Temperature measuring device and microwave oven

Abstract

The utility model provides a temperature measuring device and a microwave oven. The device comprises a microcontroller MCU, a filtering module, a voltage protection module, a thermistor RT, a protection circuit and a switching module. One end of the switching module is respectively connected with the thermistor RT and the voltage protection module through the protection circuit, the other end of the switching module is connected with one end of the microcontroller MCU through the protection circuit, the other end of the thermistor RT is respectively connected with one end of the power supply Vcc and one end of the voltage protection module, and the other ends of the voltage protection module and the switching module are grounded; the voltage protection module is connected with a sampling port ADC of the MCU through the filtering module; according to the temperature measuring device and the microwave oven, the structure of an internal circuit of the temperature measuring device can be effectively simplified, the temperature in the cavity can be accurately measured at different temperature stages of the cavity of the microwave oven, the sensitivity and the linearity of measurement are improved, and the cost of the device is reduced.

Description

Technical Field

[0001] This utility model relates to the field of temperature measurement technology, and more specifically, to a temperature measuring device and a microwave oven. Background Technology

[0002] Accurate measurement of the internal temperature of a microwave oven is crucial during its use. This measurement accuracy plays a key role in controlling the heating effect, ensuring food cooking quality, and guaranteeing the safe operation of the microwave oven. Currently, thermistors are commonly used for microwave oven cavity temperature measurement due to their low cost and fast response speed.

[0003] Most existing thermistor temperature measurement methods involve connecting the thermistor in series with a fixed resistor to perform voltage division measurement (e.g., Figure 3 (As shown). However, this method has significant drawbacks in microwave oven cavity temperature measurement scenarios. During microwave oven operation, the internal temperature varies considerably, ranging from room temperature to 250°C. When using a single fixed resistor for voltage division, the rate of change of the output voltage with temperature (i.e., sensitivity) varies greatly across different temperature ranges. In particular, the sensitivity may be too low in the low or high temperature ranges, leading to inaccurate temperature measurements and an inability to reflect changes in cavity temperature promptly and accurately. Furthermore, the high degree of nonlinearity complicates subsequent temperature calculations and control, affecting the microwave oven's performance and stability.

[0004] While some improved solutions exist for thermistor temperature measurement, most are insufficient for the specific working environment and wide temperature range requirements of microwave ovens, or suffer from issues such as complex structure and high cost. Therefore, researching ways to improve the sensitivity and linearity of temperature measurement while reducing costs by simplifying the structure of the internal temperature measurement device in a microwave oven cavity is of great significance.

[0005] In the patent CN206469994U, a kind of cooking equipment of frying, baking and baking, including: shell, heating assembly, main control board, cooking cavity and sensor for detecting temperature in cooking cavity are equipped in the shell, the working state of heating assembly is controlled according to the temperature detected by sensor by main control board, the sensor includes thermistor, the main control board is equipped with main control chip and temperature detection circuit, the temperature detection circuit includes X road voltage division branch, one end of the first voltage division branch in the X road voltage division branch is connected with one end of the thermistor, and the other end is connected with voltage input end, except the first voltage division branch, one end of X-1 voltage division branch is respectively connected with one end of the thermistor, and the other end is respectively connected with X-1 input / output I / O port of main control chip;The main control chip adjusts the resistance value of X road voltage division circuit by controlling the output level of X-1 I / O port, so as to meet the requirement of frying, baking and baking cooking equipment temperature range and detection precision, but since thermistor is connected with power supply anode through X road voltage division branch and voltage division resistance, under the action of multiple resistances, the problem that the measurement accuracy of thermistor to temperature in cavity is reduced and the nonlinearity degree is increased, and the circuit structure is more complex. Utility model content

[0006] Therefore, the utility model aims at providing a temperature measuring device and microwave oven to solve the problems of uneven sensitivity in wide temperature range, high nonlinearity degree when single fixed value resistance and thermistor are used for voltage division measurement in the existing microwave oven cavity temperature measurement technology, and complex circuit structure and high cost when multiple resistances and thermistor are used for voltage division measurement, so as to effectively simplify the internal circuit structure of temperature measuring device, accurately measure the temperature in cavity at different temperature stages of microwave oven cavity, improve the sensitivity and linearity of measurement, and reduce the cost of device.

