CN214372947U - Temperature measuring circuit for ear thermometer and ear thermometer - Google Patents

Abstract

The utility model relates to a temperature measurement circuit and ear temperature rifle of ear temperature rifle, through the reference voltage through the steady voltage all the way with the negative pole end loading power module of thermopile to make the voltage stability of the positive terminal output of thermopile, the change of its voltage corresponds with the human body temperature that detects completely, and it is accurate with this to make the human body temperature that final treater calculation obtained. And the second input end of the amplification module is also loaded with the reference voltage, so that the voltage difference between the first input end and the second input end of the amplification module is the voltage output between the positive end and the negative end of the thermopile, interference voltage cannot be introduced in the amplification of the amplification module, the voltage output by the thermopile corresponding to the ambient temperature is amplified, the voltage output by the amplification module accurately corresponds to the voltage output between the positive end and the negative end of the thermopile, and the accuracy of the human body temperature calculated by the final processor is further ensured.

Description

Temperature measuring circuit for ear thermometer and ear thermometer

Technical Field

The utility model relates to a temperature measurement circuit and ear temperature rifle of ear temperature rifle is applied to the temperature measurement equipment field.

Background

At present, a temperature measuring device for detecting the temperature of a human body, such as an ear thermometer, a forehead thermometer and the like, has a detection circuit which is mainly based on an infrared thermopile sensor, receives infrared light of the human body at a short distance through the infrared thermopile and converts the infrared light into voltage. The general infrared thermopile sensor includes a positive output terminal and a negative output terminal, a voltage difference is provided between the positive output terminal and the negative output terminal, and the voltage difference is converted into a human body temperature according to the magnitude of the detected voltage difference, i.e., the magnitude of the voltage. In the use process, the pressure difference of the infrared thermopile easily causes fluctuation to cause inaccurate detected voltage, so that inaccurate final obtained human body temperature is caused.

SUMMERY OF THE UTILITY MODEL

The utility model discloses the technical problem that needs to solve is to overcome current ear thermometer because the pressure differential of its infrared thermopile's output finally leads to the inaccurate problem of the human body temperature who obtains owing to undulant.

The utility model provides a temperature measuring circuit of an ear thermometer, which comprises a temperature measuring module based on a thermopile, an amplifying module, a power module, an analog-to-digital converter and a processor;

the temperature measurement module comprises a thermopile cathode end and a thermopile anode end, the power supply module comprises a first voltage output end, the first voltage output end outputs stabilized reference voltage, and the first voltage output end is connected with the thermopile cathode end of the temperature measurement module; the positive electrode end of the thermopile of the temperature measurement module is connected with the first input end of the amplification module;

the first voltage output end is further connected with a second input end of the amplifying module, the output end of the amplifying module is connected with a first sampling end of the analog-to-digital converter, and the output end of the analog-to-digital converter is connected with the processor.

Optionally, the first voltage output terminal is further connected to a second sampling terminal of the analog-to-digital converter.

Optionally, the temperature measurement module further includes a temperature detection output end, and the temperature detection output end is connected to the third sampling end of the analog-to-digital converter.

Optionally, the amplifying module comprises a comparator, a first resistor, a second resistor and a third resistor;

one end of the first resistor is a second input end of the amplifying module, the other end of the first resistor is connected with an inverting input end of the comparator, one end of the second resistor is a first input end of the amplifying module, the other end of the second resistor is connected with the inverting input end of the comparator, and the output end of the comparator is an output end of the amplifying module.

Optionally, the power supply module includes a voltage conversion unit, a voltage stabilization unit and a second voltage output end; the output end of the voltage conversion unit is a second voltage output end, the voltage conversion unit is used for outputting a second voltage, and the output end of the voltage stabilization unit is a first voltage output end to output a reference voltage.

Optionally, the temperature detection output end of the temperature measurement module comprises an anode output end and a cathode output end, the temperature measurement circuit further comprises a fifth resistor and a fourth resistor, one end of the fifth resistor is connected with the second voltage output end, the other end of the fifth resistor and one end of the fourth resistor are connected to the anode output end in a shared mode, the other end of the fourth resistor is connected with a third sampling end of the analog-to-digital converter, and the cathode output end is grounded.

