阅读说明：本技术 用于耳温枪的测温电路、控制方法和耳温枪 (Temperature measurement circuit for ear thermometer, control method and ear thermometer ) 是由 李勇 杨光磊 于 2020-12-04 设计创作，主要内容包括：本发明涉及一种用于耳温枪的测温电路、控制方法和耳温枪,通过增加加热模块,加热模块的工作状态受处理器控制,在耳温枪检测耳廓内的温度时,处理器控制加热模块开始工作,并读取耳廓内的温度是否达到预设温度,在达到预设温度后处理器读取热电堆检测到电压,以此并根据电压和当前耳郭内的实际温度确定人体温度。其中预设温度与人体表面的正常温度接近,从而使得热电堆的探头被加热到与人体温度接近的温度,以此接收到耳郭辐射的热量不会损失,从而输出的电压与人体的温度准确对应。以此有效提升了检测的人体温度的准确性。(The invention relates to a temperature measurement circuit and a temperature measurement method for an ear thermometer and the ear thermometer. The temperature is close to the normal temperature of the surface of a human body, so that the probe of the thermopile is heated to the temperature close to the temperature of the human body, the heat radiated by the auricle is received without loss, and the output voltage accurately corresponds to the temperature of the human body. Therefore, the accuracy of the detected human body temperature is effectively improved.)

1. A temperature measuring circuit for an ear thermometer is characterized by comprising a thermopile, a heating module, an amplifying module, an analog-to-digital converter and a processor;

the thermopile comprises a thermopile cathode end, a thermopile anode end and a temperature detection output end, the thermopile anode end is connected with the first input end of the amplification module, the thermopile cathode end and the second input end of the amplification module are connected with reference voltage, the output end of the amplification module is connected with the first sampling end of the analog-to-digital converter, the temperature detection output end is connected with the third sampling end of the analog-to-digital converter, the output end of the analog-to-digital converter is connected with the processor, and the control end of the heating module is connected with the processor;

the processor is configured to:

acquiring the voltage acquired from the first sampling end from the analog-to-digital converter, and acquiring the ambient temperature acquired from the second sampling end from the analog-to-digital converter;

controlling the heating module to work so that the ambient temperature reaches and maintains a preset temperature;

and determining the temperature of the human body according to the currently acquired environmental temperature value and the voltage value.

2. The temperature measurement circuit of claim 1, further comprising a power module outputting the regulated reference voltage, wherein the thermopile negative terminal is further connected to a second sampling terminal of the analog-to-digital converter.

3. The thermometry circuit of claim 1, wherein the processor is further configured to:

outputting a PWM signal to control the heating module to work intermittently;

and adjusting the pulse width of the PWM signal according to the obtained proximity degree of the environment temperature and the preset temperature so as to enable the environment temperature to reach and maintain the preset temperature.

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 according to claim 2, wherein the power supply module comprises a voltage conversion unit and a voltage stabilization unit; the output end of the voltage conversion unit outputs a second voltage, and the output end of the voltage stabilization unit outputs the reference voltage.

6. The thermometric circuit according to claim 5, wherein the heating module comprises a third NPN transistor, a heater, a thirteenth resistor and a twelfth resistor;

one end of the twelfth resistor is a control end of the heating module, the other end of the twelfth resistor is connected to a base of the third NPN triode, a collector of the third NPN triode is connected to one end of the heater, the other end of the heater is connected to one end of the thirteenth electronic resistor, and the other end of the thirteenth electronic resistor is connected to the second voltage.

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. A control method for ear thermometer temperature measurement based on the temperature measurement circuit for ear thermometer according to any one of claims 1 to 7, the control method comprising:

acquiring the current environment temperature;

controlling a heating module to work so that the ambient temperature reaches and maintains a preset temperature;

acquiring voltage output by a thermopile;

and determining the temperature of the human body according to the currently acquired environment temperature and the voltage.

9. The control method according to claim 8, characterized by further comprising:

controlling the heating module to work intermittently;

and controlling the intermittent working state of the heating module according to the proximity degree of the ambient temperature and the preset temperature, wherein the intermittent working state comprises the time of circulation on and the time of circulation off.

10. An ear thermometer provided with a temperature measuring circuit for an ear thermometer according to any one of claims 1 to 7.

Technical Field

The invention relates to a temperature measurement circuit and a control method for an ear thermometer and the ear thermometer, which are applied to the field of temperature measurement equipment.

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 using process, the temperature of the thermopile temperature measuring probe of the ear thermometer is greatly different from the temperature of a human body due to different environmental temperatures, and if the temperature is in a relatively cold or relatively hot environment, the infrared radiation quantity of the human body detected by the probe is inaccurate, so that the measured temperature of the human body is accurate finally.

