Teaching instrument for measuring Boltzmann constant and electron charge through noise method

Abstract

The utility model relates to a teaching instrument for measuring Boltzmann constants and electronic charges through a noise method. The teaching instrument comprises an amplifier, a change-over switch, a resistance box, a shot noise measuring device, an analog-to-digital converter and a data processing device. The fixed end of the change-over switch is electrically connected with the input end of the amplifier; a semiconductor device is arranged in the shot noise measuring device, and the switching end of the change-over switch is used for switching between the measuring end of the resistor box and the measuring end of the shot noise measuring device; the analog-to-digital converter is electrically connected with the output end of the amplifier; the input end of the data processing device is electrically connected with the output end of the analog-to-digital converter. The circuit noise is used for measuring the Boltzmann constant and the electronic charge, the data measurement object is only voltage data, the operation is simple, the learning demand of students on the circuit noise is met, and the market demand of such teaching instruments except the PN junction measurement principle is filled up. According to the teaching instrument, integrated experimental equipment is used, and two different college physics experiments can be carried out only by replacing a circuit.

Description

Technical Field

[0001] The utility model relates to the field of measuring instruments, in particular to a teaching instrument for measuring the Boltzmann constant and electron charge by a noise method. Background Art

[0002] There are many constants in physics, such as the speed of light, the gravitational constant, the electron charge, and the Boltzmann constant, which are all physical constants of great significance. The emergence of the Boltzmann constant makes it easier for people to understand some thermal problems from a mathematical perspective and to explore the microscopic world more deeply; the measurement of electron charge is the basis for human understanding of electricity and plays a key role in the development and progress of the world. It provides us with basic tools to understand and control the material world, and promotes the development of social economy and the improvement of human quality of life.

[0003] The teaching instruments currently available on the market for measuring the above two constants are to measure the Boltzmann constant through the volt-ampere characteristics of the PN junction, or to measure the electron charge through the Millikan oil drop experiment. The PN junction is overly dependent on the special properties of semiconductors, and its deep physical connotation is too abstract and difficult to understand for undergraduates with weak foundations, so the effect of cultivating students' subject literacy in experiments is not good. As a very important signal in the road of scientific research, circuit noise is even more lacking in the market for college students to learn about noise signals. Utility Model Content

[0004] In order to solve the above technical problems, the utility model provides the following technical solutions:

[0005] A teaching instrument for measuring the Boltzmann constant and electron charge using a noise method, comprising:

[0006] Amplifier;

[0007] A switching switch, wherein a fixed end of the switching switch is electrically connected to an input end of the amplifier;

[0008] A resistor box and a shot noise measuring device, wherein the shot noise measuring device is provided with a semiconductor device, and the switching end of the switching switch is used to switch between the measuring end of the resistor box and the measuring end of the shot noise measuring device;

[0009] an analog-to-digital converter, the analog-to-digital converter being electrically connected to an output end of the amplifier;

[0010] A data processing device, wherein the input end of the data processing device is electrically connected to the output end of the analog-to-digital converter.

[0011] Preferably, the resistor box comprises eight output terminals, and the resistance values ​​set at the eight output terminals are different from each other.

[0012] Preferably, the shot noise measuring device comprises:

[0013] A light-emitting circuit, the light-emitting circuit comprising a first DC power supply, a first inductor, a second inductor, an LED lamp, and a first capacitor, wherein the first DC power supply, the first inductor, the second inductor, and the LED lamp are connected in series, and the first capacitor is connected in parallel with the LED lamp;

[0014] A photosensitive circuit, the photosensitive circuit includes a second power supply, a first resistor, a second resistor, a photodiode, and a second capacitor, one end of the first resistor and one end of the second resistor are respectively connected to the positive electrode and the negative electrode of the photodiode, the other end of the first resistor and the other end of the second resistor are respectively connected to the negative electrode and the positive electrode of the second power supply, the second capacitor is connected in parallel with the second power supply, the photodiode receives light from the LED lamp, and the amplifier is used to amplify the voltage of the first resistor.

[0015] Preferably, the model of the photodiode is BPW34.

[0016] Preferably, the amplifier includes a JFE150 field effect transistor and an operational amplifier chip INA849.

[0017] Preferably, the model of the analog-to-digital converter is ADS8361.

[0018] Preferably, the data processing device is a single chip microcomputer.

[0019] Preferably, the amplifier is arranged in an electromagnetic shielding box.

[0020] The utility model has at least the following beneficial effects:

[0021] The teaching instrument for measuring the Boltzmann constant and the electron charge by the noise method of this embodiment uses circuit noise to measure the Boltzmann constant and the electron charge. The data measurement object is only voltage data. The operation is simple, which meets the students' learning needs for circuit noise and fills the market demand for such teaching instruments besides the PN junction measurement principle, giving students more choices.

