CN108572037B - A kind of thermal resistor stable state scaling method for evading self-heating effect - Google Patents

Abstract

The embodiment of the present invention discloses a steady-state calibration method for a thermistor that avoids the self-heating effect. The steady-state calibration method of the thermistor ensures that the calibration current through the thermistor is equal to the working current by adjusting the output voltage of the programmable DC power supply, and uses the arithmetic mean value of multiple sets of data to calculate the resistance value of the thermistor and the Calibrating the temperature value solves the problem of measurement accuracy such as additional temperature deviation caused by the inconsistency between the thermistor operating current and the calibration current in the existing calibration methods. It provides the necessary guarantee for the accuracy and reliability of the thermal control subsystem.

Description

A steady-state calibration method of thermistor to avoid self-heating effect

technical field

The invention belongs to the technical field of temperature sensor calibration, and in particular relates to a steady-state calibration method of a thermistor for avoiding self-heating effects.

Background technique

The thermistor is a semiconductor component that realizes temperature measurement based on the one-to-one mapping relationship between the resistance temperature and the resistance value. Compared with other types of temperature sensors, thermistors show comprehensive advantages in many aspects, such as cold and heat sensitivity, temperature change response speed, space environment adaptability, long-life reliability and process implementability. In view of this, the thermal control subsystem of spacecraft generally adopts thermistor for temperature measurement, control and compensation.

With the rapid development of space precision instruments and equipment, how to improve the temperature measurement and control accuracy of the thermal control subsystem has become an urgent problem to be solved. The requirement is not lower than 0.05℃. At present, the direct delivery accuracy of the thermistor can only meet the general temperature measurement and control requirements, and there are differences in the resistance temperature characteristics between any two, and the interchangeability is poor. Therefore, for special occasions with high temperature measurement and control accuracy requirements, the thermistor must be calibrated in a precise steady state before it can be used, that is, under the specified standard conditions, a high-precision mapping relationship between the resistance value and the calibrated temperature value is established.

In the existing thermistor steady-state calibration method, in order to avoid the additional temperature deviation caused by the self-heating effect of the resistor, it is usually necessary to ensure that the calibration current of the thermistor is in the order of microamps and the dissipation power is in the order of milliwatts. Thereby, the mapping relationship between the nominal zero-power resistance value and the nominal temperature value is obtained. Limited by the secondary power supply voltage, the actual working current through the thermistor may be much larger than the rated current, as shown in Table 1. This additional temperature deviation caused by the inconsistency between the working current and the calibration current will seriously affect the temperature measurement and control accuracy of the thermistor, and interfere with the real-time status confirmation and control strategy selection of the thermal control subsystem.

Aiming at the problems existing in the existing thermistor steady-state calibration methods, a steady-state calibration method for thermistors that avoids the self-heating effect is proposed. The accuracy and reliability of the spacecraft thermal control subsystem provide the necessary guarantee.

Table 1 Influence of self-heating effect on the resistance temperature characteristics of thermistor

SUMMARY OF THE INVENTION

Aiming at the problems existing in the existing thermistor steady-state calibration method, an embodiment of the present invention proposes a thermistor steady-state calibration method that avoids the self-heating effect. The thermistor steady-state calibration method solves the measurement accuracy problems such as additional temperature deviation caused by the inconsistency between the thermistor operating current and the calibration current in the existing calibration methods, while avoiding the self-heating effect and improving the temperature measurement and control accuracy. It also provides the necessary guarantee for the accuracy and reliability of the spacecraft thermal control subsystem.

The specific scheme of the thermistor steady-state calibration method is as follows: a thermistor steady-state calibration method for avoiding self-heating effects, comprising step S1: inserting the thermistor into an experimental container, and sealing the experimental container; Step S2: open the calibration constant temperature bath and set the target temperature until the indicated temperature reaches the target temperature and the fluctuation state is stable; Step S3: connect the thermistor, programmable DC power supply, digital multimeter, second-class standard platinum resistance, temperature scanner Connect the terminal equipment to form an electrical path; Step S4: insert the experimental container and the second-grade standard platinum resistance into the calibration hole of the calibration constant temperature bath; Step S5: adjust the output voltage of the programmable DC power supply until The calibrated current passing through the thermistor is equal to the working current, and is left to stand for a first preset time; Step S6: every second preset time, record a group of related data, and record a predetermined number of groups; Step S7: according to The recorded multiple sets of related data can calculate the resistance value and the calibration temperature value of the thermistor.