Disclosure of Invention

The invention aims to solve the technical problem that the human body temperature is inaccurate due to fluctuation of the pressure difference output by an infrared thermopile of the existing human body temperature measuring equipment.

The invention provides a temperature measuring circuit for an ear thermometer, which comprises a thermopile, a heating module, an amplifying module, an analog-to-digital converter and a processor;

the thermopile comprises a thermopile cathode end, a thermopile anode end and a temperature detection output end, the thermopile anode end is connected with the first input end of the amplification module, the thermopile cathode end and the second input end of the amplification module are connected with reference voltage, the output end of the amplification module is connected with the first sampling end of the analog-to-digital converter, the temperature detection output end is connected with the third sampling end of the analog-to-digital converter, the output end of the analog-to-digital converter is connected with the processor, and the control end of the heating module is connected with the processor;

the processor is configured to:

acquiring the voltage acquired from the first sampling end from the analog-to-digital converter, and acquiring the ambient temperature acquired from the second sampling end from the analog-to-digital converter;

controlling the heating module to work so that the ambient temperature reaches and maintains a preset temperature;

and determining the temperature of the human body according to the currently acquired environmental temperature value and the voltage value.

Optionally, the temperature measuring circuit further includes a power supply module, the power supply module outputs the regulated reference voltage, and the thermopile negative electrode end is further connected to the second sampling end of the analog-to-digital converter.

Optionally, the processor is further configured to:

outputting a PWM signal to control the heating module to work intermittently;

and adjusting the pulse width of the PWM signal according to the obtained proximity degree of the environment temperature and the preset temperature so as to enable the environment temperature to reach and maintain the preset temperature.

Optionally, the amplifying module includes 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.

Optionally, the power supply module includes a voltage conversion unit and a voltage stabilization unit; the output end of the voltage conversion unit outputs a second voltage, and the output end of the voltage stabilization unit outputs the reference voltage.

Optionally, the heating module comprises a third NPN transistor, a heater, a thirteenth resistor, and a twelfth resistor;

one end of the twelfth resistor is a control end of the heating module, the other end of the twelfth resistor is connected to a base of the third NPN triode, a collector of the third NPN triode is connected to one end of the heater, the other end of the heater is connected to one end of the thirteenth electronic resistor, and the other end of the thirteenth electronic resistor is connected to the second voltage.

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.

The invention also provides a control method for ear thermometer temperature measurement, based on the temperature measurement circuit for the ear thermometer, the control method comprises the following steps:

acquiring the current environment temperature;

controlling a heating module to work so that the ambient temperature reaches and maintains a preset temperature;

acquiring voltage output by a thermopile;

and determining the temperature of the human body according to the currently acquired environment temperature and the voltage.

Optionally, the control method further includes:

controlling the heating module to work intermittently;

and controlling the intermittent working state of the heating module according to the proximity degree of the ambient temperature and the preset temperature, wherein the intermittent working state comprises the time of circulation on and the time of circulation off.

The invention also provides the ear thermometer, which is provided with the temperature measuring circuit for the ear thermometer.

By adopting the temperature measuring circuit for the ear thermometer disclosed by the invention, the heating module is additionally arranged, the working state of the heating module is controlled by the processor, when the ear thermometer detects the temperature in the auricle, the processor controls the heating module to start working, reads whether the temperature in the auricle reaches the preset temperature or not, and reads the voltage detected by the thermopile after the preset temperature is reached, so that the temperature of a human body is determined according to the voltage and the current actual temperature in the auricle. The temperature is close to the normal temperature of the surface of a human body, so that the probe of the thermopile is heated to the temperature close to the temperature of the human body, the heat radiated by the auricle is received without loss, and the output voltage accurately corresponds to the temperature of the human body. Therefore, the accuracy of the detected human body temperature is effectively improved.

Drawings

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

FIG. 2 is a circuit diagram of a power module in an ear thermometer circuit according to an embodiment of the present invention;

FIG. 3 is a circuit diagram of a temperature measurement portion of an ear thermometer circuit according to another embodiment of the present invention;

FIG. 4 is a flowchart of a control method for ear thermometer thermometry according to an embodiment of the present invention.

