System and method for measuring thermal time constant of negative temperature coefficient thermistor

Abstract

The invention provides a system and a method for measuring a thermal time constant of a negative temperature coefficient thermistor. The system comprises a temperature environment unit, a motion control unit, a data acquisition unit and a data processing unit deployed on an upper computer, the temperature environment unit is used for respectively providing a temperature environment area A and a temperature environment area B with different environment temperatures; the motion control unit is used for accurately controlling the carried negative temperature coefficient thermistor to be measured to move from the temperature environment A area to the temperature environment 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 the resistance value to the upper computer; and the data processing unit is used for determining a corresponding temperature value aiming at the resistance value measured in real time according to a pre-established resistance value R-temperature value T equation, and obtaining a thermal time constant by combining the temperature values of the area A and the area B of the temperature environment. The method has the advantages of better measurement repeatability, smaller measurement error and simple and convenient operation process, and the reliability of the test result and the test efficiency are remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of dynamic response capability testing of temperature sensors, and in particular to a negative temperature coefficient thermistor thermal time constant measurement system and method. Background Art

[0002] Temperature is a basic physical parameter that reflects the degree of hotness and coldness of an object and its shape, and is closely related to the production and life of human society. With the development of science and technology, people have higher and higher requirements for the accuracy and response speed of temperature measurement and control. The thermal hysteresis of a temperature sensor means that when the detected temperature changes, it takes a certain amount of time for the output of the sensor to accurately output the changed value. The dynamic characteristic refers to the ability of the sensor's measured temperature value to change with the measured ambient temperature, and also reflects the degree of response lag in temperature monitoring. The time constant is generally used to characterize the dynamic response performance of a temperature sensor, that is, when the temperature sensor receives a step signal input, the time period required for its 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] Negative temperature coefficient thermistor is a temperature sensor whose resistance value decreases exponentially with the increase of temperature. It has the characteristics of high precision, fast response time and low cost. It is widely used in aerospace, marine environment and civil appliances. At present, there are relevant standards or procedures for the measurement and calibration of the dynamic characteristics of negative temperature coefficient thermistors, but it is difficult to conduct specific analysis for many different situations in actual applications. The actual test process usually relies on manual operation by the test personnel, and the overall operation is cumbersome, which brings large errors in process operation and subjective judgment to the thermal time constant test, and the test data repeatability is poor. Many metrology and testing institutions lack a negative temperature coefficient thermistor thermal time constant measurement system and method with objective and valid data, good repeatability and small error. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and to provide a negative temperature coefficient thermistor thermal time constant measurement system and method.

[0005] In order to achieve the above-mentioned object, the present invention proposes a negative temperature coefficient thermistor thermal time constant measurement system, comprising: a temperature environment unit, a motion control unit, a data acquisition processing unit, and a data processing unit deployed on a host computer; wherein,

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

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

[0008] The data acquisition unit is used to measure the resistance value of the negative temperature coefficient thermistor to be measured in real time and transmit it to the host computer;

[0009] The data processing unit is used to determine the corresponding temperature value for the resistance value measured in real time 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 zone A and zone B.

[0010] Preferably, the temperature environment zone A is a constant temperature indoor environment, and the motion control unit is deployed in the temperature environment zone A; the zone B is a constant temperature box that can set different constant temperatures, the internal size of the box is more than 1000 times the volume of the thermistor to be measured, and the temperature uniformity is within ±1°C.

[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 installed at the front end of a fixed rod, the fixed rod is connected to a linear slide, and the motion controller accurately controls the movement direction, speed and distance of the linear slide to drive the fixed rod to move, thereby realizing the movement of the negative temperature coefficient thermistor to be measured from temperature environment zone A to temperature environment zone B, wherein the linear slide is an electric linear slide.

