CN113324679A - Thermal resistance time constant measuring method and device - Google Patents
Thermal resistance time constant measuring method and device Download PDFInfo
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- CN113324679A CN113324679A CN202110602109.2A CN202110602109A CN113324679A CN 113324679 A CN113324679 A CN 113324679A CN 202110602109 A CN202110602109 A CN 202110602109A CN 113324679 A CN113324679 A CN 113324679A
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- 238000012360 testing method Methods 0.000 claims description 18
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- 239000005457 ice water Substances 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
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Abstract
The invention discloses a thermal resistance time constant measuring method and device, relates to the technical field of thermistor measurement, and mainly aims to provide a measuring method capable of accurately measuring a thermal time constant of a thermal resistance. The main technical scheme of the invention is as follows: a thermal resistance time constant measurement method, comprising: measuring a zero power resistance value of the thermistor; measuring the thermistor with the thermal time constant less than 1 second to obtain the thermal time constant of the thermistor; the thermal time constant of the thermistor after self-heating cooling is measured. The invention mainly obtains the thermal time constant of the thermistor according to the oscilloscope measurement method and the voltage-current curve, and then inputs the thermal time constant and the U-I curve into the dual-channel automatic acquisition system according to the voltage value and the current value recorded by the measurement circuit of the thermal time constant, thereby achieving the technical effect of realizing the measurement of the thermal time constant of the thermistor and improving the detection accuracy.
Description
Technical Field
The invention relates to the technical field of thermistor measurement, in particular to a thermal resistance time constant measuring method and device.
Background
Thermal resistance is one of the most commonly used temperature detectors in the medium and low temperature regions. Its main features are high measuring accuracy and stable performance. Among them, the platinum thermistor has the highest measurement accuracy, and is widely used in industrial temperature measurement and is made into a standard reference instrument. Unlike the temperature measurement principle of a thermocouple, a thermal resistor measures temperature based on the thermal effect of a resistor, that is, the characteristic that the resistance value of the resistor changes with the change of temperature. Therefore, the temperature can be measured only by measuring the resistance change of the temperature sensing thermal resistor. For thermal resistors and NTC thermistors, response performance is very important. However, the measurement of the thermal time constant is strongly required. For thermal resistors with different structures, such as a chip type or thin film thermal resistor, the thermal time is long, and the measurement of the thermal time constant of self-heating and post-cooling is needed. While the bead thermistor requires a rapid temperature change to measure its thermal time constant.
The thermal time constant is an important technical parameter of the thermistor, and the testing of the parameter is specified in the general specification of the national standard GB6663.1-2007 direct-heating type negative temperature coefficient thermistor, but for the thermistor with the time more than 5 seconds, an instrument for measuring the time is not clear. At present, most manufacturers in China adopt a measuring method that a tester presses a stopwatch, and in the practical process, the reaction of people cannot be synchronous with a digital voltmeter for indicating resistance value change. Therefore, the current measurement method firstly measures the resistance values of the thermistor at 47.1 ℃ +/-0.1 ℃ and 85 ℃ +/-0.1 ℃ and records the resistance values. Then the thermistor is sealed in a test box with the volume 100 times larger than that of the thermistor to be tested, air in the test box cannot flow, the temperature is kept within (25 +/-0.1) DEG C, a circuit is connected, the thermistor is placed in the test box, a contact AA is closed, the current I is adjusted by adjusting the resistance of a comparison arm, the ratio E/I is made to be equal to 60-80% of the zero-power resistance value at 85 ℃, and the reading is stable. And moving a bidirectional switch to close a contact BB, pressing a stopwatch by a detector when the reading of the digital voltmeter changes to a zero-power resistance value of 85 ℃, starting timing, and pressing the stopwatch again when the reading of the digital voltmeter changes to a zero-power resistance value of 47.1 ℃ to stop timing. The time shown by the stopwatch is the thermal time constant of the thermistor, but in order to accurately display the zero-power resistance value when the temperature of the thermistor changes to 85 ℃ and 47.1 ℃, the sampling speed of the digital voltmeter is required to be as fast as possible, and the faster the sampling speed is, the more the eyes of people cannot catch up with, usually, only the integer part of the displayed numerical value of the digital voltmeter can be seen clearly, but the decimal part is not seen clearly, so that the test error is difficult to estimate, and the test data is not convincing.
