A negative temperature coefficient thermistor thermal time constant measurement system and method

Abstract

The application provides a negative temperature coefficient thermistor thermal time constant measurement system and method, the system comprises: a temperature environment unit, a motion control unit, a data acquisition unit, and a data processing unit deployed on a host computer; the temperature environment unit is used for providing temperature environment A area and B area with different environmental temperatures respectively; the motion control unit is used for accurately controlling the negative temperature coefficient thermistor to be measured to move from the temperature environment A area to the B area; the data acquisition unit is used for measuring the resistance value of the negative temperature coefficient thermistor to be measured in real time and transmitting to the host computer; the data processing unit is used for determining the corresponding temperature value according to the pre-established resistance value R-temperature value T equation, combining the temperature values of the temperature environment A area and the B area, and obtaining the thermal time constant. The application has good measurement repeatability, small measurement error and simple operation process, and significantly improves the test result reliability and test efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of dynamic response capability test of temperature sensor, in particular to a negative temperature coefficient thermistor thermal time constant measurement system and method. BACKGROUND

[0002] Temperature is a basic physical parameter reflecting the cold and hot degree and form of an object, and is closely related to the production and life of human society. With the development of science and technology, the accuracy and response speed requirements of temperature measurement and control are becoming higher and higher. Thermal hysteresis of a temperature sensor refers to that when the detected temperature changes, the output of the sensor needs a certain time to accurately output the changed value. Dynamic characteristic refers to the ability of the actually measured temperature of the sensor to change with the change of the measured environment temperature, which also reflects the hysteresis degree of response in temperature monitoring. The dynamic response performance of the temperature sensor is generally represented by time constant, that is, when the temperature sensor receives a step signal input, the time period required for the output signal to reach 63.2% of the step value. The smaller the time constant, the better the dynamic performance of the temperature sensor and the faster the response speed.

[0003] The negative temperature coefficient thermistor is a temperature sensor with exponentially decreasing resistance value with the increase of temperature, and has the characteristics of high precision, fast response time and low cost, and is widely used in aerospace, marine environment and household appliances. At present, there are related standards or regulations for the dynamic characteristic measurement and calibration of the negative temperature coefficient thermistor, but it is difficult to analyze and compare many different situations in actual application, and in the actual test process, the detection personnel usually manually operate, the overall operation is relatively cumbersome, which brings greater errors in process operation and subjective judgment to the thermal time constant test, and the repeatability of the test data is poor. Many metrological detection institutions lack a negative temperature coefficient thermistor thermal time constant measurement system and method which is objective and effective, has good repeatability and small error. SUMMARY

[0004] The present application aims to overcome the defects of the prior art and provides a negative temperature coefficient thermistor thermal time constant measurement system and method.

[0005] In order to achieve the above-mentioned purpose, the present application provides a negative temperature coefficient thermistor thermal time constant measurement system, which comprises a temperature environment unit, a motion control unit, a data acquisition and processing unit, and a data processing unit arranged on an upper computer, wherein,

[0006] The temperature environment unit is used to provide temperature environments A and B with different environmental temperatures respectively;

[0007] The motion control unit is used to accurately control the motion of the carried negative temperature coefficient thermistor to be tested from the temperature environment A to the temperature environment B;

[0008] The data acquisition unit is configured to measure the resistance value of the negative temperature coefficient thermistor in real time and transmit the resistance value to the host computer.

[0009] The data processing unit is configured to determine the corresponding temperature value according to the pre-established resistance value R-temperature value T equation, in combination with the temperature values of the temperature environment A region and the temperature environment B region, to obtain the thermal time constant.

[0010] Preferably, the temperature environment A region is a constant-temperature indoor environment, and the motion control unit is disposed in the temperature environment A region; the B region is a constant-temperature oven, which can be set to different constant temperatures, and the size of the oven is more than 1000 times the volume of the thermistor to be measured, and the temperature uniformity is within ±1℃.

[0011] Preferably, the motion control unit comprises a motion controller, a linear slide and a fixed rod, wherein,

[0012] The negative temperature coefficient thermistor to be measured is mounted at the front end of the fixed rod, the fixed rod is connected to the linear slide, the motion direction, speed and distance of the linear slide are accurately controlled by the motion controller, the fixed rod is driven to move, so that the negative temperature coefficient thermistor to be measured moves from the temperature environment A region to the temperature environment B region, and the linear slide is an electric linear slide.