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

[0014] Preferably, the data processing unit comprises:

[0015] The resistance value-temperature value conversion module is used to determine the relevant 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 tested in advance, and establish the equation;

[0016] Thermal time constant calculation module, used to set the temperature of temperature environment zone A as the starting temperature T0, and the temperature of temperature environment zone B as the ending temperature T ∞ , and obtain 63.2% step temperature value T τ , based on the 63.2% step temperature value T τ The corresponding time t and the step starting time t0 are used to obtain the thermal time constant τ;

[0017] The display module is used 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 of the thermal time constant calculation module includes:

[0022] Step S1) The temperature of the temperature environment zone A is used as the starting temperature T0, and the temperature of the temperature environment zone B is used as the ending temperature T0. ∞ , and obtain the theoretical 63.2% step temperature value T τ ;

[0023] Step S2) According to the resistance value R-temperature value T equation, the resistance value R received at different sampling times t is t Convert to the corresponding temperature value T t , and take the vertical axis as the temperature value and the horizontal axis as the sampling time to draw the dynamic response curve;

[0024] Step S3) Different temperature values ​​T t Respectively with T τ Perform a difference operation and take the temperature value T corresponding to the minimum difference among all the differences t As the actual 63.2% step temperature value T τ , different temperature values ​​T t Perform difference calculation with T0 respectively, and take the difference value 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 starting time t0, and the thermal time constant τ is calculated.

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

[0026] T τ =T0+0.632(T ∞ -T0).

[0027] Preferably, the thermal time constant τ in step S3) is 63.2% of the actual step temperature value T τ The difference from the step start time t0.

[0028] On the other hand, the present invention also proposes a method for measuring the thermal time constant of a negative temperature coefficient thermistor, which is implemented based on the above system and includes:

[0029] Set the temperature environment A and B to their respective set temperatures and keep them stable;

[0030] Install the thermistor to be tested on the motion control unit;

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

[0032] When the resistance value collected by the data acquisition unit is stable, the motion control unit moves the thermistor to be tested from temperature environment zone A to zone B. The data acquisition unit measures the resistance value regularly according to the set collection time interval and uploads it to the data processing unit.

[0033] The data processing unit determines the corresponding temperature value for the resistance value measured in real time 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 zone A and zone B.

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

[0035] In the technical solution of the embodiment of the present invention, the motion control unit can accurately control the speed and distance of the thermistor to be tested; the digital multimeter in the data acquisition and processing unit can quickly and accurately measure the resistance value, and save and transmit these data to the host computer; the host computer in the data processing unit is equipped with a visual independent software, the software functions include resistance value-temperature value conversion, various parameter display of the measurement process (starting temperature, end temperature, 63.2% step temperature value, step starting time, 63.2% step temperature value corresponding time), dynamic response process temperature-time curve drawing, thermal time constant calculation, and result storage. The visual independent software is independently developed, can be used with different temperature step test systems, and can calculate the time constant according to the dynamic response data of the negative temperature coefficient thermistor. Its integrated design is easy to transplant to different host computers and systems.

[0036] Using various types of negative temperature coefficient thermistors for example tests, the thermal time constant of the measurement system was repeatedly measured, and the error of the measurement results was within ±3%. The measurement system and method of the present invention achieves good repeatability and small measurement error, effectively simplifies the complex operations and data processing steps in the traditional measurement process, and makes the entire test process more accurate, efficient and easy to execute. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0038] Figure 2 It is a flowchart of the operation of the host computer visualized independent software of the negative temperature coefficient thermistor thermal time constant measurement system of the present invention;

[0039] Figure 3 The present invention is a schematic diagram of an application example of the method for measuring the thermal time constant of a negative temperature coefficient thermistor.

[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. Constant temperature box 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. Visualize the dynamic response curve of thermistor during measurement drawn by independent software

[0048] 13. Starting temperature T0 14. Ending temperature T ∞

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

[0050] 17. The moment t when the step temperature value reaches 63.2% DETAILED DESCRIPTION

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

[0052] The technical solution adopted by the present invention is as follows:

[0053] A negative temperature coefficient thermistor thermal time constant measurement system includes 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. Among them, the temperature environment unit includes a constant temperature box and a constant temperature room environment, the constant temperature room environment is the temperature environment area A, and the constant temperature box provides a stable temperature environment area B; the data acquisition unit uses a digital multimeter, and the data processing unit is deployed in the host computer. The digital multimeter is responsible for quickly and accurately measuring the resistance value and transmitting the data to the host computer. The data processing unit realizes functions such as thermal time constant calculation through visual independent software; the motion control unit includes a motion controller, a linear slide and a fixed rod. The motion controller can accurately control the movement 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 the thermal time constant of a negative temperature coefficient thermistor is provided. Based on the negative temperature coefficient thermistor thermal time constant measuring system of the present invention, the method is implemented in the following steps:

[0055] S1, perform resistance-temperature test on the thermistor to be tested, and obtain the resistance value R-temperature value T equation (as shown in formula (1)) parameters a and b. Install the thermistor to be tested at the front end of the fixed rod. Start the thermostat and set the temperature T in zone B. ∞ , wait until the temperature in zone B 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 temperature T0 in zone A.

[0056]

[0057] S2, when the resistance value collected by the digital multimeter is observed to be stable, the motion controller is started, and the speed and distance of the linear slide are set. The linear slide drives the thermistor to move from temperature zone A to temperature zone B. During this 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. The host computer visualization independent software converts the resistance value data into temperature value data according to the RT equation of the thermistor to be tested, and calculates the starting temperature T0 and the ending temperature T ∞ , 63.2% step temperature value T τ (Calculation method is shown in formula (2)), find the 63.2% step temperature value T τ The corresponding time t and the step starting time t0 are subtracted and the difference is the thermal time constant τ.

[0059] T τ =T0+0.632(T ∞ -T0) (2)

[0060] S4, the upper computer visualization independent software draws the dynamic response temperature-time curve of the thermistor. Enter the saved file name to save the calculated data and measurement curve.

[0061] S5, repeatedly executing step S1 to step S4, thereby calculating 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 upper computer visualization independent software in step S3 is: first, the resistance value R data is converted into temperature value T data using the RT equation of the thermistor to be measured (as shown in formula (1)); then, the starting temperature T0 and the ending temperature T0 of the measurement process are determined according to the temperature fluctuation range of the constant temperature box. ∞ , step starting time t0; According to the formula (2), the 63.2% step temperature value T of the theoretical calculation is calculated. τ ; Compare the temperature value T at each moment with the theoretically calculated 63.2% step temperature value T τ The minimum value of the difference is taken as 63.2% of the actual measured step temperature value T τ ; Different temperature values ​​T t Perform difference calculation with T0 respectively, and take the difference value 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, and the 63.2% step temperature value T τ The corresponding time t minus the step start time t0 is calculated to get the time constant value τ; after the calculation is completed, the output shows the starting temperature T0 and the ending temperature T ∞ , 63.2% step temperature value T τ , thermal time constant τ, draw the temperature-time curve of the dynamic response process of the thermistor, and save the calculation results and curve graph according to the input file name.

[0063] The technical solution of the present invention is 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. Among them, the temperature environment unit 1 includes a constant temperature box 5 and a constant temperature indoor environment 6, the constant temperature indoor environment 6 is a temperature environment zone A, and the constant temperature box 5 provides a stable temperature environment zone B; different constant temperatures can be set, the internal size of the box is more than 1000 times the volume of the thermistor to be measured, and the temperature uniformity is within ±1°C. The motion control unit is deployed in the temperature environment zone A. Figure 12 in the figure is a data acquisition unit and a data processing unit, wherein the data acquisition unit adopts a digital multimeter 7, and the data processing unit is deployed in a host computer 8. The digital multimeter 7 is responsible for quickly and accurately measuring the resistance value according to the set time interval within the set resistance value measurement range, and transmits the data to the host computer 8. The data processing unit carried by the host computer 8 adopts a visual independent software to realize functions such as thermal time constant calculation; 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 movement 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, and the motion control unit is used to move the negative temperature coefficient thermistor 4 to be measured from the temperature environment zone A to the zone B. The linear slide 10 is an electric linear slide.

[0066] The data processing unit includes:

[0067] 1) A resistance value-temperature value conversion module, which is used to determine the relevant 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 tested 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, parameters a and b are determined by linear fitting.

