A multi-channel thermistor voltage effect test circuit, system and test method

Abstract

The application discloses a kind of multi-channel thermistor voltage effect test circuit, system and test method, belong to electronic circuit field, including: single-chip microcontroller, thermistor channel parallel structure, standard resistance channel parallel structure, peak voltmeter, DC regulated power supply and IGBT pulse switch;Thermistor channel parallel structure is multi-channel parallel thermistor channel, each thermistor channel includes first control switch, and first control switch and the series connection of measured thermistor;Standard resistance channel parallel structure is the standard resistance channel of multi-channel parallel, each standard resistance channel includes the series connection of second control switch and standard resistance;DC regulated power supply, thermistor channel parallel structure, standard resistance channel parallel structure and IGBT pulse switch form series loop.The application simplifies thermistor test procedure, can effectively control measurement error, improve measurement accuracy and reliability, multi-channel measurement improves measurement efficiency, reduces test time and test cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electronic circuits, and more particularly relates to a multi-channel thermistor voltage effect test circuit, system and test method. BACKGROUND

[0002] A thermistor is a resistor device that can change its resistance value according to temperature changes. It is usually made of thermosensitive material and has temperature sensitivity. At different temperatures, the resistance value of the thermistor will change, and temperature information can be obtained by measuring the change in resistance value. The voltage effect of a thermistor refers to the phenomenon that the resistance value changes when a voltage is applied to the thermistor. The voltage effect of a thermistor is a characteristic of the thermosensitive material itself and is related to temperature changes. By measuring the voltage effect of a thermistor, temperature information can be obtained and converted into an electrical signal for processing and control. The voltage effect of a thermistor has a wide range of applications in temperature measurement and control. For example, in the field of temperature measurement, the change in ambient temperature or object surface temperature can be determined by measuring the voltage across the thermistor. In the field of temperature control, the working temperature of a device can be controlled according to the voltage change of the thermistor to ensure the safety and stability of the device.

[0003] The existing voltage effect test system for thermoceramic resistors can be divided into direct measurement method and indirect measurement method. Compared with the direct measurement method, the indirect measurement method has higher measurement efficiency and more accurate measurement results. However, the existing indirect measurement method generally uses the voltammetry method for indirect measurement, which also has certain defects. For example, single measurement can only measure one sample, the process is complex and the efficiency is low; at the same time, the use of fixed voltage division ratio variable sampling resistor on the one hand fails to fully consider the error in the indirect calculation of the resistance of the sample to be measured caused by the accuracy of the peak voltage meter at low test voltage, and on the other hand the variable resistor itself also brings additional error, reducing the test accuracy; at the same time, at high test voltage, if the voltage division on the variable resistor is too high, it will also cause a large difference between the measured voltage and the actual voltage on the sample to be measured, further reducing the test accuracy. SUMMARY

[0004] In view of the defects and improvement needs of the prior art, the present application provides a multi-channel thermistor voltage effect test circuit, system and test method, which aims to improve the efficiency and test accuracy of thermistor voltage effect test.

[0005] To achieve the above-mentioned purpose, according to the first aspect of the present application, a multi-channel thermistor voltage effect test circuit is provided, comprising: a single-chip microcomputer, a thermistor channel parallel structure, a standard resistance channel parallel structure, a peak voltage meter, a direct current stabilized power supply and an IGBT pulse switch.

[0006] The parallel structure of the thermistor channels is a multi-channel parallel thermistor channel, each channel of the thermistor channel comprising a first control switch in series with a thermistor to be measured;

[0007] The parallel structure of the standard resistance channels is a multi-channel parallel standard resistance channel, each channel of the standard resistance channel comprising a second control switch and a standard resistance in series, wherein the standard resistances in the standard resistance channels are standard resistances of different resistance levels;

[0008] The DC voltage stabilizer, the parallel structure of the thermistor channels, the parallel structure of the standard resistance channels and the IGBT pulse switch form a series loop; the single-chip microcomputer is connected with the IGBT pulse switch, the first control switch and the second control switch;

[0009] The peak voltage meter is used for measuring the voltage across the parallel structure of the thermistor channels and the total voltage of the test circuit.

[0010] Further, the G pole of the IGBT pulse switch is connected with the low-voltage end of the parallel structure of the standard resistance channels, the high-voltage end of the parallel structure of the standard resistance channels is connected with the low-voltage end of the parallel structure of the thermistor channels, the high-voltage end of the parallel structure of the thermistor channels is connected with the positive pole of the DC voltage stabilizer, and the negative pole of the DC voltage stabilizer is connected with the C pole of the IGBT pulse switch, so that the DC voltage stabilizer, the parallel structure of the thermistor channels, the parallel structure of the standard resistance channels and the IGBT pulse switch form a series loop;

[0011] One end of the peak voltage meter is connected with the high-voltage end of the parallel structure of the thermistor channels, and the other end is connected with the low-voltage end of the parallel structure of the thermistor channels and the low-voltage end of the parallel structure of the standard resistance channels through two third control switches; wherein the single-chip microcomputer is further connected with the two third control switches.