Optionally, the temperature measuring circuit further comprises an infrared distance detection module; the infrared distance detection module comprises an infrared emission unit and an infrared receiving unit, and the control end of the infrared emission unit and the output end of the infrared receiving unit are respectively connected with the processor.

Optionally, the output of the analog-to-digital converter is connected to the processor via a communication data line.

The utility model discloses still provide an ear temperature rifle, ear temperature rifle is provided with foretell temperature measurement circuit.

Optionally, the ear thermometer is an ear thermometer or a forehead thermometer.

Adopt the utility model discloses a temperature measurement circuit, through the reference voltage through the steady voltage all the way with the negative pole end loading power module of thermopile to make the voltage stability of the positive terminal output of thermopile, the change of its voltage corresponds with the human body temperature that detects completely, and it is accurate with this to make the human body temperature that final treater calculation obtained. And the second input end of the amplification module is also loaded with the reference voltage, so that the voltage difference between the first input end and the second input end of the amplification module is the voltage output between the positive end and the negative end of the thermopile, interference voltage cannot be introduced in the amplification of the amplification module, the voltage output by the thermopile corresponding to the ambient temperature is amplified, the voltage output by the amplification module accurately corresponds to the voltage output between the positive end and the negative end of the thermopile, and the accuracy of the human body temperature calculated by the final processor is further ensured.

Drawings

FIG. 1 is a circuit diagram of a temperature measuring part of an ear thermometer circuit according to an embodiment of the present invention;

FIG. 2 is a circuit diagram of a temperature measurement portion of an ear thermometer circuit according to another embodiment of the present invention;

fig. 3 is a circuit diagram of a power module in an ear thermometer circuit according to an embodiment of the present invention;

fig. 4 is a circuit diagram of a temperature measuring portion of an ear thermometer circuit according to another embodiment of the present invention.

Detailed Description

It should be noted that the embodiments and features of the embodiments of the present invention may be combined with each other without conflict in structure or function. The present invention will be described in detail below with reference to examples.

The utility model provides a temperature measuring circuit for an ear thermometer, as shown in figure 1, the temperature measuring circuit comprises a thermopile-based temperature measuring module 10, an amplifying module 20, a power module 60, an analog-to-digital converter 30 and a processor 40;

the temperature measurement module 10 comprises a thermopile cathode end and a thermopile anode end, the power supply module 60 outputs a stabilized reference voltage VREF, the stabilized reference voltage VREF is connected with the thermopile cathode end of the temperature measurement module 10 through a first voltage output end, and the first voltage output end is simultaneously connected with a first input end of the analog-to-digital converter 30; the positive end of the thermopile of the temperature measurement module 10 is connected with the first input end of the amplification module 20;

the first voltage output end is further connected to a second input end of the amplifying module 20, an output end of the amplifying module 20 is connected to a second input end of the analog-to-digital converter 30, and an output end of the analog-to-digital converter 30 is connected to the processor 40.

Examples of processor 40 may include, but are not limited to, a general purpose processor, a special purpose processor, a conventional processor, a Digital Signal Processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of Integrated Circuit (IC), a state machine, and the like.

Because the output voltage between the positive terminal and the negative terminal of the thermopile is weak and generally only 50-700 uV, the voltage needs to be amplified, the output voltage is amplified through the amplification module 20, the amplification factor can be generally 100-300 times, and the amplified voltage is 0-5V and can be identified by the analog-to-digital converter 30 connected subsequently. Because the voltage difference between the positive terminal and the negative terminal is very small, if the negative terminal is directly grounded, the voltage of the positive terminal, namely 50-700 uV, is very close to zero potential, and if the voltage is directly input to the comparator IC2, the conduction voltage of the triode in the comparator IC2 is difficult to reach to enable the triode to work, so that the comparator IC2 cannot work normally to amplify the input voltage. Therefore, a voltage with a certain voltage value needs to be input to the negative terminal, in this embodiment, a voltage of 1-1.5V, for example, 1.2V, is generally input to the negative terminal, so that the voltage of the positive terminal is 1.2V + voltage difference. Its input to comparator IC2 enables comparator IC2 to operate normally to amplify the differential pressure.