Disclosure of Invention
In view of this, embodiments of the present invention provide a method and an apparatus for measuring a thermal resistance time constant, and mainly provide a method capable of accurately measuring a thermal time constant of a thermal resistance.
In order to achieve the purpose, the invention mainly provides the following technical scheme:
in one aspect, an embodiment of the present invention provides a thermal resistance time constant measurement method, where the method includes:
measuring a zero power resistance value of the thermistor;
measuring the thermistor with the thermal time constant less than 1 second to obtain the thermal time constant of the thermistor;
the thermal time constant of the thermistor after self-heating cooling is measured.
Further, the thermistor is placed in a measuring groove and is close to a standard thermometer, so that the zero-power resistance value of the thermistor reaches stable reading;
calculating and measuring zero power resistance value R of thermistorNExpressed by the formula:
in the formula, R1、R2、R3Is the resistance value of a known resistance, U0And (t) is a voltage value, and E is a voltage value of the variable temperature and voltage power supply.
Further, the temperature T is measurediAnd T0The following zero power resistance value is formulated as follows:
Ti＝T0+(T-T0)×63.2％
in the formula, T0273.15K; t is (273.15+25) K;
the voltage values were recorded according to the oscilloscope measurements and calculated to obtain T', which is expressed by the formula:
T'＝1/(ln(V1/V2)/B+1/273.15)-273.15
in the formula, V1、V2B is the material constant of the thermistor, T' is the measured temperature;
the thermal time constant Δ T of the thermistor is calculated and expressed by the formula:
ΔT＝T'-63.2％T'
V3＝100*K
in the formula, K is a thermodynamic temperature unit, V3Measuring a voltage value corresponding to the temperature T';
according to V3And voltageThe intersection point of the curves is a reference point, and the difference value between the reference point and the initial time point is the thermal time constant of the thermistor.
Further, the thermal time constant is measured at T-358.15K, T0298.15K and TiMeasuring a zero-power resistance value at the temperature and recording a test result;
closing the first and second contacts of the test circuit by adjusting the DC degeneration resistance Rs to the current ITHMake adjustment to ETH/ITHThe ratio of (A) to (B) is equal to 60-80% of zero power resistance value at 85 ℃, and the reading is stable;
closing the third contact point and the fourth contact point, and automatically recording a voltage value and a current value when data obtained by the variable current constant current source is changed to a zero-power resistance value of 85 ℃;
and automatically acquiring the U-I curve through the setting step of the dual-channel automatic acquisition system to obtain a thermal time constant and the U-I curve.
Further, the element is in a condition of no self-heating;
putting the thermistor into a measuring tank of non-corrosive and non-reducing media;
and 2mm to 10mm close to the standard thermometer, so that the thermistor reaches a stable reading with zero-power resistance value.
Further, the thermistor is placed in an air environment with a temperature of 25 ℃ and is brought into thermal equilibrium;
transferring the thermistor to a constant temperature part with the temperature of 0 ℃;
measuring thermistor reach temperature TiTime of zero power resistance value.
On the other hand, the embodiment of the present invention further provides a thermal resistance time constant measuring apparatus, including:
a zero power measurement circuit component;
the thermal resistance measuring circuit comprises a gas source, a pneumatic component, a constant temperature component, an oscilloscope and a constant current power supply, wherein the gas source is connected with the pneumatic component, the pneumatic component is provided with a thermistor, the constant temperature component is arranged at the lower part of the pneumatic component and is used for soaking the thermistor, one end of the oscilloscope is connected with the constant current power supply, and the other end of the oscilloscope is connected with the thermistor;
a test circuit part including a regulated power supply, a first contact point, a second contact point, a third contact point, a fourth contact point, a first bidirectional switch, a second bidirectional switch and a first voltmeter, both ends of the regulated power supply are connected to the first contact point and the second contact point, both ends of the first voltmeter are connected to the third contact point and the fourth contact point, respectively, the first bidirectional switch is disposed between the first contact point and the third contact point and is connected to one end of a thermistor, and the second bidirectional switch is disposed between the second contact point and the fourth contact point and is connected to the other end of the thermistor.
Further, the thermostatic component is loaded with an ice-water mixture.