[0007] To achieve the above-mentioned purpose, the technical scheme of the utility model is as follows:

[0008] The utility model relates to a kind of temperature measuring device and microwave oven, a kind of temperature measuring device, including microcontroller MCU, filter module, voltage protection module, thermistor R T , protection circuit and switching module;One end of switching module is connected with thermistor R T , voltage protection module respectively through protection circuit, the other end of switching module is connected with one end of microcontroller MCU through protection circuit, the other end of thermistor R T It is connected with power supply Vcc, one end of voltage protection module respectively, voltage protection module, the other end of switching module is all grounded;Voltage protection module is connected with the sampling port ADC of microcontroller MCU by filter module.

[0009] Further, the protection circuit comprises a protection circuit one and a protection circuit two; one end of the switching module is connected with the thermistor R T and the voltage protection module through the protection circuit one, and the other end of the switching module is connected with the control port of the microcontroller MCU through the protection circuit two.

[0010] Further, the control port of the microcontroller MCU is provided with at least two; when the control port is provided with two, the control port comprises a pin P10 and a pin P11, one end of the pin P10 and the pin P11 is arranged on the microcontroller MCU, and the other end of the pin P10 and the pin P11 is connected with the protection circuit two respectively.

[0011] Further, the protection circuit one and the protection circuit two are provided with at least two resistors.

[0012] Further, the protection circuit one and the protection circuit two are provided with two resistors; the protection circuit one comprises a first resistor R1 and a second resistor R2, and the protection circuit two comprises a third resistor R3 and a fourth resistor R4; one end of the first resistor R1 and the second resistor R2 is connected with the thermistor R T and the voltage protection module in parallel, and the other end of the first resistor R1 and the second resistor R2 is connected with one end of the third resistor R3 and the fourth resistor R4 through the switching module respectively; the other end of the third resistor R3 and the fourth resistor R4 is connected with the pin P10 and the pin P11 of the microcontroller MCU respectively.

[0013] Further, at least two triodes are arranged in the switching module.

[0014] Further, two triodes are arranged in the switching module; the switching module comprises a first triode V1 and a second triode V2; the emitter of the first triode V1 and the second triode V2 is connected with ground in parallel; the collector of the first triode V1 and the second triode V2 is connected with the first resistor R1 and the second resistor R2 respectively; the base of the first triode V1 and the second triode V2 is connected with the third resistor R3 and the fourth resistor R4 respectively.

[0015] Further, the first triode V1 and the second triode V2 are both NPN type triodes.

[0016] Further, the voltage protection module comprises a first diode D1 and a second diode D2; the negative electrode of the first diode D1 is connected with one end of the thermistor R T and the power supply Vcc respectively, the positive electrode of the first diode D1 is connected with the negative electrode of the second diode D2, the filter module, the other end of the thermistor R T , the first resistor R1 and the second resistor R2 close to one end of the thermistor R T respectively, and the positive electrode of the second diode D2 is grounded.

[0017] A microwave oven, said microwave oven comprising said temperature measuring device, said device is installed inside the cavity of the microwave oven.

[0018] Compared with the prior art, the temperature measuring device and the microwave oven have the following beneficial effects:

[0019] Through the arrangement of the temperature measuring device in the microwave oven, the structure of the internal circuit of the temperature measuring device can be effectively simplified, accurate measurement of the temperature in the cavity can be realized at different temperature stages of the microwave oven cavity, the sensitivity and linearity of the measurement are improved, and the cost of the device is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which form a part of this description, are included to provide a further understanding of the present application, and are incorporated herein for purposes of illustrating the preferred embodiments of the present application and are not intended to limit the present application. In the drawings:

[0021] Figure 1 It is an internal circuit schematic diagram of the temperature measuring device;

[0022] Figure 2a It is an equivalent state diagram of the temperature measuring circuit when different inputs (the temperature in the microwave oven cavity is in the first temperature measuring interval) schematic diagram;

[0023] Figure 2b It is an equivalent state diagram of the temperature measuring circuit when different inputs (the temperature in the microwave oven cavity is in the second temperature measuring interval) schematic diagram;

[0024] Figure 2c It is an equivalent state diagram of the temperature measuring circuit when different inputs (the temperature in the microwave oven cavity is in the third temperature measuring interval) schematic diagram;

[0025] Figure 3 It is a temperature measuring circuit diagram schematic diagram using a single fixed value resistor in series voltage division in the prior art;

[0026] Figure 4 It is a linear degree and sensitivity comparison schematic diagram before and after the circuit improvement.

