CN110568011B - Liquid nitrogen temperature zone thermoelectromotive force measuring instrument and measuring method - Google Patents
Liquid nitrogen temperature zone thermoelectromotive force measuring instrument and measuring method Download PDFInfo
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- CN110568011B CN110568011B CN201910875937.6A CN201910875937A CN110568011B CN 110568011 B CN110568011 B CN 110568011B CN 201910875937 A CN201910875937 A CN 201910875937A CN 110568011 B CN110568011 B CN 110568011B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0084—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring voltage only
Abstract
The invention discloses a thermoelectric potential measuring instrument for a liquid nitrogen temperature zone and a measuring method thereof, wherein the measuring instrument comprises an acquisition control unit, a cooling unit, a probe assembly unit, a vacuum sealing unit and a test probe unit, wherein the test probe unit is used for clamping a sample, is controlled by the acquisition control unit to heat the sample, and simultaneously transmits a temperature signal and a voltage signal to the acquisition control unit; the probe assembly unit is used for bearing the test probe unit, adjusting the probe spacing and reducing the influence of the external temperature on the test probe unit; the acquisition control unit is used for controlling the temperature of the test probe unit and receiving a probe temperature signal and a voltage signal of the test probe unit; the cooling unit is used for rapidly cooling the probe assembly unit and the sample through liquid nitrogen; the vacuum sealing unit is used for providing a vacuum environment when the test probe unit heats the sample. The equipment provided by the invention is simple and convenient to operate, short in cooling and measuring time consumption and low in cost, and can simultaneously meet the test requirements of materials with higher mechanical strength and materials with lower mechanical strength.
Description
Technical Field
The invention belongs to the field of rapid nondestructive detection of a liquid nitrogen temperature zone, and particularly relates to a measuring method of a thermoelectric potential measuring instrument of the liquid nitrogen temperature zone.
Background
The thermoelectric material is a functional material capable of realizing the interconversion of heat energy and electric energy, has the advantages of zero noise, zero pollution, no moving parts, high reliability and the like, and has irreplaceable effects in the extreme fields of thermoelectric generation, electronic refrigeration temperature control and the like. With the continuous efforts of researchers at home and abroad, the power generation and refrigeration applications based on the Seebeck (Seebeck) effect and Peltier (Peltier) effect of thermoelectric materials are expected to advance people's lives. The Seebeck (Seebeck) coefficient is an important parameter for measuring the thermoelectric performance of a material.
The thermoelectric force is generated by a difference of potential Δ V across the conductor due to the asymmetry of electron thermal motion when a temperature gradient exists across the conductor, and the ratio S ═ Δ V/Δ T is a function dependent only on temperature and material properties, called Seebeck coefficient, which is the commonly known thermoelectric force. The Seebeck coefficient is a basic property of a conductor, is independent of the shape of the conductor, the specific connection mode of a line and the like, and has linear superposition. Since the thermoelectric voltage is independent of the geometry of the sample, measurement of the thermoelectric voltage is one of the common methods for measuring physical properties in experiments.
The material coefficients are typically measured simultaneously with current commercial instruments. And electrical resistivity. At present, the mature testing commercial instruments include LRS manufactured by Linsei corporation of Germany, ZEM manufactured by ULVAC-RIKO corporation of Japan, PPMS manufactured by Quantum Design corporation of America, CTO manufactured by British European technology Limited company of Beijing Ke, and the like, and the improved Seebeck coefficient testing system is continuously provided. However, the requirements on the shape, size and mechanical strength of a sample are high, the operation is very complicated, the measurement process is slow, and the cost is high.
Taking the comprehensive Physical Property Measurement System (PPMS) of Quantum Design company in the united states as an example, the heat transport option can obtain the Seebeck coefficient from the same sample in a low temperature region. However, the four-section measurement requires that four copper bars with the width of 0.8mm are wound on a sample at equal intervals, so that the length of the sample is at least 6mm, a certain mechanical strength is provided to support the gravity of the four copper bars, the four surfaces of the sample need to be wrapped for uniform and good thermal contact of the copper bars, silver paste is needed to connect the copper bars and the sample and dry the sample, and the operation process is extremely complex, time-consuming and labor-consuming; the two-end method still needs silver paste to be connected and dried, and has certain requirements on the size and the mechanical strength of a sample. The measurement process is slow and long in time consumption due to the fact that a classical steady-state method is adopted for measurement, and cost is high due to the fact that liquid helium is adopted for PPMS to cool. And because the silver paste is adopted for connection and drying, the sample is damaged with a certain probability. Furthermore, most importantly, the mechanical strength of the test material is high, and the sample with low mechanical strength cannot support the weight of the electrode, so that the measurement cannot be carried out. Similarly, samples with low mechanical strength cannot withstand the pressure of the clamp, so that it is difficult to use a common measuring instrument for measuring the thermoelectric force.
In view of the above problems, it is necessary to provide a simple, fast and low-cost thermal potential measuring instrument for liquid nitrogen temperature region capable of measuring samples with low mechanical strength.