[0013] Preferably, the data acquisition unit comprises a digital multimeter, which is configured to measure the resistance value at a set resistance value measurement range according to a set time interval.

[0014] Preferably, the data processing unit comprises:

[0015] The resistance value-temperature value conversion module is configured to determine the related parameters of the resistance value R-temperature value T equation by a linear fitting method according to the resistance-temperature test of the negative temperature coefficient thermistor to be measured, and establish the equation.

[0016] The thermal time constant calculation module is configured to take the temperature of the temperature environment A region as the initial temperature T0, take the temperature of the temperature environment B region as the final temperature T ∞ , obtain the 63.2% step temperature value T τ , and obtain the thermal time constant τ according to the corresponding time t of the 63.2% step temperature value T τ and the step starting time t0.

[0017] The display module is configured to display the measurement and calculation results.

[0018] Preferably, the resistance value R-temperature value T equation is:

[0019]

[0020] According to a set of resistance values R and temperature values T, parameters a and b are determined by linear fitting.

[0021] Preferably, the processing procedure of the thermal time constant calculation module comprises:

[0022] Step S1) taking the temperature of the temperature environment A region as the initial temperature T0 and the temperature of the temperature environment B region as the final temperature T ∞ , obtaining the theoretical 63.2% step temperature value T τ ;

[0023] Step S2) converting the received resistance values R t at different sampling time points t into corresponding temperature values T t according to the resistance value R-temperature value T equation, and drawing a dynamic response curve with the vertical axis as the temperature value and the horizontal axis as the sampling time;

[0024] Step S3) performing difference operation on different temperature values T t and T τ respectively, taking the temperature value T t corresponding to the minimum difference value among all the difference values as the actual 63.2% step temperature value T τ , performing difference operation on different temperature values T t and T0 respectively, and taking the sampling time t corresponding to the first temperature value whose difference value is greater than the calibration temperature error T x of the temperature environment B region as the step starting time t0 to calculate the thermal time constant τ.

[0025] Preferably, the theoretical 63.2% step temperature value T τ in the step S1) satisfies the following formula:

[0026] T τ =T0+0.632(T ∞ -T0).

[0027] Preferably, the thermal time constant τ in the step S3) is the difference value between the actual 63.2% step temperature value T τ and the step starting time t0.

[0028] On the other hand, the present application also proposes a negative temperature coefficient thermistor thermal time constant measurement method, which is realized based on the above-mentioned system, and the method comprises:

[0029] Setting the temperature environment A region and the temperature environment B region to be at their respective set temperatures and to be stable;

[0030] Mounting the thermistor to be measured on the motion control unit;

[0031] After setting the resistance value collection range, the collection time interval and the total number of collected data, starting the data collection unit;

[0032] When the resistance value collected by the data collection unit is stable, the motion control unit moves the mounted to-be-tested thermistor from the temperature environment A area to the B area, and the data collection unit measures the resistance value at a set collection time interval and uploads it to the data processing unit;

[0033] The data processing unit determines the corresponding temperature value according to the real-time measured resistance value according to the pre-established resistance value R-temperature value T equation, and obtains the thermal time constant in combination with the temperature values of the temperature environment A area and the B area.

[0034] Compared with the prior art, the advantages of the present application are that:

[0035] In the technical scheme of the embodiment of the present application, the motion control unit can accurately control the speed and distance of the movement of the to-be-tested thermistor; the digital multimeter in the data collection and processing unit can quickly and accurately measure the resistance value, and save and transmit these data to the upper computer; the upper computer in the data processing unit is mounted with a visual independent software, and the functions of the software include resistance value-temperature value conversion, display of various parameters in the measurement process (initial temperature, final temperature, 63.2% step temperature value, step starting time, 63.2% step temperature value corresponding time), temperature-time curve drawing of the dynamic response process, thermal time constant calculation, and result saving. The visual independent software is independently developed, can be matched with different temperature step test systems, and can calculate the thermal time constant according to the dynamic response data of the negative temperature coefficient thermistor, and the integrated design is convenient for transplantation to different upper computers and systems.

