CN110208132B - Magnetic fluid thermal expansion coefficient measurement system and method - Google Patents
Magnetic fluid thermal expansion coefficient measurement system and method Download PDFInfo
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- CN110208132B CN110208132B CN201910544638.4A CN201910544638A CN110208132B CN 110208132 B CN110208132 B CN 110208132B CN 201910544638 A CN201910544638 A CN 201910544638A CN 110208132 B CN110208132 B CN 110208132B
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- 239000011553 magnetic fluid Substances 0.000 title claims abstract description 106
- 238000000034 method Methods 0.000 title claims abstract description 9
- 238000005259 measurement Methods 0.000 title claims description 21
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 115
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 59
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims abstract description 30
- 238000005303 weighing Methods 0.000 claims abstract description 29
- 229910052697 platinum Inorganic materials 0.000 claims abstract description 15
- 239000000523 sample Substances 0.000 claims abstract description 15
- 238000005485 electric heating Methods 0.000 claims abstract description 12
- 239000010408 film Substances 0.000 claims abstract description 11
- 239000010409 thin film Substances 0.000 claims abstract description 7
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims abstract description 5
- 238000012360 testing method Methods 0.000 claims abstract description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 9
- 229910052802 copper Inorganic materials 0.000 claims description 9
- 239000010949 copper Substances 0.000 claims description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 239000000741 silica gel Substances 0.000 claims description 6
- 229910002027 silica gel Inorganic materials 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 5
- 239000000463 material Substances 0.000 claims description 5
- 239000000853 adhesive Substances 0.000 claims description 3
- 230000001070 adhesive effect Effects 0.000 claims description 3
- 238000004590 computer program Methods 0.000 claims description 3
- 238000004891 communication Methods 0.000 claims description 2
- 239000007789 gas Substances 0.000 description 3
- 239000011261 inert gas Substances 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005674 electromagnetic induction Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
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- Investigating Or Analyzing Materials Using Thermal Means (AREA)
Abstract
The invention discloses a system and a method for measuring the thermal expansion coefficient of a magnetic fluid, wherein the system comprises a temperature controller, a PI electric heating diaphragm, a thin film platinum resistance type temperature sensor, a probe type temperature sensor, an electronic analytical balance, a computer, a nitrogen bin, a floater, a weighing component, a magnetic fluid container and a container fixing component; the electronic analysis day is horizontally placed at the bottom of the nitrogen bin, and the weighing assembly is placed on the upper surface of the electronic analysis balance; the weighing assembly consists of a base, a supporting cylinder, a transverse frame and a balancing weight, and the transverse frame is parallel to the nitrogen bin; the balancing weight is fixed at one end of the transverse frame, the other end of the transverse frame is connected with the floater through a tungsten wire, the magnetic fluid container is fixed on the bottom of the nitrogen bin through the container fixing assembly, the magnetic fluid container is internally used for placing magnetic fluid to be tested, and the floater is arranged in the magnetic fluid container and is completely immersed in the magnetic fluid to be tested during testing; the PI electrothermal film and the two sensors are connected with a temperature controller to form a temperature control system, and the computer is respectively connected with the temperature controller and an electronic analytical balance.
Description
Technical Field
The invention belongs to the field of material thermal expansion coefficient measurement, and particularly relates to a system and a method for measuring the thermal expansion coefficient of a magnetic fluid.
Background
Magnetohydrodynamic (Magneto hydrodynamic, MHD) angular vibration sensors have been applied to the fields of spacecraft in-orbit broadband micro-angular vibration measurement and the like due to the performance advantages of high bandwidth, low noise, small volume, quick response and the like.
The MHD angular vibration sensor utilizes the conductive property of magnetofluid material, and its basic idea is the principle of electromagnetic induction, and is formed from two large portions of detection circuit and sensitive element. The magnetic fluid is an important component of the sensing element and is filled into the annular cavity of the sensor to form a fluid ring. The permanent magnet is positioned in the middle of the circular ring and is fixed with the annular cavity and the carrier to be tested. When the carrier vibrates at the angular velocity omega, the viscosity of the magnetic fluid is very small, so the magnetic fluid is almost motionless relative to a fixed inertial coordinate system, a relative velocity v is generated between the magnetic fluid and the permanent magnet, the magnetic fluid cuts a magnetic induction line, an electromotive force E which is in linear relation with omega is generated between the inner electrode and the outer electrode, and the current input angular velocity omega can be obtained through detecting E.
