Application of GT4516 Hysteresis Loop Tester
GT4516 series hysteresis loop tester Hysteresis loop and basic magnetization curve of ferromagnetic materials The magnetic properties of ferromagnetic materials have been widely used in scientific research and industry. With the development of sensor technology and digital circuit technology, a high-precision digital magnetic induction tester with a Hall element as a sensor (digital Tees) Large-scale production, providing high accuracy, stable and reliable, easy to operate measurement methods for the magnetic properties of magnetic materials. This experiment uses a digital Tesla meter to measure the narrow gap between the toroidal magnetic circuit around a set of coils. The magnetic induction intensity of the uniform magnetic field, observing the hysteresis of the magnetic material, accurately measuring the hysteresis loop and magnetization curve of the material, learning and mastering the demagnetization method of the residual magnetism of the material. Measuring the hysteresis loop of the ferromagnetic material with the Hall sensor The new method has been widely used in research and production. First, the purpose of the experiment 1. Recognize the magnetization law of ferromagnetic materials and compare the dynamic magnetization characteristics of two typical ferromagnetic materials. 2. Determine the basic magnetization curve of the sample and make a μ-H curve. 3. Calculate the parameters such as Hc, Br, Bm and (Hm·Bm) of the sample. 4. Measure the hysteresis loop of the sample and estimate its hysteresis loss. Second, the experimental principle 1. Hysteresis of ferromagnetic materials Ferromagnetic materials are a kind of material with specific properties and versatility. Iron, cobalt, nickel and many other alloys and iron-containing oxides (ferrites) are ferromagnetic materials. They are characterized by strong external magnetic fields. Magnetization, so the magnetic permeability μ is very high. Another feature is hysteresis, that is, after the magnetization field stops, the ferromagnetic still retains the magnetization state. Figure 1 shows the relationship between the magnetic induction intensity B of the ferromagnetic substance and the magnetization field strength H. curve. The origin 0 in the figure indicates that the ferromagnetic substance is in a magnetic neutral state before magnetization, that is, B=H=0. When the magnetic field H increases from zero, the magnetic induction intensity B rises slowly, as indicated by line 0a, followed by B. As H grows rapidly, as shown by ab, the growth of B then becomes slower, and when H increases to Hm, B reaches the saturation value, 0abs is called the initial magnetization curve, and Figure 1 shows that when the magnetic field is gradually reduced from Hm As small as zero, the magnetic induction B does not return to the "0" point along the initial magnetization curve, but falls along the other new curve SR. Comparing the line segments 0S and SR, it can be seen that the H decreases and the B decreases accordingly, but B The change lags behind the change of H. This phenomenon is called hysteresis. The obvious characteristic of hysteresis is that when H=0, B is not zero, but the residual magnetization is retained. Figure 1 Initial magnetization curve and hysteresis loop of ferromagnetic material Figure 2 A cluster of hysteresis loops of the same ferromagnetic material When the magnetic field reverses from 0 to -HC, the magnetic induction B disappears, indicating that to eliminate the residual magnetism, a reverse magnetic field must be applied. HC is called coercive force, and its size reflects the ability of the ferromagnetic material to maintain the remanent state. The line segment RD is called the demagnetization curve. Figure 1 also shows that when the magnetic field changes in the order of Hm → 0 → HC → -Hm → 0 → HC → Hm, the corresponding magnetic induction B changes along the closed curve SRDS'R'D'S, this closed curve is called magnetic Hysteresis loop, so when the ferromagnetic material is in an alternating magnetic field (such as the core in a transformer), it will be repeatedly magnetized → demagnetized → reverse magnetized → reverse demagnetized along the hysteresis loop. In the process It consumes extra energy and is released from the ferromagnetic material in the form of heat. This loss is called hysteresis loss. It can be proved that the hysteresis loss is proportional to the area enclosed by the hysteresis loop. It should