Disclosure of Invention
The invention aims to provide a thermoelectric potential measuring instrument for a liquid nitrogen temperature zone, which is simple and convenient to operate, short in cooling and measuring time consumption and low in cost, and can simultaneously meet the test requirements of materials with higher mechanical strength and materials with lower mechanical strength.
The invention is realized by the following technical scheme: a thermo-electromotive force measuring instrument for liquid nitrogen temperature zone comprises an acquisition control unit, a cooling unit, a probe assembly unit, a vacuum sealing unit and a test probe unit,
the test probe unit is used for clamping a sample, is controlled by the acquisition control unit to heat the sample, and simultaneously transmits a temperature signal and a voltage signal to the acquisition control unit;
the probe assembly unit is used for bearing the test probe unit, adjusting the probe spacing and reducing the influence of the external temperature on the test probe unit;
the acquisition control unit is used for controlling the temperature of the test probe unit and receiving a probe temperature signal and a probe voltage signal of the test probe unit;
the cooling unit is used for rapidly cooling the probe assembly unit and the sample through liquid nitrogen;
the vacuum sealing unit is used for providing a vacuum environment when the test probe unit heats the sample.
Furthermore, the test probe unit comprises an upper probe and a lower probe, the probe assembly unit comprises a support and an elastic device, the upper probe is fixedly mounted at the upper end in the support, the lower probe slides at the lower end in the support through the elastic device, and the upper probe and the lower probe are correspondingly arranged.
Furthermore, the elastic device is connected to the lower end in the support in a sliding manner and comprises a lower probe support, a spring and a spring base, the two ends of the spring are respectively connected with the lower probe support and the spring base, a limit groove is formed in the upper end of the lower probe support, and the lower probe is fixedly installed in the limit groove of the lower probe support.
Further, probe subassembly unit still includes supporting block, lower supporting shoe, upper screw, lower screw and aviation plug, go up the upper end of supporting block part spiro union in the support, lower extreme of lower supporting shoe part spiro union in the support, go up supporting block and lower supporting shoe and all be equipped with the spacing groove, go up the upper end of probe through setting up fixed mounting in the support in the spacing groove of last supporting shoe, and resilient means sliding connection is in the spacing groove of lower supporting shoe, and the spacing groove tank bottom of going up supporting shoe and lower supporting shoe respectively opens a screw through-hole, go up the screw spiro union and pass the screw through-hole of last supporting shoe and fasten the upper probe in the spacing groove of last supporting shoe, the screw spiro union of lower supporting shoe and insert in the hole that spring base lower extreme was equipped with, aviation plug installs in last supporting shoe upper end.
Furthermore, the test probe unit further comprises an upper reed type electrode, a lower reed type electrode, an upper clamping type electrode and a lower clamping type electrode, wherein the upper reed type electrode and the upper clamping type electrode are installed on the lower end face of the upper probe, and the lower reed type electrode and the lower clamping type electrode are installed on the upper end face of the lower probe.
Furthermore, one third of the upper reed type electrode is connected with the upper clamping type electrode, and two thirds of the upper reed type electrode is separated from the upper clamping type electrode; one third of the lower reed type electrode is connected with the lower clamping type electrode, and two thirds of the lower reed type electrode is separated from the lower clamping type electrode.
Furthermore, the test probe unit further comprises an upper heater, a lower heater, an upper temperature sensor and a lower temperature sensor, wherein the upper temperature sensor and the lower temperature sensor are respectively embedded in the upper probe and the lower probe, and the upper heater and the lower heater are respectively installed on the upper probe and the lower probe.
Further, the upper heater and the lower heater are both polyimide heating films, and are respectively wound on the upper probe and the lower probe.
Further, the cooling unit comprises a liquid nitrogen dewar and a sample rod, and when the probe assembly unit is cooled, the probe assembly unit is connected with the lower end of the sample rod and is arranged in the liquid nitrogen dewar.
Further, the vacuum sealing unit comprises a vacuum cavity, a sealing cover, a stop valve, a release valve, a corrugated pipe and a vacuum pump, wherein the vacuum cavity is connected with the vacuum pump through the corrugated pipe, the stop valve and the release valve are installed between the vacuum cavity and the corrugated pipe, the sealing cover is respectively provided with a sealing aviation socket from top to bottom, when the probe assembly unit needs to be heated in a vacuum environment, the probe assembly unit is connected to the sealing aviation socket below the sealing cover, and the sealing aviation socket above the sealing cover is connected with the acquisition control unit as a wiring end.
Further, the liquid nitrogen temperature zone thermoelectric potential measuring instrument further comprises a computer, and the computer is used for sending a control instruction to the acquisition control unit, receiving and displaying a detection result signal of the acquisition control unit.
Furthermore, the upper supporting block, the support, the lower screw, the lower probe support and the spring base are all made of polytetrafluoroethylene, the lower supporting block is made of bakelite, and the upper probe and the lower probe are cylindrical copper probes.