In practical application, the environmental temperature of the MHD angle vibration sensor changes, and the volume of the magnetic fluid in the annular cavity correspondingly changes, so that the pressure in the cavity changes sharply. This not only has an impact on the performance of the sensor, but even damages the structure of the sensor in severe cases. To address this problem, it is desirable to accurately measure the thermal expansion coefficient of the magnetic fluid and provide data support when optimally designing the sensor structure. The prior thermal expansion coefficient measuring device has the following problems: (1) no stable temperature control system; (2) The measurement error caused by air oxidation cannot be avoided without a gas environment protection device; (3) Manual reading during measurement, larger error, low automation degree, incapability of real-time measurement and the like. Therefore, the prior art is difficult to meet the requirement of measuring the thermal expansion coefficient of the magnetic fluid.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a system and a method for measuring the thermal expansion coefficient of a magnetic fluid, which can more accurately measure the thermal expansion coefficient of the magnetic fluid and provide data support for structural optimization of an MHD angular vibration sensor.
The invention aims at realizing the following technical scheme:
the magnetic fluid thermal expansion coefficient measuring system comprises a temperature controller, a PI electric heating diaphragm, a thin film platinum resistance type temperature sensor, a probe type temperature sensor, an electronic analytical balance, a computer, a nitrogen bin, a floater, a weighing component, a magnetic fluid container and a container fixing component; the PI electric heating diaphragm, the thin film platinum resistance type temperature sensor, the probe type temperature sensor, the magnetic fluid container, the container fixing component, the weighing component and the electronic analytical balance are positioned in the nitrogen bin; the temperature controller and the computer are arranged outside the nitrogen bin;
the electronic analysis day is horizontally placed at the middle position of the bottom of the nitrogen bin, and the weighing assembly is placed at the middle position of the upper surface of the electronic analysis balance; the weighing assembly consists of a base, a supporting cylinder, a transverse frame and a balancing weight, and the transverse frame is parallel to the nitrogen bin; the balancing weight is fixed at one end of the transverse frame, the other end of the transverse frame is connected with the floater through a tungsten wire, the magnetic fluid container is fixed on the bottom of the nitrogen bin at one side of the electronic analytical balance through the container fixing assembly, the magnetic fluid container is internally used for placing magnetic fluid to be tested, and the floater is arranged in the magnetic fluid container and is completely immersed in the magnetic fluid to be tested during testing;
the PI electrothermal film is glued in the middle of the outer wall of the magnetic fluid container through heat conduction silica gel, the thin film platinum resistance type temperature sensor is glued and fixed in the lower of the outer wall of the magnetic fluid container through heat conduction silica gel, the probe type temperature sensor is placed in the magnetic fluid to be tested, the PI electrothermal film, the thin film platinum resistance type temperature sensor and the probe type temperature sensor are connected with the temperature controller to form a temperature control system, and the computer is connected with the temperature controller and the electronic analytical balance respectively.
Further, the nitrogen bin is used for isolating air and preventing the magnetic fluid from being oxidized; during measurement, nitrogen is filled into the nitrogen bin and kept at one atmosphere; the nitrogen bin is provided with an air outlet, an air inlet and a nitrogen bin operation port, and is also provided with a barometer.
Further, the base of the weighing assembly is placed on an electronic analytical balance, the supporting cylinder is fastened on the base through threads, and the cross frame is fastened on the supporting cylinder through screws; the balancing weight is fixed at one end of the transverse frame through an adhesive and used for eliminating the influence of moment on measurement accuracy.
Further, the container fixing assembly comprises a bottom plate, copper columns and a supporting plate; the bottom plate is provided with a circular groove, the bottom plate is placed at the bottom of the nitrogen bin at one side of the electronic analytical balance, and the cylindrical magnetic fluid container is embedded into the circular groove; the two copper columns are connected to the bottom plate through threads; the supporting plate is fastened on the copper column through a screw, a circular hole is formed in the middle of the supporting plate, and the magnetic fluid container penetrates through the circular hole in the middle of the supporting plate.