[0027] Explanation of reference signs: 1, filter module; 2, voltage protection module; 3, protection circuit; 31, protection circuit 1; 32, protection circuit 2; 4, switching module. DETAILED DESCRIPTION

[0028] The utility novel concepts of the present disclosure will be described below using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. However, these utility novel concepts can be embodied in many different forms and should not be considered limited to the embodiments described herein.

[0029] It should be noted that the embodiments in the present utility novel and the features in the embodiments can be combined with each other without conflict.

[0030] The present utility novel will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0031] The present embodiment is directed to the temperature measuring device, which is the same as the conventional temperature measuring device, and the overall structure is composed of wires and resistors.

[0032] In order to solve the problems of uneven sensitivity and high nonlinearity in a wide temperature range when a single fixed value resistor and a thermistor are used for voltage division measurement in the existing microwave oven cavity temperature measurement technology, and the problem of complex circuit structure and high cost when multiple resistors and thermistors are used for voltage division measurement, the present embodiment proposes a temperature measuring device and a microwave oven. The temperature measuring device is a device that uses a triode to switch series resistors to achieve high sensitivity measurement of thermistors in a wide temperature range, which includes a microcontroller MCU, a filter module 1, a voltage protection module 2, a thermistor R T , a protection circuit 3, and a switching module 4. One end of the switching module 4 is connected to the thermistor R T and the voltage protection module 2 through the protection circuit 3, and the other end of the switching module 4 is connected to one end of the microcontroller MCU through the protection circuit 3. The other end of the thermistor R T is connected to the power supply Vcc and one end of the voltage protection module 2, and the other end of the voltage protection module 2 and the switching module 4 are grounded; the voltage protection module 2 is connected to the sampling port ADC of the microcontroller MCU through the filter module 1. In the present embodiment, the power supply Vcc is +Vcc.

[0033] Through the arrangement of the temperature measuring device in the microwave oven, the structure of the internal circuit of the temperature measuring device can be effectively simplified, the temperature inside the cavity can be accurately measured at different temperature stages of the microwave oven cavity, the sensitivity and linearity of the measurement can be improved, and the cost of the device can be reduced. In addition, through the arrangement of the thermistor R T , the temperature change inside the microwave oven cavity can be sensed in real time, and the temperature change can be converted into resistance change.

[0034] The protection circuit 3 includes a protection circuit 31 and a protection circuit 32. One end of the switching module 4 is connected to the thermistor R T, the other end of the switching module 4 is connected with the control port of the microcontroller MCU through the protection two circuit 32. Among them, the control port of the microcontroller MCU is provided with at least two. Preferably, the control port includes pin P10 and pin P11, one end of the pin P10 and the pin P11 is arranged on the microcontroller MCU, and the other end of the pin P10 and the pin P11 is connected with the protection two circuit 32 respectively.

[0035] Through the cooperation of the protection one circuit 31 and the protection two circuit 32, the safety and stability of the temperature measuring device can be improved, the reliability of the switching module 4 and MCU can be ensured, and the circuit structure in the device can be simplified on the basis of reducing the cost of the device.

[0036] Specifically, the protection one circuit 31 and the protection two circuit 32 are provided with at least two resistors. Preferably, the protection one circuit 31 and the protection two circuit 32 are provided with two resistors. The protection one circuit 31 includes a first resistor R1 and a second resistor R2, and the protection two circuit 32 includes a third resistor R3 and a fourth resistor R4. One end of the first resistor R1 and the second resistor R2 is connected with the thermistor R T , the other end of the first resistor R1 and the second resistor R2 is connected with one end of the third resistor R3 and the fourth resistor R4 through the switching module 4 respectively; the other end of the third resistor R3 and the fourth resistor R4 is connected with the pin P10 and the pin P11 of the microcontroller MCU respectively. Among them, the first resistor R1, the second resistor R2, the third resistor R3 and the fourth resistor R4 are constant value resistors.