[0012] Further, the G pole of the IGBT pulse switch is connected with the low-voltage end of the parallel structure of the thermistor channels, the high-voltage end of the parallel structure of the thermistor channels is connected with the low-voltage end of the parallel structure of the standard resistance channels, the high-voltage end of the parallel structure of the standard resistance channels is connected with the positive pole of the DC voltage stabilizer, and the negative pole of the DC voltage stabilizer is connected with the C pole of the IGBT pulse switch, so that the DC voltage stabilizer, the parallel structure of the thermistor channels, the parallel structure of the standard resistance channels and the IGBT pulse switch form a series loop;

[0013] One end of the peak voltmeter is connected with the low voltage end of the thermistor channel parallel structure, and the other end is connected with the high voltage end of the thermistor channel parallel structure and the high voltage end of the standard resistance channel parallel structure through two third control switches respectively; wherein, the single-chip microcomputer is also connected with two third control switches.

[0014] Further, if the current test voltage is greater than the preset first voltage threshold, the selection standard of the standard resistance channel best matched with the to-be-tested thermistor connected with each of the thermistor channels is:

[0015] The standard resistance voltage corresponding to the selected standard resistance channel is less than the preset second voltage threshold, and the ratio of the to-be-tested thermistor voltage to the standard resistance voltage is greater than 99:1;

[0016] Under the premise of meeting the standard, the channel with the largest standard resistance value is selected as the standard resistance channel best matched with the to-be-tested thermistor.

[0017] Further, if the current test voltage is less than or equal to the preset first voltage threshold, the selection standard of the standard resistance channel best matched with the to-be-tested thermistor connected with each of the thermistor channels is:

[0018] The standard resistance voltage corresponding to the selected standard resistance channel is less than the preset second voltage threshold, and the ratio of the to-be-tested thermistor voltage to the standard resistance voltage is greater than 97:3;

[0019] Under the premise of meeting the standard, the channel with the largest standard resistance value is selected as the standard resistance channel best matched with the to-be-tested thermistor.

[0020] Further, the pulse width τ of the pulse signal sent by the single-chip microcomputer, the amplitude V of the pulse signal, and the measurement power P of the to-be-tested thermistor satisfy: s s

[0021]

[0022]

[0023] Wherein, δ is the dissipation coefficient of the to-be-tested thermistor; α is the temperature coefficient of the to-be-tested thermistor; T is the period of the pulse signal; R is the resistance measurement range of the to-be-tested thermistor.

[0024] Further, the pulse width τ of the pulse signal is between 4-20ms.

[0025] Further, the standard resistance channel is 8 channels.

[0026] ​​The resistance value grades of the standard resistors in the standard resistance channels are respectively 1Ω, 10Ω, 100Ω, 1kΩ, 5kΩ, 10kΩ, 50kΩ and 100kΩ.

[0027] According to the second aspect of the present application, a multi-channel thermistor voltage effect test system is provided, comprising: a host computer, a temperature control meter, an electric furnace and the multi-channel thermistor voltage effect test circuit according to any one of the first aspect.

[0028] The host computer is connected with the temperature control meter, the single-chip microcomputer in the multi-channel thermistor voltage effect test circuit, the peak voltage meter and the direct current stabilized power supply respectively; the temperature control meter is connected with the electric furnace through a TC temperature control thermocouple, and the thermistor to be tested is placed in the electric furnace.

[0029] According to the third aspect of the present application, a method for testing the voltage effect of multi-channel thermistor by the test system according to the second aspect is provided, comprising:

[0030] S1, setting the test voltage, test temperature and the number of thermistors to be tested on the host computer, and traversing the set test temperature;

[0031] S2, heating the electric furnace to the target temperature of the current test;

[0032] S3, traversing the thermistor channel according to the set number of thermistors to be tested;

[0033] S4, selecting the current thermistor channel to be tested, and traversing the set test voltage;

[0034] S5, outputting the current test voltage, testing the voltage effect of the current thermistor to be tested by the multi-channel thermistor voltage effect test circuit, and saving the test result;

[0035] S6, judging whether the test voltage is traversed, if not, selecting the next test voltage as the current test voltage and jumping to S5;

[0036] If yes, judging whether the thermistor channel is traversed, if not, selecting the thermistor to be tested on the next thermistor channel as the current thermistor to be tested and jumping to S4;

[0037] If yes, judging whether the test temperature is traversed, if not, selecting the next test temperature as the current test temperature and jumping to S2;

[0038] If yes, the test is ended; and the corresponding thermistor voltage effect curve is obtained according to the test result.

[0039] Overall, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0040] (1) The multi-channel thermistor voltage effect test circuit of the present application, by designing a thermistor channel parallel structure and a standard resistance channel parallel structure, and corresponding measurement loops with a peak voltage meter, a DC stabilized power supply and an IGBT pulse switch, can indirectly measure the resistance value of the thermistor to be measured by the method of collecting the voltage division on the thermistor to be measured and the total voltage of the circuit by the peak voltage meter.

[0041] At the same time, by switching the corresponding test thermistor channel, the measurement of multiple thermistors to be measured at the current test voltage and test temperature can be realized, improving the test efficiency and simplifying the operation process of the test personnel.