Preferably, the experimental container adopts a glass tube.

Preferably, the orifice of the glass tube is sealed with a rubber stopper and polyimide tape.

Preferably, in the step S4, a limit clip is used to separate the temperature sensing position of the thermistor in the experimental container from the bottom of the calibration constant temperature bath by a first preset distance, and in the step S4, a limit clip is used to separate the The second-grade standard platinum resistance temperature sensing position is separated from the bottom of the calibration constant temperature bath by a first preset distance.

Preferably, the range of the first preset distance is 10 mm to 30 mm.

Preferably, the range of the first preset time is 30 minutes to 60 minutes.

Preferably, the range of the second preset time is 20 seconds to 60 seconds.

Preferably, the relevant data includes the voltage value measured by the digital multimeter, the current value measured by the digital multimeter, and the temperature value measured by the second-class standard platinum resistance.

Preferably, the predetermined number of groups is greater than or equal to 30 groups.

Preferably, in step S7, an equivalent resistance value is calculated according to each group of voltage values and current values, and the resistance value of the thermistor is equal to the difference between the arithmetic mean value of the equivalent resistance value and the sampling resistance value of the DC current gear of the digital multimeter .

Drawing from the above technical solutions, the embodiments of the present invention have the following characteristics:

The steady-state calibration method of the thermistor provided in the embodiment of the present invention ensures that the calibration current passing through the thermistor is equal to the working current by adjusting the output voltage of the programmable DC power supply, and uses the arithmetic mean value of multiple sets of data to calculate the thermal value. The resistance value of the thermistor and the calibration temperature value solve the problems of measurement accuracy such as additional temperature deviation caused by the inconsistency between the thermistor operating current and the calibration current in the existing calibration methods. At the same time, it also provides the necessary guarantee for the accuracy and reliability of the spacecraft thermal control subsystem.

Description of drawings

1 is a schematic flowchart of a steady-state calibration method for a thermistor for avoiding self-heating effects provided in an embodiment of the present invention;

FIG. 2 is a schematic diagram of device connection of a thermistor steady-state calibration method for avoiding self-heating effect provided in an embodiment of the present invention;

FIG. 3 is a schematic diagram of the resistance value measurement of a steady-state calibration method for a thermistor that avoids the self-heating effect provided in an embodiment of the present invention.

Description of reference numbers:

10. Calibration thermostat 20. Terminal equipment 30. Programmable DC power supply

40. The first digital multimeter 50, the temperature scanner 60, the second digital multimeter

70, standard platinum resistance 80, experimental container 90, thermistor

K. switch

Detailed ways

In order for those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only Embodiments of some, but not all, of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The terms "first", "second", "third", "fourth", etc. (if present) in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It is to be understood that data so used may be interchanged under appropriate circumstances so that the embodiments described herein can be practiced in sequences other than those illustrated or described. Furthermore, the terms "comprising" and "having" and any other variations are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those expressly listed steps or units, but may include other steps or units not expressly listed or inherent to these processes, methods, products or devices.

As shown in FIG. 1 , a schematic flowchart of a steady-state calibration method for a thermistor that avoids the self-heating effect provided in an embodiment of the present invention. In this embodiment, the steady-state calibration method of the thermistor includes 7 steps, and the specific steps are as follows:

Step S1: Insert the thermistor into the experimental container, and seal the experimental container. In a specific embodiment, the experimental vessel is a glass tube, and a rubber stopper and polyimide tape are used to seal the mouth of the glass tube. The diameter of the glass tube is adaptively selected according to the external dimension of the thermistor. When the thermistor adopts MF501 glass-encapsulated negative temperature coefficient thermistor, the diameter of the glass tube is selected as 8 mm. Preferably, before the thermistor is inserted into the glass tube, the temperature-sensing glass beads (ie, the temperature-sensing position) of the thermistor are cleaned with a fine gauze cloth dipped in absolute ethanol. When the thermistor is inserted into the glass tube, make sure that the temperature-sensing glass beads of the thermistor (that is, the temperature-sensing position) are in full contact with the bottom of the glass tube. As known to those skilled in the art, other types of experimental containers with heat conduction function other than glass tubes can also be used for the experimental container.