[0071] 2) Thermal time constant calculation module, used to take the temperature of temperature environment zone A as the starting temperature T0, and the temperature of temperature environment zone B as the ending temperature T ∞ , and obtain 63.2% step temperature value T τ , based on the 63.2% step temperature value T τ The corresponding time t and the step starting time t0 are used to obtain the thermal time constant τ; the specific processing process is:

[0072] Step S1) The temperature of the temperature environment zone A is used as the starting temperature T0, and the temperature of the temperature environment zone B is used as the ending temperature T0. ∞ , and 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 received at different sampling times t is t Convert to the corresponding temperature value Tt , and take the vertical axis as the temperature value and the horizontal axis as the sampling time to draw the dynamic response curve;

[0075] Step S3) Different temperature values ​​T t Respectively with T τ Perform a difference operation and take the temperature value T corresponding to the minimum difference among all the differences t As the actual 63.2% step temperature value T τ , different temperature values ​​T t Perform difference calculation with T0 respectively, and take the difference value 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 starting time t0, and the thermal time constant τ is calculated:

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

[0077] 3) Display module, which displays intermediate results, measurement results, and calculation results in various ways such as numerical values, tables, and graphics.

[0078] Example 2

[0079] Embodiment 2 of the present invention proposes a method for measuring the thermal time constant of a negative temperature coefficient thermistor. Based on the negative temperature coefficient thermistor thermal time constant measuring system of embodiment 1, the method is implemented in the following steps:

[0080] Set the temperature environment A and B to their respective set temperatures and keep them stable;

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

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

[0083] When the resistance value collected by the data acquisition unit is stable, the motion control unit moves the thermistor to be tested from temperature environment zone A to zone B. The data acquisition unit measures the resistance value regularly 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 for the resistance value measured in real time 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 zone A and zone B.

[0085] The following details:

[0086] S1, conduct resistance-temperature test on the thermistor to be tested, obtain the resistance value R-temperature value T equation (as shown in formula (1)), and determine the parameters a and b through linear fitting.

[0087] Install the thermistor to be tested on the front end of the fixed rod. Start the thermostat and set the temperature of zone B to T ∞ , wait until the temperature in area B 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 temperature T0 in area A.

[0088]

[0089] S2, when the resistance value collected by the digital multimeter is observed to be stable, the motion controller is started, and the speed and distance of the linear slide are set. The linear slide drives the thermistor to move from temperature zone A to temperature zone B. During this 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.

[0090] S3, the data processing unit saves the resistance value data uploaded by the digital multimeter, and uses visual independent software to convert the resistance value data into temperature value data according to the RT equation of the thermistor to be tested. For the specific flow chart, see Figure 2 . Calculate the starting temperature T0 and the ending temperature T ∞ , 63.2% step temperature value T τ (Calculation method is shown in formula (2)), find the 63.2% step temperature value T τ The corresponding time t and the step starting time t0 are subtracted and the difference is the thermal time constant T.

[0091] T τ =T0+0.632(T ∞ -T0) (2)

[0092] S4, based on the sampling time and the collected resistance value, the host computer visualization independent software draws the dynamic response temperature-time curve of the thermistor, such as Figure 3 As shown. 12 is the dynamic response curve of the thermistor during the measurement process drawn by the visual independent software, 13 is the starting temperature T0, and 14 is the ending temperature T ∞ , 15 is 63.2% of the step temperature value T τ , 16 is the step starting time t0, and 17 is the time t when the step temperature value reaches 63.2%.

[0093] Enter a file name to save the calculated data and measurement curve.

[0094] S5, repeatedly executing step S1 to step S4, thereby calculating multiple measurement results of the thermal time constant of the same thermistor, and calculating the measurement error and repeatability of the thermal time constant.

[0095] In the dynamic response characteristic analysis of the negative temperature coefficient thermistor, the thermistor can be regarded as a first-order inertial system, and its transfer function is shown in formula (3), where K represents the gain constant and τ represents the time constant. When the sensor quickly transfers 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 excitation of the step signal, the response process of the thermistor can be expressed by formula (4). It can be seen from formula (4) that when the specific conditions are met, that is, the equation of formula (5) is established, the difference between the current time t and the step start 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 can be calculated using formula (2): τ The host computer software compares the temperature value T at each moment t t With 63.2% step temperature value T τ The relationship between the temperature and the starting time t0 of the step is used to find the closest temperature value. The difference between the corresponding time t and the starting time t0 of the step is the time constant value τ.