In the prior art, the negative terminal of the thermopile is generally connected to a common dc voltage, which is not stabilized, so that there is a certain ripple coefficient to make the voltage fluctuate, and thus the corresponding positive terminal also fluctuates in response to the output, because the output voltage between the positive terminal and the negative terminal of the thermopile is weak, even a small ripple causes a large interference to the original voltage, so that the finally output voltage generates a large error, and finally the processor 40 calculates the human body temperature according to the voltage value obtained by the analog-to-digital converter 30 to generate a large error. In the scheme of this embodiment, the stabilized reference voltage VREF of the power module 60 is loaded to the negative terminal of the thermopile, so that the voltage output by the positive terminal of the thermopile is stable, and the change of the voltage completely corresponds to the detected human body temperature, so that the human body temperature calculated by the final processor 40 is accurate. And the reference voltage VREF is also loaded on the second input terminal of the amplification module 20, so that the voltage difference between the first input terminal and the second input terminal of the amplification module 20 is the voltage output between the positive terminal and the negative terminal of the thermopile, and no interference voltage is introduced in the amplification of the amplification module 20, and only the voltage output by the thermopile corresponding to the ambient temperature is amplified, so that the voltage output by the amplification module 20 accurately corresponds to the voltage output between the positive terminal and the negative terminal of the thermopile, and the accuracy of the human body temperature calculated by the final processor 40 is further ensured.

In some embodiments of the present invention, as shown in fig. 2, the first voltage output terminal is further connected to the second sampling terminal of the analog-to-digital converter 30. In this embodiment, the analog-to-digital converter 30 also samples the reference voltage value VREF at the same time, because the reference voltage VREF is the voltage output by the power module 60 through voltage stabilization, but even though the voltage is the voltage through voltage stabilization, the voltage value still has a slight deviation, when the voltage value is applied to a large number of products, the voltage value cannot be completely the same, and some small upper and lower deviations still exist, so that the output voltage of the thermopile read by the processor 40, which is amplified by the amplifying module 20 and converted by the analog-to-digital converter 30, correspondingly has a small deviation, and thus the human body temperature calculated according to the same algorithm also has a small fluctuation, i.e., an inaccurate phenomenon. In order to solve the problem, the processor 40 reads the reference voltage VREF value through the analog-to-digital converter 30, determines whether the reference voltage VREF value has a deviation from a pre-stored standard voltage, and calibrates an algorithm according to the deviation value if the reference voltage VREF value has a deviation, so that the calculated human body temperature is accurate and reliable. Thereby further promoting the accuracy that the temperature measurement circuit detected human temperature.

In some embodiments of the present invention, as shown in fig. 1 or fig. 2, the temperature measuring module 10 further includes a temperature detecting output end, and the temperature detecting output end is connected to the third sampling end of the analog-to-digital converter 30. Namely, the temperature measurement module 10 also detects the ambient temperature, and the temperature measurement module 10 is internally provided with a thermistor, the resistance value of which corresponds to the temperature, so that the temperature detection output end is connected with other resistors to form a voltage division circuit with the thermistor, so that the temperature detection output end outputs a voltage corresponding to the temperature change to the third sampling end of the analog-to-digital converter 30, and then the analog-to-digital conversion output value processor 40, and the processor 40 calculates the accurate human body temperature by a related algorithm by combining the acquired ambient temperature value and the voltage value output by the thermopile. The formula of the combined calculation based on the ambient temperature and the output voltage of the thermopile is the prior art, and is not described herein again.