Detailed Description

It is to be noted that the embodiments and features of the embodiments 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 invention provides a temperature measuring circuit for an ear thermometer, as shown in fig. 1, the temperature measuring circuit comprises a thermopile 10, a heating module 70, an amplifying module 20, an analog-to-digital converter 30 and a processor 40;

the thermopile 10 includes thermopile negative pole end The +, thermopile positive pole end The + and temperature detection output, The first input of amplifying module 20 is connected to thermopile positive pole end The +, reference voltage is connected to thermopile negative pole end The-and The second input of amplifying module 20, The first sample terminal of adc 30 is connected to The output of amplifying module 20, The third sample terminal of adc 30 is connected to The temperature detection output, treater 40 is connected to adc 30's output, treater 40 is connected to The control end of heating module 70.

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.

The processor 40 is configured to: acquiring the voltage acquired from the first sampling end from the analog-to-digital converter 30, and acquiring the ambient temperature acquired from the second sampling end from the analog-to-digital converter 30; controlling the heating module 70 to work so that the ambient temperature reaches a preset temperature; and determining the temperature of the human body according to the currently acquired environmental temperature value and the voltage value.

Due to the difference of the temperature of the environment where the ear thermometer is used, such as in winter and summer, the temperature difference between the temperature of the detection probe of the ear thermometer, namely the probe of the thermopile 10, and the temperature of the human body is large, and if the detection probe is used in winter, the temperature of the detection probe is low, and when the detection probe penetrates into the auricle to detect the temperature, the heat radiated by the tympanic membrane in the auricle contacts the surface of the detection probe with low temperature and is attenuated, so that the radiation heat detected by the detection probe is inaccurate, and finally the temperature of the detected human body is inaccurate. To solve this problem, the embodiment of the present invention adds a heating module 70, wherein the heating module 70 includes a heating wire and an associated control circuit, and the heating wire is disposed in contact with the detection probe of the thermopile 10 to raise the temperature of the detection probe when the detection probe is operated. The working state of the heating module 70 is controlled by the processor 40, when the ear thermometer detects the temperature in the auricle, the processor 40 controls the heating module 70 to start working, reads whether the temperature in the auricle reaches the preset temperature, and after the preset temperature is reached, the processor 40 reads the voltage detected by the thermopile 10, so that the human body temperature is determined according to the voltage and the actual temperature in the current auricle. The preset temperature is close to the normal temperature of the surface of the human body, and if the preset temperature is 34 ℃, the probe of the thermopile 10 is heated to the temperature close to the temperature of the human body, so that the heat radiated by the pinna cannot be lost, and the output voltage accurately corresponds to the temperature of the human body. Therefore, the accuracy of the detected human body temperature is effectively improved.

Because the output voltage between the positive terminal and the negative terminal of the thermopile 10 is weak and generally only 50-700 uV, the voltage needs to be amplified, the output voltage is amplified by the amplification module 20, the amplification factor can be generally 100-300 times, and the amplified voltage is a voltage between 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, i.e., 50 to 700uV, is very close to zero potential, and if the voltage is directly input to an amplifying circuit, such as a comparator, of the amplifying module 20, it is difficult to reach the conduction voltage of a triode inside the comparator to enable the triode to work, so that the comparator 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 the comparator enables the comparator to operate normally to amplify the differential pressure.

In some embodiments of the invention, the processor 40 is further configured to: and outputting the PWM signal to control the heating module 70 to operate intermittently, and adjusting the pulse width of the PWM signal according to the proximity of the acquired ambient temperature and the preset temperature, so that the ambient temperature reaches and maintains the preset temperature. In this embodiment, the processor 40 outputs the PWM signal to control the heating wire L1 of the heating module 70 to operate in the intermittent operation state, wherein the operation time is the effective time in the PWM signal, and the power of the operation of the heating wire L1 can be adjusted by the PWM signal to adjust the heating speed at any time. Because the operation of the heating wire L1 is controlled to make the temperature of the detection probe of the thermopile 10 reach and maintain the preset temperature, the power of the heating wire L1 needs to be finely controlled, otherwise, even if the preset temperature is reached in the operation process, the preset temperature is easily maintained in a large fluctuation, so that the temperature of the probe cannot be stably maintained at the preset temperature, and errors are brought to the detection. Therefore, the power of the heating wire L1 is controlled by the PWM signal, and the PWM pulse width is adjusted by the proximity degree of the current environment temperature and the preset temperature, if the difference between the environment temperature and the preset temperature is large, the larger pulse width can be adopted to control the power of the heating wire to be higher, so that the temperature of the detection probe is faster to be increased, when the difference between the environment temperature and the preset temperature is small, the pulse width is reduced, the power of the heating wire L1 is reduced, the temperature of the detection probe is more stable to be close to the preset temperature, the minimum pulse width is adopted to control the heating wire L1 to work after the preset temperature is reached, so that the temperature of the detection probe is stably maintained at the preset temperature, the temperature of the detection probe is in a constant temperature state, and the accuracy of the final detection temperature is ensured.

