A thermocouple adaptive temperature measurement circuit

Abstract

The present invention provides a thermocouple self-adaptive temperature measurement circuit, the gain of the amplifier circuit of which can be adjusted, thereby improving the measurement accuracy. The circuit comprises a first-stage amplifier circuit connected to the thermocouple, characterized in that: one output end and two output ends of the first-stage amplifier circuit are respectively connected to one input end and two input ends of the second-stage amplifier circuit, one output end of the first-stage amplifier circuit is also connected to the input end of a comparison circuit, the input end of the comparison circuit is also respectively connected to the output end of a first standard voltage reference circuit and the output end of a second standard voltage reference circuit, the output end of the comparison circuit is connected to the input end of a selection circuit, and the input end and the output end of the selection circuit are also respectively connected to the output end and the two input ends of the second-stage amplifier circuit.

Description

Technical Field

[0001] The invention relates to the technical field of K-type thermocouple temperature measurement circuits, in particular to a thermocouple self-adaptive temperature measurement circuit. Background Art

[0002] As a temperature sensor, K-type thermocouple can directly measure the surface temperature of liquid vapor, gas medium and solid in various production processes. Generally speaking, when K-type thermocouple tests temperature, an amplifier circuit is connected to the back end to improve its measurement accuracy. However, since the thermocouple has a wide temperature measurement range, generally from 0°C to above 1000°C, and the gain of the amplifier circuit connected to the back end is a fixed value, the output voltage or current is very low when testing low temperatures, and the output voltage or current is high when measuring high temperatures, even exceeding the input range of the A / D converter, thus affecting the accuracy of the test. Summary of the invention

[0003] Aiming at the problem that the gain of the amplifier circuit connected to the back end of the existing K-type thermocouple cannot be adjusted, resulting in low measurement accuracy, the present invention provides a thermocouple adaptive temperature measurement circuit, whose amplifier circuit gain can be adjusted, thereby improving the measurement accuracy.

[0004] The technical scheme is as follows: a thermocouple self-adaptive temperature measurement circuit, comprising a first-stage amplifier circuit connected to a thermocouple, characterized in that: one output end and two output ends of the first-stage amplifier circuit are respectively connected to one input end and two input ends of the second-stage amplifier circuit, one output end of the first-stage amplifier circuit is also connected to the input end of a comparison circuit, the input end of the comparison circuit is also respectively connected to the output end of a first standard voltage reference circuit and the output end of a second standard voltage reference circuit, the output end of the comparison circuit is connected to the input end of a selection circuit, and the input end and the output end of the selection circuit are also respectively connected to the output end and the second input end of the second-stage amplifier circuit;

[0005] The further feature is that the first-stage amplifier circuit comprises an AD8495 thermocouple AD8495 thermocouple amplifier U1, wherein the 1-pin of the AD8495 thermocouple amplifier U1 is connected to one end of a resistor R4, one end of a capacitor C2 and one end of a capacitor C3, the other end of the resistor R4 is connected to one end of a resistor R2 and an input end VSS, the other end of the resistor R2 is connected to the other end of the capacitor C2 and is grounded, the other end of the capacitor C3 is connected to one end of a resistor R3, one end of a capacitor C1 and the 8-pin of the AD8495 thermocouple amplifier U1, the other end of the resistor R3 is connected to the input end VIN, the other end of the capacitor C1 is connected to the 3-pin of the AD8495 thermocouple amplifier U1 and is grounded, and the AD8495 thermocouple amplifier The 7-pin of the thermocouple amplifier U1 is connected to the 2-pin of the power interface P2, one end of the capacitor C6 and one end of the capacitor C5, the 1-pin and 3-pin of the power interface P2 are connected to the 5V and 15V power supplies respectively, the other end of the capacitor C6 is connected to the other end of the capacitor C5 and then grounded, the 2-pin of the AD8495 thermocouple amplifier U1 is connected to one end of the capacitor C4 and one end of the resistor R14 and grounded, the other end of the resistor R14 is connected to the two input ends of the secondary amplifier circuit and the output end of the selection circuit, the 5-pin and 6-pin of the AD8495 thermocouple amplifier U1 are connected and then connected to one end of the resistor R5, the other end of the resistor R5 is connected to the other end of the capacitor C4, one input end of the secondary amplifier circuit and the input end of the comparison circuit;