be noted that when the ferromagnetic material whose initial state is H=B=0, the magnetic field of the alternating magnetic field is magnetized from weak to strong, and the magnetization is sequentially performed, and a cluster of hysteresis whose area is expanded from small to large can be obtained. The line, as shown in Figure 2. The line connecting the vertices of these hysteresis loops is called the basic magnetization curve of the ferromagnetic material, so that the magnetic permeability μ=B/H can be approximated, because the relationship between B and H is non- Linear, so the ferromagnetic material μ is not constant, but varies with H (as shown in Figure 3). The relative magnetic permeability of ferromagnetic materials can be as high as several thousand or even tens of thousands, which is the main reason for its wide application. One. Figure 3 Relationship between ferromagnetic materials and H Figure 4 Hysteresis loops of different materials It can be said that the magnetization curve and the hysteresis loop are the main basis for the classification and selection of ferromagnetic materials. Figure 4 shows two typical hysteresis loops. Among them, the hysteresis loop of the soft magnetic material is narrow, coercive, and remanent. And the hysteresis loss is small, it is the main material for manufacturing transformers, motors, and AC magnets. The hard magnetic material has a wide hysteresis loop, large coercive force and strong residual magnetism, which can be used to manufacture permanent magnets. 2. The experimental principle and circuit for observing and measuring hysteresis loops with an oscilloscope The lines for observing and measuring the hysteresis loop and the basic magnetization curve are shown in Figure 5. The sample to be tested is an EI-type silicon steel sheet, N1 is a field winding, N2 is a winding for measuring the magnetic induction intensity B. R1 is an excitation current sampling resistor, and the AC excitation current through N1 is ii, according to the Ampere loop law, Magnetization field strength of the sample L is the average magnetic path length of the sample, where So have In the formula, N1, L, and R1 are all known constants, so HH can be determined by H. Figure 5 Experimental principle line Under the alternating magnetic field, the instantaneous value B of the magnetic induction of the sample is given by the measuring winding and the R2C2 circuit. According to the Faraday's law of electromagnetic induction, the magnitude of the induced electromotive force generated in the measuring coil due to the change of the magnetic flux Φ in the sample for S is the cross-sectional area of ​​the sample. If the self-induced electromotive force and circuit loss are ignored, the loop equation is ε2=i2R2+UB Where i2 is the induced current, UB is the integral capacitor C2 voltage is set in Δt time, i2 to the capacitor C2 charging power is Q, then If you select R2 and C2 large enough to make i2R2>>Q/C2, then ε2=i2R2 In the above formula, C2, R2, N2 and the average S are known constants. Therefore, it can be determined by UB. In summary, as long as the UH and UB in Figure 5 are added to the "X input" and "Y input" of the oscilloscope respectively, the BH curve of the sample can be observed, and the UH and UB values ​​can be measured by an oscilloscope, and then calculated according to the formula. B and H; using this method, parameters such as saturation magnetic induction BS, remanence Br, coercive force HC, hysteresis loss WBH and magnetic permeability μ can be obtained. Third, the experimental content 1. Circuit connection: Select sample 1 and connect the circuit according to the circuit diagram given on the experiment instrument, and let R1=2.5Ω, “U selection†is set to 0. UH and UB are connected to “X input†and “Y input†of the oscilloscope respectively. ", the jack is public. 2. Sample demagnetization: Turn on the power of the experiment instrument and demagnetize the sample, that is, turn the “U selection†knob clockwise to increase U from 0 to 3V. Then turn the knob counterclockwise to reduce U from the maximum value to 0. The purpose is to eliminate residual magnetism. Ensure that the sample is in a magnetic neutral state, ie B = H = 0, as shown in Figure 6. 