In addition, the invention also provides a technical scheme of a method for measuring the thermal expansion coefficient of the magnetic fluid, which specifically comprises the following steps:
(1) Slowly filling nitrogen into the nitrogen bin, and observing a pressure gauge to ensure that the air pressure in the nitrogen bin is stabilized at one atmosphere;
(2) Starting a computer, starting a temperature controller and an electronic analytical balance through an upper computer interface, preheating for 30 minutes, and recording the total weight m of the weighing assembly when the weighing assembly is not subjected to buoyancy;
(3) Operating an instrument in the nitrogen bin through an operation port of the nitrogen bin, adding magnetic fluid to be detected into the magnetic fluid container, and completely immersing the floater in the magnetic fluid to be detected;
(4) Heating the magnetic fluid to a set temperature T 1 ，T 2 ，…，T m ，…,T n …, recording temperature and corresponding apparent weight W of weighing assembly 1 ，W 2 ，…，W m ，…,W n …, the magnetic fluid densities at this time are set as follows: ρ 1 ，ρ 2 ，…，ρ m ,…,ρ n …, the volumes of the floats are respectively: v (V) 1 ，V 2 ，…，V m ,…,Vn n …, according to the archimedes buoyancy principle, there are:
mg-W m ＝ρ m V m g, ①
mg-W n ＝ρ n V n g， ②
let the thermal expansion coefficient of the float be β', the volume of the float also changes due to temperature changes:
V n ≈V m [1+β′(T n -T m )]， ③
set the magnetic fluid at t m →t n The time average thermal expansion coefficient is beta, and the following are:
ρ n ≈ρ m [1+β(T n -T m )]， ④
simultaneously (1) - (4) can obtain the magnetic fluid to be measured at t m →t n Average coefficient of thermal expansion β:
the thermal expansion coefficient beta' of the floater can be obtained by referring to a common material thermal expansion coefficient table.
(5) Selecting a proper temperature gradient to heat the magnetic fluid to be detected, establishing communication between a computer and a temperature control system and between the computer and an electronic analytical balance through a serial port line, and reading temperature and weighing apparent weight data in real time; and (3) calculating the average thermal expansion coefficient beta under each temperature difference through a computer program written according to the formula (5), and then performing polynomial fitting to finally obtain a temperature-thermal expansion coefficient curve of the magnetic fluid to be measured.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
(1) According to the invention, the temperature of the magnetic fluid to be measured is changed in real time through the temperature control device, and the temperature is controlled more accurately through the comparison of two temperature sensing difference values of the surface-mounted sensor on the outer wall of the magnetic fluid container and the probe-type sensor in the magnetic fluid;
(2) According to the invention, the thermal expansion coefficient of the magnetic fluid is converted into the buoyancy measurement borne by the floater through the electronic analytical balance, the weighing assembly and the floater device, and the thermal expansion coefficient can be calculated by measuring the buoyancy value, so that the operation is simpler, and the measurement result is more accurate.
(3) During measurement, the nitrogen bin is filled with inert gas, the nitrogen bin is kept at one atmosphere, the air inlet and outlet holes are closed, and at the moment, the magnetic fluid is placed in the inert gas atmosphere, so that measurement errors caused by oxidization of the magnetic fluid are avoided. Meanwhile, no gas flows in the nitrogen bin, so that the influence of the gas flow on a measurement system is avoided.
(4) The device has high degree of automation, and the computer acquires the data of the temperature control system and the electronic analytical balance in real time to obtain the thermal expansion coefficients of the magnetic fluid at different temperatures.
(5) The device has simple and reasonable structure and low cost.