Furthermore, the zero power measurement circuit component comprises a variable temperature and voltage power supply, a first resistor, a second resistor, a third resistor and a second voltmeter, wherein one end of the variable temperature and voltage power supply is respectively connected with the first resistor and the second resistor, the other end of the variable temperature and voltage power supply is respectively connected with the third resistor and the thermistor, one end of the second voltmeter is connected with the first resistor and the third resistor, and the other end of the second voltmeter is connected with the second resistor and the thermistor.
Compared with the prior art, the invention has the following technical effects:
in the technical scheme provided by the embodiment of the invention, the zero power resistance value of the thermistor is measured by the measuring circuit, so that the measurement of the thermal resistance with the thermal time constant more than 5 seconds is realized, then measuring the thermistor with thermal time constant less than 1 second by a measuring circuit with thermistor less than 1 second, so that the ambient temperature is changed rapidly, the thermistor is changed from the ambient temperature to 0 ℃ rapidly, then measuring the time of the thermistor reaching zero power resistance value, obtaining the thermal time constant of the thermistor according to the oscilloscope measurement method and the voltage curve, inputting the thermal time constant and the current value recorded by the measurement circuit into a dual-channel automatic acquisition system according to the voltage value and the current value of the thermal time constant, forming the thermal time constant and a U-I curve, therefore, the technical effect of measuring the time constant of the thermistor is achieved, and the detection accuracy is improved.
Drawings
Fig. 1 is a schematic structural diagram of a zero-power measurement circuit component according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a thermal resistance measurement circuit component according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a test circuit according to an embodiment of the present invention;
FIG. 4 is a graph of thermal time constant measurements according to an embodiment of the present invention;
FIG. 5 is a graph of thermal time constant measurements for self-heating post-cooling according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
To further illustrate the method for measuring the time constant of a thermal resistor of the present invention, the embodiments, structures, features and effects thereof are described in detail below. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Before describing a method for measuring a thermal resistance time constant in detail, it is necessary to further describe the related materials and operations mentioned in the present invention to achieve better results.
Negative Temperature Coefficient (NTC) thermistors have the characteristics of small volume, quick temperature sensing and sensitivity to temperature, are widely applied to temperature measurement, temperature control, temperature compensation, surge suppression and the like, and are particularly applied to the fields of aerospace, deep sea, medicine, biological thermophysics, microfluid, combustible gas detection and the like. The common NTC thermistor material is prepared by doping partial metal oxides in transition metal oxides such as Mn, Co, Ni, Fe, Zn and the like as raw materials and processing the raw materials through a semiconductor ceramic process, so that thermistors with different nominal resistance values R25 and thermistor temperature constant B values are obtained.
Nominal resistance R25(Ω)
Nominal resistance value R25(omega) refers to the resistance of the thermosensitive material measured at 25 ℃, and is also known as the resistance of an NTC thermistor.
Material constant B (K)
The material constant B is also called thermal sensitivity index, thermal sensitivity constant, and reflects the sensitivity of the resistance value of the material at a certain temperature corresponding to the temperature change. In general, the larger the value of the thermal sensitive constant B is, the higher the sensitivity is and the narrower the temperature zone is; the smaller the B value is, the lower the sensitivity is and the temperature range is wide.
Thermal time constant
The thermal time constant is a parameter describing the thermal inertia of the thermistor, and is the time τ required for the NTC thermistor to change from its own temperature to 63.2% of the difference from the ambient temperature when the ambient temperature abruptly changes to another specific temperature in a state of zero power consumption in the stationary air. That is, under the condition of zero power, when the temperature changes suddenly, the time required by the two temperature differences of 63.2% at the beginning and the end of the temperature change of the thermistor is shorter, and the smaller tau is, the smaller the thermal inertia of the NTC thermistor is.
In one aspect, an embodiment of the present invention provides a thermal resistance time constant measurement method, where the method includes:
step 1, measuring the zero power resistance value of the thermistor.
The step 1 comprises the following steps:
and 2, placing the thermistor into a measuring groove and enabling the thermistor to be close to a standard thermometer, so that the zero-power resistance value of the thermistor reaches stable reading.
The step 2 comprises the following steps:
and 3, the elements are under the condition of no self-heating, namely, all the elements are in a zero-power state for measurement, so that the measurement accuracy is improved.
