GT4607 liquid surface tension meter instruction manual I. Overview GT4607 liquid surface tension coefficient measuring instrument is a new type of pull-off liquid surface tension coefficient measuring instrument. It is developed by Hangzhou Dahua Instrument Manufacturing Co., Ltd. Compared with the original measuring instrument, it has the following three advantages: 1. Using a silicon pressure resistance sensor (also known as a semiconductor strain gauge) to measure the surface tension of the liquid in contact with the metal. The sensor has high sensitivity, good linearity and stability, and is displayed by a digital voltmeter. 2. Replace the original fine platinum wire ring or platinum wire knife edge with a thin metal ring and metal piece of a certain height. The new lifting ring is not easy to be deformed, and it is not easy to be damaged or lost after repeated use. 3. The dimensions of the lifting ring are specially designed and experimentally tested. Generally, the direct measurement results do not need to be corrected, and more accurate and reliable results can be obtained. The instrument measures the surface tension coefficient of liquid with small error and good repeatability; it is beneficial to students to learn and master the principle and method of silicon pressure resistance sensor. This instrument is the ideal quality for physical and physical chemistry experiments in various colleges and secondary schools. instrument. Second, use 1. Calibrate the silicon pressure resistance sensor with a weight, calculate the sensitivity of the sensor, and learn the calibration method of the sensor. 2. Observe the physical and physical phenomena of the surface tension of the liquid by the pull-off method, and analyze and study the basic concepts and laws of physics to deepen the understanding of the physical laws. 3. Measure the surface tension coefficient of pure water and other liquids. 4. Measure the relationship between the concentration of the liquid and the surface tension coefficient (such as the surface tension coefficient at different concentrations of alcohol) Third, the instrument composition and technical indicators 1. Silicon pressure resistance sensor (1) Forced range: 0-0.098N (2) Sensitivity: about 3.00V/N (calibrated by weight quality) (3) Nonlinear error: ≤0.2% (4) Power supply voltage: DC 3 to 6 volts 3. Force sensitive sensor fixing bracket, lifting platform, bottom plate and level adjusting device 5, a diameter of φ12.00cm or φ13.00cm glassware 2, the display part (1) Reading display: 200 mV three-and-a-half digital display (2) Zero adjustment: manual multi-turn potentiometer (3) Connection method: 5-core aviation plug 4, lifting ring: outer diameter φ3.5cm, inner diameter φ3.3, height 0.8cm aluminum alloy rings. 6, the weight plate and the 0.5 gram weight 7 only. 7. The error of the surface tension coefficient of liquid such as water is ≤5% Fourth, the use of the whole machine 1. The lifting ring must be strictly cleaned. After washing the oil or impurities with NaOH solution, rinse it with clean water and dry it with a hot air blower. 2, the level of the lifting ring must be adjusted well, pay attention to the deviation 10, the measurement error is 0.5%; the deviation 20, the error is 1.6%. 3. The instrument needs to be warmed up for 15 minutes. 4. When rotating the lifting platform, try to make the fluctuation of the liquid as small as possible. 5, there is no wind in the laboratory, so as to avoid the swing of the lifting ring causing zero fluctuation, the measured coefficient is not correct. 6. If the liquid is pure water, prevent dust, oil and other impurities from being contaminated during use, especially pay attention to the fingers not touching the liquid to be tested. 7, the force sensor should not be used when the force is greater than 0.098N. Excessive tension sensor is easy to damage. 8. At the end of the experiment, the rings should be dried with cleaning paper, wrapped with cleaning paper and placed in a drying cylinder. Five, the use of steps 1, boot preheating. 2. Clean glassware and rings. 3. Put the liquid to be tested in the glassware and place it on the lifting platform. (The bottom of the glass container can be fixed with the double-sided adhesive and the lifting table) 4. Hang the weight on the hook of the force sensor. 5. If the whole machine has been preheated for more than 15 minutes, the force sensitive sensor can be calibrated. Before the weight is added, the instrument should be zeroed first. The weight should be as light as possible, and it can be read after it stops shaking. . 