3. Observe the hysteresis loop: turn on the oscilloscope power supply, make the light spot at the center of the coordinate grid, let U=2.2V, and adjust the sensitivity of the X and Y axes of the oscilloscope separately, so that the hysteresis of the appropriate size of the graphic appears on the display. Line. If a small braided ring appears at the top of the graph, as shown in Figure 7, the channel input mode of the oscilloscope should be checked. The X channel should be connected to the AC input, the Y channel should be DC input, and the excitation voltage should be appropriately reduced. U will eliminate). Figure 6 Schematic diagram of demagnetization Figure 7 Distortion caused by improper adjustment 4. Observe the basic magnetization curve: Demagnetize the sample according to step 2. Starting from U=0, increase the excitation voltage step by step, and a cluster of hysteresis loops with a small area to one large on the display screen will be recorded. The line connecting the vertices of these hysteresis loops is the basic magnetization curve of the sample. In addition, if a long afterglow oscilloscope is used, the trace of the curve can be observed. 5. Adjust U=3.0V, R1=0.5Ω, determine a set of UB and UH values ​​of sample 1, and according to the known conditions: L=75mm, S=120mm2, N1=150åŒ, N2=150åŒ, C2= 20μF, R2=10KΩ, calculate the corresponding values ​​of B and H. 6. According to the obtained values ​​of B and H, the curve of B~H is used, and the parameters such as Bm, Br, and Hc are obtained according to the curve, and the area of ​​the curve is estimated to obtain WBH. 7. Mapping μ~H curve: Determine the ten groups of UB and UH values ​​when U=0.5, 1.0...3.5V, and calculate the corresponding Hm, Bm and μ values, and make μ~H curves. 8. Change R1 to observe different magnetization curves. 9. Observe, measure and compare the magnetization properties of samples 1 and 2. Appendix GT4516 Hysteresis Loop Tester Instruction Manual Magnetic materials are widely used, from commonly used permanent magnets, transformer cores to recording, video recording, magnetic tapes for computer storage, magnetic disks, etc. Magnetic hysteresis loops and basic magnetization curves reflect the main magnetic materials. Features. This instrument can be used to observe the basic magnetization curve and hysteresis loop of ferromagnetic materials, and calculate the corresponding Hm, Bm and μ values ​​to estimate the hysteresis loss. First, the instrument composition The instrument consists of excitation power, sample, experimental panel and other devices. 1, excitation power supply After the transformer is used to isolate and depressurize 220V and 50Hz mains, the magnetization voltage of the sample is provided, which is divided into 11 files, namely 0, 0.5, 0.9, 1.2, 1.5, 1.8, 2.1, 2.4, 2.7, 3.0 and 3.5V. Different magnetization voltages can be selected by the band switch 2, the sample Both sample 1 and sample 2 use an EI core, the size (average magnetic path length L and cross-sectional area S) is the same, but the magnetic permeability is different. The number of turns of the field winding N1 and the number of turns of the measuring winding are also equal. The values ​​are: N1=150, N2=150, L=75mm, S=120 mm2. 3. Experimental panels and other components The panel is equipped with a power switch, sample 1, sample 2, excitation power "U selection" and excitation current sampling resistor "R1 selection", and integral circuit components R2, C2 set for measuring magnetic induction B. Special wire connections are available for experimentation. The left side of the panel also has UB, UH output jacks for connecting to the oscilloscope to observe hysteresis loops or to measure with an AC millivoltmeter. Second, the instrument use and maintenance This instrument is easy to use. Just turn on the power switch and connect as shown in Figure 5. The output of UH and UB is connected to the X and Y axes of the oscilloscope. The oscilloscope selects the “X, Y†mode to adjust the oscilloscope gain. A hysteresis loop can be observed. It should be noted that the sample should be demagnetized before measuring the hysteresis loop. After using the instrument, turn off the power and close the cover. If it is not used for a long time, unplug the power cord and keep it in a safe place. Under the condition that the user obeys the maintenance and the use rules, within 12 months from the date of delivery, the fault occurs due to poor manufacturing quality, resulting in the instrument not working properly. The manufacturer is responsible for free maintenance for the user, and even replaces the product. During the period of failure, the factory should still provide good service. 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