Step 4, putting the thermistor into a measuring tank without corrosion and non-reduction media, wherein the media in the measuring tank usually adopt water, certainly; the medium may be any non-corrosive and non-reducing medium.
And 5, approaching the standard thermometer for 2mm to 10mm, enabling the zero power resistance value of the thermistor to reach stable reading, and reading the degree after the degree of the voltmeter is stable.
Step 6, calculating and measuring the zero power resistance value R of the thermistorNExpressed by the formula:
in the formula, R1、R2、R3Is the resistance value of a known resistance, U0(t) is the voltage value, E is the voltage value of the variable temperature voltage power supply, in the above formula, U0The value of (t) is usually 0, and the subsequent steps can be performed, at which the zero power resistance value R of the thermistor is calculatedN。
And 7, measuring the thermistor with the thermal time constant less than 1 second to obtain the thermal time constant of the thermistor.
The step 7 comprises the following steps:
step 8, measuring the temperature TiAnd T0The following zero power resistance value is formulated as follows:
Ti＝T0+(T-T0)×63.2％
in the formula, T0273.15K; t is (273.15+25) K;
of 273.15K, K is kelvin temperature, 0K is the lowest temperature in nature, called absolute zero, 0K-273.15 ℃, so 273.15K equals 0 ℃ and T is 25 ℃.
Step 8 comprises the following steps:
step 9, the thermistor is placed in an air environment with a temperature of 25 ℃ and is brought into thermal equilibrium so that the thermistor is located in an air environment with a temperature of 25 ℃, that is, the thermistor is now nominally electrically chargedResistance R25(Ω)。
step 11, measuring the thermistor reaching temperature TiTime of zero power resistance value and record, TiIs the thermal time constant of the ambient temperature change.
Step 12, recording the voltage value according to an oscilloscope measurement method, and calculating to obtain T', which is expressed by the following formula:
T'＝1/(ln(V1/V2)/B+1/273.15)-273.15
in the formula, V1、V2B is the material constant of the thermistor, T' is the measured temperature;
step 13, calculating the thermal time constant Δ T of the thermistor, and expressing the thermal time constant Δ T by the following formula:
ΔT＝T'-63.2％T'
V3＝100*K
in the formula, K is a thermodynamic temperature unit, V3Measuring a voltage value corresponding to the temperature T';
according to V3The intersection point of the reference point and the voltage curve is a reference point, and the difference value between the reference point and the initial time point is the thermal time constant of the thermistor.
And step 14, measuring the thermal time constant of the thermistor after self-heating cooling.
Step 14 comprises the steps of:
step 15, measuring the thermal time constant at T-358.15K, T0298.15K and TiMeasuring the zero power resistance value at temperature and recording the test result, according to the measuring circuit in fig. 1, the thermistor is tested at T ═358.15K，T0298.15K and TiMeasuring the zero-power resistance value at temperature and recording the test result, TiCalculated according to the following formula:
Ti＝T0+(T-T0)×63.2％；
step 16, closing the first contact point and the second contact point of the test circuit, and adjusting the direct current negative feedback resistor Rs to the current ITHMake adjustment to ETH/ITHThe ratio of (A) to (B) is equal to 60-80% of zero power resistance value at 85 ℃, and the reading is stable;
step 17, closing the third contact point and the fourth contact point, and automatically recording a voltage value and a current value when data obtained by the variable current constant current source is changed to a zero-power resistance value of 85 ℃;
and 18, automatically acquiring the U-I curve through the double-channel automatic acquisition system setting step to obtain a thermal time constant and the U-I curve.