In some embodiments of the present invention, as shown in fig. 1 or fig. 2, the amplification module 20 includes a comparator IC2, a first resistor R1, a second resistor R2, and a third resistor R3;

one end of the first resistor R1 is a second input end of the amplifying module 20, the other end of the first resistor R1 is connected to the inverting input end of the comparator IC2, one end of the second resistor R2 is a first input end of the amplifying module 20, the other end of the second resistor R2 is connected to the inverting input end of the comparator IC2, and the output end of the comparator IC2 is an output end of the amplifying module 20.

In some embodiments of the present invention, as shown in fig. 3, the power supply module 60 includes a voltage conversion unit 61 and a voltage stabilization unit 62 and a second voltage output terminal; the output terminal of the voltage converting unit 61 is a second voltage output terminal to output a second voltage VDD, and the output terminal of the voltage stabilizing unit 62 is a first voltage output terminal to output a reference voltage VREF. The voltage converting unit 61 is a voltage converting circuit mainly composed of a voltage converting integrated circuit IC5, and converts the input voltage into another voltage, i.e., a second voltage VDD, by boosting or reducing the voltage, so as to provide the voltage required for the operation of the processor 40, the amplifying module 20, and the analog-to-digital converter 30, and since the devices have low operating voltages, the voltage converting unit 61 is generally a voltage reducing circuit, for example, converting the input 5V voltage into a 3.3V voltage. The voltage stabilizing unit 62 mainly includes a twelfth resistor R12, a high-precision voltage stabilizing source IC6, a thirteenth resistor R13 and a fourteenth resistor R14, wherein the high-precision voltage stabilizing source IC6 may be a high-precision voltage stabilizing source IC such as TL431, for example, TL431 is taken as an example, one end of the twelfth resistor R12 is an input end of the voltage stabilizing unit 62, the other end of the twelfth resistor R12 is commonly connected with a cathode of the TL431, a reference electrode of the TL431 and one end of the thirteenth resistor R13, an anode of the TL431 is grounded, the other end of the thirteenth resistor R13 and one end of the fourteenth resistor R14 are output ends of the voltage stabilizing unit 62, and the other end of the fourteenth resistor R14 is grounded. The input voltage is isolated and divided by a twelfth resistor R12, a high-precision voltage is output by the cathode of the TL431 to the ground, and the input voltage is divided by a voltage dividing resistor consisting of a thirteenth resistor R13 and a fourteenth resistor R14 to output a proper voltage value, and if the input voltage is 5V, a high-precision reference voltage of 1.2V can be output.

In some embodiments of the utility model, as shown in fig. 1 or fig. 2, the temperature detection output end of temperature measurement module 10 includes positive output end and negative output end, the temperature measurement circuit still includes fifth resistance R5 and fourth resistance R4, the second voltage output end is connected to fifth resistance R5's one end, the fifth resistance R5 other end and fourth resistance R4 one end connect in the positive output end altogether, the third sample terminal of adc 30 is connected to fourth resistance R4's the other end, negative output end ground. The fifth resistor R5 and the thermistor of the temperature measuring module 10 form a voltage dividing circuit, and the voltage dividing circuit is isolated by the fourth resistor R4 to output a voltage consistent with the resistance value of the temperature detected by the thermistor.

In some embodiments of the present invention, the output of the analog-to-digital converter 30 is connected to the processor 40 via a communication data line. Because the analog-to-digital converter 30 can perform analog-to-digital conversion on multiple input voltages, when the processor 40 reads corresponding values of the multiple input voltages, the corresponding values can be read based on a communication mode with the analog-to-digital converter 30, so that data reading is convenient and fast.