[0006] The secondary amplifier circuit includes a TLV2371 operational amplifier U2, wherein pin 1 of the TLV2371 operational amplifier U2 is connected to one end of a resistor R19 and the input end of the selection circuit, and the other end of the resistor R19 is grounded, pin 5 of the TLV2371 operational amplifier U2 is connected to pin 2 of a power interface P3 and one end of a capacitor C7, and the other end of the capacitor C7 is connected to pin 2 of the TLV2371 operational amplifier U2 and then grounded, pin 3 of the TLV2371 operational amplifier U2 is connected to the other end of the resistor R5 and the other end of the capacitor C4, and pin 4 of the TLV2371 operational amplifier U2 is connected to the other end of the resistor R14;

[0007] The standard voltage reference circuit 1 and the standard voltage reference circuit 2 respectively include TPS73201TPS73201 regulator U5 and TPS73201TPS73201 regulator U6, the 1st pin and the 3rd pin of the TPS73201 regulator U5 are connected to the 5V power supply and one end of the capacitor C10, the other end of the capacitor C10 is connected to the 2nd pin of the TPS73201 regulator U5 and grounded, the 4th pin of the TPS73201 regulator U5 is connected to one end of the resistor R6, one end of the capacitor C11 and one end of the resistor R7, the 5th pin of the TPS73201 regulator U5 is connected to the other end of the resistor R6, the other end of the capacitor C11, the input of the comparison circuit The 1st pin and the 3rd pin of the TPS73201 voltage regulator U6 are connected to the 5V power supply and the 2nd pin of the TPS73201 voltage regulator U6 and the ground, the 4th pin of the TPS73201 voltage regulator U6 is connected to the 1st end of the resistor R9, the 1st end of the capacitor C17 and the 1st end of the resistor R10, the 5th pin of the TPS73201 voltage regulator U6 is connected to the 1st end of the resistor R9, the 1st end of the capacitor C17, the 1st end of the comparison circuit and the 1st end of the capacitor C18, and the 1st end of the capacitor C18 is connected to the 2nd end of the resistor R10 and the ground;

[0008] The comparison circuit includes a dual comparator U8, wherein the 2nd and 6th pins of the dual comparator U8 are connected to the 3rd pin of the operational amplifier U2, the 1st pin of the dual comparator U8 is connected to one end of a resistor R25, one end of a resistor R27 and the input end of the selection circuit, the other end of the resistor R27 is connected to the anode of a light-emitting diode D1, the cathode of the light-emitting diode D1 is grounded, the 3rd pin of the dual comparator U8 is connected to the other end of the resistor R25 and one end of a resistor R22, and the resistor R The other end of 22 is connected to the 5th pin of the TPS73201 voltage regulator U5, the 7th pin of the dual comparator U8 is connected to one end of the resistor R26, one end of the resistor R28 and the input end of the selection circuit, the other end of the resistor R28 is connected to the anode of the light-emitting diode D2, the cathode of the light-emitting diode D2 is grounded, the 5th pin of the dual comparator U8 is connected to the other end of the resistor R26 and one end of the resistor R23, and the other end of the resistor R23 is connected to the 5th pin of the TPS73201 voltage regulator U6;

[0009] The selection circuit includes a multiple-address selector U7, wherein pin 10 of the multiple-address selector U7 is connected to one end of a resistor R16 and the collector of a transistor Q2, the base of the transistor Q2 is connected to pin 7 of the dual-path comparator U8 via a resistor R18, the other end of the resistor R16 is connected to pin 2 of a power interface P4 and one end of a resistor R15, the other end of the resistor R15 is connected to pin 11 of the multiple-address selector U7 and the collector of a transistor Q1, the base of the transistor Q1 is connected to pin 1 of the dual-path comparator U8 via a resistor R17, the base of the transistor Q1 is connected to the base of the transistor Q2 and then to ground, and pins 1, 2, 4, 5, 6 and 9 of the multiple-address selector U7 are connected and then connected to one end of a resistor R21 , the other end of the resistor R21 is grounded, the 3rd pin of the multiple address selector is connected to the 3rd pin of the operational amplifier U2, the 12th, 13th, 14th and 15th pins of the multiple address selector are respectively connected to one end of the resistor R20, one end of the resistor R8, one end of the resistor R11 and one end of the resistor R12, the other end of the R20, the other end of the resistor R8, the other end of the resistor R11 and the other end of the resistor R12 are connected and then connected to the 1st pin of the operational amplifier U2, the 7th and 8th pins of the multiple address selector U7 are connected and then connected to one end of the capacitor C13 and grounded, the other end of the capacitor C13 is connected to the 2nd pin of the power interface P5 and the 16th pin of the multiple address selector U7, the 1st and 3rd pins of the power interface P5 are respectively connected to the 5V power supply and the 15V power supply;