[0037] Through the protection one circuit 31 and the protection two circuit 32, on the one hand, the voltage division of the temperature measuring circuit in the device can be realized under the action of the MCU. On the other hand, through the setting of the protection one circuit 31, the current limiting protection can be realized, which can prevent the switching module 4 or the thermistor R T from being damaged due to overcurrent; can also adjust the sensitivity, optimize the linearity of the working interval of the thermistor R T , make the voltage output easier to process; can also realize the temperature compensation of the static working point, ensure that the circuit in the device can work stably in the required wide temperature range. Through the setting of the protection two circuit 32, the pin overload of the MCU can be prevented, the running safety and reliability of the MCU can be improved; can also play a role in protecting the switching module 4; can also play a role in inhibiting noise and oscillation, reducing signal sensitivity, and preventing the occurrence of false triggering.

[0038] At least two triodes are arranged in the switching module 4. The types of triodes include any one of NPN and PNP. Preferably, two triodes are arranged in the switching module 4. The switching module 4 includes a first triode V1 and a second triode V2. The emitters of the first triode V1 and the second triode V2 are connected in parallel to ground; the collectors of the first triode V1 and the second triode V2 are connected to the first resistor R1 and the second resistor R2 respectively; the bases of the first triode V1 and the second triode V2 are connected to the third resistor R3 and the fourth resistor R4 respectively. The first triode V1 and the second triode V2 are both NPN type triodes.

[0039] Through the arrangement of the triodes, the switching of the thermistor R T The output signal is amplified, the accuracy of the information collected by the microcontroller MCU is improved, and the switching control is also improved. Under the action of the MCU, the switching of the resistors with different resistance values in different environmental temperature ranges is realized.

[0040] The voltage protection module 2 includes a first diode D1 and a second diode D2. The negative poles of the first diode D1 are respectively connected to one end of the thermistor R T and the power supply Vcc, the positive poles of the first diode D1 are respectively connected to the negative pole of the second diode D2, the filtering module 1, the other end of the thermistor R T , the first resistor R1 and the second resistor R2 close to one end of the thermistor R T ; and the positive pole of the second diode D2 is grounded.

[0041] Through the arrangement of D1 and D2, voltage clamping can be achieved to prevent damage to the sampling port ADC of the microcontroller MCU.

[0042] The filtering module 1 is a low-pass filtering module. The filtering module 1 includes a fifth resistor R5 and a capacitor C1. One end of the fifth resistor R5 is connected to the positive pole of the first diode D1 of the voltage protection module 2, and the other end of the fifth resistor R5 is respectively connected to one end of the capacitor C1 and the sampling port ADC of the microcontroller MCU. The capacitor C1 is grounded. The fifth resistor is a fixed resistor.

[0043] Through the arrangement of R5 and C1 in the filtering module 1, low-pass filtering can be achieved to filter out power supply ripple, high-frequency switching noise and electromagnetic interference, improve the signal-to-noise ratio of the MCU sampling signal, and make the temperature measurement more accurate. It can also protect the ADC input of the MCU and improve the anti-interference ability of the system.

[0044] A microwave oven, the microwave oven includes the temperature measuring device, the device is installed inside the cavity of the microwave oven.

[0045] By the temperature measuring device in the present application, only two NPN triodes and five constant value resistors are used, so that the circuit structure is simple, easy to realize, and the cost is reduced, which is suitable for large-scale application in microwave oven production. In addition, by the threshold switching under the action of resistors with different resistance values, MCU and switching module 4, the linearity can be effectively improved, and the reliability and stability of the microwave oven can be improved. In addition, by switching resistors with different resistance values in different temperature intervals, the change rate of the output voltage Uo with the microwave oven cavity temperature is more uniform, so that higher comprehensive sensitivity of measurement can be realized in a wider temperature range, the cavity temperature change can be reflected in time and accurately, which is helpful for optimizing the heating control of the microwave oven.

[0046] Working principle of the circuit in the temperature measuring device:

[0047] Thermistor R T The end away from the power supply Vcc, the end of the constant value resistors R1 and R2 in parallel are connected with the signal output end Uo. The microcontroller MCU controls the conduction and cutoff state of NPN triodes V1 and V2 by outputting different control signals Ui1, Ui2 according to the current measured microwave oven cavity temperature, so as to realize the switching of different resistors. Among them, Ui1 is the input signal of the end of R3 away from V1; Ui2 is the input signal of the end of R4 away from V2.