[0036] A variety of models of negative temperature coefficient thermistors are used for example testing, the thermal time constant of the measurement system is measured repeatedly, and the measurement error is within ±3%. The measurement system and method of the present application realize good repeatability and small measurement error, effectively simplify the complex operation and data processing steps in the traditional measurement process, and make the whole test process more accurate, efficient and easy to perform. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 FIG. 1 is a structural schematic diagram of a negative temperature coefficient thermistor thermal time constant measurement system of the present application;

[0038] Figure 2 FIG. 4 is a flowchart of the operation of the upper computer visual independent software of the negative temperature coefficient thermistor thermal time constant measurement system of the present application;

[0039] Figure 3 FIG. 5 is an application example schematic diagram of the negative temperature coefficient thermistor thermal time constant measurement method of the present application.

[0040] REFERENCE NUMERALS

[0041] 1, temperature environment unit 2, data acquisition unit and data processing unit

[0042] 3, motion control unit 4, negative temperature coefficient thermistor to be measured

[0043] 5, thermostat 6, constant temperature indoor environment

[0044] 7, digital multimeter 8, host computer

[0045] 9, motion controller 10, linear slide

[0046] 11, fixed rod

[0047] 12, visual independent software draws dynamic response curve of thermistor in measurement process

[0048] 13, initial temperature T0 14, final temperature T ∞

[0049] 15, 63.2% step temperature value T τ 16, step starting time t0

[0050] 17, the time t when reaching 63.2% step temperature value DETAILED DESCRIPTION

[0051] The present application aims to solve the shortcomings of the existing test method in data validity, measurement repeatability, measurement error and operation complexity, and provides a negative temperature coefficient thermistor thermal time constant measurement system and method with smaller measurement error and simple and effective operation.

[0052] The technical scheme adopted by the present application is as follows:

[0053] A negative temperature coefficient thermistor thermal time constant measurement system, comprising a temperature environment unit, a data acquisition unit and a data processing unit, a motion control unit, and a negative temperature coefficient thermistor to be measured. The temperature environment unit comprises a thermostat and a constant temperature indoor environment, the constant temperature indoor environment is temperature environment A area, and the thermostat provides stable temperature environment B area; the data acquisition unit adopts a digital multimeter, and the data processing unit is deployed in a host computer. The digital multimeter is responsible for quickly and accurately measuring the resistance value and transmitting the data to the host computer, and the data processing unit realizes functions such as thermal time constant calculation through visual independent software; the motion control unit comprises a motion controller, a linear slide and a fixed rod, the motion controller can accurately control the motion direction, speed and distance of the linear slide, so that the linear slide drives the fixed rod to move; the negative temperature coefficient thermistor to be measured is installed at the front end of the fixed rod.

[0054] A method for measuring thermal time constant of negative temperature coefficient thermistor, based on the negative temperature coefficient thermistor thermal time constant measurement system, the implementation steps of the method are as follows:

[0055] S1, resistance-temperature test is carried out on the measured thermistor, and the resistance value R-temperature value T equation (such as formula (1)) parameters a, b are obtained. The measured thermistor is installed at the front end of the fixed rod. Start the thermostat, set the B zone temperature T ∞ , wait until the B zone temperature is stable, start the digital multimeter, set the resistance value range, collection time interval, and total number of collected data, and start collecting the resistance value of the thermistor at the A zone temperature T0.

[0056]

[0057] S2, when the resistance value collected by the digital multimeter is observed to be stable, start the motion controller, set the speed and distance of the linear slide, and drive the thermistor to move from the temperature A zone to the temperature B zone. During the process, the digital multimeter continuously collects and records the resistance value of the thermistor. After the collection is completed, the digital multimeter uploads the collected resistance value data to the host computer.

[0058] S3, the host computer saves the resistance value data uploaded by the digital multimeter, and the R-T equation of the measured thermistor is converted into temperature value data by the visual independent software of the host computer, the starting temperature T0, the terminal temperature T ∞ , the 63.2% step temperature value T τ (computing method as shown in formula (2)), the corresponding time t and the step starting time t0 of the 63.2% step temperature value T τ are found and the difference is calculated, which is the thermal time constant τ.

[0059] T τ =T0+0.632(T ∞ -T0) (2)

[0060] S4, the host computer visual independent software draws the dynamic response temperature-time curve of the thermistor. Input the saved file name, and save the calculation data and measurement curve.

