High-precision temperature measurement system and method based on dual-frequency modulation

Abstract

The invention relates to the technical field of precision measurement, and provides a high-precision temperature measurement system and method based on double-frequency modulation, and the system comprises a temperature detection module which comprises a Wheatstone bridge which is composed of three fixed-value resistors and a temperature probe to form four bridge arms; the temperature probe comprises an NTC thermistor and a large-capacitance capacitor connected in parallel with the NTC thermistor; the double-frequency modulation module is used for performing mixed modulation on the low-frequency signal and the high-frequency signal and outputting a double-frequency modulation signal to the temperature detection module; wherein when a low-frequency signal passes through the temperature probe, the temperature probe is dominated by the thermistor impedance; when a high-frequency signal passes through the temperature probe, the temperature probe is dominated by the capacitor impedance; the signal demodulation module is used for carrying out differential demodulation on the voltage change signal output by the temperature detection module to obtain a resistance change signal of the NTC thermistor; the resistance change signal is used for representing a temperature measurement result.

Description

Technical Field

[0001] The present invention relates to the field of precision measurement technology, and more specifically, to a high-precision temperature measurement system and method based on dual-frequency modulation. Background Art

[0002] Space science experiments are scientific experiments conducted in space through carriers such as satellite platforms. The special environment of space, such as vacuum, microgravity, and strong radiation, provides unique experimental conditions and opportunities for scientific research, which makes space science experiments an important direction for human exploration of the universe. For example, space gravitational wave detection, high-precision earth gravity field measurement, and microgravity research projects are all typical space science experiment projects. Space science experiments usually require a very harsh experimental environment, including a very stable temperature environment. During the experiment, it is inevitable to measure the temperature environment for a long time with high precision.

[0003] In recent years, more and more research has focused on high-resolution temperature measurement. However, the measurement circuits and sensors suitable for space science experiments must not only meet the requirements of long-term and high-precision measurement, but also be able to withstand the severe vibration, high temperature and other environmental tests when the launch vehicle is launched, as well as the satellite's restrictions on volume and power consumption. Traditional NTC thermistor sensors have become the first choice for space temperature detection due to their high sensitivity, low power consumption, and small size, and have been widely used in the field of temperature environment measurement. In space measurement, the temperature sensor is fixed on the measured point rather than on the circuit board, so it is often necessary to use a cable to connect the sensor and the circuit board. However, in some cases, the satellite structure layout causes the cable length to be too long, so the line resistance and its fluctuations cannot be ignored, affecting high-precision temperature measurement. Usually, a single frequency signal is used to modulate the circuit in the experiment, but because the line resistance of the wire in the circuit is always connected in series with the measured resistance, when a single frequency signal is used to modulate the temperature signal, the line resistance and the noise and errors generated by the stress and ambient temperature fluctuations are coupled into the measurement of the measured resistance, introducing additional errors to the high-precision temperature measurement, thereby affecting the temperature measurement accuracy. Summary of the invention

[0004] In order to overcome the defect in the prior art that an additional error is introduced into high-precision temperature measurement when a single-frequency signal is used to modulate a circuit, thereby affecting the temperature measurement accuracy, the present invention provides a high-precision temperature measurement system and method based on dual-frequency modulation.

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0006] A high-precision temperature measurement system based on dual-frequency modulation, comprising:

[0007] A temperature detection module, comprising a Wheatstone bridge, wherein the Wheatstone bridge is composed of three fixed value resistors and a temperature probe constituting its four bridge arms; the temperature probe comprises an NTC thermistor and a large capacitance capacitor connected in parallel with the NTC thermistor;

[0008] A dual-frequency modulation module, used for mixed modulation of a low-frequency signal and a high-frequency signal, and outputting a dual-frequency modulation signal to the temperature detection module; wherein, when the low-frequency signal passes through the temperature probe, the thermistor impedance is dominant in the temperature probe; and when the high-frequency signal passes through the temperature probe, the capacitor impedance is dominant in the temperature probe;

[0009] The signal demodulation module is used to perform differential demodulation on the voltage change signal output by the temperature detection module to obtain a resistance change signal of the NTC thermistor; the resistance change signal is used to characterize the temperature measurement result.