Specifically, when determining the human body temperature according to the currently acquired environmental temperature value and voltage value, a two-dimensional table may be used, where the voltage V _ TP corresponding to the human body infrared signal detected by the thermopile 10 and acquired by the processor 40 from the analog-to-digital converter 30, and the environmental temperature T1 output by the temperature detection output end of the thermopile 10 and the human body temperature T2 form a two-dimensional table, as shown in the following diagram:

t1_ a, T1_ b, and T1_ D correspond to three different temperature values of T1, respectively, and T2_ A, T2_ B, T2_ D is three different body temperatures obtained by corresponding to the three different temperature values under the current voltage V _ TP.

By using a table look-up method to calculate a formula, the processing capacity of the processor 40 can be reduced, and the accuracy of the obtained human body temperature can be improved under the condition that the table is relatively fine.

In the prior art, the extreme of the thermopile 10 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 correspondingly, because the voltage output between the extreme and the negative terminal of the thermopile 10 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 solution of this embodiment, the extreme of the thermopile 10 is loaded with one path of the reference voltage VREF of the power module 60, 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 extreme terminal and the negative terminal of the thermopile 10, and the accuracy of the human body temperature calculated by the final processor 40 is further ensured.

In some embodiments of The present invention, The thermometry circuit further comprises a power module 60 for outputting a regulated reference voltage VREF, The thermopile cathode terminal The-being further connected to The second sampling terminal of The analog-to-digital converter 30. As shown in fig. 1, The power module 60 is connected to The thermopile cathode end of The temperature measuring module via The regulated reference voltage VREF via The first voltage output end, in The prior art, The cathode end of The thermopile 10 is generally connected to a common dc voltage, and The voltage is not regulated, so that there is a certain ripple factor to make The voltage fluctuate, so that The corresponding anode end also fluctuates, because The voltage output between The anode end and The cathode end of The thermopile 10 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. Further, the first voltage output terminal is also connected to a second sampling terminal of the analog-to-digital converter 30. 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, even though the voltage is subjected to voltage stabilization, the voltage value still has a slight deviation, when the voltage 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 amplification 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.

As shown in fig. 2, the power module 60 includes a voltage conversion unit 61, a voltage regulation 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 invention, as shown in fig. 1 or fig. 2, the temperature detection output terminal of the thermopile 10 includes a positive output terminal and a negative output terminal, the temperature measurement circuit further includes a fifth resistor R5 and a fourth resistor R4, one end of the fifth resistor R5 is connected to the second voltage output terminal, the other end of the fifth resistor R5 and one end of the fourth resistor R4 are commonly connected to the positive output terminal, the other end of the fourth resistor R4 is connected to the third sampling terminal of the analog-to-digital converter 30, and the negative output terminal is grounded. The fifth resistor R5 and the thermistor of the thermopile 10 constitute a voltage divider circuit, and a voltage corresponding to the resistance of the temperature detected by the thermistor is isolated and outputted via the fourth resistor R4.

In some embodiments of the 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 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.

In some embodiments of the invention, the heating module 70 includes a third NPN transistor Q3, a heater L1, a thirteenth resistor R13, and a twelfth resistor R12; one end of the twelfth resistor R12 is a control end of the heating module 70, the other end of the twelfth resistor R12 is connected to a base of the third NPN transistor Q3, a collector of the third NPN transistor Q3 is connected to one end of the heater L1, the other end of the heater L1 is connected to one end of the thirteenth resistor R13, and the other end of the thirteenth resistor R13 is connected to the second voltage VDD.