[0048] Specifically, the collector-emitter saturation voltage V CES of the triode is ignored, and V CES =0 is allowed, and the high and low levels are represented by positive logic, that is, the high level is "1" and the low level is "0". The working state of the temperature measuring circuit in the device is as follows:

[0049] When the microwave oven cavity temperature is in the first temperature measuring interval, that is, the temperature is in the lower temperature interval, the microcontroller MCU makes Ui1="1" and Ui2="0", at this time V1 is turned on and V2 is turned off, only constant value resistor R1 and thermistor R T are connected in series for voltage division measurement (see the attached drawings in the description). Figure 2a At this time, the signal output voltage is: .

[0050] When the cavity temperature is in the second temperature measuring interval, that is, the cavity temperature rises to a certain degree, the microcontroller MCU makes Ui1="0" and Ui2="1", at this time V1 is turned off and V2 is turned on, constant value resistor R2 and thermistor R T are connected in series, which changes the voltage division ratio and improves the measurement sensitivity in this temperature interval, so that the temperature change can be captured more accurately (see the attached drawings in the description). Figure 2b At this time, the signal output voltage is: .

[0051] When the cavity temperature is in the third temperature measurement interval, i.e., the cavity temperature is further increased relative to the temperature of the second temperature measurement interval, the microcontroller MCU sets Ui1 = "1", Ui2 = "1", at this time both triodes are turned on, the fixed value resistors R1 and R2 are connected in parallel, and then the parallel connection is connected with the thermistor R T in series, further adjusting the voltage division ratio to adapt to the measurement requirements of a higher temperature interval, ensuring accurate measurement within the entire temperature range of the microwave oven (see the description of the accompanying drawings Figure 2c ). At this time, the signal output voltage is: .

[0052] By reasonably selecting resistors of different resistance values and switching thresholds, the nonlinearity problem of the resistance-temperature characteristic of the thermistor R T can be effectively improved, the relationship between the output voltage Uo and the cavity temperature of the microwave oven is closer to linear, the complexity of subsequent temperature calculation and control is reduced, and the stability and reliability of the microwave oven are improved.

[0053] Embodiment 1:

[0054] Generally, a negative temperature coefficient thermistor NTC is usually selected as a temperature sensor, and its resistance value calculation formula is as follows:

[0055] .

[0056] Wherein, R T is the resistance of the thermistor at temperature T (Ω);

[0057] R T0 is the resistance of the thermistor at reference temperature T0 (Ω);

[0058] B is the material constant of the thermistor (K), also known as B value;

[0059] T is the absolute temperature of the thermistor (K), T(K)=t(℃)+273.15, t is the Celsius temperature value (℃);

[0060] T0 is the absolute temperature of the reference temperature (K), the commonly used reference temperature t0=25℃, then T0=t0+273.15=25+273.15=298.15K.

[0061] It is known that the resistance R T0 of a certain NTC thermistor selected at temperature (t0=25℃, T0=298.15K) is 10KΩ, and the B value is 3950. +Vcc=+5V, R1=1KΩ, R2=0.2KΩ are selected.

[0062] The temperature measuring interval (0-300 DEG C) is divided into three intervals (0-100 DEG C, 101-200 DEG C, 201-300 DEG C), and the pins P10, P11 ports of the microcontroller MCU output "10", "01", "11" respectively, so that the measuring circuit is connected with R1, R2, R1 / / R2 respectively, and the sensitivity and linearity trend obtained before and after the improvement of the calculation analysis circuit are as shown in Figure 4.

[0063] In the temperature measuring interval (0-100 DEG C), the sensitivity and linearity of the improved circuit are the same as those of the original circuit, the sensitivity is 0.0294V / DEG C, and the linear determination coefficient R 2 0.9703.

[0064] In the temperature measuring interval (101-100 DEG C), the sensitivity of the improved circuit is increased from 0.0157 V / DEG C of the original circuit to 0.0259V / DEG C, and the linear determination coefficient R 2 is increased from 0.9473 to 0.9963.

[0065] In the temperature measuring interval (201-300 DEG C), the sensitivity of the improved circuit is increased from 0.0024 V / DEG C of the original circuit to 0.0101V / DEG C, and the linear determination coefficient R 2 is increased from 0.953 to 0.9723.