[0010] It also includes a power supply circuit, which includes an LM7805S voltage regulator U3. Pin 1 of the LM7805S voltage regulator U3 is connected to a 15V power supply and one end of a capacitor C20. Pins 2 and 4 of the LM7805S voltage regulator U3 are connected and then connected to the other end of the capacitor C20 and grounded. Pin 3 of the LM7805S voltage regulator U3 outputs a 5V power supply and is connected to one end of a capacitor C8. The other end of the capacitor C8 is grounded.

[0011] After adopting the above structure, since the output ends of the first-stage amplifier circuit are connected to the input end of the second-stage amplifier circuit respectively, and the output end of the first-stage amplifier circuit is connected to the input end of the comparison circuit, and the input end of the comparison circuit is also connected to the output end of the standard voltage reference circuit one and the output end of the standard voltage reference circuit two respectively, the comparison circuit compares the output electromotive force of the first-stage amplifier circuit with the standard electromotive force one output by the standard voltage reference circuit one and the standard electromotive force two output by the standard voltage reference circuit two, and sends the comparison signal to the selection circuit. Since the input end and the output end of the selection circuit are respectively connected to the output end and the input end of the second-stage amplifier circuit, the second-stage amplifier circuit is controlled to automatically change the gain through different signals sent by the selection circuit, thereby improving the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1It is the overall structure flow chart of the present invention;

[0013] Figure 2 A circuit schematic diagram showing the connection between the primary amplifying circuit and the secondary amplifying circuit of the present invention;

[0014] Figure 3 is a circuit schematic diagram of a standard voltage reference circuit 1 of the present invention;

[0015] Figure 4 It is a circuit principle diagram of the second standard voltage reference circuit of the present invention;

[0016] Figure 5 is a circuit schematic diagram of a comparison circuit of the present invention;

[0017] Figure 6 A circuit schematic diagram of a circuit selected for the present invention;

[0018] Figure 7 It is a circuit principle diagram of the power supply circuit of the present invention. DETAILED DESCRIPTION

[0019] like Figure 1 As shown, a thermocouple adaptive temperature measurement circuit includes a first-stage amplifier circuit connected to the thermocouple, one output terminal and two output terminals of the first-stage amplifier circuit are respectively connected to one input terminal and two input terminals of the second-stage amplifier circuit, one output terminal of the first-stage amplifier circuit is also connected to the input terminal of the comparison circuit, the input terminal of the comparison circuit is also respectively connected to the output terminal of the first standard voltage reference circuit and the output terminal of the second standard voltage reference circuit, and the output terminal of the comparison circuit is connected to the input terminal of the selection circuit.

[0020] The input and output ends of the selection circuit are also connected to the output end and the two-way input end of the secondary amplifier circuit respectively;

[0021] like Figure 1As shown, the first-stage amplifier circuit includes an AD8495 thermocouple AD8495 thermocouple amplifier U1, pin 1 of the AD8495 thermocouple amplifier U1 is connected to one end of a resistor R4, one end of a capacitor C2 and one end of a capacitor C3, the other end of the resistor R4 is connected to one end of a resistor R2 and an input terminal VSS, the other end of the resistor R2 is connected to the other end of the capacitor C2 and is grounded, the other end of the capacitor C3 is connected to one end of a resistor R3, one end of a capacitor C1 and pin 8 of the AD8495 thermocouple amplifier U1, the other end of the resistor R3 is connected to the input terminal VIN, the other end of the capacitor C1 is connected to pin 3 of the AD8495 thermocouple amplifier U1 and is grounded, the AD8495 thermocouple amplifier U Pin 7 of 1 is connected to pin 2 of power interface P2, one end of capacitor C6 and one end of capacitor C5, pin 1 and pin 3 of power interface P2 are connected to 5V and 15V power supplies respectively, the other end of capacitor C6 is connected to the other end of capacitor C5 and then grounded, pin 2 of AD8495 thermocouple amplifier U1 is connected to one end of capacitor C4 and one end of resistor R14 and grounded, the other end of resistor R14 is connected to two input ends of the secondary amplifier circuit and the output end of the selection circuit, pins 5 and 6 of AD8495 thermocouple amplifier U1 are connected and then connected to one end of resistor R5, the other end of resistor R5 is connected to the other end of capacitor C4, one input end of the secondary amplifier circuit and the input end of the comparison circuit.