[0042] In addition, using multiple standard resistance channels instead of variable resistors avoids the problem of test accuracy caused by the error between the actual resistance value of the variable resistor and the set resistance value, improving the reliability of the test.

[0043] (2) Further, the peak voltage meter is connected to the thermistor channel parallel structure and the standard resistance channel parallel structure through two third control switches, so that the present application can collect the required data with only one peak voltage meter, reducing the cost of one peak voltage meter.

[0044] (3) Further, in order to take into account the measurement range of the thermistor to be measured and the problem that the output of the power supply is not greater than the range of the measuring instrument (peak voltage meter) and the difference between the measured voltage and the actual voltage on the thermistor to be measured under high test voltage (test voltage greater than the preset first voltage threshold), the present application designs a standard resistance channel selection standard that best matches the thermistor to be measured. Based on this standard, the voltage division on the standard resistance will not be too high, and the resistance value within the range of the thermistor to be measured can be accurately measured.

[0045] (4) Further, under low test voltage (test voltage does not exceed the preset first voltage threshold), based on the standard resistance channel selection standard designed by the present application that best matches the thermistor to be measured, the voltage division on the standard resistance will not be too low, and the indirect calculation error of the sample resistance caused by the accuracy of the peak voltage meter under low test voltage is fully considered, further improving the measurement accuracy.

[0046] (5) Further, the millisecond level pulse width can be effectively detected by the peak voltage meter under the condition of meeting the "zero power" requirement of the thermistor test.

[0047] (6) Further, the channel thermistor voltage effect test system of the present application is an automatic test system, which can automatically switch the to-be-tested thermistor, select and switch the standard resistance grade, control the temperature and control the test voltage through the upper computer, without additional operation in the test process, and the process is simple.

[0048] In summary, the present application simplifies the thermistor test process, effectively controls the error, improves the precision and reliability, and reduces the test time and test cost through the multi-channel thermistor channel, the selection of multiple standard resistance grades, the reuse of the peak value table and the IGBT pulse voltage control. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 It is a multi-channel thermistor voltage effect test circuit structure schematic diagram in the embodiment 1 of the present application.

[0050] Figure 2 It is a multi-channel thermistor voltage effect test system structure schematic diagram in the embodiment 2 of the present application.

[0051] Figure 3 It is an automatic test flow chart of the multi-channel thermistor voltage effect test system in the embodiment 2 of the present application.

[0052] Figure 4 It is a thermistor voltage effect diagram corresponding to the test voltage of 100V, 200V and 400V in the embodiment 2 of the present application.

[0053] Figure 5 It is a thermistor voltage effect diagram corresponding to the test voltage of 100V in the embodiment 2 of the present application.

[0054] In all the drawings, the same reference signs are used to represent the same elements or structures, wherein:

[0055] 1 - single-chip microcomputer, 2 - first control switch, 3 - to-be-tested thermistor, 4 - second control switch, 5 - standard resistance, 6 - peak voltage meter, 7 - third control switch, 8 - direct current stabilized power supply, 9 - IGBT pulse switch. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0057] In the present application, the terms "first", "second", and the like in the present application and the accompanying drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence.

[0058] Embodiment 1

[0059] As Figure 1 shown, the multi-channel thermistor voltage effect test circuit of the present application mainly includes a single-chip microcomputer 1, a thermistor channel parallel structure, a standard resistance channel parallel structure, a peak voltage meter 6, a direct current stabilized power supply 8, and an IGBT pulse switch 9.

[0060] The thermistor channel parallel structure is a plurality of parallel thermistor channels, each of which includes a first control switch 2 in series with a thermistor 3 to be tested. The standard resistance channel parallel structure is a plurality of parallel standard resistance channels, each of which includes a second control switch 4 in series with a standard resistance 5, wherein the standard resistance 5 in each standard resistance channel is a standard resistance with different resistance values.

[0061] The direct current stabilized power supply 8, the thermistor channel parallel structure, the standard resistance channel parallel structure, and the IGBT pulse switch 9 form a series loop. The single-chip microcomputer is connected with the IGBT pulse switch 9, the first control switch 2, and the second control switch 4.

[0062] The peak voltage meter 6 is used to measure the voltage across the thermistor channel parallel structure and the total voltage of the test circuit, respectively.

[0063] Specifically, as Figure 1 shown, the G pole (gate) of the IGBT pulse switch 9 is connected with the low voltage end of the standard resistance channel parallel structure, the high voltage end of the standard resistance channel parallel structure is connected with the low voltage end of the thermistor channel parallel structure, and the high voltage end of the thermistor channel parallel structure is connected with the positive pole of the direct current stabilized power supply 8. The negative pole of the direct current stabilized power supply 8 is connected with the C pole (collector) of the IGBT pulse switch 9, and the E pole (emitter) of the IGBT pulse switch 9 is connected with the single-chip microcomputer 1.

[0064] At this time, correspondingly, one end of the peak voltage meter 6 is connected with the high voltage end of the thermistor channel parallel structure, and the other end is connected with the low voltage end of the thermistor channel parallel structure and the low voltage end of the standard resistance channel parallel structure through two third control switches 7, respectively. The single-chip microcomputer 1 is also connected with the third control switch 7. In the embodiment of the present application, the low voltage end of the standard resistance channel parallel structure is the common end of the standard resistances, and the high voltage end of the thermistor channel parallel structure is the common end of the first control switches.