A measurement method of a liquid nitrogen temperature zone thermoelectric potential measuring instrument is based on the liquid nitrogen temperature zone thermoelectric potential measuring instrument, and the measurement method comprises the following steps:
s1, the thermoelectric potential detector is in a calibration state, and thermoelectric potential calibration is carried out;
s2 installing and fixing a sample;
s3, the thermoelectric force detector is in a temperature measuring state, and the sample is cooled;
s4, transferring the probe assembly unit into a vacuum cavity for vacuum sealing;
s5 measures the thermoelectric potential of the sample.
The invention has the beneficial effects that:
(1) the modular design of each unit is small, the size of each unit is small, the disassembly and the replacement are convenient, and the functions of thermoelectric potential testing, thermoelectric potential calibration, probe cooling and the like can be realized through different combinations among the units.
(2) And liquid nitrogen is adopted for soaking and cooling, so that compared with cold head refrigeration, the cooling speed is high, and the cost is low.
(3) The vacuum environment is adopted for measurement, a good heat insulation environment can be provided, the temperature controllability is better, meanwhile, the interference of gas heat conduction and condensed water vapor is eliminated, and a stable test environment is provided.
(4) The two electrode forms are configured, so that the method is suitable for detecting samples with different mechanical strengths and shapes, can be used for measuring samples with lower mechanical strength, greatly reduces the requirements on the mechanical strength, the size and the shape of the measured samples, and widens the variety of thermoelectric force measuring materials.
Drawings
FIG. 1 is a block diagram of a thermoelectric potential measuring instrument for liquid nitrogen temperature zone according to the present invention;
FIG. 2a is a front view of the probe assembly unit;
FIG. 2b is a side view of FIG. 2 a;
FIG. 2c is a cross-sectional view of the probe assembly unit;
FIG. 3a is a front view of a clamped electrode and a reed electrode;
FIG. 3b is a top view of FIG. 3 a;
FIG. 3c is a side view of FIG. 3 a;
FIG. 4 is a schematic view of a probe cooling unit;
FIG. 5 is a schematic view of a vacuum sealing unit;
FIG. 6a is a graph of measurement results for a clamped electrode;
fig. 6b is a graph of the measurement results of the reed-type electrode.
The device comprises a computer 1, an acquisition control unit 2, a cooling unit 3, a liquid nitrogen dewar 31, a sample rod 32, a probe assembly unit 4, an aviation plug 41, an upper support block 42, a support 43, a lower support block 44, a polytetrafluoroethylene support 441, a spring 442, a polytetrafluoroethylene spring base 443, a lower screw 45, a vacuum sealing unit 5, a vacuum chamber 51, a sealing cover 52, a stop valve 53, a vent valve 54, a bellows 55, a bellows 56, a vacuum pump 6, a test probe unit 61, an upper probe 62, an upper heater 63, an upper temperature sensor 64, a lower temperature sensor 65, a lower probe 65, a lower heater 66, an upper reed electrode 67, a lower reed electrode 68, an upper clamping electrode 69, a lower clamping electrode 610 and a thermoelectric potential calibration assembly 7.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, the present invention provides a thermoelectric potential measuring instrument for liquid nitrogen temperature zone, comprising an acquisition control unit 2, a cooling unit 3, a probe assembly unit 4, a vacuum sealing unit 5 and a test probe unit 6, wherein,
the test probe unit 6 is used for clamping a sample, is controlled by the acquisition control unit 2 to heat the sample, and simultaneously transmits a temperature signal and a voltage signal to the acquisition control unit 2;
the probe assembly unit 4 is used for bearing the test probe unit 6, adjusting the probe spacing and reducing the influence of the external temperature on the test probe unit 6;
the acquisition control unit 2 is used for controlling the temperature of the test probe unit 6 and receiving a probe temperature signal and a voltage signal of the test probe unit 6;
the cooling unit 3 is used for rapidly cooling the probe assembly unit 4 and the sample through liquid nitrogen;
and a vacuum sealing unit 5 for providing a vacuum environment when the test probe unit 6 heats the sample.
Specifically, the test probe unit 6 is arranged in the probe assembly unit 4, and the test probe unit 6 clamps, heats and detects parameters of the sample, wherein when the test probe unit 6 and the sample are cooled or heated, the probe assembly unit 4 needs to be correspondingly transferred into the cooling unit 3 or the vacuum sealing unit 5. The combined structure of the probe unit assembly 4 and the test probe unit 6 can fix a sample of any shape and any mechanical strength. The thermoelectric-potential measuring instrument has two working states, namely a detection state and a cooling state. In a detection state, a sample to be detected is loaded on the probe assembly unit 4, the probe assembly unit 4 is positioned in the vacuum sealing unit 5, and a voltage signal is collected. In the cooling state, the probe assembly unit 4 is in the cooled unit 3, so that the probe is rapidly cooled.