The steps of the double-channel automatic acquisition system are as follows:
step 01 Start:1.000E-006A Stop:2.000E-5A Step:2.000E-6A Source Delay:1.00000s LimitV:2.000E+1V Measure Range:AUTO
Step 02 Start:2.500E-5A Stop:2.000E-4A Step:1.000E-5A Source Delay:3.00000s LimitV:5.000E+1V Measure Range:AUTO
Step 03, Start:2.500E-4A Stop:1.000E-3A Step:5.000E-5A Source Delay:6.00000s LimitV:5.000E+1V Measure Range:AUTO
Step 04 Start:1.000E-3A Stop:1.000E-2A Step:2.000E-4A Source Delay:8.00000s LimitV:8.000E+1V Measure Range:AUTO
Step 05 Start:1.000E-5A Stop:5.000E-6A Step:1.000E-8A Source Delay:0.10000s LimitV:8.000E+1V Measure Range:AUTO
In the technical scheme provided by the embodiment of the invention, the zero power resistance value of the thermistor is measured by the measuring circuit, so that the measurement of the thermal resistance with the thermal time constant more than 5 seconds is realized, then measuring the thermistor with thermal time constant less than 1 second by a measuring circuit with thermistor less than 1 second, so that the ambient temperature is changed rapidly, the thermistor is changed from the ambient temperature to 0 ℃ rapidly, then measuring the time of the thermistor reaching zero power resistance value, obtaining the thermal time constant of the thermistor according to the oscilloscope measurement method and the voltage curve, inputting the thermal time constant and the current value recorded by the measurement circuit into a dual-channel automatic acquisition system according to the voltage value and the current value of the thermal time constant, forming the thermal time constant and a U-I curve, therefore, the technical effect of measuring the time constant of the thermistor is achieved, and the detection accuracy is improved.
On the other hand, as shown in fig. 1 to 5, an embodiment of the present invention further provides a thermal resistance time constant measuring apparatus, including:
a zero power measurement circuit component;
the thermal resistance measuring circuit comprises a gas source 211, a pneumatic component 212, a constant temperature component 213, an oscilloscope 214 and a constant current power supply 215, wherein the gas source 211 is connected with the pneumatic component 212, the thermistor 116 is arranged on the pneumatic component 212, the constant temperature component 213 is arranged at the lower part of the pneumatic component 212 and is used for soaking the thermistor 116, one end of the oscilloscope 214 is connected with the constant current power supply 215, and the other end of the oscilloscope 214 is connected with the thermistor 116;
the testing circuit component comprises a regulated power supply 311, a first contact point 312, a second contact point 313, a third contact point 314, a fourth contact point 315, a first bidirectional switch 316, a second bidirectional switch 317 and a first voltmeter 318, wherein two ends of the regulated power supply 311 are respectively connected to the first contact point 312 and the second contact point 313, two ends of the first voltmeter 318 are respectively connected to the third contact point 314 and the fourth contact point 315, the first bidirectional switch 316 is arranged between the first contact point 312 and the third contact point 314 and is connected to one end of the thermistor 116, and the second bidirectional switch 317 is arranged between the second contact point 313 and the fourth contact point 315 and is connected to the other end of the thermistor 116.
In the technical scheme provided by the embodiment of the invention, the zero power resistance value of the thermistor 116 is measured through the measuring circuit, so that the measurement of the thermal resistance with the thermal time constant more than 5 seconds is realized, then the thermistor 116 with the thermal time constant less than 1 second is measured through the measuring circuit with the thermistor less than 1 second, so that the environmental temperature is changed rapidly, the thermistor 116 is changed from the environmental temperature to 0 ℃ rapidly, then the time for the thermistor 116 to reach the zero power resistance value is measured, the thermal time constant of the thermistor 116 is obtained according to the measuring method of the oscilloscope 214 and the voltage curve, then the voltage value and the current value recorded by the measuring circuit of the thermal time constant are input into the dual-channel automatic acquisition system to form the thermal time constant and the U-I curve, so that the technical effect of measuring the time constant of the thermistor is realized, and the detection accuracy is improved.