[0065] In other embodiments, the direct current stabilized power supply 8, the thermistor channel parallel structure, the standard resistance channel parallel structure and the IGBT pulse switch 9 form a series loop, and the G pole of the IGBT pulse switch 9 is connected with the low voltage end of the thermistor channel parallel structure, the high voltage end of the thermistor channel parallel structure is connected with the low voltage end of the standard resistance channel parallel structure, and the high voltage end of the standard resistance channel parallel structure is connected with the positive pole of the direct current stabilized power supply 8; the negative pole of the direct current stabilized power supply 8 is connected with the C pole of the IGBT pulse switch 9, and the E pole of the IGBT pulse switch 9 is connected with the single-chip microcomputer 1.

[0066] At this time, correspondingly, one end of the peak voltage meter 6 is connected with the low voltage end of the thermistor channel parallel structure, and the other end is connected with the high voltage end of the thermistor channel parallel structure and the high voltage end of the standard resistance channel parallel structure through two third control switches 7 respectively; the single-chip microcomputer 1 is also connected with the third control switch 7.

[0067] The first control switch 2, the second control switch 4 and the third control switch 7 can be control switches such as control relays or triodes. In the embodiment of the present application, the control switch is a control relay.

[0068] In the embodiment of the present application, the thermistor channel parallel structure is a 6-way parallel thermistor channel; and the standard resistance channel parallel structure is an 8-way parallel standard resistance channel. The resistance values of the 8-way parallel standard resistance corresponding to the 8 gears are 1Ω, 10Ω, 100Ω, 1kΩ, 5kΩ, 10kΩ, 50kΩ and 100kΩ respectively.

[0069] The direct current stabilized power supply 8 provides controllable and continuous stable test voltage, which is converted into pulse test voltage with settable pulse width through the IGBT pulse switch 9 and is applied to the two ends of the tested thermistor or the tested thermistor and the standard resistance.

[0070] The single-chip microcomputer is connected with the corresponding control switch and the E pole of the IGBT pulse switch, and is used for controlling the switching of the tested thermistor and the standard resistance in the test process, the switching of the peak voltage meter and the control of the IGBT pulse width.

[0071] In work, under the current test voltage and test temperature, the single-chip microcomputer 1 controls the first control switch 2 in the selected thermistor channel (i.e. the thermistor channel corresponding to the current tested thermistor) to be closed, controls the second control switch 4 in the selected standard resistance channel to be closed according to the standard resistance channel selection, and controls the first control switch 2 in other thermistor channels and the second control switch 4 in other standard resistance channels to be disconnected; the direct current stabilized power supply 8, the thermistor channel with the closed first control switch 2, the standard resistance channel with the closed second control switch 4 and the IGBT pulse switch 9 form a series loop, and the loop current is I.

[0072] The single-chip microcomputer 1 controls the corresponding third control switch 7 to be closed or opened, and the peak voltmeter 6 measures the voltage V across the thermistor 3 in the thermistor channel closed by the first control switch 2, respectively samp and the total voltage V of the test circuit sum (the sum of the voltage across the thermistor under test and the selected standard resistance); assuming that the resistance of the thermistor under test is R samp , and the resistance of the standard resistance closed by the second control switch 4 is R stad , then according to:

[0073]

[0074]

[0075] By combining formula (1) and formula (2), we can get:

[0076]

[0077] As can be seen from formula (3), only the sample voltage value and the total circuit voltage value need to be measured, and the resistance of the thermistor under test can be indirectly calculated.

[0078] By replacing the thermistor channel, multiple thermistors under test can be measured at the current test voltage and test temperature.

[0079] The multi-channel thermistor voltage effect test circuit of the present application indirectly measures the resistance of the thermistor under test by designing the parallel structure of the thermistor channel and the parallel structure of the standard resistance channel, and corresponding measurement loops are formed with the peak voltmeter, the DC voltage stabilizer and the IGBT pulse switch. The resistance of the thermistor under test can be indirectly measured by the method of collecting the voltage division on the thermistor under test and the total voltage of the circuit by the peak voltmeter. Compared with the existing indirect measurement method of the volt-ampere method, the present application only needs to test the voltage, the data type is the same, and the measurement result is more accurate and reliable. At the same time, by switching the corresponding test thermistor channel, multiple thermistors under test can be measured at the current test voltage and test temperature, improving the test efficiency and simplifying the operation process of the test personnel.

[0080] Using multiple standard resistance channels instead of variable resistors avoids the problem of test accuracy caused by the error between the actual resistance value of the variable resistor and the set resistance value, and improves the reliability of the test.

[0081] The peak voltmeter is connected to the parallel structure of the thermistor channel and the parallel structure of the standard resistance channel through two third control switches 7, respectively, so that only one peak voltmeter is needed to collect the required data, reducing the cost of one peak voltmeter.