[0010] Furthermore, the present invention also proposes a high-precision temperature measurement method based on dual-frequency modulation, and applies the high-precision temperature measurement system based on dual-frequency modulation proposed by the present invention. The method comprises the following steps:

[0011] Input a low-frequency signal and a high-frequency signal, and perform mixed modulation on the low-frequency signal and the high-frequency signal to obtain a dual-frequency modulation signal;

[0012] The dual-frequency modulated signal is output to a Wheatstone bridge equipped with a temperature probe, wherein the temperature probe is equipped with an NTC thermistor; wherein when a low-frequency signal passes through the temperature probe, the thermistor impedance is dominant in the temperature probe; and when a high-frequency signal passes through the temperature probe, the capacitor impedance is dominant in the temperature probe;

[0013] The voltage change signal output from the Wheatstone bridge is collected and differentially demodulated to obtain a resistance change signal of the NTC thermistor; the resistance change signal is used to characterize the temperature measurement result.

[0014] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0015] The present invention measures the NTC thermistor and the wire resistance to be measured simultaneously by two frequency signals, and further eliminates the error caused by the wire resistance fluctuation in the low-frequency signal by differential demodulation, thereby improving the temperature measurement accuracy;

[0016] The present invention adopts a temperature probe composed of a large-capacitance capacitor connected in parallel with an NTC thermistor to measure temperature, and can distinguish different signal source measurements in different signal modulation circuits; specifically, when a low-frequency signal passes through the temperature probe, the capacitor impedance is much larger than the thermistor impedance, and the circuit measures the thermistor resistance change and the line resistance change at this time; when a high-frequency signal passes through the temperature probe, the capacitor impedance is much smaller than the thermistor impedance, and the thermistor resistance change contributes little to the total impedance change, and the circuit only measures the line resistance change at this time, and further through differential demodulation, the line resistance disturbance in the low-frequency signal can be eliminated, thereby optimizing the high-precision temperature measurement result. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The figure is a schematic diagram of a high-precision temperature measurement system based on dual-frequency modulation according to an embodiment of the present invention.

[0018] Figure 2 FIG. 4 is a circuit diagram of a high-precision temperature measurement system according to an embodiment of the present invention.

[0019] Figure 3 The figure is a schematic diagram of the structure of a temperature probe according to an embodiment of the present invention.

[0020] Figure 4 The figure is a flow chart of a high-precision temperature measurement method based on dual-frequency modulation according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples of devices and methods consistent with some aspects of the present invention as detailed in the appended claims.

[0022] The terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "the" and "the" used in the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0023] It should be understood that although the terms first, second, third, etc. may be used in the present invention to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0024] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Example 1

[0026] This embodiment proposes a high-precision temperature measurement system based on dual-frequency modulation. Figure 1 , which is an architecture diagram of a high-precision temperature measurement system based on dual-frequency modulation according to this embodiment.

[0027] The high-precision temperature measurement system based on dual-frequency modulation proposed in this embodiment includes:

[0028] A temperature detection module 1, comprising a Wheatstone bridge 110, wherein the Wheatstone bridge 110 is composed of three fixed value resistors and a temperature probe 120 constituting four bridge arms; the temperature probe 120 comprises an NTC thermistor 121 and a large capacitance capacitor 122 connected in parallel with the NTC thermistor 121;

[0029] The dual-frequency modulation module 2 is used to perform mixed modulation of the low-frequency signal and the high-frequency signal, and output the dual-frequency modulation signal to the temperature detection module 1; wherein, when the low-frequency signal passes through the temperature probe 120, the impedance of the thermistor 121 in the temperature probe 120 is dominant; when the high-frequency signal passes through the temperature probe 120, the impedance of the capacitor in the temperature probe 120 is dominant;

[0030] The signal demodulation module 3 is used to perform differential demodulation on the voltage change signal output by the temperature detection module 1 to obtain a resistance change signal of the NTC thermistor 121; the resistance change signal is used to characterize the temperature measurement result.