[0022] The secondary amplifier circuit includes a TLV2371 operational amplifier U2, wherein pin 1 of the TLV2371 operational amplifier U2 is connected to one end of a resistor R19 and an input end of a selection circuit, the other end of the resistor R19 is grounded, pin 5 of the TLV2371 operational amplifier U2 is connected to pin 2 of a power interface P3 and one end of a capacitor C7, the other end of the capacitor C7 is connected to pin 2 of the TLV2371 operational amplifier U2 and then grounded, pin 3 of the TLV2371 operational amplifier U2 is connected to the other end of the resistor R5 and the other end of the capacitor C4, and pin 4 of the TLV2371 operational amplifier U2 is connected to the other end of the resistor R14.

[0023] like Figure 3 and Figure 4As shown, the standard voltage reference circuit 1 and the adjustable reference circuit 2 include TPS73201TPS73201 regulator U5 and TPS73201TPS73201 regulator U6 respectively. The 1st pin and the 3rd pin of the TPS73201 regulator U5 are connected to the 5V power supply and one end of the capacitor C10. The other end of the capacitor C10 is connected to the 2nd pin of the TPS73201 regulator U5 and grounded. The 4th pin of the TPS73201 regulator U5 is connected to one end of the resistor R6, one end of the capacitor C11 and one end of the resistor R7. The 5th pin of the TPS73201 regulator U5 is connected to the other end of the resistor R6, the other end of the capacitor C11 and the comparison circuit. The input end and one end of capacitor C12, the other end of capacitor C12 is connected to the other end of resistor R7 and grounded; pin 1 and pin 3 of TPS73201 voltage regulator U6 are connected and then connected to a 5V power supply and one end of capacitor C15, the other end of capacitor C15 is connected to pin 2 of TPS73201 voltage regulator U6 and grounded, pin 4 of TPS73201 voltage regulator U6 is connected to one end of resistor R9, one end of capacitor C17 and one end of resistor R10, pin 5 of TPS73201 voltage regulator U6 is connected to the other end of resistor R9, the other end of capacitor C17, the input end of the comparison circuit and one end of capacitor C18, the other end of capacitor C18 is connected to the other end of resistor R10 and grounded.

[0024] like Figure 5 As shown, the comparison circuit includes a dual comparator U8, wherein the 2nd and 6th pins of the dual comparator U8 are connected to the 3rd pin of the operational amplifier U2, the 1st pin of the dual comparator U8 is connected to one end of the resistor R25, one end of the resistor R27 and the input end of the selection circuit, the other end of the resistor R27 is connected to the anode of the light-emitting diode D1, and the cathode of the light-emitting diode D1 is grounded, the 3rd pin of the dual comparator U8 is connected to the other end of the resistor R25 and one end of the resistor R22, the other end of the resistor R22 is connected to the 5th pin of the TPS73201 regulator U5, the 7th pin of the dual comparator U8 is connected to one end of the resistor R26, one end of the resistor R28 and the input end of the selection circuit, the other end of the resistor R28 is connected to the anode of the light-emitting diode D2, and the cathode of the light-emitting diode D2 is grounded, the 5th pin of the dual comparator U8 is connected to the other end of the resistor R26 and one end of the resistor R23, and the other end of the resistor R23 is connected to the 5th pin of the TPS73201 regulator U6.