Step S2: Open the calibration constant temperature bath and set the target temperature until the indicated temperature reaches the target temperature and the fluctuation state is stable. Turn on the calibration bath by applying power to the calibration bath. Before turning on the calibration bath, it is necessary to fill the calibration bath with distilled water until the minimum water level of the calibration bath is exceeded. Preferably, after the indicated temperature of the calibration constant temperature bath reaches the target temperature and the fluctuation state is stable, let it stand for a period of time, specifically 5min, 10min, 15min, etc., to ensure that the target temperature state is stable.

Step S3: Connect the thermistor, the programmable DC power supply, the digital multimeter, the second-class standard platinum resistance resistance, the temperature scanner and the terminal device into an electrical path. As shown in FIG. 2 , a schematic diagram of a device connection of a steady-state calibration method for a thermistor that avoids the self-heating effect provided in an embodiment of the present invention. In this embodiment, the thermistor 90 , the programmable DC power supply 30 , the first digital multimeter 40 , the second digital multimeter 60 , the second-class standard platinum resistance 70 , the temperature scanner 50 and the terminal are connected by silver-plated copper core wires. The devices 20 are connected in electrical paths. The terminal device 20 is mainly used for the calculation and display of data, and specifically includes a general-purpose computer in the market or a special-purpose processor with a display, and the like. In this embodiment, the digital multimeter includes a first digital multimeter 40 and a second digital multimeter 60 . The first digital multimeter 40 is set in the current file for detecting the current in the circuit. The second digital multimeter 60 is set in the voltage range for detecting the voltage in the circuit. In this embodiment, the accuracy requirements for related devices are as follows: the temperature stability of the calibration constant temperature bath 10≯±0.8mK, the temperature uniformity≯±2mK; the temperature measurement stability of the second-class standard platinum resistance 70≯±2mK, the measurement Temperature accuracy≯±6mK; accuracy of temperature scanner 50≯±5mK; voltage resolution of programmable DC power supply 30 1mV, accuracy ±0.03%+10mV; DC current resolution of first digital multimeter 40 0.1μA , the accuracy is ±1.5%; the resolution of the DC voltage of the second digital multimeter 60 is 1mV and the accuracy is ±0.5%.

Step S4: Insert the experimental container and the second-grade standard platinum resistance into the calibration hole of the calibration constant temperature bath. Continuing to refer to FIG. 2 , in this embodiment, a limit clip is used to separate the temperature sensing position of the thermistor 90 in the glass tube 80 from the bottom of the calibration thermostatic bath 10 by a first preset distance, and a limit clip is used to separate the two The temperature sensing part of the standard platinum resistance 70 is separated from the bottom of the calibration thermostatic bath 10 by a first preset distance. The range of the first preset distance is 10 mm to 30 mm. In this embodiment, the first preset distance is 20 mm.

Step S5: Adjust the output voltage of the programmable DC power supply until the rated current passing through the thermistor is equal to the working current, and stand for a first preset time. The range of the first preset time is 30 minutes to 60 minutes. In the specific embodiment shown in FIG. 2 , the first preset time is 30 minutes, until the calibration system shown in FIG. 2 reaches a steady state.

Step S6: Record a group of related data and record a predetermined number of groups every second preset time. The range of the second preset time is 20 seconds to 60 seconds. The relevant data includes the voltage value measured by the digital multimeter, the current value measured by the digital multimeter, and the temperature value measured by the second-class standard platinum resistance. The range of the predetermined number of groups includes more than or equal to 30 groups. In the specific embodiment shown in FIG. 2 , a group of voltage values measured by the second digital multimeter 60 , current values measured by the first digital multimeter 40 and temperature values measured by the second-grade standard platinum resistance 70 are recorded every 60 seconds. , and record 60 sets of data.

As shown in FIG. 3 , a schematic diagram of the resistance value measurement of a steady-state calibration method for a thermistor that avoids the self-heating effect provided in the embodiment of the present invention. When the switch K is turned off, the second digital multimeter 60 measures the voltage value between the two ends of the first digital multimeter 40 and the thermistor 90 in series; current, and the second digital multimeter 60 continues to measure the voltage value at both ends of the first digital multimeter 40 and the thermistor 90 in series. Since the programmable DC power supply 30 is connected in parallel with both ends of the first digital multimeter 40 and the thermistor 90 , the voltage value measured by the second digital multimeter 60 is also equivalent to the voltage value adjusted by the programmable DC power supply 30 .