6. Before changing the lifting ring, first measure the inner and outer diameter of the lifting ring, then hang the lifting ring. During the process of measuring the surface tension coefficient of the liquid, the buoyancy and tension of the liquid can be observed. When turning the large nut of the lifting table clockwise When the liquid level rises, when the lower edge portion of the ring is immersed in the liquid, the nut is turned counterclockwise, and then the liquid surface is lowered (or pulled up relative to the lifting ring), and the observation ring is immersed in the liquid and from the liquid. The physical process and phenomenon when pulling up. In particular, note that the digital voltmeter reading value is U1 immediately before the lifting ring is pulled off the liquid column, and the instantaneous digital voltmeter reading is U2 when breaking. Record these two values. Sixth, experimental data examples 1. Silicon pressure resistance sensor calibration The force sensors are respectively added with various mass weights to measure the corresponding voltage output values. The experimental results are shown in Table 1. Table 1 Force sensor calibration Weight mass m/g 0.500 1.000 1.500 2.000 2.500 3.000 3.500 Output voltage V/mV 15.0 29.8 44.9 59.9 74.9 87.4 103.0 The sensitivity of the instrument fitted by the least squares method is K=2.938×103mV/N, and the linear correlation coefficient of the fitting is r=0.9997. The gravitational acceleration in Hangzhou is g=9.794m/S2. 2. Measurement of surface tension coefficient of water and other liquids Use a vernier caliper to measure the metal ring: outer diameter D1=3.496cm, inner diameter D2=3.310cm, adjust the riser frame, the digital voltmeter reads U1 when the recording ring is about to pull off the water column, and the U2 reading of the digital voltmeter when it is broken. See the result. Table 2. Table 2 Measurement of surface tension coefficient of pure water (water temperature 24.30 ° C) Number of measurements U1/mV U2/mV â–³U/mV f/×10-3N α×10-3N/m 1 131.3 84.8 46.5 15.59 72.91 2 139.5 93.4 46.1 15.45 72.26 3 144.3 98.6 45.7 15.32 71.66 4 59.4 13.8 46.6 15.62 73.06 5 65.2 18.6 46.6 15.62 73.06 6 25.6 -20.5 46.1 15.45 72.26 The surface tension coefficient of water at this temperature is 72.54×10-3N/m. After checking the table, the surface tension coefficient of water is 72.14×10-3N/m at T=24.30°C, and the percentage error is 0.55%. Table 3 Measurement of surface tension coefficient of ethanol (temperature of ethanol T=25.20 °C) Number of measurements U1/mV U2/mV â–³U /mV f/×10-3N α×10-3N/m 1 9.3 -4.6 13.9 4.66 21.80 2 9.4 -4.5 13.9 4.66 21.80 3 10.6 -3.4 14.0 4.69 21.94 4 13.8 -0.1 13.9 4.66 21.80 5 16.9 2.9 14.0 4.69 21.94 6 18.9 5.0 13.9 4.66 21.80 The surface tension coefficient of ethanol at this temperature was 21.85×10-3N/m. After looking up the table, the surface tension coefficient of ethanol was 21.95×10-3N/m at T=25.20°C, and the percent error was 0.46%. Table 4 Measurement of surface tension coefficient of glycerol (glycerol) (temperature of glycerol: T = 24.30 ° C) Number of measurements U1/mV U2/mV â–³U /mV f/×10-3N α×10-3N/m 1 19.0 -18.0 37.0 12.4 58.00 2 50.0 13.1 36.9 12.4 58.00 3 52.6 15.7 36.9 12.4 58.00 4 55.8 18.8 37.0 12.4 58.00 5 58.3 20.8 37.5 12.6 58.93 6 62.7 26.8 36.9 1.24 58.00 The surface tension coefficient of glycerin at this temperature is 58.16×10-3N/m. After looking up the table, the surface tension coefficient of glycerin is 59.40×10-3N/m at T=24.30°C, and the percent error is 2.1%. A metal ring is fixed on the sensor, the ring is immersed in the liquid, and the ring is gradually pulled up. When it is pulled off from the liquid surface, the tension difference f of the sensor is f=Ï€(D1+D2)α (1) Where: D1, D2 are the outer diameter and inner diameter of the ring, α is the liquid surface tension coefficient, and g is the gravitational acceleration, so the liquid surface tension coefficient is: α=f/[Ï€(D1+D2)] (2) From the formula (1), the surface tension of the liquid f=(U1-U2)/K (3) K is the sensitivity of the force sensor, in units of V/N. Seven, structure diagram 1. Adjusting screw 2. Lifting screw 3. Glassware 4, lifting ring 5, force sensor 6, bracket 7, fixing screws 8, aviation plug 9, base 10, digital voltmeter 11, zero adjustment Determination of liquid surface tension coefficient The surface tension of a liquid is an important parameter for characterizing the properties of a liquid. There are several methods for measuring the surface tension coefficient of a liquid. The pull-off method is one of the commonly used methods for measuring the surface tension coefficient of a liquid. The method is characterized in that the surface tension of the liquid is directly measured by a weighing instrument, and the measuring method is intuitive and the concept is clear. The pull-off method is used to measure the surface tension of the liquid, and the instrument for measuring the force is required to be high. Since the tension of the liquid surface is measured by the pull-off method to be between 1×10-3 and 1×10-2 N, a range of ranges is required. Small, sensitive, and stable measuring instrument. In recent years, the newly developed silicon piezoresistive force sensor tensile tester can meet the needs of measuring the surface tension of liquid. It has higher sensitivity, better stability and digital signal display than traditional coke scales and torsion scales. Conducive to computer real-time measurement, in order to have a deep understanding of the different surface tension coefficients of various types of liquid, after measuring the water, then measuring the different concentrations of alcohol solution, so that the surface tension coefficient can be clearly observed with the liquid concentration The phenomenon of change and change, thus deepening the understanding of this concept. [Purpose] 1. Measuring the surface