In this preferred embodiment, the test probe unit 6 includes an upper probe 61 and a lower probe 65, the probe assembly unit 4 includes a bracket 43 and an elastic device, the upper probe 61 is fixedly mounted at the upper end of the bracket 43, the lower probe 65 slides at the lower end of the bracket 43 through the elastic device, and the upper probe 61 and the lower probe 65 are correspondingly arranged.
Specifically, the upper probe 61 and the lower probe 65 are both arranged in the bracket 43, and the sample is clamped by adjusting the relative positions of the upper probe 61 and the lower probe 65, wherein the upper probe 61 is fixed in position during the measurement process, and the elastic potential energy is provided by the elastic device to support the lower probe 65, so that the sample is tightly pressed between the upper probe 61 and the lower probe 65.
In this preferred embodiment, the elastic device is slidably connected to the lower end of the bracket 43 and comprises a lower probe bracket 441, a spring 442 and a spring base 443, wherein two ends of the spring 442 are respectively connected to the lower probe bracket 441 and the spring base 443, a limit groove is formed at the upper end of the lower probe bracket 441, and the lower probe 65 is fixedly installed in the limit groove of the lower probe bracket 441.
Specifically, in the present embodiment, the position of the elastic device is adjustable, specifically, the position of the spring base 443, and thus the position of the lower probe 65, is adjusted by adjusting the position of the lower probe support 441. The use of the spring 442 is significant in that the spring 442 not only provides a clamping force between the upper probe 61 and the lower probe 65, but also has a dynamic adjustment function, and the dynamic adjustment capability is certainly stronger for samples with different mechanical strengths and sizes.
In the preferred embodiment of this section, the probe assembly unit 4 further includes an upper support block 42 and a lower support block 44, go up screw 421, lower screw 45 and aviation plug 41, go up the upper end of support block 42 part spiro union in support 43, lower extreme of support block 44 part spiro union in support 43, go up support block 42 and lower support block 44 and all be equipped with the spacing groove, go up probe 61 through set up in the upper end of support block 42 fixed mounting in support 43 in the spacing groove, resilient means sliding connection is in the spacing groove of support block 44 down, the spacing groove tank bottom of going up support block 42 and lower support block 44 respectively opens a screw through-hole, go up screw 421 spiro union and pass the screw through-hole of support block 42 and fasten probe 61 in the spacing groove of support block 42, lower screw 45 spiro union and pass the screw through-hole of support block 44 down and insert in the hole that spring base 443 lower extreme was equipped with, aviation plug 41 installs in last support block 42 upper end.
Specifically, before clamping a sample, because the shape of the sample to be clamped is indefinite, the position of the upper probe 61 may need to be adjusted correspondingly, the position of the upper probe 61 in the limiting groove of the upper supporting block 42 can be adjusted by rotating the upper screw 421, after the upper probe 61 is fixed, the position of the teflon spring base 443 is adjusted by manually rotating the lower screw 45, the lower probe support 441 is supported by the pretightening force of the spring 442, and the lower probe 65 is made to approach the upper probe 61, so that the upper probe 61 and the lower probe 65 clamp the sample to be tested. The use of the spring 442 prevents poor contact due to sample shrinkage at low temperatures, and the spring 442 allows dynamic adjustment of the distance between the upper and lower probes.
The threaded holes at the two ends of the bracket 43 are M2 threaded holes, the threaded hole of the upper support block 42 is M3 threaded hole, and the threaded hole of the lower support block 44 is M8 threaded hole. The limiting grooves in the lower probe support 441, the upper support block 42 and the lower support block 44 are all cylindrical grooves, and the outermost peripheral shapes of the lower probe support 441, the spring base 443, the lower portion of the upper support block 42 and the upper portion of the lower support block 44 are matched with the cylindrical grooves.
In this preferred embodiment, the test probe unit 6 further includes an upper reed electrode 67, a lower reed electrode 68, an upper clamp electrode 69, and a lower clamp electrode 610, the upper reed electrode 67 and the upper clamp electrode 69 being mounted on the lower end face of the upper probe 61, and the lower reed electrode 68 and the lower clamp electrode 610 being mounted on the upper end face of the lower probe 65.
In the preferred embodiment of this section, one third of the upper reed electrode 67 is connected to the upper clamp electrode 69, and two thirds of the upper reed electrode 67 are separated from the upper clamp electrode 69; one-third of the lower reed electrode 68 is connected to the lower pinch electrode 610 and two-thirds of the lower reed electrode 68 is separated from the lower pinch electrode 610.