[0061] S5, repeat steps S1-S4, thereby calculating the multiple measurement results of the thermal time constant of the same thermistor, and calculating the measurement error and repeatability of the thermal time constant.

[0062] The time constant calculation method of the host computer visualization independent software in step S3 is as follows: First, the resistance value R data is converted into temperature value T data using the RT equation of the thermistor under test (as shown in formula (1)); then, the starting temperature T0 and the ending temperature T0 during the measurement process are determined according to the temperature fluctuation range of the constant temperature chamber. ∞ The step start time t0; according to the formula (2) shown, the theoretically calculated 63.2% step temperature T is obtained. τ Compare the temperature value T at each moment with the theoretically calculated 63.2% step temperature value T. τ The difference is calculated, and the minimum difference is taken as the actual measured 63.2% step temperature value T. τ ; Different temperature values ​​T t Calculate the difference between each value and T0, and take the difference value that is greater than the calibration temperature error T of temperature environment zone B. x The sampling time t corresponding to the first temperature value is the step start time t0, using the 63.2% step temperature value T. τ Subtract the step start time t0 from the corresponding time t to calculate the time constant value τ; after the calculation is completed, the output displays the start temperature T0 and the end temperature T. ∞ 63.2% step temperature value T τ Calculate the thermal time constant τ, plot the temperature-time curve of the dynamic response process of the thermistor, and save the calculation results and curves according to the input file name.

[0063] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0064] Example 1

[0065] like Figure 1 As shown, Embodiment 1 of the present invention proposes a negative temperature coefficient thermistor thermal time constant measurement system, including a temperature environment unit 1, a data acquisition unit and a data processing unit 2, a motion control unit 3, and a negative temperature coefficient thermistor to be measured 4. The temperature environment unit 1 includes a constant temperature chamber 5 and a constant temperature chamber environment 6. The constant temperature chamber environment 6 is temperature environment zone A, and the constant temperature chamber 5 provides a stable temperature environment zone B. Different constant temperatures can be set, the internal size of the chamber is more than 1000 times the volume of the thermistor to be measured, and the temperature uniformity is within ±1℃. The motion control unit is deployed in temperature environment zone A. Figure 1The data acquisition unit and the data processing unit in the device are respectively a digital multimeter 7 and a host computer 8. The digital multimeter 7 is responsible for measuring the resistance value quickly and accurately according to the set time interval under the set resistance value measurement range, and transmits the data to the host computer 8. The data processing unit of the host computer 8 is implemented by a visual independent software to realize the functions of thermal time constant calculation and the like. The motion control unit 3 includes a motion controller 9, a linear slide 10 and a fixed rod 11. The motion controller 9 can accurately control the motion direction, speed and distance of the linear slide 10, so that the linear slide 10 drives the fixed rod 11 to move. The negative temperature coefficient thermistor 4 to be measured is installed at the front end of the fixed rod 11. The motion control unit is used to move the negative temperature coefficient thermistor 4 to be measured from the temperature environment A area to the B area. The linear slide 10 is an electric linear slide.

[0066] The data processing unit includes:

[0067] 1) Resistance value-temperature value conversion module, which is used to determine the related parameters of the resistance value R-temperature value T equation by the linear fitting method according to the resistance-temperature test of the negative temperature coefficient thermistor to be measured in advance, and establish the equation.

[0068] The resistance value R-temperature value T equation is:

[0069]

[0070] According to a set of resistance values R and temperature values T, the parameters a and b are determined by linear fitting.

[0071] 2) Thermal time constant calculation module, which is used to take the temperature of the temperature environment A area as the initial temperature T0, and take the temperature of the temperature environment B area as the terminal temperature T ∞ , to obtain the 63.2% step temperature value T τ , and obtain the thermal time constant τ according to the corresponding time t of the 63.2% step temperature value T τ and the step starting time t0. The specific processing process is:

[0072] Step S1) Take the temperature of the temperature environment A area as the initial temperature T0, and take the temperature of the temperature environment B area as the terminal temperature T ∞ , to obtain the theoretical 63.2% step temperature value T τ :

[0073] T τ = T0+0.632(T ∞ -T0)

[0074] Step S2) According to the resistance value R-temperature value T equation, the resistance value R t received at different sampling times t is converted into the corresponding temperature value Tt And take the longitudinal axis as the temperature value, and the horizontal axis as the sampling time, draw the dynamic response curve;

[0075] Step S3) difference operation of different temperature values T t respectively and T τ , take the temperature value T t corresponding to the minimum difference value in all difference values as the actual 63.2% step temperature value T τ , difference operation of different temperature values T t respectively and T0, take the first temperature value corresponding to the difference value greater than the calibration temperature error T x of the temperature environment B area as the step starting time t0, and calculate the thermal time constant τ:

[0076] The thermal time constant τ is the difference value of the actual 63.2% step temperature value T τ and the step starting time t0.