tension coefficient of liquid at room temperature by pull-off method 2. Learning calibration method for force sensitive sensor [Experimental principle] The force required to measure the surface tension coefficient of a liquid sheet of a known circumference from the surface of the liquid to be tested is called the pull-off method. If the metal piece is a ring-shaped hanging piece, considering the first-order approximation, it can be considered that the breaking force is the surface tension coefficient multiplied by the circumference of the detached surface, that is, F=α·π(D1 åD2) (1) Where F is the breaking force, D1, D2 are the outer diameter and inner diameter of the ring, respectively, and α is the surface tension coefficient of the liquid. The silicon piezoresistive force sensor consists of an elastic beam and a sensor chip attached to the beam. The chip is composed of four silicon diffusion resistors and integrated with an unbalanced bridge. When external pressure acts on the metal beam, under pressure, electricity The bridge is out of balance, at this time there will be a voltage signal output, and the output voltage is equal to the applied external force, ie â–³U=KF (2) Where F is the magnitude of the external force, K is the sensitivity of the silicon piezoresistive force sensor, and ΔU is the magnitude of the sensor output voltage. [experimental device] The picture on the right shows the experimental device diagram, in which the liquid surface tension meter includes the power supply of the silicon diffusion resistance unbalanced bridge and the digital voltmeter that measures the output voltage when the bridge is out of balance. Other devices include iron stand, fine-tuning lift table, fixed rod with force-sensitive sensor, glass dish with liquid and circular ring. Experiments show that when the diameter of the ring is around 3cm, the contact angle of liquid and metal ring is similar. When it is zero, the result of using formula (1) to measure the surface tension coefficient of various liquids is correct. [Experimental content] First, must do part 1. Calibration of force sensitive sensor The sensitivity of each force sensor is different. Before the experiment, it should be scaled first. The calibration steps are as follows: (1) Turn on the instrument's power switch to warm up the instrument. (2) In the small end of the sensor beam, hang the weight plate and adjust the zero adjustment knob to make the digital voltmeter display zero. (3) On the weight plate, such as weights of 0.5g, 1.0g, 1.5g, 2.0g, 2.5g, 3.0g, etc., record the reading value of the digital voltmeter under the action of these weights F . (4) Using the least squares method for straight line fitting, find the sensor sensitivity K. 2. Measurement and cleaning of the ring: (1) Measuring the outer diameter D1 and inner diameter D2 of the metal ring with a vernier caliper (2) The surface condition of the ring has a great relationship with the measurement results. Before the experiment, the metal ring-shaped hanging piece should be immersed in the NaOH solution for 20-30 seconds, then washed with clean water. 3, the surface tension coefficient of the liquid (1) Hang the metal ring-shaped hanging piece on the small hook of the sensor, adjust the lifting platform, raise the liquid to the lower edge of the ring piece, and observe whether the lower edge of the ring-shaped hanging piece is parallel with the liquid surface to be tested. If it is not parallel After the metal ring piece is removed, the filament on the hanging piece is adjusted so that the hanging piece is parallel to the liquid surface to be tested. (2) Adjust the lifting platform under the container to gradually rise, immerse the lower edge of the ring piece in the liquid to be tested, and then adjust the lifting table in reverse to gradually lower the liquid level. At this time, the metal ring piece and the liquid An annular liquid film is formed between the faces, and the liquid level is continuously lowered. The reading value of the digital voltmeter U1 and the reading value of the digital voltmeter immediately after the liquid film is broken are measured U2. ΔU=U1-U2 (3) The experimental data are substituted for the formulas (2) and (1), and the surface tension coefficient of the liquid is obtained and compared with the standard value. Second, choose the part Measure the surface tension coefficient of other liquids to be tested, such as alcohol, ether, acetone, etc. at different concentrations Third, experimental data and records 1, sensor sensitivity measurement table 5 Weight / g 0.500 1.000 1.500 2.000 2.500 3.000 Voltage / mV Fitted by least squares method to obtain K = mV / N, the linear correlation coefficient of the fit r = 2. Measurement of the surface tension coefficient of water Metal ring outer diameter D1 = cm, inner diameter D2 = cm, water temperature: t = °C. Table 6 Numbering U--1/mV U2/mV â–³U/mV F/N //Nm-1 1 2 3 4 5 average value: Attachment: Standard value of surface tension coefficient of water: Water temperature t/°C 10 15 20 25 30 //Nm-1 0.074 22 0.073 22 0.072 75 0.071 97 0.071 18 Sideboard Cabinet,Narrow Sideboard,Cheap Sideboards,White Buffet Cabinet BOSA FURNITURE CO.,LTD. , https://www.bosafurniture.com = N/m