Drawings
FIG. 1 is a schematic diagram of a system for measuring the thermal expansion coefficient of a magnetic fluid according to the present invention;
FIG. 2 is a schematic cross-sectional view of a magnetic fluid container and its fastening assembly in accordance with the present invention;
reference numerals: the temperature controller comprises a 1-temperature controller, a 2-air outlet, a 3-magnetic fluid container, a 4-tungsten wire, a 5-air inlet, a 6-nitrogen bin, a 7-transverse frame, an 8-weighing component, a 9-electronic analytical balance, a 10-barometer, an 11-balancing weight, a 12-computer, a 13-nitrogen bin operation port, a 14-container fixing component, a 15-PI electric heating diaphragm, a 16-film platinum resistance type temperature sensor, a 17-probe type temperature sensor, a 18-floater and 19-magnetic fluid to be measured.
Detailed Description
The invention is described in further detail below with reference to the drawings and the specific examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
As shown in fig. 1 and 2, a measuring system for the thermal expansion coefficient of a magnetic fluid comprises a temperature controller 1, a PI electric heating diaphragm 15, a thin film platinum resistance type temperature sensor 16, a probe type temperature sensor 17, an electronic analytical balance 9, a computer 12, a nitrogen bin 6, a float 18, a weighing assembly 8, a magnetic fluid container 3 and a container fixing assembly 14. The PI electric heating diaphragm 15, the film platinum resistance type temperature sensor 16, the probe type temperature sensor 17, the magnetic fluid container 3, the container fixing component 14, the weighing component 8 and the electronic analytical balance 9 are positioned in the nitrogen bin 6.
The weighing assembly 8 comprises a base, a supporting cylinder, a cross frame 7 and a balancing weight 11. The base is placed on an electronic analytical balance 9; the supporting cylinder is fastened on the base through threads, the transverse frame 7 is fastened on the supporting cylinder through screws, the balancing weight 11 is fixed at one end of the transverse frame 7 through an adhesive, the other end of the transverse frame 7 is connected with the floater 18, and the balancing weight 11 has the function of eliminating the influence of moment on measurement accuracy. The material of the float in this embodiment is tungsten.
The container fixing assembly 14 comprises a bottom plate, copper columns and a supporting plate; the bottom plate is provided with a circular groove, and is placed in the nitrogen bin 6 at the left side, and the cylindrical magnetic fluid container 3 is embedded into the circular groove; the two copper columns are respectively connected to the bottom plate through threads; the supporting plate is fastened on the copper column through a screw, a circular hole is formed in the middle of the supporting plate, and the magnetic fluid container 3 passes through the circular hole in the middle of the supporting plate. The magnetic fluid container 3 in this embodiment is copper.
The electronic analytical balance 9 is positioned at the middle position of the nitrogen bin 6, the weighing assembly 8 is placed at the middle position on the electronic analytical balance 9, and the transverse frame 7 is parallel to the nitrogen bin 6; the right end of the transverse frame is fixed with a balancing weight 11, and the left end is connected with a floater 18 through a tungsten wire 4; the float is completely immersed in the magnetic fluid 19 to be measured; the magnetic fluid container 3 is fixed through the container fixing component 14 to prevent overturning; the PI electric heating diaphragm 15 is fixedly surrounded at the middle part of the outer wall of the magnetic fluid container 3 through heat conduction silica gel cementing, and is connected with the temperature controller 1; the film platinum resistance type temperature sensor 16 is fixed at the lower part of the outer wall of the magnetic fluid container 3 through the cementing of heat conduction silica gel and is used for measuring the temperature and the temperature change of the outer wall of the magnetic fluid container and transmitting the measurement data to the temperature controller 1; the probe type temperature sensor 17 is arranged in the magnetic fluid 19 to be measured and is used for measuring the temperature and the temperature change of the magnetic fluid to be measured; the two are measured in a contact mode, and measurement data are transmitted to the temperature controller 1; the PI electric heating diaphragm 15, the film platinum resistance type temperature sensor 16 and the probe type temperature sensor 17 are all connected with the temperature controller 1 to form a temperature control system for controlling the temperature of the magnetic fluid 19 to be measured. The computer 12 is connected with the temperature control system 1 and the electronic analytical balance 9 through serial lines; the computer is programmed with a software program for processing data.
The nitrogen bin 6 is used for isolating air and preventing the magnetic fluid from being oxidized; during measurement, nitrogen is filled into the nitrogen bin and kept at one atmosphere; the wall of the nitrogen bin 6 is provided with an air outlet hole 2, an air inlet hole 5 and a nitrogen bin operation opening 13, and the nitrogen bin is also provided with a barometer 10.