[0031] In this embodiment, the NTC thermistor 121 to be measured and the wire resistance are measured simultaneously by two frequency signals, and the error caused by the wire resistance fluctuation in the low frequency signal is further eliminated by differential demodulation, thereby improving the temperature measurement accuracy.

[0032] In this embodiment, a temperature probe 120 composed of a large-capacitance capacitor 122 connected in parallel with an NTC thermistor 121 is used to measure temperature, which can distinguish different signal sources for measurement in different signal modulation circuits.

[0033] Specifically, when a low-frequency signal passes through the temperature probe 120, the capacitor impedance is much larger than the impedance of the thermistor 121. At this time, the circuit measures the resistance change of the thermistor 121 and the line resistance change; when a high-frequency signal passes through the temperature probe 120, the capacitor impedance is much smaller than the impedance of the thermistor 121. The resistance change of the thermistor 121 contributes little to the total impedance change. At this time, the circuit only measures the line resistance change. The line resistance disturbance in the low-frequency signal can be eliminated by differential demodulation, thereby optimizing the high-precision temperature measurement result.

[0034] In an optional embodiment, the dual-frequency modulation module 2 includes a first AC power supply 210 for outputting a low-frequency signal, a second AC power supply 220 for outputting a high-frequency signal, and an adding circuit 230 for mixed modulation of the low-frequency signal and the high-frequency signal; wherein the first AC power supply 210 and the second AC power supply 220 output sinusoidal voltage signals.

[0035] For example, Figure 2 FIG. 1 is a circuit diagram of a high-precision temperature measurement system according to an embodiment of the present invention.

[0036] The low-frequency signal and the high-frequency signal respectively outputted by the first AC power source 210 and the second AC power source 220 are superimposed and modulated in the adding circuit 230, and then input into the Wheatstone bridge 110 composed of a fixed-value resistor, a temperature probe 120, a capacitor connected in parallel with the fixed-value resistor, and a wire resistance, and the temperature probe 120 is connected in series with two resistors as wire resistances; in this embodiment, for the convenience of calculation, it is assumed that R line (t) = R line1 (t)+R line2 (t)~1Ω, and considering the balance point of the Wheatstone bridge, the capacitance of the Wheatstone bridge is equal to the capacitance of the capacitor connected in parallel to the temperature probe 120, and the resistance of the Wheatstone bridge is equal to the resistance of the thermistor 121 on the temperature probe 120. The temperature change on the side of the temperature probe and the change of the line resistance will cause the voltage signal output by the bridge to change. The voltage change signal is obtained by collecting the output signal of the Wheatstone bridge 110, and the resistance change signal of the NTC thermistor 121 is further obtained by differential demodulation of the signal demodulation module 3.

[0037] Exemplarily, the outputs of the first AC power source 210 and the second AC power source 220 in this embodiment are sinusoidal voltage signals, which are expressed as follows:

[0038]

[0039] Among them, V1 and V2 represent the signal amplitudes of the low-frequency signal and the high-frequency signal respectively; ω1 and ω2 represent the signal frequencies of the low-frequency signal and the high-frequency signal respectively; and t represents time.