The zero-power measuring circuit component is used for measuring the zero-power resistance value of the thermistor; the thermal resistance measuring circuit component is used for measuring the thermal time constant of the thermistor 116, which is less than 1 second, and comprises an air source 211, a pneumatic component 212, a constant temperature component 213, an oscilloscope 214 and a constant current power supply 215, wherein the air source 211 is connected with the pneumatic component 212, the thermistor 116 is arranged on the pneumatic component 212, the constant temperature component 213 is arranged at the lower part of the pneumatic component 212, for soaking the thermistor 116, one end of the oscilloscope 214 is connected with the constant current power supply 215, the other end is connected with the thermistor 116, the air source 211 provides power for the pneumatic component 212, when the pneumatic component 212 needs to be started, the valve is opened, the pneumatic component 212 pushes the thermistor 116 to move towards the constant temperature component 213 until the medium in the constant temperature component 213 completely soaks the thermistor 116, the oscilloscope 214 records data and forms a voltage curve, and the constant current power supply 215 continuously outputs stable current to the oscilloscope 214; the test circuit components, which are used for measuring the thermal time constant of the thermistor 116 after self-heating and cooling, include a regulated power supply 311, a first contact point 312, a second contact point 313, a third contact point 314, a fourth contact point 315, a first bidirectional switch 316, a second bidirectional switch 317, and a first voltmeter 318, and the regulated power supply 311 has two end portionsA first contact point 312 and a second contact point 313, wherein two ends of a first voltmeter 318 are respectively connected with the third contact point 314 and the fourth contact point 315, a first bidirectional switch 316 is arranged between the first contact point 312 and the third contact point 314 and connected with one end of the thermistor 116, a second bidirectional switch 317 is arranged between the second contact point 313 and the fourth contact point 315 and connected with the other end of the thermistor 116, during measurement, the first bidirectional switch 316 is connected with the first contact point 312, the second bidirectional switch 317 is connected with the second contact point 313, and the current I is adjusted by adjusting the direct current negative feedback resistance RsTHMake adjustment to ETH/ITHThe ratio of the voltage to the current is equal to 60% -80% of the zero power resistance value at 85 ℃, the reading is stable, the reading is recorded, then the first bidirectional switch 316 is connected with the third contact point 314, the second bidirectional switch 317 is connected with the fourth contact point 315, when the data obtained by the variable current constant current source is changed to the zero power resistance value at 85 ℃, the voltage value and the current value are automatically recorded, then the U-I curve is automatically acquired through a dual-channel automatic acquisition system, and the thermal time constant measurement diagram of self-heating after-cooling shown in figure 5 is formed, so that the technical effect of measuring the time constant of the thermistor is achieved, and the detection accuracy is improved.
Further, the thermostatic part 213 is loaded with an ice-water mixture. The ice-water mixture enables the temperature inside the thermostatic member 213 to be closer to 0 ℃, thereby improving the accuracy of the detection.
Further, the zero power measurement circuit component includes a variable temperature and voltage power supply 111, a first resistor 112, a second resistor 113, a third resistor 114 and a second voltmeter 115, one end of the variable temperature and voltage power supply 111 is connected to the first resistor 112 and the second resistor 113, the other end is connected to the third resistor 114 and the thermistor 116, one end of the second voltmeter 115 is connected to the first resistor 112 and the third resistor 114, and the other end is connected to the second resistor 113 and the thermistor 116. In this embodiment, a zero power measuring circuit component is further defined, the first resistor 112, the second resistor 113, the third resistor 114 and the thermistor 116 are sequentially connected to form a ring structure, one end of the variable temperature and voltage power supply 111 is respectively connected to the first resistor 112 and the second resistor 113, the other end is respectively connected to the third resistor 114 and the thermistor 116, one end of the second voltmeter 115 is connected to the first resistor 112 and the third resistor 114, and the other end is connected to the second resistor 113 and the thermistor 116, that is, the second voltmeter 115 is arranged in the middle of the ring structure, so as to achieve the technical effect of measuring the zero power resistance value of the thermistor 116.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (9)
1. A thermal resistance time constant measuring method is characterized by comprising the following steps:
measuring a zero power resistance value of the thermistor;
measuring the thermistor with the thermal time constant less than 1 second to obtain the thermal time constant of the thermistor;
the thermal time constant of the thermistor after self-heating cooling is measured.
2. The method of measuring of claim 1, wherein measuring the zero-power resistance value of the thermistor comprises:
putting the thermistor into a measuring groove and enabling the thermistor to be close to a standard thermometer, so that the zero-power resistance value of the thermistor reaches stable reading;
calculating and measuring zero power resistance value R of thermistorNExpressed by the formula:
in the formula, R1、R2、R3For known electricityResistance value of the resistor, U0And (t) is a voltage value, and E is a voltage value of the variable temperature and voltage power supply.