[0077] 3) display module, display intermediate results, measurement results, calculation results in various forms such as numerical value, table and graph.

[0078] Embodiment 2

[0079] Embodiment 2 of the present application proposes a negative temperature coefficient thermistor thermal time constant measurement method, based on the negative temperature coefficient thermistor thermal time constant measurement system of embodiment 1, the implementation steps of the method are as follows:

[0080] Set temperature environment A area and B area to be at their respective set temperatures and keep stable;

[0081] Install the to-be-measured thermistor on the motion control unit;

[0082] After setting the range of collected resistance values, the collection time interval and the total number of collected data, start the data collection unit;

[0083] When the resistance value collected by the data collection unit is stable, the motion control unit moves the to-be-measured thermistor carried thereon from the temperature environment A area to the B area, the data collection unit measures the resistance value at regular time intervals according to the set collection time interval, and uploads it to the data processing unit;

[0084] The data processing unit determines the corresponding temperature value according to the real-time measured resistance value according to the pre-established resistance value R-temperature value T equation, and obtains the thermal time constant in combination with the temperature values of the temperature environment A area and the B area.

[0085] The following will be described in detail:

[0086] S1, resistance-temperature test is performed on the tested thermistor to obtain the resistance value R-temperature value T equation (as shown in formula (1)), and parameters a, b are determined by linear fitting.

[0087] The tested thermistor is installed at the front end of the fixed rod. The thermostat is started, and the temperature T of the B zone is set ∞ . After the temperature of the B zone is stable, the digital multimeter is started, and the resistance value range to be collected, the collection time interval, and the total number of collected data are set. The resistance value of the thermistor at the temperature T0 of the A zone is collected.

[0088]

[0089] S2, when it is observed that the resistance value collected by the digital multimeter is stable, the motion controller is started, the speed and distance of the linear slide are set, the linear slide drives the thermistor to move from the temperature A zone to the temperature B zone, and the digital multimeter continuously collects and records the resistance value of the thermistor during the process. After the collection is completed, the digital multimeter uploads the collected resistance value data to the upper computer.

[0090] S3, the data processing unit saves the resistance value data uploaded by the digital multimeter, and converts the resistance value data into temperature value data according to the R-T equation of the tested thermistor by using a visual independent software, and the specific flow chart is shown in Figure 2 . The starting temperature T0, the ending temperature T ∞ , the 63.2% step temperature value T τ (calculated in the manner shown in formula (2)), the corresponding time t of the 63.2% step temperature value T τ , and the step starting time t0 are found and the difference is the thermal time constant T.

[0091] T τ = T0 + 0.632 (T ∞ -T0) (2)

[0092] S4, according to the sampling time and the collected resistance value, the visual independent software of the upper computer draws the dynamic response temperature-time curve of the thermistor, as shown in Figure 3 . Among them, 12 is the dynamic response curve of the thermistor in the measurement process drawn by the visual independent software, 13 is the starting temperature T0, 14 is the ending temperature T ∞ , 15 is the 63.2% step temperature value T τ , 16 is the step starting time t0, and 17 is the time t of reaching the 63.2% step temperature value.

[0093] The saved file name is input, and the calculation data and the measurement curve are saved.

[0094] S5, repeat the steps S1-S4, thereby calculating the thermal time constant of the same thermistor multiple measurements, the measurement error and repeatability of the thermal time constant.

[0095] In the dynamic response characteristics of the thermistor, the thermistor can be regarded as a first-order inertial system, its transfer function is shown in formula (3), wherein K represents the gain constant, τ represents the time constant. When the sensor is quickly transferred from one stable temperature environment to another stable temperature environment, this process can be compared to applying a step signal input to the thermistor. Under the step signal excitation, the response process of the thermistor can be represented by formula (4). According to formula (4), when a certain condition is met, that is, the equation of formula (5) is established, the difference between the current time t and the step starting time t0 is the thermal time constant of the temperature sensor.