[0082] In the working process, the signals sent by the single-chip microcomputer to the two third control switches are mutually exclusive signals, that is, the single-chip microcomputer receives a target switching signal sent by the upper computer to the peak voltage table, and then controls one of the two third control switches to be opened and the other to be closed, so that the control switch does not connect incorrectly when the peak voltage table measures the object, and the reliability of the test is further improved.

[0083] As a further design of the present application, considering that the resistance value of the thermistor will increase from 10 2 ~ 10 3 Ω to 10 5 ~ 10 6 Ω order of magnitude during the temperature rise, the measurement range of the thermistor to be measured is relatively large, in order to accurately measure each resistance value within the range of the thermistor to be measured, and limited by the range and accuracy of the measuring instrument itself, in order to meet the condition that the output of the power supply is not greater than the range of the measuring instrument (the maximum range of the peak voltage table in the embodiment of the present application is 1000V) under high test voltage (the test voltage is greater than the preset first voltage threshold), and to solve the problem of large difference between the measured voltage and the actual voltage on the thermistor to be measured caused by excessive voltage division on the standard resistor, the selection criteria for the standard resistor channel (i.e. the standard resistor gear) best matched with the thermistor to be measured are:

[0084] The voltage division of the standard resistor corresponding to the selected standard resistor channel is less than the preset second voltage threshold; and the ratio of the voltage division of the thermistor to be measured to the voltage division of the standard resistor is greater than 99:1;

[0085] Under the above criteria, the channel with the largest standard resistor resistance value is selected as the standard resistor channel best matched with the thermistor to be measured.

[0086] The preset first voltage threshold can meet the zero power test condition, and in the embodiment of the present application, the preset first test voltage is 300V; the second voltage threshold is related to the accuracy of the peak voltage table, the higher the accuracy of the peak voltage table, the smaller the second voltage threshold, and in the embodiment of the present application, the preset second voltage threshold is 5V.

[0087] Further, when the test voltage is relatively low, i.e. the test voltage is less than or equal to the preset first voltage threshold, the voltage division on the standard resistor cannot be too low, otherwise the effective number of bits of the voltage division on the standard resistor measured by the peak voltage table will be too low, causing resistance calculation error, therefore, the selection criteria for the standard resistor channel (i.e. the standard resistor gear) corresponding to the thermistor to be measured are:

[0088] The voltage division of the standard resistor corresponding to the selected standard resistor channel is less than the preset second voltage threshold; and the ratio of the voltage division of the thermistor to be measured to the voltage division of the standard resistor is greater than 97:3;

[0089] Under the premise of meeting the above criteria, the channel with the largest standard resistance value is selected as the standard resistance channel that is best matched with the to-be-tested thermistor.

[0090] Specifically, the present application theoretically analyzes that when the test voltage is low, if the voltage division on the standard resistance is too low, the effective number of bits of the voltage division on the standard resistance measured by the peak voltmeter will be too low, resulting in a resistance calculation error.

[0091] The voltage of the to-be-tested resistance collected by the peak voltmeter is V samp , the total voltage of the circuit is V sum , the resistance value of the to-be-tested thermistor is R samp , the resistance value of the selected standard resistance is R stad , and the standard resistance voltage division formula is:

[0092]

[0093] In the embodiment of the present application, when the test voltage is 15V and the standard resistance gear is selected as the second gear, the resistance value of the to-be-tested resistance is 323.3Ω, and the minimum voltage division on the to-be-tested resistance value is 0.45V, that is, two significant digits.

[0094] Suppose the collected voltage division of the to-be-tested resistance is V samp_test , the indirect measurement calculation result of the to-be-tested resistance value is R samp_test , and the actual resistance value is R samp , the relationship is:

[0095]

[0096] According to formula (5), in the embodiment of the present application, when the test voltage is above 90V, the maximum error reaches 0.1%, and as the test voltage further increases, the error decreases, and the general value is about 0.025%. Therefore, when the test voltage is low, if the voltage division on the standard resistance is too low, the effective number of bits of the voltage division on the standard resistance measured by the peak voltmeter will be too low, resulting in a resistance calculation error.

[0097] Based on the above gear selection standard, eight standard resistance gears are designed: 1Ω, 10Ω, 100Ω, 1kΩ, 5kΩ, 10kΩ, 50kΩ, and 100kΩ (when the first gear is selected, the default sample resistance value is too small, which is equivalent to a short circuit); within the test voltage range of 15V-900V, theoretically, the to-be-tested resistance in the range of 32.3Ω-17.9MΩ can be accurately tested, which can meet the requirement of a large measurement range of the thermistor and can also obtain high measurement accuracy.