[0100] The time constant calculation method of the upper computer visualization independent software in step S3 is: first, the resistance value R data is converted into temperature value T data using the RT equation of the thermistor to be measured; then, the starting temperature T0 and the ending temperature T0 of the measurement process are determined according to the temperature fluctuation range of the constant temperature box. ∞ , step starting time t0; According to the formula (2), the 63.2% step temperature value T of the theoretical calculation is calculated. τ ; Compare the temperature value T at each moment with the theoretically calculated 63.2% step temperature value T τ The minimum value of the difference is taken as 63.2% of the actual measured step temperature value T τ ; Using 63.2% step temperature value T τ The corresponding time t minus the step start time t0 is calculated to get the time constant value τ; after the calculation is completed, the output shows the starting temperature T0 and the ending temperature T ∞ , 63.2% step temperature value T τ, thermal time constant τ, draw the temperature-time curve of the dynamic response process of the thermistor, and save the calculation results and curve graph according to the input file name.

[0101] In the technical solution of the embodiment of the present invention, the motion control unit 3 can accurately control the speed and displacement of the thermistor 4 to be tested; the digital multimeter 7 can quickly and accurately measure the resistance value, and save and transmit these data to the host computer 8; the data processing unit is deployed on the host computer 8, and a visual independent software is used, the software functions include resistance value-temperature value conversion, various parameter display of the measurement process (starting temperature, end 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 storage. The visual independent software is independently developed, can be used with different temperature step test systems, and can calculate the time constant according to the dynamic response data of the negative temperature coefficient thermistor. Its integrated design is easy to transplant to different host computers and systems.

[0102] Using various types of negative temperature coefficient thermistors for example tests, the thermal time constant of the measurement system was repeatedly measured, and the error of the measurement results was within ±3%. The measurement system and method of the present invention achieves good repeatability and small measurement error, effectively simplifies the complex operations and data processing steps in the traditional measurement process, and makes the entire test process more accurate, efficient and easy to execute.

[0103] exist Figure 3 In the schematic diagram of the application example shown, the temperature zone A is room temperature 25°C, and the temperature uniformity is ±1°C; the temperature range of the thermostat 5 can be set from room temperature + 10°C to 125°C, the internal size of the box is 55cm×55cm×45cm, the temperature uniformity is ±1°C, and the temperature zone B is set to 75°C; the movement speed of the linear slide 10 is 1m / s, and the moving distance is 30cm; the digital multimeter 7 is a six-and-a-half-digit digital multimeter, the sampling time interval is set to 1ms, the resistance range is set to 0-10kΩ, and the total number of collected data is set to 10 4 In the dynamic response temperature-resistance curve 12 of the thermistor 4 to be tested, the thermal time constant measurement result is 837ms, the average value of 8 repeated measurements is 845.6ms, and the error is within ±3%. The test results are summarized in Table 1:

[0104] Table 1. Data of repeated measurements of the application examples of the method of the present invention.

[0105]

[0106] In this application example, the parameter a of the RT equation is 0.00051404, the parameter b is 0.00032343, and the temperature error of the constant temperature box is T x is 1℃, the digital multimeter collects the time interval t x is 1ms, the starting temperature T0 is 25.12℃, and the ending temperature T ∞ is 75.31℃, the step starting point t0 is 1.975s, the time constant corresponding to the temperature point t is 2.812s, and the 63.2% step temperature value T τ It is 56.84℃ and the time constant τ is 837ms.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. A negative temperature coefficient thermistor thermal time constant measurement system, characterized in that: include: Temperature environment unit, motion control unit, data acquisition unit, and data processing unit deployed on the host computer; wherein, The temperature environment unit is used to provide temperature environment zones A and B with different ambient temperatures respectively; The motion control unit is used to accurately control the movement of the negative temperature coefficient thermistor to be tested from temperature environment zone A to zone B; The data acquisition unit is used to measure the resistance value of the negative temperature coefficient thermistor to be measured in real time and transmit it to the host computer; The data processing unit is used to determine the corresponding temperature value for the resistance value measured in real time 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 zone A and zone B.