Specifically, the upper probe 61 and the lower probe 65 are spaced and arranged opposite to each other, a space for accommodating and fixing a sample is formed between the pair of probes, the upper probe 61 is fixedly connected to the cylindrical limiting groove of the upper supporting block 42, and the lower probe 65 is detachably connected to the cylindrical limiting groove of the lower probe holder 441. As shown in fig. 2 a-2 c, the upper support block 42 and the lower support block 44 are respectively provided with a threaded hole for matching with the upper screw 421 and the lower screw 45, the upper screw 421 is a fastening screw and passes through a hole on the support block 42 and then is inserted into the threaded hole of the upper probe 61, so as to fix the upper probe 61, the lower screw 45 passes through a hole on the lower support block 44 and then is inserted into a hole under the spring base 443 connected with the spring 442, so as to adjust the distance between the lower probe 65 and the upper probe 61, and finally clamp and fix the sample. When a blocky sample with higher mechanical strength is detected, the lower screw 45 is loosened, the sample is placed on the clamping type electrode 610, the lower screw 45 is screwed to adjust the distance between the upper clamping type electrode 69 and the lower clamping type electrode 610, the sample is finally clamped, and the gold foil is filled between the sample and the upper and lower clamping type electrodes to ensure good thermal contact and electrical contact between the sample and the electrodes.
When a sample with lower mechanical strength is measured, the distance between the upper reed-type electrode 67 and the lower reed-type electrode 68 can be adjusted in the same way, after the distance is adjusted to be proper, a filler with good insulating and heat-insulating properties is filled between the upper clamping type electrode and the lower clamping type electrode, the lower screw 45 is screwed to fix the relative position of the electrodes, then coating a small amount of low-temperature silver paste on the upper reed type electrode 67 and the lower reed type electrode 68 respectively, putting two ends of the sample on the upper reed type electrode 67 and the lower reed type electrode 68 respectively, slightly pressing the sample to ensure that the sample and the upper and lower probes keep good thermal contact and electric contact, heating to 350K by using an upper heater 62 and a lower heater 66 of the device, drying for 5 minutes, wherein the reed type electrodes have good elasticity, therefore, the method can ensure that the electrodes are not contacted tightly and the sample or the electrodes are not damaged due to sample shrinkage in the rapid cooling process and at low temperature. The silver paste is only required to be dripped to the two ends of the sample for fixation, so that the testing process is greatly simplified, and the testing time is shortened. The two electrodes are not influenced mutually, and can adapt to samples with different shapes and mechanical strength without switching.
3a, 3b and 3c show the structure of the electrode, and referring to the electrode shown in FIG. 3b, the electrode includes two parts, namely a lower clamping electrode 610 and a lower reed electrode 68, and one third of the lower reed electrode 68 is connected with the lower clamping electrode 610, so as to ensure good thermal contact between the lower reed electrode 68 and the lower clamping electrode 610, and further ensure the accuracy of temperature measurement and control; the remaining two-thirds part of the lower reed-type electrode 68 is separated from the lower clamping-type electrode 610, so that the lower reed-type electrode 68 is ensured to have good elasticity, and further the conditions that the contact of the electrode is not tight and the sample or the electrode is damaged due to the contraction of the sample in the rapid cooling process and at a low temperature are avoided. Similarly, the upper reed electrode 67 and the upper pinch electrode 610 are connected in the same manner and operate on the same principle as the lower pinch electrode 610 and the lower reed electrode 68.
In this preferred embodiment, the test probe unit 6 further includes an upper heater 62, a lower heater 66, an upper temperature sensor 63, and a lower temperature sensor 64, the upper temperature sensor 63 and the lower temperature sensor 64 being embedded in the upper probe 61 and the lower probe 65, respectively, and the upper heater 62 and the lower heater 66 being mounted on the upper probe 61 and the lower probe 65, respectively.
In the preferred embodiment of this section, the upper heater 62 and the lower heater 66 are both polyimide heating films, and the upper heater 62 and the lower heater 66 are wound around the upper probe 61 and the lower probe 65, respectively.
Specifically, in the present embodiment, the upper heater 62 and the lower heater 66 are used for heating the upper probe 61 and the lower probe 65, and the upper support block 42 and the lower probe support 441 are respectively arranged around the upper probe 61 and the lower probe 65, so as to reduce the influence of the environment on the upper probe during the measurement process.
Referring to fig. 4, in the present preferred embodiment, the cooling unit 3 includes a liquid nitrogen dewar 31 and a sample rod 32, and when the probe unit assembly 4 is cooled, the probe unit assembly 4 is connected to the lower end of the sample rod 32 and is placed in the liquid nitrogen dewar 31.
Referring to fig. 5, in this preferred embodiment, the vacuum sealing unit 5 includes a vacuum chamber 51, a sealing cover 52, a stop valve 53, a release valve 54, a bellows 55 and a vacuum pump 56, the vacuum chamber 51 is connected to the vacuum pump 56 through the bellows 55, the stop valve 53 and the release valve 54 are installed between the vacuum chamber 51 and the bellows 55, the sealing cover 52 is provided with a sealing aerial socket at the upper and lower sides, the probe assembly unit 4 is connected to the sealing aerial socket below the sealing cover 52 when the probe assembly unit 4 is to be heated in a vacuum environment, and the sealing aerial socket above the sealing cover 52 is connected to the acquisition control unit 2 as a terminal.