Taking the circuit shown in fig. 2 as an example, the operating principle of the circuit is as follows: the negative output end of The thermopile is loaded with a 1.2V reference voltage VREF, The voltage output by The positive output end of The thermopile + changes on The basis of 1.2V, The voltage difference relative to The negative output end of The thermopile-is a voltage value reflecting The detected human body temperature, The voltage is amplified by The comparator IC2, The voltage difference is amplified because The voltage difference is very small, and therefore The voltage difference needs to be amplified to a larger multiple, generally 200-300 times, such as 250 times, The amplified voltage value of The human body temperature is input to The analog-to-digital converter 30, The analog-to-digital converter 30 is mainly an analog-to-digital conversion integrated circuit IC3, The human body temperature voltage value obtained by analog-to-digital conversion is read by The processor 40, meanwhile, The thermistor integrated in The thermopile collects The ambient temperature, The temperature value is output to The third voltage sampling end of The analog-to-digital converter 30 through The fourth resistor R4 via The voltage dividing circuit composed of The fifth resistor R5, meanwhile, the second voltage sampling end of the analog-to-digital converter 30 also collects the reference voltage VREF, so that the processor 40 finally obtains a human body temperature voltage value, an environment temperature voltage value and a reference voltage VREF value, the human body temperature is obtained according to the human body temperature voltage value and the environment temperature voltage value through calculation according to a formula, the reference voltage VREF value is further compared with a prestored reference voltage VREF value, the human body temperature is calibrated according to the deviation of the human body temperature value and the environment temperature voltage value, the calibration can be obtained according to the formula or table lookup, and the accurate human body temperature is finally obtained.

Further, since the amplification factor of the comparator is large, if a single-stage comparator is adopted, the comparator with high amplification parameter is provided, so that the price is high, multi-stage amplification can be adopted, and if two comparators with low amplification factors and low prices are adopted for amplification, the amplification factor of each comparator can be reduced by about 10 times, so that the cost can be saved.

In this embodiment, the processor 40 and the analog-to-digital converter 30 communicate using the existing IC2 protocol, but two communication lines are required.

In some embodiments of the present invention, as shown in fig. 4, the present invention further includes an infrared distance detection module 50; the infrared distance detecting module 50 includes an infrared emitting unit 51 and an infrared receiving unit 52, and a control terminal of the infrared emitting unit 51 and an output terminal of the infrared receiving unit 52 are respectively connected to the processor 40. For some ear thermometers such as the ear thermometer, when the probe of the ear thermometer extends into the ear guo, the situation that the thermopile detection end is not aligned to the tympanic membrane easily occurs, and at the moment, the temperature of the ear guo is detected instead of the temperature of the tympanic membrane, so that the inaccuracy occurs, when the probe is not aligned to the tympanic membrane but is aligned to the ear guo, the distance between the probe and the target is different, and therefore, the requirement for determining whether the probe is aligned to the tympanic membrane or not can be met by adding the infrared distance detection module 50. If the requirement is not met, the ear thermometer can give a corresponding prompt based on display or sound, so that a user can adjust the position of the probe until the probe is aligned with the tympanic membrane, and the accuracy of temperature detection is guaranteed.

The infrared emitting unit 51 mainly includes a second NPN triode Q2, an infrared emitting diode D3, a seventh resistor R7 and an eighth resistor R8, one end of the seventh resistor R7 is connected to the second voltage output terminal, the other end of the seventh resistor R7 is connected to the anode of the infrared emitting diode D3, the cathode of the infrared emitting diode D3 is connected to the collector of the second NPN triode Q2, the base of the second NPN triode Q2 is connected to one end of the eighth resistor R8, the emitter of the second NPN triode Q2 is grounded, and the other end of the eighth resistor R8 is the control terminal of the infrared emitting unit 51.

The infrared receiving unit 52 comprises an infrared receiving tube Q1, a tenth resistor R10, an eleventh resistor R11, a first diode D1 and a second diode D2, the emitter of the infrared receiving tube Q1 is grounded, the collector of the infrared receiving tube Q1 is connected with one end of the tenth resistor R10, the anode of the first diode D1, one end of the eleventh resistor R11 and the cathode of the second diode D2 in a common mode, the other end of the tenth resistor R10 and the anode of the first diode D1 are connected to the ground in a common mode, and the other end of the eleventh resistor R11 is the output end of the infrared receiving unit 52.