[0022] The teaching instrument uses integrated experimental equipment, and two different university physics experiments can be carried out by simply replacing the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the structure of a teaching instrument for measuring the Boltzmann constant and electron charge using a noise method according to an embodiment of the utility model;

[0024] Figure 2A circuit diagram of a shot noise measuring device of a teaching instrument for measuring the Boltzmann constant and electron charge using a noise method according to an embodiment of the utility model;

[0025] Figure 3 A circuit diagram of an amplifier of a teaching instrument for measuring the Boltzmann constant and electron charge using a noise method according to an embodiment of the utility model;

[0026] Figure numerals: 1. amplifier; 2. switching switch; 3. resistor box; 4. shot noise measuring device; 5. analog-to-digital converter; 6. data processing device; 7. first DC power supply; 8. first inductor; 9. second inductor; 10. LED lamp; 11. first capacitor; 12. second power supply; 13. first resistor; 14. second resistor; 15. photodiode; 16. second capacitor; 17. measuring point. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution of the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings of the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model, not all of the embodiments. Based on the described embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the utility model.

[0028] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the usual meanings understood by persons with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "one" do not indicate quantity restrictions, but indicate the existence of at least one. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship also changes accordingly.

[0029] The embodiments of the present utility model are described in detail below in conjunction with the accompanying drawings.

[0030] like Figure 1As shown, the embodiment of the utility model provides a teaching instrument for measuring the Boltzmann constant and the electron charge by the noise method, comprising an amplifier 1, a switching switch 2, a resistor box 3, a shot noise measuring device 4, an analog-to-digital converter 5, and a data processing device 6. The fixed end of the switching switch 2 is electrically connected to the input end of the amplifier 1; the shot noise measuring device 4 is provided with a semiconductor device, and the switching end of the switching switch 2 is used to switch between the measuring end of the resistor box 3 and the measuring end of the shot noise measuring device 4; the analog-to-digital converter 5 is electrically connected to the output end of the amplifier 1; and the input end of the data processing device 6 is electrically connected to the output end of the analog-to-digital converter 5.

[0031] The principle of measuring the Boltzmann constant by the thermal noise method is that thermal noise is a fluctuation phenomenon caused by the irregular thermal motion of carriers in a conductor. Any resistor will have thermal noise as long as the temperature is higher than absolute zero, which is equivalent to a pure resistor and a voltage source in series. When measuring the Boltzmann constant by the teaching instrument of this embodiment, the conversion switch is connected to the resistor box 3, the resistor voltage signal in the resistor box 3 is amplified by the amplifier 1, and then collected by the analog-to-digital converter 5 to obtain a one-dimensional array of voltage with respect to time, and then the data processing device 6 is used to perform a discrete Fourier transform on this set of data, and the square of its modulus can be obtained to obtain the power spectrum density Sv of the resistor thermal noise. The power spectrum density of the resistor thermal noise is only related to the resistance value R and the system temperature T, that is, Sr = 4RkT, k is the Boltzmann constant. By replacing resistors with different resistance values ​​to obtain multiple sets of data, the Boltzmann constant k can be obtained by linear fitting using the noise of Sv = Sr + S (S is the amplifier).

[0032] The measurement principle of the shot noise method for measuring electron charge: Shot noise is the noise generated by the fluctuation of carriers inside the semiconductor. Like thermal noise, it is white noise and its spectrum does not change in a wide frequency band. The power spectrum density of shot noise can be calculated by Campbell's theorem: Se = 2eR 2 Find, among which When the electronic charge is measured by the teaching instrument of this embodiment, the conversion switch is connected to the shot noise measurement device 4, and the sampled average voltage data is directly divided by the known resistance to obtain By changing the current size, different power spectrum densities Sv are obtained, and Sv=Se+S′ (S′ is other environmental noise) is used, and then linear fitting is performed to obtain the electron charge e.

[0033] The teaching instrument for measuring the Boltzmann constant and the electron charge by the noise method of this embodiment uses circuit noise to measure the Boltzmann constant and the electron charge. The data measurement object is only voltage data. The operation is simple, which meets the students' learning needs for circuit noise and fills the market demand for such teaching instruments other than the PN junction measurement principle, giving students more choices. In addition, the teaching instrument uses an integrated experimental device, and two different university physics experiments can be carried out by simply replacing the circuit.

[0034] In this embodiment, the resistor box 3 includes eight output terminals, and the resistance values ​​set at the eight output terminals are different from each other. During the measurement process, eight different interfaces are replaced to measure the voltages of eight resistors with different resistance values, and finally the Boltzmann constant is obtained through linear fitting.

[0035] like Figure 2 As shown, the shot noise measuring device 4 includes a light-emitting circuit and a photosensitive circuit. The light-emitting circuit includes a first DC power supply 7, a first inductor 8, a second inductor 9, an LED lamp 10, and a first capacitor 11. The first DC power supply 7, the first inductor 8, the second inductor 9, and the LED lamp 10 are connected in series, and the first capacitor 11 is connected in parallel with the LED lamp 10; the photosensitive circuit includes a second power supply 12, a first resistor 13, a second resistor 14, a photodiode 15, and a second capacitor 16. One end of the first resistor 13 and one end of the second resistor 14 are connected to the positive electrode and the negative electrode of the photodiode 15, respectively, and the other end of the first resistor 13 and the other end of the second resistor 14 are connected to the negative electrode and the positive electrode of the second power supply 12, respectively, and the second capacitor 16 is connected in parallel with the second power supply 12. The photodiode 15 receives light from the LED lamp 10, and the amplifier 1 is used to amplify the voltage of the first resistor 13.