In the preferred embodiment of this part, the liquid nitrogen temperature zone thermoelectric potential measuring instrument further comprises a computer 1, and the computer 1 is used for sending a control instruction to the acquisition control unit 2, and receiving and displaying a detection result signal of the acquisition control unit 2.
Specifically, the upper heater 62, the lower heater 66, the upper temperature sensor 63, the lower temperature sensor 64, the upper and lower clamping electrodes, and the upper and lower reed electrodes are all electrically connected with the acquisition control unit 2 through the aviation plug 41 connection terminals. The collecting and controlling unit 2 is further configured to receive temperature information measured by the upper temperature sensor 63 and the lower temperature sensor 64, and voltage information of the upper and lower clamping electrodes and the upper and lower reed electrodes, and to send a first control signal for adjusting a heating temperature to the upper heater 62 and the lower heater 66 according to the temperature information, and the upper heater 62 and the lower heater 66 are configured to adjust the heating temperature in response to the control signal. The acquisition control unit 2 specifically adopts an astronomical AI518P temperature controller and a voltmeter keithley2000, based on technical development, can complete temperature control of the test probe unit 6 and acquisition of probe temperature and voltage data, and has a small power supply, thereby reducing the volume of the whole detector. The upper temperature sensor 63 and the lower temperature sensor 64 are platinum resistors.
In the preferred embodiment of this section, the upper support block 42, the bracket 43, the lower screw 45, the lower probe bracket 441, and the spring mount 443 are all made of teflon, the lower support block 44 is made of bakelite, and the upper probe 61 and the lower probe 65 are cylindrical copper probes.
Specifically, the upper supporting block 42, the bracket 43, the lower screw 45, the lower probe bracket 441 and the spring base 443 are all made of polytetrafluoroethylene, and have the functions of insulation and heat insulation. The lower support block 44 is made of bakelite and provides sufficient mechanical strength to withstand the severe temperature changes that occur upon contact with liquid nitrogen, while providing insulation and thermal insulation.
FIG. 6a shows the result of the present invention when the clamped electrode is applied to a sample I at different heating rates, the temperature difference between the two ends of the sample is 10K, and the heating rates are respectively 3K/min and 5K/min. FIG. 6b shows the test results of different heating rates and temperature differences of the reed electrode of the present invention on sample two, the temperature difference between two ends of the sample is 5K or 10K, and the heating rates are respectively 3K/min, 5K/min and 10K/min. The measurement results are almost coincident, the influence of the selection of the temperature difference and the temperature rise rate on the measurement results is proved to be not great, parameters can be freely set in a large range according to requirements, and meanwhile, the method has good stability and repeatability under wider conditions.
In this embodiment, a thermoelectric potential calibration assembly 7 for calibrating the device is further introduced, the thermoelectric potential calibration assembly 7 comprises block and sheet standard samples Bi2Te3, when thermoelectric potential calibration is performed, the test probe unit 6 is installed on the probe assembly unit 4, the block standard samples are used for calibrating the upper clamping electrode 69 and the lower clamping electrode 610, the sheet sample is used for calibrating the upper spring electrode 67 and the lower spring electrode 68, the measured thermoelectric potential is the thermoelectric potential in the system, the thermoelectric potential value is a stable value, and the thermoelectric potential calibration assembly is measured before each sample measurement to judge whether the thermoelectric potential measurement is stable.
A measuring method of a thermoelectric potential measuring instrument in a liquid nitrogen temperature zone comprises the following steps:
s1, the thermoelectric potential detector is in a calibration state, and thermoelectric potential calibration is carried out;
s2 installing and fixing a sample;
s3, the thermoelectric force detector is in a temperature measuring state, and the sample is cooled;
s4, transferring the probe assembly unit into a vacuum cavity for vacuum sealing;
s5 measures the thermoelectric potential of the sample.
Wherein, step S1 specifically includes:
s11, carrying out thermoelectric potential calibration on the clamping electrode; or
S12 thermoelectric voltage calibration is performed for the reed electrode.
The thermoelectric potential calibration of the clamping type electrode by adopting the thermoelectric potential measuring instrument mainly comprises the following steps:
s111, adjusting the distance between the upper clamping type electrode and the lower clamping type electrode to be slightly larger than the length of the block standard sample;
s112, padding a gold foil on the sample pad and placing the sample pad on the clamping electrode;
s113, adjusting the distance between the probes to clamp the standard sample;
s114, measuring a thermoelectric potential value;
s115, judging whether the thermoelectric voltage is a stable value or not to judge whether the thermoelectric voltage measurement is stable or not.
The thermoelectric potential calibration of the reed type electrode by adopting the thermoelectric potential measuring instrument mainly comprises the following steps:
s121, adjusting the distance between the upper reed type electrode and the lower reed type electrode to be slightly smaller than the length of the thin slice standard sample;
s122, respectively placing two ends of the thin sheet sample on the reed electrodes;
s123, fixing two ends of the sheet standard sample by using silver paste;
s124, measuring a thermoelectric potential value;
s125, judging whether the thermoelectric voltage is a stable value or not to judge whether the thermoelectric voltage measurement is stable or not.