[0098] In the specific operation process of the embodiment of the present application, for the selected thermistor channel (i.e. the thermistor to be measured in the thermistor channel with the first control switch 2 closed), starting from the lowest gear in the standard resistance channel (corresponding to the smallest resistance value of the standard resistance in the standard resistance channel), the single-chip microcomputer controls the second control switch 4 corresponding to the lowest gear to be closed, and the second control switches 4 corresponding to the other standard resistance channels are opened, the single-chip microcomputer controls the signals of the two third control switches to control the switching of the target of the peak voltmeter, and the voltages across the thermistor to be measured and the total circuit are collected respectively, the host computer judges whether the selection standard of the best matching standard resistance channel is met by calculating the voltage division across the thermistor to be measured and the voltage across the selected gear standard resistance, if not, the single-chip microcomputer controls the second control switch 4 on the currently selected standard resistance channel to be opened, and the next standard resistance gear is selected again to judge the selection standard of the best matching standard resistance channel until the selected standard resistance gear meets the selection standard of the best matching standard resistance channel. In the embodiment of the present application, the corresponding control is sent to the single-chip microcomputer by the host computer, and the single-chip microcomputer controls the on-off control of the corresponding control switch after receiving the corresponding control signal.

[0099] Specifically, the multi-channel thermistor voltage effect test circuit of the present application selects the corresponding standard resistance channel according to the standard resistance channel selection standard when working, including:

[0100] S1, the single-chip microcomputer controls the second control switch 4 on the current standard resistance channel to be closed, and the second control switches 4 on the other standard resistance channels are opened;

[0101] S2, the single-chip microcomputer controls the peak voltmeter to collect the voltage across the thermistor to be measured and the voltage of the total circuit (across the thermistor to be measured and the standard resistance on the current standard resistance channel) respectively;

[0102] S3, the host computer judges whether the selection standard of the best matching standard resistance channel is met according to the calculation of the voltage across the thermistor to be measured and the voltage of the total circuit, if not, the next standard resistance channel is switched as the current standard resistance channel, and jumps to S1, if yes, the largest standard resistance channel corresponding to the above best matching standard resistance channel selection standard is selected as the standard resistance channel best matched with the thermistor to be measured.

[0103] The present application selects the appropriate standard resistance according to the specific voltage division condition by the single-chip microcomputer, which can reduce the reading and calculation error caused by the minimum accuracy of the peak voltmeter due to the fact that the standard resistance is much smaller than the thermistor to be measured, while meeting the standard voltage and not causing too much voltage division error.

[0104] As a further design of the present application, in order to ensure that the heat-sensitive measurement process meets the "zero power" condition, the pulse signal sent by the single-chip microcomputer controls the IGBT pulse switch 9 to convert the stable controllable test voltage provided by the direct-current stabilized power supply 8 into a pulse test voltage with controllable pulse width; wherein the pulse width τ of the pulse signal sent by the single-chip microcomputer, the amplitude V of the pulse signal and the measurement power P of the to-be-measured thermistor satisfy: s s

[0105]

[0106]

[0107] Wherein δ is the dissipation coefficient (mW / ℃) of the to-be-measured thermistor; α is the temperature coefficient (% / ℃) of the to-be-measured thermistor; 1 / 1000 is the zero-power measurement requirement, that is, the measurement power that causes the resistance change to be not more than 0.1%; T is the period (1s) of the pulse signal; R is the resistance measurement range of the to-be-measured thermistor.

[0108] Then the temperature rise Q of the to-be-measured thermistor in the measurement process is:

[0109]

[0110] Wherein R(t) represents the change of the to-be-measured thermistor with time.

[0111] Under the condition that the test voltage and other parameters are unchanged, by reducing the pulse width τ, the temperature rise of the sample resistance in the test process can be reduced.

[0112] In the embodiment of the present application, through experiments and calculations, the pulse width τ of milliseconds can meet the condition that the resistance change is not more than 0.1%, that is, zero-power test. As a preferred, the pulse width τ of the pulse signal is between 4 and 20 ms.

[0113] Embodiment 2

[0114] As shown in Figure 2 , based on the multi-channel thermistor voltage effect test circuit in embodiment 1, the present application further provides a multi-channel thermistor voltage effect test system, comprising: a host computer, a temperature control meter, an electric furnace and the multi-channel thermistor voltage effect test circuit in embodiment 1;

[0115] The host computer is connected with the temperature control meter, the single-chip microcomputer in the multi-channel thermistor voltage effect test circuit, the peak voltage meter and the direct-current stabilized power supply; the temperature control meter is used for collecting the temperature inside the circuit and controlling the temperature rise process inside the circuit; the temperature control meter is connected with the electric furnace through a TC temperature control thermocouple, and the to-be-measured thermistor is placed inside the electric furnace.

[0116] ​​Specifically, in the embodiment of the present application, the host computer is a PC, which is used to control the overall automatic operation process, control the voltage of the direct current stabilized power supply to set the current test voltage, control the temperature of the temperature control meter, send control signals for each control switch and the control signal for the IGBT pulse switch to the single-chip microcomputer, and receive the voltage and temperature information collected by the peak voltage meter and the temperature control meter; the single-chip microcomputer receives the control signals from the host computer, controls the test circuit to meet the requirements through the corresponding control switch; the temperature control meter receives the temperature control signal from the host computer to heat the temperature in the electric furnace, and returns the temperature data in the electric furnace to the host computer; the peak voltage meter reads the voltage between the two ends of the tested thermistor and the total resistance of the circuit and transmits it to the host computer; after the host computer receives all the voltage and temperature information and ends the test process, the data is automatically analyzed, and the test results are intuitively displayed in the form of charts and reports.