[0025] like Figure 6As shown, the selection circuit includes a multiple-address selector U7, which adopts a CD4051 multiple-address selector. Pin 10 of the multiple-address selector U7 is connected to one end of a resistor R16 and the collector of a transistor Q2. The base of the transistor Q2 is connected to pin 7 of a dual comparator U8 through a resistor R18. The other end of the resistor R16 is connected to pin 2 of a power interface P4 and one end of a resistor R15. The other end of the resistor R15 is connected to pin 11 of the multiple-address selector U7 and the collector of a transistor Q1. The base of the transistor Q1 is connected to pin 1 of the dual comparator U8 through a resistor R17. The base of the transistor Q1 is connected to the base of the transistor Q2 and then to ground. Pins 1, 2, 4, 5, 6 and 9 of the multiple-address selector U7 are connected and then to Connect one end of resistor R21, the other end of resistor R21 is grounded, pin 3 of the multiple-address selector is connected to pin 3 of the operational amplifier U2, pins 12, 13, 14 and 15 of the multiple-address selector are respectively connected to one end of resistor R20, one end of resistor R8, one end of resistor R11 and one end of resistor R12, the other end of R20, the other end of resistor R8, the other end of resistor R11 and the other end of resistor R12 are connected and then connected to pin 1 of the operational amplifier U2, pins 7 and 8 of the multiple-address selector U7 are connected and then connected to one end of capacitor C13 and grounded, the other end of capacitor C13 is connected to pin 2 of power interface P5 and pin 16 of the multiple-address selector U7, and pins 1 and 3 of the power interface P5 are respectively connected to a 5V power supply and a 15V power supply.

[0026] like Figure 7 As shown, it also includes a power supply circuit, which includes an LM7805S voltage regulator U3. Pin 1 of the LM7805S voltage regulator U3 is connected to a 15V power supply and one end of a capacitor C20. Pins 2 and 4 of the LM7805S voltage regulator U3 are connected and then connected to the other end of the capacitor C20 and grounded. Pin 3 of the LM7805S voltage regulator U3 outputs a 5V power supply and is connected to one end of a capacitor C8, and the other end of the capacitor C8 is grounded.

[0027] The working principle of the present invention is as follows: the measuring range of the thermocouple self-adaptive temperature measurement circuit is 0-1000°C. Since the thermocouple amplifier AD8495 of the primary amplification circuit provides an output voltage of 5mV / °C, that is, the output voltage of the thermocouple amplifier AD8495 is 5V at the highest temperature, the thermocouple self-adaptive temperature measurement circuit divides the 0-1000°C acquisition temperature into 3 levels of 0-250°C, 250-400°C, and 400-1000°C for amplification. Since the highest output voltage at 0-250°C is 1.25V, the highest output voltage at 100-400°C is 2V, and the highest output voltage at 400-1000°C is 5V, the output voltages at 0-250°C, 100-400°C, and 700-1000°C need to be amplified by 4 times, 2.5 times, and 1 times.

[0028] from Figure 3It can be calculated that VREF1=1.204(1+382 / 10000)≈1.25(V),

[0029] Since the AD8495 provides an output voltage of 5mV / ℃, the first temperature point of the amplifier gain conversion is 1.25 / 0.005=250℃.

[0030] from Figure 4 It can be calculated that VREF2=1.204(1+6610 / 10000)≈2.0(V),

[0031] Since the AD8495 provides an output voltage of 5mV / ℃, the second temperature point of the amplifier gain conversion is 2.0 / 0.005=400℃.

[0032] The reference voltages VREF1 and VREF2 are outputted respectively by the standard voltage reference circuit 1 and the standard voltage reference circuit 2 connected to the input end of the comparison circuit. Since the input end of the comparison circuit is also connected to one output end of the first-stage amplifier circuit, one output end of the first-stage amplifier circuit outputs the voltage VSENSE. By comparing the reference voltages VREF1 and VREF2 with the output voltage VSENSE, the level of the outputs 1 and 7 pins D1 and D2 of the dual comparator TLV3492 of the comparison circuit is determined; D1 and D2 are respectively connected to the bases of the transistors Q1 and Q2 through the resistors R17 and R18, respectively, to control the level of the A of the transistor Q1 and the B of the transistor Q2, thereby realizing the site selection function of the multi-address selector CD4051, and further realizing the automatic gain conversion of the operational amplifier TLV2371.