[0040] In an optional embodiment, the signal demodulation module 3 includes a differential amplifier 310, a first demodulator 320, a first filter 330, a second demodulator 340 and a second filter 350; wherein:

[0041] The voltage change signal output by the Wheatstone bridge 110 is input into the differential amplifier 310 for differential amplification, and then input into the first demodulator 320 and the second demodulator 340 respectively to be demodulated with the original signal;

[0042] The low frequency signal and the high frequency signal in the dual frequency modulation module 2 are respectively input into the first demodulator 320 and the second demodulator 340 for demodulation;

[0043] The output ends of the first demodulator 320 and the second demodulator 340 are connected to the input ends of the first filter 330 and the second filter 350 respectively, so as to perform low-pass filtering on the demodulated signal.

[0044] Furthermore, in an optional embodiment, when the low-frequency signal passes through the temperature probe 120, the impedance in the temperature probe 120 is dominated by the NTC thermistor 121, and its voltage change signal It is expressed as:

[0045]

[0046] in, Represents the signal amplitude of the low-frequency signal; Z T (t) is the probe impedance at time t, R line (t) is the resistance of the wire at time t, and R0 is the resistance of the fixed resistor on the Wheatstone bridge 110;

[0047] When the high-frequency signal passes through the temperature probe 120, the impedance in the temperature probe 120 is dominated by the large-capacitance capacitor 122, and its voltage change signal It is expressed as:

[0048]

[0049] in, is the signal amplitude of the high-frequency signal; ω2 is the signal frequency of the high-frequency signal, C0 is the capacitance of the capacitor in the Wheatstone bridge 110; G is the gain of the differential amplifier 310; is the phase, and

[0050]

[0051] For the target measurement temperature, the resistance value of the NTC thermistor 121 in the temperature probe 120 is expressed as:

[0052]

[0053] Wherein, T0 is the nominal temperature of the NTC thermistor 121 , R0 is the resistance value of the NTC thermistor 121 at the nominal temperature; T is the temperature of the NTC thermistor 121 at time t; and β is the temperature coefficient of the NTC thermistor 121 .

[0054] When a low-frequency signal passes through the temperature probe 120, the equivalent impedance of the capacitor must be much smaller than the resistance. At this time, the probe impedance is dominated by the thermistor 121:

[0055]

[0056] When a high-frequency signal passes through the temperature probe 120, the equivalent impedance of the capacitor must be much greater than the resistance. At this time, the probe impedance is dominated by the capacitor:

[0057]

[0058] Therefore, when the low-frequency signal passes through the temperature probe 120, the impedance in the temperature probe 120 is dominated by the NTC thermistor 121, and the differential amplifier 310 outputs a voltage change signal When the high frequency signal passes through the temperature probe 120, the impedance in the temperature probe 120 is dominated by the large capacitance capacitor 122, and the differential amplifier 310 outputs a voltage change signal. And from the above formula, we can know that the voltage change signal Only with line resistance R line (t)Related.

[0059] Further, in an optional embodiment, in the signal demodulation module 3, when the resistance change signal of the NTC thermistor 121 is obtained by differential demodulation, the following steps are performed:

[0060] Obtain the low-frequency signal V1 and the high-frequency signal V2 before mixed frequency modulation in the dual-frequency modulation module 2, and the voltage change signal output by the temperature detection module 1 and After demodulation and low-pass filtering, a dual-frequency measurement signal is obtained; its expression is:

[0061]

[0062] Among them, V low (t) and V high (t) is the voltage change signal of the NTC thermistor 121 under the modulation of the low frequency signal and the high frequency signal;

[0063] The current wire resistance R is calculated by the dual-frequency measurement results. line (t) and the resistance change signal R of the NTC thermistor 121T (t); its expression is:

[0064]

[0065] From the above formula, it can be seen that the resistance change signal R of the NTC thermistor 121 is T (t) and the resistance change signal R line (t) After addition, if the line resistance R line (t) performs effective measurement, and its disturbance will be coupled to the resistance R of the NTC thermistor 121 T (t), is considered as part of the temperature signal, resulting in measurement error.