Taking the circuit shown in fig. 1 as an example, the circuit operation principle is as follows: when The ear thermometer starts to collect The human body temperature, The negative output end The-of The thermopile 10 is loaded with The reference voltage VREF of 1.2V, The voltage output by The positive output end The + changes on The basis of 1.2V, The voltage difference relative to The negative output end The-is The 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 small, The voltage difference needs to be amplified by a larger multiple, generally 200 times or 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 10 collects The ambient temperature, The temperature value is output to The third voltage sampling end of The analog-to-digital converter 30 through The voltage dividing circuit composed of The fifth resistor R5 and The fourth resistor R4, meanwhile, the second voltage sampling terminal of the analog-to-digital converter 30 also collects a reference voltage VREF. So that the processor 40 finally obtains the human body temperature voltage value, the environment temperature voltage value and the reference voltage VREF value. The processor firstly obtains the current environment temperature according to the table lookup or calculation of the environment temperature voltage value, the processor 40 outputs a PWM signal to control the heating wire L1 to be in a gap working state through the third NPN triode Q3, the environment temperature is compared with the preset temperature, the pulse width of the PWM signal is adjusted according to the proximity degree of the environment temperature and the preset temperature, so that the working temperature of the temperature sensing probe of the ear thermometer is increased and maintained at the preset temperature, at the moment, the processor determines the human body temperature according to the currently detected environment temperature and the human body temperature voltage value, the human body temperature can be obtained according to the two-dimensional table query in the embodiment, 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 invention, as shown in fig. 3, an infrared distance detection module 50 is further included; 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 human body temperature measuring devices such as an ear thermometer, when a probe of the human body temperature measuring device extends into an auricle, the situation that the detection end of a thermopile is not aligned to the tympanic membrane easily occurs, and the temperature of the auricle 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 auricle, the distance between the probe and the auricle is different, and therefore, whether the distance between the probe and a target meets the requirement or not can be detected by adding the infrared distance detection module 50 so as to judge whether the probe is aligned to the tympanic membrane or not. If the requirement is not met, the human body temperature measurement equipment 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 ensured.

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 human body temperature measurement equipment such as an ear thermometer is placed correctly. 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 invention further provides a control method for measuring the temperature of the ear thermometer, based on the temperature measuring circuit for the ear thermometer mentioned in the above embodiment, as shown in fig. 4, the control method comprises:

step S100, acquiring the current ambient temperature;

step S200, controlling the heating module to work so that the ambient temperature reaches and maintains a preset temperature;

step S300, acquiring voltage output by the thermopile;

and step S400, determining the temperature of the human body according to the currently acquired environment temperature and voltage.

When the ear thermometer starts to work, the current environment temperature is firstly acquired, the heating module is controlled to work so that the environment temperature is increased to reach and be maintained at the preset temperature, the voltage output by the thermopile is acquired at the moment, and finally the human body temperature is determined according to the environment temperature and the voltage. The problem of inaccurate human body temperature of final determination caused by inaccurate radiant heat of the tympanic membrane detected by a detection probe of the thermopile when temperature measurement is carried out when the difference between the ambient temperature and the normal temperature of the human body is large is solved, and therefore the accuracy of the detected human body temperature is effectively improved.

In a further embodiment of the invention, the control method further comprises:

step S210, controlling the heating module to work intermittently;

and step S220, controlling the intermittent working state of the heating module according to the proximity degree of the ambient temperature and the preset temperature, wherein the intermittent working state comprises the time of circulation on and the time of circulation off.

In this embodiment, the processor may output a PWM signal to control the heating module to perform intermittent operation, so that the heating module is in a cycle state of the switch, where the time of the operation cycle is the effective time in the PWM signal, and the PWM signal may adjust the operating power of the heating module, so as to adjust the heating speed at any time. Because the operation of the heating element of the heating module, such as the heating wire, is controlled to make the temperature of the detection probe of the thermopile reach and maintain the preset temperature, the power of the heating wire needs to be finely controlled, otherwise, even if the preset temperature is reached in the working process, the preset temperature is maintained later, and large fluctuation is generated, so that the temperature of the probe cannot be stably maintained at the preset temperature, and errors are brought to detection. Therefore, the power of the heating wire is controlled by the PWM signal, and the PWM pulse width is adjusted by the proximity degree of the current environment temperature and the preset temperature, if the distance between the environment temperature and the preset temperature is far away, the power of the heating wire can be controlled to be higher by adopting a larger pulse width, so that the temperature of the detection probe is quickly increased, when the difference between the environment temperature and the preset temperature is smaller, the pulse width is reduced, the power of the heating wire is reduced, so that the temperature of the detection probe is more stable and close to the preset temperature, the heating wire is controlled to work by adopting the minimum pulse width after the preset temperature is reached, so that the temperature of the detection probe is stably maintained at the preset temperature, so that the temperature of the detection probe is in a constant temperature state, and the accuracy of the final detection temperature is ensured.

The invention also provides ear thermometer equipment, wherein the temperature measuring circuit for the ear thermometer is arranged in the ear thermometer equipment, the heating module is additionally arranged in the circuit, so that the temperature of the probe of the ear thermometer is increased and maintained at the preset temperature during temperature measurement of the ear thermometer, the accuracy of the ear thermometer for detecting the temperature of a human body is effectively improved, and the probe is heated, so that the probe of the ear thermometer can not cause discomfort of a person due to the low temperature of the probe when contacting with the auricle during temperature measurement in the cold environment temperature, and the use experience of the person is also 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 "central," "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 are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the 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," "secured," and the like are to be construed broadly and can, 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 meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. 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 above, 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 within the scope of the present invention.