[0096]

[0097]

[0098] T t -T0=0.632(T ∞ -T0) (5)

[0099] Therefore, the 63.2% step temperature value T τ can be calculated by formula (2). The host computer software compares the temperature value T t at each time t with the 63.2% step temperature value T τ , finds the closest temperature value, and the difference between the corresponding time t and the step starting time t0 is the time constant value τ.

[0100] The time constant calculation method of the host computer visualization independent software in the step S3 is: first, the R-T equation of the thermistor to be measured is used to convert the resistance value R data into temperature value T data; then the starting temperature T0, the ending temperature T ∞ , and the step starting time t0 in the measurement process are determined according to the temperature fluctuation range of the thermostat; according to the formula (2), the theoretical calculation of the 63.2% step temperature value T τ is calculated; the difference between the temperature value T at each time and the theoretical calculation of the 63.2% step temperature value T τ is calculated, and the minimum value of the difference is taken as the actual measurement of the 63.2% step temperature value T τ ; the time constant value τ is calculated by subtracting the step starting time t0 from the corresponding time t of the 63.2% step temperature value T τ ; after the calculation is completed, the starting temperature T0, the ending temperature T ∞ , and the 63.2% step temperature value T τThe temperature-time curve of the dynamic response process of the thermistor is drawn, and the calculation results and the curve are saved according to the input file name.

[0101] In the technical scheme of the embodiment of the application, the motion control unit 3 can accurately control the speed and displacement of the motion of the thermistor 4 to be measured; the digital multimeter 7 can quickly and accurately measure the resistance value, and save and transmit the data to the host computer 8; the data processing unit is arranged in the host computer 8, and uses a visual independent software, the functions of the software include resistance value-temperature value conversion, display of various parameters in the measurement process (start temperature, end temperature, 63.2% step temperature value, step start time, 63.2% step temperature value corresponding time), temperature-time curve drawing of the dynamic response process, thermal time constant calculation, and result saving. The visual independent software is independently developed, can be matched with different temperature step test systems, and can calculate the thermal time constant according to the dynamic response data of the negative temperature coefficient thermistor, and the integrated design is convenient for transplantation to different host computers and systems.

[0102] The thermal time constant of the measurement system is measured repeatedly by using various types of negative temperature coefficient thermistors, and the measurement error is within ±3%. The measurement system and method of the application realize good repeatability and small measurement error, effectively simplify the complex operation and data processing steps in the traditional measurement process, and make the whole test process more accurate, efficient and easy to perform.

[0103] In Figure 3 In the application example schematic diagram shown, the temperature A area is room temperature 25℃, and the temperature uniformity is ±1℃; the temperature range that can be set by the thermostat 5 is room temperature+10℃ to 125℃, the size of the box body is 55cm*55cm*45cm, and the temperature uniformity is ±1℃, and the temperature B area is set to 75℃; the motion speed of the straight line sliding table 10 is 1m / s, and the moving distance is 30cm; the digital multimeter 7 is a six-bit half digital multimeter, the sampling time interval is set to 1ms, the resistance value range is set to 0-10kΩ, and the total number of collected data is set to 10 4 In the dynamic response temperature-resistance value curve 12 of the thermistor 4 to be measured, the thermal time constant measurement result is 837ms, the average value of 8 repeated measurements is 845.6ms, the error is within ±3%, and the test result is shown in Table 1:

[0104] Table 1: Multiple repeated measurement result data of the application method of the application

[0105]

[0106] In the application example, the parameter a of the R-T equation is 0.00051404, the parameter b is 0.00032343, the temperature error T x of the thermostat is 1℃, the digital multimeter acquisition time interval t x is 1ms, the initial temperature T0 is 25.12℃, the final temperature T ∞ is 75.31℃, the step starting point t0 is 1.975s, the time constant corresponding temperature point t is 2.812s, the 63.2% step temperature value T τ is 56.84℃, and the time constant τ is 837ms.