Step S7: Calculate the resistance value of the thermistor and the calibration temperature value according to the recorded multiple sets of related data. Calculate the equivalent resistance value according to the voltage value and current value of each group. The resistance value of the thermistor is equal to the difference between the arithmetic mean of the equivalent resistance value and the sampling resistance value of the DC current gear of the digital multimeter.

The resistance value of the thermistor corresponding to different temperature values is calibrated by setting different target temperatures and repeating the steps of the steady state calibration method of the thermistor. Specifically, starting from step S2, the target temperature of the calibration constant temperature bath is reset, and steps S3 to S7 are repeated to complete the steady-state calibration of the resistance-temperature characteristic of the planned target temperature point.

The steady-state calibration method of the thermistor provided in the embodiment of the present invention ensures that the calibration current passing through the thermistor is equal to the working current by adjusting the output voltage of the programmable DC power supply, and uses the arithmetic mean value of multiple sets of data to calculate the thermal value. The resistance value and the calibrated temperature value of the varistor can avoid self-heating effects and improve the accuracy of temperature measurement and control, and also provide the necessary guarantee for the accuracy and reliability of the spacecraft thermal control subsystem.

In the description of this specification, description with reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples", etc., mean specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples, without conflicting each other.

Although the embodiments of the present invention have been shown and described above, it should be understood that the above-mentioned embodiments are exemplary and should not be construed as limiting the present invention. Embodiments are subject to variations, modifications, substitutions and variations.

Claims (10)

1. a thermistor steady-state calibration method that avoids self-heating effect, is characterized in that, described calibration method comprises the following steps: Step S1: insert the thermistor into the experimental container, and seal the experimental container; Step S2: open the calibration constant temperature bath and set the target temperature until the indicated temperature reaches the target temperature and the fluctuation state is stable; Step S3: connecting the thermistor, the programmable DC power supply, the digital multimeter, the second-class standard platinum resistance, the temperature scanner and the terminal device into an electrical path; Step S4: inserting the experimental container and the second-grade standard platinum resistance into the calibration hole of the calibration constant temperature bath; Step S5: adjusting the output voltage of the programmable DC power supply until the calibrated current passing through the thermistor is equal to the working current, and leaving it for a first preset time; Step S6: every second preset time, record one group of related data, and record the predetermined group number; Step S7: Calculate the resistance value and the calibration temperature value of the thermistor according to the recorded multiple sets of related data. 2 . A thermistor steady-state calibration method for avoiding self-heating effect according to claim 1 , wherein the experimental container adopts a glass tube. 3 . 3. A thermistor steady-state calibration method for avoiding self-heating effect according to claim 2, characterized in that, a rubber stopper and a polyimide tape are used to seal the mouth of the glass tube. 4. a kind of thermistor steady-state calibration method that avoids self-heating effect according to claim 1, it is characterized in that, in described step S4, adopt limit clip to measure temperature position of thermistor in described experiment container There is a first preset distance from the bottom of the calibration constant temperature bath, and in step S4, a limit clip is used to separate the second-grade standard platinum resistance temperature sensing position from the bottom of the calibration constant temperature bath by a first preset distance. 5 . The steady-state calibration method for a thermistor to avoid self-heating effects according to claim 4 , wherein the range of the first preset distance is 10 mm to 30 mm. 6 . 6 . The steady-state calibration method for a thermistor to avoid self-heating effects according to claim 1 , wherein the first preset time ranges from 30 minutes to 60 minutes. 7 . 7 . The steady-state calibration method for a thermistor to avoid self-heating effects according to claim 1 , wherein the second preset time ranges from 20 seconds to 60 seconds. 8 . 8. A thermistor steady-state calibration method for avoiding self-heating effect according to claim 1, wherein the relevant data comprises a voltage value measured by the digital multimeter and a current value measured by the digital multimeter and the temperature value measured by the second-class standard platinum resistance. 9 . The steady-state calibration method for a thermistor to avoid self-heating effects according to claim 1 , wherein the predetermined number of groups is greater than or equal to 30 groups. 10 . 10. A thermistor steady-state calibration method for avoiding self-heating effect according to claim 1, wherein in step S7, an equivalent resistance value is calculated according to each group of voltage values and current values, and the thermistor The resistance value of the device is equal to the difference between the arithmetic mean value of the equivalent resistance value and the sampling resistance value of the DC current gear of the digital multimeter.