Specifically, the PI electric heating diaphragm 15, the film platinum resistance type temperature sensor 16 and the probe type temperature sensor 17 are all connected with the temperature controller 1 to form a temperature control system, the PI electric heating diaphragm is used for heating the magnetic fluid to be detected through the set target temperature, and when the temperature difference I delta I of the temperature sensors 16 and 17 is less than 0.1 ℃ and stable, the data of the temperature controller 1 and the electronic analytical balance 9 are acquired through a computer, and the measurement result is calculated and displayed in real time;
specifically, a method for measuring the thermal expansion coefficient of a magnetic fluid comprises the following steps:
(1) Slowly filling nitrogen into the nitrogen bin, and observing a pressure gauge to enable the pressure gauge to be stable at one atmosphere;
(2) Starting a computer, starting a temperature controller and an electronic analytical balance through an upper computer interface, preheating a system for 30 minutes, and recording the total weight m of the weighing assembly when the weighing assembly is not subjected to buoyancy;
(3) Operating an instrument in the nitrogen bin through an operation port of the nitrogen bin, adding magnetic fluid to be detected into the magnetic fluid container, and completely immersing the floater in the magnetic fluid to be detected;
(4) Setting a target temperature on a computer, and transmitting the target temperature to a temperature controller by the computer through a data line to heat the magnetic fluid to be detected;
(5) When the temperature difference I delta I of the two sensors is less than 0.1 ℃ and stable, the computer collects the current temperature T of the magnetic fluid to be measured n And an electronic analytical balance visual display number W n ；
(6) Repeating the steps (2) and (3) according to a certain temperature gradient to obtain data at each temperature, and calculating by an upper computer program to obtain the thermal expansion coefficient beta of the magnetic fluid to be measured at each temperature.
The invention is not limited to the embodiments described above. The above description of specific embodiments is intended to describe and illustrate the technical aspects of the present invention, and is intended to be illustrative only and not limiting. Numerous specific modifications can be made by those skilled in the art without departing from the spirit of the invention and scope of the claims, which are within the scope of the invention.
Claims (5)
1. The magnetic fluid thermal expansion coefficient measuring system is characterized by comprising a temperature controller (1), a PI electric heating diaphragm (15), a thin film platinum resistance type temperature sensor (16), a probe type temperature sensor (17), an electronic analytical balance (9), a computer (12), a nitrogen bin (6), a floater (18), a weighing component (8), a magnetic fluid container (3) and a container fixing component (14); the PI electric heating diaphragm (15), the film platinum resistance type temperature sensor (16), the probe type temperature sensor (17), the magnetic fluid container (3), the container fixing component (14), the weighing component (8) and the electronic analytical balance (9) are positioned in the nitrogen bin (6); the temperature controller (1) and the computer (12) are arranged outside the nitrogen bin (6);
the electronic analytical balance (9) is placed at the middle position of the bottom of the nitrogen bin (6), and the weighing assembly (8) is placed at the middle position of the upper surface of the electronic analytical balance (9); the weighing assembly (8) consists of a base, a supporting cylinder, a transverse frame (7) and a balancing weight (11), and the transverse frame (7) is parallel to the nitrogen bin (6); the balancing weight (11) is fixed at one end of the transverse frame (7), the other end of the transverse frame (7) is connected with the floater (18) through a tungsten wire (4), the magnetic fluid container (3) is fixed on the bottom of the nitrogen bin (6) at one side of the electronic analytical balance (9) through the container fixing component (14), the magnetic fluid container (3) is internally used for placing magnetic fluid (19) to be tested, and the floater (18) is arranged in the magnetic fluid container (3) and is completely immersed in the magnetic fluid (19) to be tested during testing;
PI electrical heating diaphragm (15) encircle glued in the outer wall middle part position of magnetic fluid container (3) through heat conduction silica gel, and film platinum resistance type temperature sensor (16) are glued through heat conduction silica gel and are fixed in the outer wall lower part position of magnetic fluid container (3), and probe type temperature sensor (17) are arranged in magnetic fluid (19) to be measured, PI electrical heating diaphragm (15), film platinum resistance type temperature sensor (16) and probe type temperature sensor (17) all with temperature controller (1) link to each other and constitute temperature control system jointly, and computer (12) are connected with temperature controller (1) and electronic analysis balance (9) respectively.