2. The negative temperature coefficient thermistor thermal time constant measurement system according to claim 1, characterized in that: The temperature environment zone A is a constant temperature indoor environment, and the motion control unit is deployed in the temperature environment zone A; the zone B is a constant temperature box that can set different constant temperatures. The internal size of the box is more than 1000 times the volume of the thermistor to be tested, and the temperature uniformity is within ±1°C.

3. The negative temperature coefficient thermistor thermal time constant measurement system according to claim 2, characterized in that: The motion control unit comprises: a motion controller, a linear slide and a fixed rod, wherein: The negative temperature coefficient thermistor to be measured is installed at the front end of a fixed rod, the fixed rod is connected to a linear slide, and the motion controller accurately controls the movement direction, speed and distance of the linear slide to drive the fixed rod to move, thereby realizing the movement of the negative temperature coefficient thermistor to be measured from temperature environment zone A to temperature environment zone B, wherein the linear slide is an electric linear slide.

4. The negative temperature coefficient thermistor thermal time constant measurement system according to claim 1, characterized in that: The data acquisition unit includes a digital multimeter, which is used to measure the resistance value at a set time interval within a set resistance value measurement range.

5. The negative temperature coefficient thermistor thermal time constant measurement system according to claim 1, characterized in that: The data processing unit comprises: The resistance value-temperature value conversion module is used to determine the relevant 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 tested in advance, and establish the equation; Thermal time constant calculation module, used to set the temperature of temperature environment zone A as the starting temperature T0, and the temperature of temperature environment zone B as the ending temperature T ∞ , and obtain 63.2% step temperature value T τ , based on the 63.2% step temperature value T τ The corresponding time t and the step starting time t0 are used to obtain the thermal time constant τ; The display module is used to display the measurement and calculation results.

6. The negative temperature coefficient thermistor thermal time constant measurement system according to claim 5, characterized in that: The resistance value R-temperature value T equation is: According to a set of resistance values ​​R and temperature values ​​T, parameters a and b are determined by linear fitting.

7. The negative temperature coefficient thermistor thermal time constant measurement system according to claim 5, characterized in that: The processing process of the thermal time constant calculation module includes: Step S1) The temperature of the temperature environment zone A is used as the starting temperature T0, and the temperature of the temperature environment zone B is used as the ending temperature T0. ∞ , and obtain the theoretical 63.2% step temperature value T τ ; Step S2) According to the resistance value R-temperature value T equation, the resistance value R received at different sampling times t is t Convert to the corresponding temperature value T t , and take the vertical axis as the temperature value and the horizontal axis as the sampling time to draw the dynamic response curve; Step S3) Different temperature values ​​T t Respectively with T τ Perform a difference operation and take the temperature value T corresponding to the minimum difference among all the differences t As the actual 63.2% step temperature value T τ , different temperature values ​​T t Perform difference calculation with T0 respectively, and take the difference value 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 starting time t0, and the thermal time constant τ is calculated.

8. The negative temperature coefficient thermistor thermal time constant measurement system according to claim 7, characterized in that: In step S1), the theoretical 63.2% step temperature value T τ Satisfy the following formula: T τ =T0+0.632(T ∞ -T0)。 9. The negative temperature coefficient thermistor thermal time constant measurement system according to claim 7, characterized in that: The thermal time constant τ in step S3) is 63.2% of the actual step temperature value T τ The difference from the step start time t0.

10. A method for measuring a thermal time constant of a negative temperature coefficient thermistor, implemented based on the system according to any one of claims 1 to 9, the method comprising: Set the temperature environment A and B to their respective set temperatures and keep them stable; Install the thermistor to be tested on the motion control unit; After setting the range of the collected resistance value, the collection time interval and the total number of collected data, the data collection unit is started; When the resistance value collected by the data acquisition unit is stable, the motion control unit moves the thermistor to be tested from temperature environment zone A to zone B. The data acquisition unit measures the resistance value regularly according to the set collection time interval and uploads it to the data processing unit. The data processing unit determines the corresponding temperature value for the resistance value measured in real time 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 zone A and zone B.

Images