[0033] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by anyone familiar with the technology within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A thermocouple adaptive temperature measurement circuit, comprising a primary amplifier circuit connected to a thermocouple, characterized in that: One output terminal and two output terminals of the first-stage amplifier circuit are connected to one input terminal and two input terminals of the second-stage amplifier circuit respectively, one output terminal of the first-stage amplifier circuit is also connected to the input terminal of the comparison circuit, the input terminal of the comparison circuit is also connected to the output terminal of the first standard voltage reference circuit and the output terminal of the second standard voltage reference circuit respectively, the output terminal of the comparison circuit is connected to the input terminal of the selection circuit, and the input terminal and the output terminal of the selection circuit are also connected to the output terminal and the two input terminals of the second-stage amplifier circuit respectively; The first-stage amplifier circuit includes an AD8495 thermocouple amplifier U1, wherein pin 1 of the AD8495 thermocouple amplifier U1 is connected to one end of a resistor R4, one end of a capacitor C2 and one end of a capacitor C3, the other end of the resistor R4 is connected to one end of a resistor R2 and an input terminal VSS, the other end of the resistor R2 is connected to the other end of the capacitor C2 and is grounded, the other end of the capacitor C3 is connected to one end of a resistor R3, one end of a capacitor C1 and pin 8 of the AD8495 thermocouple amplifier U1, the other end of the resistor R3 is connected to the input terminal VIN, the other end of the capacitor C1 is connected to pin 3 of the AD8495 thermocouple amplifier U1 and is grounded, and pin 7 of the AD8495 thermocouple amplifier U1 is connected to the input terminal VIN. Pin 1 and pin 3 of the power interface P2 are connected to 5V and 15V power supplies respectively, the other end of the capacitor C6 is connected to the other end of the capacitor C5 and then grounded, pin 2 of the AD8495 thermocouple amplifier U1 is connected to one end of the capacitor C4 and one end of the resistor R14 and grounded, the other end of the resistor R14 is connected to two input ends of the secondary amplifier circuit and the output end of the selection circuit, pins 5 and 6 of the AD8495 thermocouple amplifier U1 are connected and then connected to one end of the resistor R5, the other end of the resistor R5 is connected to the other end of the capacitor C4, one input end of the secondary amplifier circuit and the input end of the comparison circuit; The measurement range of the thermocouple adaptive temperature measurement circuit is 0-1000℃. The thermocouple adaptive temperature measurement circuit divides the collected temperature of 0-1000℃ into 3 levels of 0-250℃, 250-400℃, and 400-1000℃ for amplification; the output voltage of 0-250℃, 100-400℃, and 700-1000℃ is amplified by 4 times, 2.5 times, and 1 times.

2. A thermocouple adaptive temperature measurement circuit according to claim 1, characterized in that: The secondary amplifier circuit includes a TLV2371 operational amplifier U2, wherein pin 1 of the TLV2371 operational amplifier U2 is connected to one end of a resistor R19 and the input end of the selection circuit, and the other end of the resistor R19 is grounded, pin 5 of the TLV2371 operational amplifier U2 is connected to pin 2 of a power interface P3 and one end of a capacitor C7, and the other end of the capacitor C7 is connected to pin 2 of the TLV2371 operational amplifier U2 and then grounded, pin 3 of the TLV2371 operational amplifier U2 is connected to the other end of the resistor R5 and the other end of the capacitor C4, and pin 4 of the TLV2371 operational amplifier U2 is connected to the other end of the resistor R14.

3. A thermocouple adaptive temperature measurement circuit according to claim 2, characterized in that: The standard voltage reference circuit 1 and the standard voltage reference circuit 2 respectively include a TPS73201 voltage regulator U5 and a TPS73201 voltage regulator U6. The 1st pin and the 3rd pin of the TPS73201 voltage regulator U5 are connected to a 5V power supply and one end of a capacitor C10. The other end of the capacitor C10 is connected to the 2nd pin of the TPS73201 voltage regulator U5 and grounded. The 4th pin of the TPS73201 voltage regulator U5 is connected to one end of a resistor R6, one end of a capacitor C11 and one end of a resistor R7. The 5th pin of the TPS73201 voltage regulator U5 is connected to the other end of the resistor R6, the other end of the capacitor C11, the input end of the comparison circuit and a capacitor C12. end, the other end of the capacitor C12 is connected to the other end of the resistor R7 and grounded; pin 1 and pin 3 of the TPS73201 voltage regulator U6 are connected to a 5V power supply and one end of a capacitor C15, the other end of the capacitor C15 is connected to pin 2 of the TPS73201 voltage regulator U6 and grounded, pin 4 of the TPS73201 voltage regulator U6 is connected to one end of a resistor R9, one end of a capacitor C17 and one end of a resistor R10, pin 5 of the TPS73201 voltage regulator U6 is connected to the other end of the resistor R9, the other end of the capacitor C17, the input end of the comparison circuit and one end of a capacitor C18, and the other end of the capacitor C18 is connected to the other end of the resistor R10 and grounded.