Step S2 specifically includes:
s21, mounting a block sample with higher mechanical strength; or
S22 mounting the sheet or strip sample having lower mechanical strength.
The method for installing the blocky sample with higher mechanical strength by adopting the thermoelectric potential measuring instrument at the liquid nitrogen temperature region mainly comprises the following steps:
s211, adjusting the distance between the upper clamping type electrode and the lower clamping type electrode to be slightly larger than the length of the block sample;
s212, padding gold foils on two ends of the block sample and placing the block sample on the clamping electrode;
s213, adjusting the distance between the probes to clamp the block-shaped sample;
s214, measuring a thermoelectric potential value;
s215, judging whether the contact is good or not by judging whether the contact is a stable value or not.
The method for installing the sheet or strip sample with lower mechanical strength by adopting the liquid nitrogen temperature zone thermoelectromotive potential measuring instrument mainly comprises the following steps:
s221, adjusting the distance between the upper reed type electrode and the lower reed type electrode to be slightly smaller than the length of the sheet or strip sample;
s222, respectively placing two ends of a sheet or strip sample on reed electrodes;
s223, fixing two ends of the sheet or strip sample by silver paste;
s224, measuring a thermoelectric potential value;
s225, whether the contact of the sample is good or not is judged by judging whether the contact is a stable value or not.
Step S3 specifically includes:
s31, placing the probe assembly unit 4 and the test probe unit 6 in the liquid nitrogen Dewar 31 to be completely immersed in the liquid nitrogen;
s32 observing the temperature reading, and reducing the temperature reading to 77K;
s33 was stable at around 77K for 5 min.
Step S4 specifically includes:
s41 taking out and rapidly putting the probe assembly unit 4 and the test probe unit 6 into the vacuum chamber 51;
s42, sealing the sealing cover;
s43, opening the vacuum pump 56 and the stop valve 53 to perform air suction;
and S44 pumping air for five minutes and closing the stop valve 53 and the vacuum pump 56.
Step S5 specifically includes:
s51, the thermoelectric potential detector is in the thermoelectric potential measuring state, and the measuring software is turned on in the computer 1;
s52 setting a temperature-raising program and then running the program;
and S53, acquiring and storing data. If the test precision needs to be improved, the hot end and the cold end can be exchanged and tested again, and the influence of parasitic potential is eliminated by averaging after the results are subtracted.
Claims (12)
1. The thermo-electromotive force measuring instrument for the liquid nitrogen temperature zone is characterized by comprising an acquisition control unit (2), a cooling unit (3), a probe assembly unit (4), a vacuum sealing unit (5) and a test probe unit (6),
the test probe unit (6) is used for clamping a sample, is controlled by the acquisition control unit (2) to heat the sample, and simultaneously transmits a temperature signal and a voltage signal to the acquisition control unit (2);
the probe assembly unit (4) is used for bearing the test probe unit (6), adjusting the probe distance and reducing the influence of the external temperature on the test probe unit (6);
the acquisition control unit (2) is used for controlling the temperature of the test probe unit (6) and receiving a probe temperature signal and a probe voltage signal of the test probe unit (6);
the cooling unit (3) is used for rapidly cooling the probe assembly unit (4) and the sample through liquid nitrogen;
the vacuum sealing unit (5) is used for providing a vacuum environment when the test probe unit (6) heats a sample,
one third of the upper reed-type electrode (67) is connected with the upper clamping-type electrode (69), and two thirds of the upper reed-type electrode (67) is separated from the upper clamping-type electrode (69); one third of the lower reed electrode (68) is connected to the lower clamp electrode (610), and two thirds of the lower reed electrode (68) are separated from the lower clamp electrode (610).
2. The thermoelectric potential measuring instrument for liquid nitrogen temperature zones is characterized in that the test probe unit (6) comprises an upper probe (61) and a lower probe (65), the probe assembly unit (4) comprises a bracket (43) and an elastic device, the upper probe (61) is fixedly arranged at the upper end in the bracket (43), the lower probe (65) slides at the lower end in the bracket (43) through the elastic device, and the upper probe (61) and the lower probe (65) are correspondingly arranged.
3. The thermoelectric potential measuring instrument for liquid nitrogen temperature zone as claimed in claim 2, wherein the elastic device is slidably connected to the lower end of the inside of the bracket (43), and comprises a lower probe bracket (441), a spring (442) and a spring base (443), two ends of the spring (442) are respectively connected to the lower probe bracket (441) and the spring base (443), the upper end of the lower probe bracket (441) is provided with a limiting groove, and the lower probe (65) is fixedly installed in the limiting groove of the lower probe bracket (441).