3. The measurement method of claim 1, wherein measuring the thermistor with a thermal time constant of less than 1 second, and obtaining the thermal time constant of the thermistor comprises:
measuring the temperature TiAnd T0The following zero power resistance value is formulated as follows:
Ti＝T0+(T-T0)×63.2％
in the formula, T0273.15K; t is (273.15+25) K;
the voltage values were recorded according to the oscilloscope measurements and calculated to obtain T', which is expressed by the formula:
T'＝1/(ln(V1/V2)/B+1/273.15)-273.15
in the formula, V1、V2B is the material constant of the thermistor, T' is the measured temperature;
the thermal time constant Δ T of the thermistor is calculated and expressed by the formula:
ΔT＝T'-63.2％T'
V3＝100*K
in the formula, K is a thermodynamic temperature unit, V3Measuring a voltage value corresponding to the temperature T';
according to V3The intersection point of the reference point and the voltage curve is a reference point, and the difference value between the reference point and the initial time point is the thermal time constant of the thermistor.
4. The method of measurement according to claim 1, wherein measuring the thermal time constant of the thermistor after self-heating cooling comprises:
measuring the thermal time constant at T-358.15K, T0298.15K andTimeasuring a zero-power resistance value at the temperature and recording a test result;
closing the first and second contacts of the test circuit by adjusting the DC degeneration resistance Rs to the current ITHMake adjustment to ETH/ITHThe ratio of (A) to (B) is equal to 60-80% of zero power resistance value at 85 ℃, and the reading is stable;
closing the third contact point and the fourth contact point, and automatically recording a voltage value and a current value when data obtained by the variable current constant current source is changed to a zero-power resistance value of 85 ℃;
and automatically acquiring the U-I curve through the setting step of the dual-channel automatic acquisition system to obtain a thermal time constant and the U-I curve.
5. The method of claim 2, wherein placing the thermistor in the measurement well and in proximity to a standard thermometer to achieve a stable reading of the thermistor at zero power resistance comprises:
the element is in a condition of no self-heating;
putting the thermistor into a measuring tank of non-corrosive and non-reducing media;
and 2mm to 10mm close to the standard thermometer, so that the zero-power resistance value of the thermistor reaches a stable reading.
6. Measuring method according to claim 3, characterized in that the measured temperature TiAnd T0The following zero power resistance values include:
placing the thermistor in an air environment with a temperature of 25 ℃ and achieving thermal equilibrium;
transferring the thermistor to a constant temperature part with the temperature of 0 ℃;
measuring thermistor reach temperature TiTime of zero power resistance value.
7. A thermal resistance time constant measuring device, comprising:
a zero power measurement circuit component;
the thermal resistance measuring circuit comprises a gas source, a pneumatic component, a constant temperature component, an oscilloscope and a constant current power supply, wherein the gas source is connected with the pneumatic component, the pneumatic component is provided with a thermistor, the constant temperature component is arranged at the lower part of the pneumatic component and is used for soaking the thermistor, one end of the oscilloscope is connected with the constant current power supply, and the other end of the oscilloscope is connected with the thermistor;
a test circuit part including a regulated power supply, a first contact point, a second contact point, a third contact point, a fourth contact point, a first bidirectional switch, a second bidirectional switch and a first voltmeter, both ends of the regulated power supply are connected to the first contact point and the second contact point, both ends of the first voltmeter are connected to the third contact point and the fourth contact point, respectively, the first bidirectional switch is disposed between the first contact point and the third contact point and is connected to one end of a thermistor, and the second bidirectional switch is disposed between the second contact point and the fourth contact point and is connected to the other end of the thermistor.
8. The measurement device of claim 7,
the thermostatic part is loaded with an ice-water mixture.
9. The measurement device of claim 7,
the zero power measurement circuit component comprises a variable temperature and voltage power supply, a first resistor, a second resistor, a third resistor and a second voltmeter, wherein one end of the variable temperature and voltage power supply is respectively connected with the first resistor and the second resistor, the other end of the variable temperature and voltage power supply is respectively connected with the third resistor and the thermistor, one end of the second voltmeter is connected with the first resistor and the third resistor, and the other end of the second voltmeter is connected with the second resistor and the thermistor.
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| CN102331444A (en) * | 2011-06-17 | 2012-01-25 | 华中科技大学 | Device for automatically testing aging performance and thermal time constant of thermistor |
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| CN102331444A (en) * | 2011-06-17 | 2012-01-25 | 华中科技大学 | Device for automatically testing aging performance and thermal time constant of thermistor |
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