4. A thermocouple adaptive temperature measurement circuit according to claim 3, characterized in that: The comparison circuit includes a dual comparator U8 implemented based on TLV3492, wherein the 2nd and 6th pins of the dual comparator U8 are connected and then connected to the 3rd pin of the operational amplifier U2, the 1st pin of the dual comparator U8 is connected to one end of the resistor R25, one end of the resistor R27 and the input end of the selection circuit, the other end of the resistor R27 is connected to the anode of the light-emitting diode D1, the cathode of the light-emitting diode D1 is grounded, and the 3rd pin of the dual comparator U8 is connected to the other end of the resistor R25 and one end of the resistor R22. The other end of the resistor R22 is connected to pin 5 of the TPS73201 regulator U5, pin 7 of the dual comparator U8 is connected to one end of resistor R26, one end of resistor R28 and the input end of the selection circuit, the other end of the resistor R28 is connected to the anode of the light-emitting diode D2, the cathode of the light-emitting diode D2 is grounded, pin 5 of the dual comparator U8 is connected to the other end of resistor R26 and one end of resistor R23, and the other end of the resistor R23 is connected to pin 5 of the TPS73201 regulator U6.

5. A thermocouple adaptive temperature measurement circuit according to claim 4, characterized in that: The selection circuit includes a multiple-address selector U7 implemented based on CD4051, wherein pin 10 of the multiple-address selector U7 is connected to one end of a resistor R16 and the collector of a transistor Q2, the base of the transistor Q2 is connected to pin 7 of the dual-path comparator U8 via a resistor R18, the other end of the resistor R16 is connected to pin 2 of a power interface P4 and one end of a resistor R15, the other end of the resistor R15 is connected to pin 11 of the multiple-address selector U7 and the collector of a transistor Q1, the base of the transistor Q1 is connected to pin 1 of the dual-path comparator U8 via a resistor R17, the base of the transistor Q1 is connected to the base of the transistor Q2 and then to ground, and pins 1, 2, 4, 5, 6 and 9 of the multiple-address selector U7 are connected and then connected to resistor One end of the resistor R21, the other end of the resistor R21 is grounded, pin 3 of the multiple-address selector is connected to pin 3 of the operational amplifier U2, pins 12, 13, 14 and 15 of the multiple-address selector are respectively connected to one end of the resistor R20, one end of the resistor R8, one end of the resistor R11 and one end of the resistor R12, the other end of R20, the other end of the resistor R8, the other end of the resistor R11 and the other end of the resistor R12 are connected and then connected to pin 1 of the operational amplifier U2, pins 7 and 8 of the multiple-address selector U7 are connected and then connected to one end of the capacitor C13 and grounded, the other end of the capacitor C13 is connected to pin 2 of the power interface P5 and pin 16 of the multiple-address selector U7, and pins 1 and 3 of the power interface P5 are respectively connected to a 5V power supply and a 15V power supply.

6. A thermocouple adaptive temperature measurement circuit according to claim 5, characterized in that: It also includes a power supply circuit, which includes an LM7805S voltage regulator U3. Pin 1 of the LM7805S voltage regulator U3 is connected to a 15V power supply and one end of a capacitor C20. Pins 2 and 4 of the LM7805S voltage regulator U3 are connected and then connected to the other end of the capacitor C20 and grounded. Pin 3 of the LM7805S voltage regulator U3 outputs a 5V power supply and is connected to one end of a capacitor C8. The other end of the capacitor C8 is grounded.

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