[0066] In this embodiment, after differential demodulation of the dual-frequency signal, the voltage change signal V of the NTC thermistor 121 modulated by the low-frequency signal and the high-frequency signal can be obtained. low (t) and V high (t), where V high (t) only the line resistance R line (t) is an unknown quantity, so the time domain signal R of the line resistance can be obtained line (t), which is further used to solve the resistance change signal R of the NTC thermistor 121 T (t), the disturbance of line resistance can be eliminated and high-precision measurement results can be obtained.

[0067] The resistance change signal R of the NTC thermistor 121 in this embodiment T (t) Characterizes the temperature measurement results.

[0068] Furthermore, in the temperature probe 120 in this embodiment, a low thermal conductivity material is further provided between the NTC thermistor 121 and the large-capacitance capacitor 122 ; and a packaging material is provided on the outer surface of the temperature probe 120 .

[0069] like Figure 3 , which is a schematic structural diagram of the temperature probe 120 of this embodiment.

[0070] In this embodiment, the large-capacitance capacitor 122 and the thermistor 121 are insulated by using a low thermal conductivity material to prevent thermal coupling between the capacitor and the measured surface to the greatest extent and avoid introducing additional noise.

[0071] Exemplarily, an aerogel felt is further provided between the NTC thermistor 121 and the large-capacitance capacitor 122 .

[0072] Exemplarily, the outer surface of the temperature probe 120 is provided with an aluminum nitride ceramic shell.

[0073] Example 2

[0074] This embodiment proposes a high-precision temperature measurement method based on dual-frequency modulation, which is applied to the high-precision temperature measurement system based on dual-frequency modulation proposed in Embodiment 1. Figure 4 FIG. 1 is a flow chart of a high-precision temperature measurement method based on dual-frequency modulation according to an embodiment of the present invention.

[0075] The high-precision temperature measurement method based on dual-frequency modulation proposed in this embodiment includes the following steps:

[0076] Input a low-frequency signal and a high-frequency signal, and perform mixed modulation on the low-frequency signal and the high-frequency signal to obtain a dual-frequency modulation signal;

[0077] The dual-frequency modulated signal is output to a Wheatstone bridge 110 equipped with a temperature probe 120, wherein the temperature probe 120 is equipped with an NTC thermistor 121; wherein when a low-frequency signal passes through the temperature probe 120, the impedance of the thermistor 121 is dominant in the temperature probe 120; and when a high-frequency signal passes through the temperature probe 120, the impedance of the capacitor is dominant in the temperature probe 120;

[0078] The voltage change signal output from the Wheatstone bridge 110 is collected and differentially demodulated to obtain a resistance change signal of the NTC thermistor 121; the resistance change signal is used to characterize the temperature measurement result.

[0079] In an optional embodiment, the low-frequency signal and the high-frequency signal are sinusoidal AC signals. The expression is:

[0080]

[0081] Among them, V1 and V2 represent the signal amplitudes of the low-frequency signal and the high-frequency signal respectively; ω1 and ω2 represent the signal frequencies of the low-frequency signal and the high-frequency signal respectively.

[0082] In an optional embodiment, when the low-frequency signal passes through the temperature probe 120, the impedance in the temperature probe 120 is dominated by the NTC thermistor 121, and its voltage change signal It is expressed as:

[0083]

[0084] in, Represents the signal amplitude of the low-frequency signal; Z T (t) is the probe impedance at time t, R line (t) is the resistance of the wire at time t, and R0 is the resistance of the fixed resistor in the Wheatstone bridge 110;

[0085] When the high-frequency signal passes through the temperature probe 120, the impedance in the temperature probe 120 is dominated by the large-capacitance capacitor 122, and its voltage change signal It is expressed as:

[0086]

[0087] in, is the signal amplitude of the high-frequency signal; ω2 is the signal frequency of the high-frequency signal, C0 is the capacitance of the capacitor in the Wheatstone bridge 110; G is the gain of the differential amplifier 310; is the phase, and