[0117] In the embodiment of the present application, the furnace body is generally cylindrical, which ensures that each part in the electric furnace is uniformly heated and the structure is stable; the furnace body material is high-purity (99%) alumina ceramic, which has been widely used in many industries as an excellent ceramic material. This material has excellent performance in electrical insulation, high thermal conductivity, high chemical resistance, good wear resistance, and low thermal expansion. It is commonly used to make high-temperature crucibles, refractory furnace tubes, and special wear-resistant materials such as ceramic bearings, ceramic seals, and water valve pieces; two mica heat insulation sheets and one ceramic baffle are installed on the front and back sides of the furnace body, the high-temperature mica sheet can withstand 850℃ under continuous use conditions, and 1050℃ under intermittent use conditions, has excellent high-temperature insulation performance, the maximum temperature resistance can reach 1000℃, and has good cost performance among high-temperature insulation materials. In addition, it has excellent electrical insulation performance, excellent bending strength, good processing performance, and environmental protection performance (no smoke and odor).

[0118] As shown in Figure 3 the process of the multi-channel thermistor voltage effect test system in the embodiment of the present application when working includes:

[0119] S1, the user sets the test parameters (including the current test voltage, test temperature, and the number of tested thermistors) on the host computer, and the system traverses according to the set test temperature;

[0120] S2, the electric furnace is heated to the target temperature of the current test; and the temperature of the electric furnace is stabilized;

[0121] S3, the thermistor channel is traversed according to the set number of tested thermistors;

[0122] S4, the current tested thermistor channel is selected, and the test voltage is traversed according to the set voltage parameter;

[0123] S5, control the direct current voltage regulator to output the current test voltage, adopt the multi-channel thermistor voltage effect test circuit to carry out voltage effect test to the current to-be-tested thermistor under the current test voltage and test temperature, and save the measurement result;

[0124] S6, judge whether the test voltage is traversed or not, if not, select the next test voltage as the current test voltage, and jump to S5;

[0125] If yes, judge whether the thermistor channel is traversed or not, if not, select the to-be-tested thermistor on the next thermistor channel as the current to-be-tested thermistor, and jump to S4;

[0126] If yes, judge whether the test temperature is traversed or not, if not, select the next test temperature as the current test temperature, and jump to S2; if yes, the test is ended; and draw the corresponding thermistor voltage effect graph and extract the key parameters of the thermistor according to the test result.

[0127] Based on the multi-channel thermistor voltage effect test system of the application, in the embodiment of the application, the number of to-be-tested thermistors is 1, the pulse period of IGBT is 4s, the temperature parameters to be traversed include the initial temperature of 20°, the maximum temperature of 500° and the temperature interval of 5°, and the test voltages are set to 100V, 200V and 400V respectively. In the embodiment of the application, in addition to starting and forcibly interrupting the test process, the thermistor voltage effect graph obtained after the test is ended is as shown in Figure 4 , wherein the three curves A, B and C in the graph correspond to the thermistor voltage effect graphs obtained when the test voltages are 100V, 200V and 400V respectively. The thermistor voltage effect graph corresponding to the test voltage of 100V is enlarged as shown in Figure 5 . It can be seen that the multi-channel thermistor voltage effect test circuit and system of the application can accurately determine the resistance-temperature effect curve of the to-be-tested sample resistance under different test voltages, directly display the changes of the sample resistance with temperature and voltage, and facilitate the user to analyze the resistance-temperature and voltage effect properties of the to-be-tested sample.

[0128] It should be noted that due to the influence of the performance of the electric furnace itself, the to-be-tested thermistor ceramic resistance cannot be tested at higher voltage and higher temperature in this embodiment. In theory, the pulse voltage set in the application can be as high as 900V.

[0129] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the application and is not used to limit the application, and any modification, equivalent replacement and improvement made within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A multi-channel thermistor voltage effect test circuit, characterized by, The application relates to a single-chip microcomputer (1), a parallel structure of thermistor channels, a parallel structure of standard resistance channels, a peak voltage meter (6), a direct-current stabilized power supply (8) and an IGBT pulse switch (9). The parallel structure of thermistor channels is a plurality of parallel thermistor channels, each of which comprises a first control switch (2) and a thermistor (3) connected in series. The parallel structure of standard resistance channels is a plurality of parallel standard resistance channels, each of which comprises a second control switch (4) and a standard resistance (5) connected in series, wherein the standard resistances (5) in the standard resistance channels are standard resistances with different resistance values. The direct-current stabilized power supply (8), the parallel structure of thermistor channels, the parallel structure of standard resistance channels and the IGBT pulse switch (9) form a series loop; the single-chip microcomputer (1) is connected with the IGBT pulse switch (9), the first control switch (2) and the second control switch (4). The peak voltage meter (6) is used for measuring the voltage between the parallel structure of thermistor channels and the total voltage of a test circuit. The G pole of the IGBT pulse switch (9) is connected with the low-voltage end of the parallel structure of standard resistance channels, the high-voltage end of the parallel structure of standard resistance channels is connected with the low-voltage end of the parallel structure of thermistor channels, the high-voltage end of the parallel structure of thermistor channels is connected with the positive pole of the direct-current stabilized power supply (8), and the negative pole of the direct-current stabilized power supply (8) is connected with the C pole of the IGBT pulse switch (9), so that the direct-current stabilized power supply (8), the parallel structure of thermistor channels, the parallel structure of standard resistance channels and the IGBT pulse switch (9) form a series loop.