4. The thermoelectric potential measuring instrument for liquid nitrogen temperature zones according to claim 3, wherein the probe assembly unit (4) further comprises an upper support block (42), a lower support block (44), an upper screw (421), a lower screw (45) and an aviation plug (41), the upper support block (42) is partially screwed to the upper end of the support (43), the lower support block (44) is partially screwed to the lower end of the support (43), the upper support block (42) and the lower support block (44) are both provided with a limit groove, the upper probe (61) is fixedly mounted at the upper end of the support (43) through the limit groove of the upper support block (42), the elastic device is slidably connected to the limit groove of the lower support block (44), the bottoms of the limit grooves of the upper support block (42) and the lower support block (44) are respectively provided with a threaded through hole, the upper screw (421) is screwed to pass through the threaded through hole of the upper support block (42) and fastens the upper probe (61) to the limit groove of the upper support block (42) The lower screw (45) is in threaded connection and penetrates through a threaded through hole of the lower supporting block (44) and is inserted into a hole formed in the lower end of the spring base (443), and the aviation plug (41) is mounted at the upper end of the upper supporting block (42).
5. The thermoelectric potential measuring instrument for the liquid nitrogen temperature zone according to claim 2, wherein the test probe unit (6) further comprises an upper reed electrode (67), a lower reed electrode (68), an upper clamping electrode (69) and a lower clamping electrode (610), the upper reed electrode (67) and the upper clamping electrode (69) are installed on the lower end face of the upper probe (61), and the lower reed electrode (68) and the lower clamping electrode (610) are installed on the upper end face of the lower probe (65).
6. The thermoelectric potential measuring instrument for liquid nitrogen temperature zones according to claim 5, wherein the test probe unit (6) further comprises an upper heater (62), a lower heater (66), an upper temperature sensor (63) and a lower temperature sensor (64), the upper temperature sensor (63) and the lower temperature sensor (64) are respectively embedded in the upper probe (61) and the lower probe (65), and the upper heater (62) and the lower heater (66) are respectively mounted on the upper probe (61) and the lower probe (65).
7. The thermoelectric potential measuring instrument for liquid nitrogen temperature zones as claimed in claim 6, wherein the upper heater (62) and the lower heater (66) are polyimide heating films, and the upper heater (62) and the lower heater (66) are respectively wound on the upper probe (61) and the lower probe (65).
8. The thermoelectric voltage measuring instrument for liquid nitrogen temperature zone according to claim 1, wherein said cooling unit (3) comprises a liquid nitrogen dewar (31) and a sample rod (32), and when the probe assembly unit (4) is cooled, the probe assembly unit (4) is connected with the lower end of said sample rod (32) and is placed in said liquid nitrogen dewar (31).
9. The thermoelectric potential measuring instrument for the liquid nitrogen temperature zone according to claim 1, wherein the vacuum sealing unit (5) comprises a vacuum cavity (51), a sealing cover (52), a stop valve (53), a release valve (54), a bellows (55) and a vacuum pump (56), the vacuum cavity (51) is connected with the vacuum pump (56) through the bellows (55), the stop valve (53) and the release valve (54) are installed between the vacuum cavity (51) and the bellows (55), the sealing cover (52) is respectively provided with a sealing aviation socket at the upper and lower parts, when the probe assembly unit (4) needs to be heated in a vacuum environment, the probe assembly unit (4) is connected to the sealing aviation socket below the sealing cover (52), and the sealing aviation socket above the sealing cover (52) is connected with the acquisition control unit (2) as a terminal.
10. The thermoelectric potential measuring instrument for the liquid nitrogen temperature zone according to claim 1, further comprising a computer (1), wherein the computer (1) is used for sending a control command to the acquisition control unit (2), receiving and displaying a detection result signal of the acquisition control unit (2).
11. The thermoelectric potential measuring instrument for liquid nitrogen temperature zones as claimed in any one of claims 1 to 10, wherein the upper supporting block (42), the bracket (43), the lower screw (45), the lower probe bracket (441) and the spring base (443) are all made of polytetrafluoroethylene, the lower supporting block (44) is made of bakelite, and the upper probe (61) and the lower probe (65) are cylindrical copper probes.
12. A measurement method of a liquid nitrogen temperature zone thermoelectric potential measurement instrument is based on any one of claims 1 to 11, and is characterized by comprising the following steps:
s1, the thermoelectric potential detector is in a calibration state, and thermoelectric potential calibration is carried out;
s2 installing and fixing a sample;
s3, the thermoelectric force detector is in a temperature measuring state, and the sample is cooled;
s4, transferring the probe assembly unit into a vacuum cavity for vacuum sealing;
s5 measures the thermoelectric potential of the sample.
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| WO2012116227A2 (en) * | 2011-02-23 | 2012-08-30 | California Institute Of Technology | Measuring seebeck coefficient |
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| CN101957334A (en) * | 2010-09-26 | 2011-01-26 | 东南大学 | Low-temperature physical property measuring device of solid material |
| CN202305574U (en) * | 2011-09-23 | 2012-07-04 | 中国地质大学北京 | Sample clamping device for measuring thermoelectrical potential |
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