[0107] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the examples, those skilled in the art should understand that modifications or equivalent replacements to the technical solutions of the present application do not deviate from the spirit and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A negative temperature coefficient thermistor thermal time constant measurement system, characterized in that, The system comprises a temperature environment unit, a motion control unit, a data acquisition unit, and a data processing unit deployed on a host computer. The temperature environment unit is configured to provide temperature environment zones A and B with different temperatures. The motion control unit is configured to accurately control the movement of a to-be-tested negative temperature coefficient thermistor from the temperature environment zone A to the temperature environment zone B. The data acquisition unit is configured to measure the resistance value of the to-be-tested negative temperature coefficient thermistor in real time and transmit the resistance value to the host computer. The data processing unit is configured to determine the corresponding temperature value according to the pre-established resistance value R-temperature value T equation, and obtain the thermal time constant by combining the temperature values of the temperature environment zones A and B. The data processing unit comprises a resistance value-temperature value conversion module configured to determine the related parameters of the resistance value R-temperature value T equation by linear fitting based on the pre-established resistance-temperature test of the to-be-tested negative temperature coefficient thermistor, and establish the equation. The temperature environment zone B can be set to different constant temperatures, and the size of the box is more than 1000 times the volume of the to-be-tested thermistor, and the temperature uniformity is within ±1℃. The data acquisition unit comprises a digital multimeter configured to measure the resistance value at a set resistance value measurement range according to a set time interval. a thermal time constant calculation module, configured to take the temperature of the temperature environment A region as a starting temperature T0, take the temperature of the temperature environment B region as a terminal temperature T ∞ , obtain a 63.2% step temperature value T τ , according to the corresponding moment t of the 63.2% step temperature value T τ and the step starting moment t0, obtain a thermal time constant τ.

2. The negative temperature coefficient thermistor thermal time constant measurement system of claim 1, wherein, The data processing unit further comprises a display module configured to display the measurement and calculation results.

3. The negative temperature coefficient thermistor thermal time constant measurement system of claim 1, wherein, The resistance value R-temperature value T equation is determined by linear fitting based on a set of resistance values R and temperature values T.

4. The negative temperature coefficient thermistor thermal time constant measurement system of claim 1, wherein, The processing process of the thermal time constant calculation module comprises 9. A negative temperature coefficient thermistor thermal time constant measurement method based on the system of any one of claims 1-8, the method comprising:

5. The negative temperature coefficient thermistor thermal time constant measurement system of claim 1, wherein, setting the temperature environment zones A and B to be at their respective set temperatures and keeping stable; installing the to-be-tested thermistor on the motion control unit; 6. The negative temperature coefficient thermistor thermal time constant measurement system of claim 1, wherein, setting the resistance value acquisition range, the acquisition time interval, and the total number of acquisition data, and then starting the data acquisition unit; Step S1 ) the temperature of the temperature environment A zone is taken as the starting temperature T0, the temperature of the temperature environment B zone is taken as the end temperature T ∞ , to obtain a theoretical 63.2% step temperature value T τ ; Step S2) according to the resistance value R-temperature value T equation, the received resistance value R of different sampling time t is converted into corresponding temperature value T t t And taking the longitudinal axis as the temperature value and the horizontal axis as the sampling time, the dynamic response curve is drawn.​ Step S3) difference operation between different temperature values T t and T0, and the minimum difference value corresponds to the temperature value T τ as the actual 63.2% step temperature value T t . Step S4) difference operation between different temperature values T τ and T0, and the first temperature value greater than the calibration temperature error T t of the temperature environment B area corresponds to the sampling time t as the step starting time t0, and the thermal time constant τ is calculated. x ​ 7. The negative temperature coefficient thermistor thermal time constant measurement system of claim 6, wherein, The step S1) theoretical 63.2% step temperature value T τ satisfies the following equation: T τ = T0+ 0.632(T ∞ - T0).

8. The negative temperature coefficient thermistor thermal time constant measurement system of claim 6, wherein, The thermal time constant τ in said step S3) is the actual 63.2% step temperature value T τ The difference from the step start time to t0. when the resistance value acquired by the data acquisition unit is stable, the motion control unit moves the to-be-tested thermistor from the temperature environment zone A to the temperature environment zone B, and the data acquisition unit measures the resistance value at a set acquisition time interval and uploads the resistance value to the data processing unit; the data processing unit determines the corresponding temperature value according to the pre-established resistance value R-temperature value T equation, and obtains the thermal time constant by combining the temperature values of the temperature environment zones A and B. ​ ​ ​ ​

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