by said thermocouple for generating a first amplifier signal;
a solid state, semiconductor cold junction compensator means generating a voltage responding to the temperature of said cold junction;
a second amplifier having its input electrically connected to said solid state cold junction compensator means and responsive to said voltage signal generated thereby for generating a second amplified signal;
a reference temperature signal generator means generating a third signal representing the actuating temperature of the switch circuit;
a summing-comparator responsive to the summation of said first, second and third signals for generating a fourth signal whenever the magnitude summation of said first and second signal exceeds the magnitude of said third signal; and
a solid state switching means responsive to said fourth signal for changing its state of conduction.
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Abstract
A thermocouple system for catalytic controllers uses a PN junction at the cold junction for cold junction compensation. The linearity of the voltage drop across the PN junction permits accurate scaling for direct reading of the temperature at the output of the system. A switching circuit is described wherein the desired switching temperature is electrically entered into the circuit and when the compensated temperature signal is equal to the entered signal, the output of the switching circuit is switched.
47 Citations
8 Claims
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1. A solid state thermocouple actuated electronic switch circuit with solid state cold junction compensation, said circuit comprising:
- a thermocouple having a junction of two dissimilar metals with each metal being a current conducting member;
a first amplifier having its input terminals electrically connected respectively to said current conducting members of said thermocouple forming a cold junction and responsive to the voltage signal generated by said thermocouple for generating a first amplifier signal;
a solid state, semiconductor cold junction compensator means generating a voltage responding to the temperature of said cold junction;
a second amplifier having its input electrically connected to said solid state cold junction compensator means and responsive to said voltage signal generated thereby for generating a second amplified signal;
a reference temperature signal generator means generating a third signal representing the actuating temperature of the switch circuit;
a summing-comparator responsive to the summation of said first, second and third signals for generating a fourth signal whenever the magnitude summation of said first and second signal exceeds the magnitude of said third signal; and
a solid state switching means responsive to said fourth signal for changing its state of conduction.
- a thermocouple having a junction of two dissimilar metals with each metal being a current conducting member;
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2. A solid state thermocouple actuated electronic switch circuit according to claim 1 wherein said cold junction compensator means is a PN junction having linear voltage-temperature characteristic.
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3. A solid state thermocouple actuated electronic switch circuit according to claim 2 wherein said PN junction is a silicon diode.
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4. A solid state thermocouple actuated electronic switch according to claim 2 wherein said solid state switching means is a square wave generator and electrically connected thereto is an indicator means for indicating when the temperature of said thermocouple exceeds the reference temperature.
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5. A solid state thermocouple actuated electronic switch circuit according to claim 4 wherein said indicator means is a meter for indicating the temperature of said thermocouple.
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6. A solid state temperature measuring probe comprising a tubular housing enclosed at one end, a thermocouple having a juNction at one end of two dissimilar metals with each metal being a current conducting member, said junction positioned in a spaced relationship to said enclosed end of said housing and the other end of said current conducting members extending beyond said open end of said housing, insulation means supporting said thermocouple and maintaining said thermocouple in a spaced relationship to the interior walls of said housing, solid state circuit means having its input electrically connected to the other end of each of said current conducting members of said thermocouple said circuit means having a solid state semiconductor cold junction compensator means and a summing amplifier means for generating an output signal in response to the signals generated by said thermocouple and said solid state cold junction compensation means;
- and a housing member integrally connected to the open end of said housing for supporting and maintaining said circuit means in close proximity with the said other end of each of said current conducting members for the shortest and most direct connection of said current conducting members to said solid state circuit means.
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7. A solid state temperature measuring probe in accordance with claim 6 above and further including a radiation shield positioned between the dissimilar junction end of the thermocouple and the housing member.
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8. A solid state temperature measuring probe comprising:
- a tubular housing enclosed at one end, a thermocouple having a junction at one end of two dissimilar metals with each metal being a current conducting member, said junction positioned in a spaced relationship to said enclosed end of said housing and the other end of said current conducting members extending beyond said open end of said housing, insulation means supporting said thermocouple and maintaining said thermocouple in a spaced relationship to the interior walls of said housing, solid state circuit means having its input electrically connected to the other end of each of said current conducting members of said thermocouple, said circuit means having a first solid state signal amplifier means for amplifying a first signal generated by the thermocouple in response to the temperature at the dissimilar junction end of the thermocouple, a solid state, semiconductor cold junction compensator means generating a second signal responsive to the temperature at the said other end of said current conducting members of said thermocouple, a second solid state signal amplifier means for amplifying said second signal, and a summing amplifier means for generating an output signal in response to the first and second signals generated by said thermocouple and said solid state cold junction compensation means; and
a housing member integrally connected to the open end of said housing for supporting and maintaining said circuit means.
- a tubular housing enclosed at one end, a thermocouple having a junction at one end of two dissimilar metals with each metal being a current conducting member, said junction positioned in a spaced relationship to said enclosed end of said housing and the other end of said current conducting members extending beyond said open end of said housing, insulation means supporting said thermocouple and maintaining said thermocouple in a spaced relationship to the interior walls of said housing, solid state circuit means having its input electrically connected to the other end of each of said current conducting members of said thermocouple, said circuit means having a first solid state signal amplifier means for amplifying a first signal generated by the thermocouple in response to the temperature at the dissimilar junction end of the thermocouple, a solid state, semiconductor cold junction compensator means generating a second signal responsive to the temperature at the said other end of said current conducting members of said thermocouple, a second solid state signal amplifier means for amplifying said second signal, and a summing amplifier means for generating an output signal in response to the first and second signals generated by said thermocouple and said solid state cold junction compensation means; and
Specification