[0088]

[0089] In an optional embodiment, the voltage change signal output from the Wheatstone bridge 110 is collected and differentially demodulated to obtain the resistance change signal of the NTC thermistor 121, including the following steps:

[0090] The voltage change signal output from the Wheatstone bridge 110 is converted by using the low frequency signal V1 and the high frequency signal V2. and After demodulation and low-pass filtering, a dual-frequency measurement signal is obtained; its expression is:

[0091]

[0092] Among them, V low (t) and V high (t) is the voltage change signal of the NTC thermistor 121 under the modulation of the low frequency signal and the high frequency signal;

[0093] The current wire resistance R is calculated by the dual-frequency measurement results. line (t) and the resistance change signal R of the NTC thermistor 121 T (t); its expression is:

[0094]

[0095] It can be understood that the system of this embodiment corresponds to the system of the above-mentioned embodiment 1, and the options in the above-mentioned embodiment 1 are also applicable to this embodiment, so they are not described repeatedly here.

[0096] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A high-precision temperature measurement system based on dual-frequency modulation, characterized in that: include: A temperature detection module, comprising a Wheatstone bridge, wherein the Wheatstone bridge is composed of three fixed value resistors and a temperature probe constituting its four bridge arms; the temperature probe comprises an NTC thermistor and a large capacitance capacitor connected in parallel with the NTC thermistor; A dual-frequency modulation module, used for mixed modulation of a low-frequency signal and a high-frequency signal, and outputting a dual-frequency modulation signal to the temperature detection module; wherein, when the low-frequency signal passes through the temperature probe, the thermistor impedance is dominant in the temperature probe; and when the high-frequency signal passes through the temperature probe, the capacitor impedance is dominant in the temperature probe; The signal demodulation module is used to perform differential demodulation on the voltage change signal output by the temperature detection module to obtain a resistance change signal of the NTC thermistor; the resistance change signal is used to characterize the temperature measurement result.

2. The high-precision temperature measurement system based on dual-frequency modulation according to claim 1, characterized in that: The dual-frequency modulation module includes a first AC power supply for outputting a low-frequency signal, a second AC power supply for outputting a high-frequency signal, and an adding circuit for mixed modulation of the low-frequency signal and the high-frequency signal; Wherein, the first AC power supply and the second AC power supply output sinusoidal voltage signals.

3. The high-precision temperature measurement system based on dual-frequency modulation according to claim 1, characterized in that: The signal demodulation module includes a differential amplifier, a first demodulator, a first filter, a second demodulator and a second filter; wherein: The voltage change signal output by the Wheatstone bridge is input into the differential amplifier for differential amplification, and then respectively input into the first demodulator and the second demodulator to be demodulated with the original signal; The low frequency signal and the high frequency signal in the dual frequency modulation module are respectively input into the first demodulator and the second demodulator for demodulation; The output ends of the first demodulator and the second demodulator are connected to the input ends of the first filter and the second filter respectively, and are used to perform low-pass filtering on the demodulated signal.

4. The high-precision temperature measurement system based on dual-frequency modulation according to claim 3 is characterized in that: When the low-frequency signal passes through the temperature probe, the impedance in the temperature probe is dominated by the NTC thermistor, and its voltage change signal V low It is expressed as: in, Represents the signal amplitude of the low-frequency signal; Z T (t) is the probe impedance at time t, R line (t) is the resistance of the wire at time t, R0 is the resistance of the fixed resistor in the Wheatstone bridge; When a high-frequency signal passes through the temperature probe, the impedance in the temperature probe is dominated by the large-value capacitor, and its voltage change signal It is expressed as: in, is the signal amplitude of the high-frequency signal; ω2 is the signal frequency of the high-frequency signal, C0 is the capacitance of the capacitor in the Wheatstone bridge; G is the gain of the differential amplifier; is the phase, and 5. The high-precision temperature measurement system based on dual-frequency modulation according to claim 4, characterized in that: In the signal demodulation module, when the resistance change signal of the NTC thermistor is obtained by differential demodulation, the following steps are performed: Obtain the low-frequency signal V1 and the high-frequency signal V2 before mixed frequency modulation in the dual-frequency modulation module, and the voltage change signal output by the temperature detection module and Perform demodulation and low-pass filtering to obtain a dual-frequency measurement signal; Its expression is: Among them, V low (t) and V high (t) is the voltage change signal of the NTC thermistor under the modulation of low-frequency signal and high-frequency signal; The current wire resistance R is calculated by the dual-frequency measurement results. line (t) and the resistance change signal R of the NTC thermistor T (t); its expression is:

6. The high-precision temperature measurement system based on dual-frequency modulation according to any one of claims 1 to 5, characterized in that: In the temperature probe, a low thermal conductivity material is further arranged between the NTC thermistor and the large-capacitance capacitor; and a packaging material is arranged on the outer surface of the temperature probe.

7. A high-precision temperature measurement method based on dual-frequency modulation, applied to the high-precision temperature measurement system according to any one of claims 1 to 6, characterized in that: The following steps are involved: Input a low-frequency signal and a high-frequency signal, and perform mixed modulation on the low-frequency signal and the high-frequency signal to obtain a dual-frequency modulation signal; The dual-frequency modulated signal is output to a Wheatstone bridge equipped with a temperature probe, wherein the temperature probe is equipped with an NTC thermistor; wherein when a low-frequency signal passes through the temperature probe, the thermistor impedance is dominant in the temperature probe; and when a high-frequency signal passes through the temperature probe, the capacitor impedance is dominant in the temperature probe; The voltage change signal output from the Wheatstone bridge is collected and differentially demodulated to obtain a resistance change signal of the NTC thermistor; the resistance change signal is used to characterize the temperature measurement result.

8. The high-precision temperature measurement method based on dual-frequency modulation according to claim 7, characterized in that: The low-frequency signal and the high-frequency signal are sinusoidal AC signals; the expressions thereof are: Among them, V1 and V2 represent the signal amplitudes of the low-frequency signal and the high-frequency signal respectively; ω1 and ω2 represent the signal frequencies of the low-frequency signal and the high-frequency signal respectively.

9. The high-precision temperature measurement method based on dual-frequency modulation according to claim 7, characterized in that: When a low-frequency signal passes through the temperature probe, the impedance in the temperature probe is dominated by the NTC thermistor, and its voltage change signal It is expressed as: in, Represents the signal amplitude of the low-frequency signal; Z T (t) is the probe impedance at time t, R line (t) is the resistance of the wire at time t, R0 is the resistance of the fixed resistor in the Wheatstone bridge; When a high-frequency signal passes through the temperature probe, the impedance in the temperature probe is dominated by the large-value capacitor, and its voltage change signal It is expressed as: in, is the signal amplitude of the high-frequency signal; ω2 is the signal frequency of the high-frequency signal, C0 is the capacitance of the capacitor in the Wheatstone bridge; G is the gain of the differential amplifier; is the phase, and 10. The high-precision temperature measurement method based on dual-frequency modulation according to claim 9, characterized in that: The step of collecting the voltage change signal output from the Wheatstone bridge and performing differential demodulation to obtain the resistance change signal of the NTC thermistor comprises the following steps: The voltage change signal output from the Wheatstone bridge is measured using the low-frequency signal V1 and the high-frequency signal V2. and After demodulation and low-pass filtering, a dual-frequency measurement signal is obtained; its expression is: Among them, V low (t) and V high (t) is the voltage change signal of the NTC thermistor under the modulation of low-frequency signal and high-frequency signal; The current wire resistance R is calculated by the dual-frequency measurement results. line (t) and the resistance change signal R of the NTC thermistor T (t); its expression is:

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