2. The system for measuring the thermal expansion coefficient of the magnetic fluid according to claim 1, wherein the nitrogen bin (6) is used for isolating air and preventing the magnetic fluid from being oxidized; during measurement, nitrogen is filled into the nitrogen bin (6) and kept at one atmosphere; the nitrogen bin (6) is provided with an air outlet (2), an air inlet (5) and a nitrogen bin operation port (13) on the bin wall, and the nitrogen bin (6) is also provided with a barometer (10).
3. -a system for measuring the thermal expansion coefficient of a magnetic fluid according to claim 1, characterized in that the base of the weighing assembly (8) is placed on an electronic analytical balance (9), the support cylinder is fastened to the base by means of a screw, and the cross-frame (7) is fastened to the support cylinder by means of a screw; the balancing weight (11) is fixed at one end of the transverse frame through an adhesive, and the balancing weight (11) is used for eliminating the influence of moment on measurement accuracy.
4. The system for measuring the thermal expansion coefficient of a magnetic fluid according to claim 1, wherein the container holding assembly (14) comprises a base plate, a copper pillar and a support plate; the bottom plate is provided with a circular groove, the bottom plate is placed at the bottom of a nitrogen bin at one side of the electronic analytical balance (9), and the cylindrical magnetic fluid container (3) is embedded into the circular groove; the two copper columns are connected to the bottom plate through threads; the magnetic fluid container (3) passes through the round hole in the middle of the supporting plate.
5. A method for measuring the thermal expansion coefficient of a magnetic fluid based on the system for measuring the thermal expansion coefficient of a magnetic fluid according to claim 1, comprising the steps of:
(1) Slowly filling nitrogen into the nitrogen bin, and observing a pressure gauge to ensure that the air pressure in the nitrogen bin is stabilized at one atmosphere;
(2) Starting a computer, starting a temperature controller and an electronic analytical balance through an upper computer interface, preheating for 30 minutes, and recording the total weight m of the weighing assembly when the weighing assembly is not subjected to buoyancy;
(3) Operating an instrument in the nitrogen bin through an operation port of the nitrogen bin, adding magnetic fluid to be detected into the magnetic fluid container, and completely immersing the floater in the magnetic fluid to be detected;
(4) Heating the magnetic fluid to a set temperature T 1 ，T 2 ，...，T m ，...，T n .., the temperature and the corresponding apparent weight W of the weighing assembly are recorded 1 ，W 2 ，...，W m ，...，W n .., the magnetic fluid densities at this time are set to be: ρ 1 ，ρ 2 ，...，ρ m ，...，ρ n .., the volumes of the floats are respectively: v (V) 1 ，V 2 ，...，V m ，...，V n .. according to the archimedes buoyancy principle there are:
mg-W m ＝ρ m V m g， ①
mg-W n ＝ρ n V n g， ②
let the thermal expansion coefficient of the float be β', the volume of the float also changes due to temperature changes:
V n ≈V m [1+β′(T n -T m )]， ③
set the magnetic fluid at t m →t n The time average thermal expansion coefficient is beta, and the following are:
ρ n ≈ρ m [1+β(T n -T m )]， ④
simultaneously (1) - (4) can obtain the magnetic fluid to be measured at t m →t n Average coefficient of thermal expansion β:
wherein, the thermal expansion coefficient beta' of the floater can be obtained by referring to a common material thermal expansion coefficient table;
(5) The method comprises the steps that 2 ℃ is used as a temperature gradient, a magnetic fluid to be detected is heated in sequence, a computer establishes communication with a temperature control system and an electronic analytical balance through serial port lines, and data of temperature and weighing apparent weight are read in real time; and (3) calculating the average thermal expansion coefficient beta under each temperature difference through a computer program written according to the formula (5), and then performing polynomial fitting to finally obtain a temperature-thermal expansion coefficient curve of the magnetic fluid to be measured.
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