2. The test circuit of claim 1, wherein, One end of the peak voltage meter (6) is connected with the high-voltage end of the parallel structure of thermistor channels, and the other end is connected with the low-voltage end of the parallel structure of thermistor channels and the low-voltage end of the parallel structure of standard resistance channels through two third control switches (7); wherein the single-chip microcomputer (1) is also connected with the two third control switches (7). The G pole of the IGBT pulse switch (9) is connected with the low-voltage end of the parallel structure of thermistor channels, the high-voltage end of the parallel structure of thermistor channels is connected with the low-voltage end of the parallel structure of standard resistance channels, the high-voltage end of the parallel structure of standard resistance channels is connected with the positive pole of the direct-current stabilized power supply (8), and the negative pole of the direct-current stabilized power supply (8) is connected with the C pole of the IGBT pulse switch (9), so that the direct-current stabilized power supply (8), the parallel structure of thermistor channels, the parallel structure of standard resistance channels and the IGBT pulse switch (9) form a series loop.

3. The test circuit of claim 1, wherein, ​ One end of the peak voltmeter (6) is connected with the low voltage end of the thermistor channel parallel structure, and the other end is connected with the high voltage end of the thermistor channel parallel structure and the high voltage end of the standard resistance channel parallel structure through two third control switches (7) respectively; wherein, the single-chip microcomputer (1) is also connected with two third control switches (7).

4. The test circuit according to any one of claims 1 to 3, characterized in that, If the current test voltage is greater than the preset first voltage threshold, the selection criteria of the standard resistance channel best matched with the to-be-tested thermistor connected with each of the thermistor channels are: The standard resistance voltage division of the selected standard resistance channel is less than the preset second voltage threshold, and the ratio of the to-be-tested thermistor voltage division to the standard resistance voltage division is greater than 99:1; Under the premise of meeting the criteria, the channel with the largest standard resistance value is selected as the standard resistance channel best matched with the to-be-tested thermistor.

5. The test circuit of claim 4, wherein, If the current test voltage is less than or equal to the preset first voltage threshold, the selection criteria of the standard resistance channel best matched with the to-be-tested thermistor connected with each of the thermistor channels are: The standard resistance voltage division of the selected standard resistance channel is less than the preset second voltage threshold, and the ratio of the to-be-tested thermistor voltage division to the standard resistance voltage division is greater than 97:3; Under the premise of meeting the criteria, the channel with the largest standard resistance value is selected as the standard resistance channel best matched with the to-be-tested thermistor.

6. The test circuit of claim 1, wherein, The pulse width τ and the amplitude V of the pulse signal emitted by the microcontroller (1) s and the measurement power P of the thermistor under test s The following conditions must be met: Wherein, δ is the dissipation coefficient of the to-be-tested thermistor; α is the temperature coefficient of the to-be-tested thermistor; T is the period of the pulse signal; R is the resistance measurement range of the to-be-tested thermistor.

7. The test circuit of claim 6, wherein, The pulse width τ of the pulse signal is between 4-20 ms.

8. The test circuit of claim 1, wherein, The standard resistance channels are 8; The resistance value of the standard resistance in the standard resistance channel is 1Ω, 10Ω, 100Ω, 1kΩ, 5kΩ, 10kΩ, 50kΩ, 100kΩ respectively.

9. A multi-channel thermistor voltage effect testing system, characterized in that, It comprises: The host computer, the temperature control meter, the electric furnace and the multi-channel thermistor voltage effect test circuit of any one of claims 1-8; The host computer is connected with the temperature control meter, the single-chip microcomputer (1) in the multi-channel thermistor voltage effect test circuit, the peak voltmeter (6) and the DC stabilized power supply (8) respectively; the temperature control meter is connected with the electric furnace through the TC temperature control thermocouple, and the to-be-tested thermistor is placed in the electric furnace.

10. A method of performing a multi-channel thermistor voltage effect test using the test system of claim 9, wherein, It comprises: S1, setting the test voltage, the test temperature and the number of to-be-tested thermistors on the host computer, and traversing the set test temperature; S2, heating the electric furnace to the target temperature of the current test; S3, traversing the thermistor channels according to the set number of to-be-tested thermistors; S4, selecting the current to-be-tested thermistor channel and traversing the set test voltage; S5, outputting the current test voltage, testing the current to-be-tested thermistor by using the multi-channel thermistor voltage effect test circuit, and saving the test result; S6, judging whether the test voltage is traversed, if not, selecting the next test voltage as the current test voltage and jumping to S5; If yes, it is judged whether the thermistor channel is traversed or not, if not, the next thermistor on the thermistor channel is selected as the current thermistor to be tested, and jumps to S4; If yes, it is judged whether the test temperature is traversed or not, if not, the next test temperature is selected as the current test temperature, and jumps to S2; If yes, the test is ended; And the corresponding thermistor voltage effect curve is obtained according to the test result.

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