[0066] Through the measurement of the sensitivity and the linear determination coefficient of the device before and after the improvement in different temperature measuring intervals, it is not difficult to see that, compared with before the improvement, the setting of the application can not only effectively improve the real-time temperature measurement sensitivity of the device to the microwave oven cavity, but also effectively improve the linearity of the measurement, and guarantee the accuracy and reliability of the measurement result.

[0067] In the utility model, for any temperature measuring device, can include the temperature measuring device structure that one kind described in the embodiment, and on the basis that the voltage protection module 2, the switching module 4 of the related structure and the assembly relation provided in the embodiment, the temperature measuring device still includes the conventional component of the structure such as electric wire, resistance;In view of its all being prior art, here do not repeat.

[0068] The above only describes preferred embodiments of the utility model, and does not limit the utility model, and any modification, equivalent replacement, improvement, etc. within the spirit and principle of the utility model should be included in the protection scope of the utility model.

Claims

1. A temperature measuring device, characterized by The application relates to a voltage protection circuit, which comprises a microcontroller MCU, a filter module (1), a voltage protection module (2), a thermistor R T , a protection circuit (3) and a switching module (4); one end of the switching module (4) is connected with the thermistor R T , the voltage protection module (2) through the protection circuit (3), the other end of the switching module (4) is connected with one end of the microcontroller MCU through the protection circuit (3), the other end of the thermistor R T is connected with a power supply Vcc and one end of the voltage protection module (2) respectively, and the other ends of the voltage protection module (2) and the switching module (4) are grounded; the voltage protection module (2) is connected with a sampling port ADC of the microcontroller MCU through the filter module (1).

2. A temperature measuring device according to claim 1, characterised in that The protection circuit (3) comprises a protection circuit (31) and a protection circuit (32); one end of the switching module (4) is connected with the thermistor R T through the protection circuit (31), and the other end of the switching module (4) is connected with the control port of the microcontroller MCU through the protection circuit (32).

3. A temperature measuring device according to claim 2, characterised in that The control port of the microcontroller MCU is provided with at least two; when the control port is provided with two, the control port includes a pin P10 and a pin P11, one end of the pin P10 and the pin P11 is provided on the microcontroller MCU, and the other end of the pin P10 and the pin P11 is connected with the protection two circuit (32) respectively.

4. A temperature measuring device according to claim 3, characterised in that The protection one circuit (31) and the protection two circuit (32) are provided with at least two resistors.

5. A temperature measuring device according to claim 4, characterised in that The protection circuit (31) and the protection circuit (32) are provided with two resistors; the protection circuit (31) comprises a first resistor R1 and a second resistor R2, and the protection circuit (32) comprises a third resistor R3 and a fourth resistor R4; one end of the first resistor R1 and the second resistor R2 is connected in parallel and then connected with the thermistor R T , respectively; the other end of the first resistor R1 and the second resistor R2 is connected with one end of the third resistor R3 and the fourth resistor R4 through the switching module (4), respectively; and the other end of the third resistor R3 and the fourth resistor R4 is connected with the pin P10 and the pin P11 of the microcontroller MCU, respectively.

6. A temperature measuring device according to claim 5, characterised in that The switching module (4) is provided with at least two triodes.

7. A temperature measuring device according to claim 6, characterised in that The switching module (4) is provided with two triodes; the switching module (4) includes a first triode V1 and a second triode V2; the emitter of the first triode V1 and the second triode V2 is connected with the ground in parallel; the collector of the first triode V1 and the second triode V2 is connected with a first resistor R1 and a second resistor R2 respectively; the base of the first triode V1 and the second triode V2 is connected with a third resistor R3 and a fourth resistor R4 respectively.

8. A temperature measuring device according to claim 7, characterised in that The first triode V1 and the second triode V2 are both NPN type triodes.

9. The temperature measuring device of claim 5, wherein, The voltage protection module (2) comprises a first diode D1 and a second diode D2; the negative pole of the first diode D1 is connected with one end of the thermistor R T , and the power supply Vcc, the positive pole of the first diode D1 is connected with the negative pole of the second diode D2, the filter module (1), the other end of the thermistor R T , the first resistor R1 and the second resistor R2 close to one end of the thermistor R T ; and the positive pole of the second diode D2 is grounded.

10. A microwave oven characterized by comprising: The microwave oven includes the temperature measuring device in any one of claims 1-9, and the device is installed inside the cavity of the microwave oven.

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