[0036] The current intensity of the photodiode 15 varies with the light intensity of the LED lamp 10. When a reverse voltage is applied to both ends of the photodiode 15, a built-in electric field can be formed to accelerate the movement speed of electrons in the reverse direction, thereby more efficiently collecting photons from the LED lamp 10.

[0037] During the measurement process, the voltage data of the measuring point 17 of the first resistor 13 is measured, and then the current data is obtained using Ohm's law to calculate the shot noise power spectrum density. The current of multiple groups of photodiodes 15 is obtained by adjusting the brightness of the LED lamp 10, and finally the electron charge is obtained through linear fitting.

[0038] In this embodiment, the model of the photodiode 15 can be BPW34, the model of the analog-to-digital converter 5 can be ADS8361, and the data processing device 6 can be a single-chip microcomputer. Using mature modular instruments, homemade waveform generators and virtual oscilloscopes greatly reduces the cost of the experiment.

[0039] Figure 3 The circuit diagram of the amplifier 1 of this embodiment is shown in FIG. The JFE150 field effect tube and the operational amplifier chip INA849 together form a low-noise differential amplifier. The first stage amplification is achieved by the JFE150 field effect tube, and then the second stage amplification is achieved by the operational amplifier chip INA849, and the amplification factor can reach 750 times. The noise of the amplifier 1 itself can be controlled, and its measurement accuracy can be comparable to that of professional commercial amplifiers while reducing costs. In addition, the amplifier 1 is set in an electromagnetic shielding box. The extremely low noise of the amplifier 1 and the electromagnetic shielding box can save the cumbersome operation of phase-locked amplification in university teaching experiments.

[0040] The above embodiments are used to further illustrate the present invention, but the present invention is not limited to these specific implementations. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention should be understood to be within the protection scope of the present invention.

Claims

1. A teaching instrument for measuring the Boltzmann constant and electron charge by the noise method, characterized in that: include: Amplifier (1); A switching switch (2), wherein a fixed end of the switching switch (2) is electrically connected to an input end of the amplifier (1); A resistor box (3) and a shot noise measuring device (4), wherein the shot noise measuring device (4) is provided with a semiconductor device, and the switching end of the switching switch (2) is used to switch between the measuring end of the resistor box (3) and the measuring end of the shot noise measuring device (4); an analog-to-digital converter (5), the analog-to-digital converter (5) being electrically connected to an output end of the amplifier (1); A data processing device (6), wherein an input end of the data processing device (6) is electrically connected to an output end of the analog-to-digital converter (5).

2. The teaching instrument for measuring the Boltzmann constant and electron charge by the noise method according to claim 1, characterized in that: The resistor box (3) comprises eight output terminals, and the resistance values ​​set at the eight output terminals are different from each other.

3. The teaching instrument for measuring the Boltzmann constant and electron charge by the noise method according to claim 1, characterized in that: The shot noise measuring device (4) comprises: A light-emitting circuit, the light-emitting circuit comprising a first direct current power supply (7), a first inductor (8), a second inductor (9), an LED lamp (10), and a first capacitor (11), wherein the first direct current power supply (7), the first inductor (8), the second inductor (9), and the LED lamp (10) are connected in series, and the first capacitor (11) and the LED lamp (10) are connected in parallel; A photosensitive circuit, the photosensitive circuit comprising a second power supply (12), a first resistor (13), a second resistor (14), a photodiode (15), and a second capacitor (16); one end of the first resistor (13) and one end of the second resistor (14) are respectively connected to the positive electrode and the negative electrode of the photodiode (15); the other end of the first resistor (13) and the other end of the second resistor (14) are respectively connected to the negative electrode and the positive electrode of the second power supply (12); the second capacitor (16) is connected in parallel with the second power supply (12); the photodiode (15) receives light from the LED lamp (10); and the amplifier (1) is used to amplify the voltage of the first resistor (13).

4. The teaching instrument for measuring the Boltzmann constant and electron charge by the noise method according to claim 3, characterized in that: The model of the photodiode (15) is BPW34.

5. The teaching instrument for measuring the Boltzmann constant and electron charge by the noise method according to claim 1, characterized in that: The amplifier (1) comprises a JFE150 field effect tube and an operational amplifier chip INA849.

6. The teaching instrument for measuring the Boltzmann constant and electron charge by the noise method according to claim 1, characterized in that: The model of the analog-to-digital converter (5) is ADS8361.

7. The teaching instrument for measuring the Boltzmann constant and electron charge by the noise method according to claim 1, characterized in that: The data processing device (6) is a single chip microcomputer.

8. The teaching instrument for measuring the Boltzmann constant and electron charge by the noise method according to claim 1, characterized in that: The amplifier (1) is arranged in an electromagnetic shielding box.

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