When the infrared distance detection module 50 works, the processor 40 outputs a controllable signal to control the infrared emitting diode D3 to work through the second NPN triode Q2, so as to output an infrared signal, the infrared signal is reflected by a target and then received by the infrared receiving tube Q1, an output voltage signal of the infrared emitting diode D3 is isolated and input to the processor 40 through the eleventh resistor R11, and the processor 40 judges the strength of the received infrared signal according to the magnitude of the voltage, so as to judge whether the ear thermometer, such as an ear thermometer, is correctly placed. The first diode D1 and the second diode D2 are clamping terminals for the positive electrode of the power supply and the ground, respectively, and play a role in eliminating interference signals. The infrared distance detection module 50 is added to further ensure the accuracy of the placement position of the device where the temperature measurement circuit is located when the temperature of the human body is measured, so that the detected temperature of the human body is accurate.

The utility model discloses still provide an ear temperature rifle, ear temperature rifle is provided with the temperature measurement circuit that above-mentioned embodiment mentioned. By applying the temperature measuring circuit, the accuracy of temperature measurement can be obviously improved.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like, indicate the orientation or positional relationship indicated based on the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," and "fixed" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

In the present application, unless expressly stated or limited otherwise, the first feature may be directly on or directly under the second feature or indirectly via intermediate members. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

Although embodiments of the present invention have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art without departing from the scope of the present invention.

Claims (9)

1. A temperature measurement circuit for an ear thermometer is characterized by comprising a temperature measurement module based on a thermopile, an amplification module, a power supply module, an analog-to-digital converter and a processor;

the temperature measurement module comprises a thermopile cathode end and a thermopile anode end, the power supply module comprises a first voltage output end, the first voltage output end outputs stabilized reference voltage, and the first voltage output end is connected with the thermopile cathode end of the temperature measurement module; the positive electrode end of the thermopile of the temperature measurement module is connected with the first input end of the amplification module;

the first voltage output end is further connected with a second input end of the amplifying module, an output end of the amplifying module is connected with a first sampling end of the analog-to-digital converter, and an output end of the analog-to-digital converter is connected with the processor.

2. The thermometric circuit of claim 1, wherein the first voltage output terminal is further coupled to a second sampling terminal of the analog-to-digital converter.

3. The temperature measurement circuit of claim 1, wherein the temperature measurement module further comprises a temperature detection output terminal, and the temperature detection output terminal is connected to the third sampling terminal of the analog-to-digital converter.

4. The thermometric circuit of claim 1, wherein the amplification module comprises a comparator, a first resistor, a second resistor, and a third resistor;

one end of the first resistor is a second input end of the amplifying module, the other end of the first resistor is connected with an inverting input end of the comparator, one end of the second resistor is a first input end of the amplifying module, the other end of the second resistor is connected with the inverting input end of the comparator, and an output end of the comparator is an output end of the amplifying module.

5. The temperature measuring circuit of claim 3, wherein the power module comprises a voltage converting unit, a voltage stabilizing unit and a second voltage output terminal; the output end of the voltage conversion unit is a second voltage output end, the voltage conversion unit is used for outputting a second voltage, and the output end of the voltage stabilization unit is a first voltage output end to output a reference voltage.

6. The temperature measurement circuit according to claim 5, wherein the temperature detection output terminal of the temperature measurement module comprises a positive output terminal and a negative output terminal, the temperature measurement circuit further comprises a fifth resistor and a fourth resistor, one end of the fifth resistor is connected to the second voltage output terminal, the other end of the fifth resistor and one end of the fourth resistor are connected to the positive output terminal, the other end of the fourth resistor is connected to the third sampling terminal of the analog-to-digital converter, and the negative output terminal is grounded.

7. The thermometric circuit of claim 1, further comprising an infrared distance detection module; the infrared distance detection module comprises an infrared emission unit and an infrared receiving unit, and the control end of the infrared emission unit and the output end of the infrared receiving unit are respectively connected with the processor.

8. The thermometric circuit of claim 1, wherein the output of the analog-to-digital converter is coupled to the processor via a communication data line.

9. An ear thermometer, characterized in that it is provided with a temperature measuring circuit according to any one of claims 1 to 8.

Images