GT4507 intelligent / A microcomputer type Franck-Hertz experiment instrument

user's manual

I. Overview

The Frank-Hertz experiment is a classic experiment in modern physics. This experiment uses the methods of German scientists Frank and Hertz to make slow electrons collide with atoms in a thin gas, and simply and subtly directly confirm the existence of atomic energy levels. And the realization of the controllable excitation of the atom, thus providing strong evidence for the Bohr atom theory.

The tester consists of four sets of programmable DC power supply (one of which: the second gate voltage can also be automatically scanned), the micro current detector and the single-chip controller. There are two modes of manual and automatic operation. GT4507 intelligent experiment The instrument can manually map the climbing curve point by point, or in the case of slow automatic scanning, only record the current value of each point to draw the climbing curve; also observe the climbing curve on the ordinary oscilloscope, real-time Observing the formation process of the climbing curve. In addition to all the functions of the GT4507, the GT4507A microcomputer model instrument can be connected to the computer, so that the climbing curve can be observed on the computer, and the result can be calculated automatically, and the data can be saved. Take, as well as screen printing and database operations.

After adding a hardware module and a software module, the GT4507 intelligent experiment instrument can be easily upgraded to the GT4507A microcomputer type experiment instrument.

In the experiment, the tester should be connected with a specially equipped test rig equipped with an argon-filled tube. In addition, it can be connected to an ordinary oscilloscope. The argon-filled tube can be tested without external heating, which is extremely convenient to use. In the "automatic" mode, the formation process of the climbing curve can be observed in real time on the ordinary oscilloscope screen. With the increase of the second grid pressure of the automatic scanning, the climbing screen slowly draws a peak curve with six peaks. After the automatic scanning is completed, the climbing curve can still be displayed stably until the “clear” key (“set” key + “auto/manual” key) is pressed in the “manual” mode.

Second, the main technical indicators

The instrument is used to measure the excitation potential of argon atoms. Observe its special volt-ampere characteristics. Study the quantum properties of atomic energy levels.

1. Franck-Hertz tube: argon tube Tube structure: 4-pole

The number of peaks (or valleys) ≥ 6

Life ≥3000HRS

2, four-way control power supply (four-digit display):

Filament voltage: DC 0 ~ 5.9V, 1A, minimum voltage step: 0.1V, maximum voltage step: 1V.

The first gate voltage VG1K: DC 0 ~ 7.9V, 10mA, the minimum voltage step value: 0.1V, the maximum voltage step value: 1V.

Rejection voltage VG2A: DC 0 ~ 9.9V, 10mA, minimum voltage step value: 0.1V, maximum voltage step value: 1V.

The second gate voltage VG2K: DC 0 ~ 85.3V, 5mA, the minimum voltage step value: 0.2V, the maximum voltage step value: 10V. In the "automatic" mode, the second gate voltage is automatically scanned from 0V to 85.3V.

3, micro current measuring instrument (four-digit display)

Measuring range: 10-6~10-9A, ±1%.

4, the power supply voltage: ~ 220V, 50Hz, fuse: 1.25A.

GT4507 Frank-Hertz experiment instrument front panel

GT4507 Frank-Hertz experiment instrument rear panel diagram

1, GT-DS3 data collector

1) One analog signal output channel, output range 0~5V, using 10-bit D/A output;

2) One analog signal acquisition channel, 4-bit half A/D sampling, sampling frequency 3 times/second;

3) One-way oscilloscope signal output interface and one trigger signal output interface; oscilloscope signal output adopts 12-bit parallel high-speed D/A converter; output interface adopts Q9 oscilloscope standard interface;

4) Computer interface: USB;

Frank-Hertz test stand

GT-DS3 data collector front panel

GT-DS3 data collector rear panel

Third, the Franck-Hertz experiment instrument configuration

normal type:

1. Manually measure the excitation potential of the argon atom of the Franck-Hertz tube, describe its special volt-ampere characteristic phenomenon, and study the quantum characteristics of the atomic energy level.

2, configuration: GT4507 Frank-Hertz experiment instrument + Franck-Hertz tube test stand.

smart:

1. The data acquisition function is added on the basis of the common type. The volt-ampere characteristic curve of the Frank-Hertz tube can be automatically measured and the measured curve can be dynamically displayed by an ordinary oscilloscope to obtain a stable climbing curve.

2, configuration: GT4507 Frank-Hertz experiment instrument + Franke-Hertz tube test frame + GT-DS3 data collector (without computer interface).

normal type

Microcomputer type:

1. Add computer interface and computer software on the basis of intelligent type. The volt-ampere characteristic curve measurement of the Franck-Hertz tube can be automatically controlled by the computer. The computer software provides single sampling and continuous sampling, and the interface is friendly and easy to operate.

2, configuration: GT4507 Frank-Hertz experiment instrument + Franke-Hertz tube test frame + GT-DS3 data collector (with computer interface) + computer software.

smart

Microcomputer type

Fourth, the experimental steps

1, GT4507 intelligent Fran-Kertz experiment instrument

Manual mode experiment steps

1) Connect the four pairs of sockets on the panel (filament voltage, VG2K: second grid voltage, VG1K: first grid voltage, VG2A: repellent voltage) according to the wiring diagram on the panel and the corresponding socket on the tube test stand. The line is connected. Note: Each pair of plug-in should be seated in a pair, and you must not insert it wrong! Doing so can damage the tube or instrument. Connect the “Signal Output” and “Synchronous Output” to the oscilloscope. Or simply connect the “Signal Output” to the oscilloscope and use the oscilloscope's internal synchronization. The microcurrent detector is connected internally.

2) “Auto/Manual” is in the “Manual” position when the power is turned on, and the “Manual” light is on.

3) Four-speed current file: 10-9A, 10-8A, 10-7A and 10-6A, at the "10-9A" position when starting up.

To switch the current range, you can only press one of the four buttons “10-9”, “10-8”, “10-7” and “10-6” in manual mode. The lamp is lit. Note: When converting the current range, the new range display is only displayed after the second grid pressure is changed. It is recommended that the instrument be fixed in the “10-9” block.

4) The filament voltage value has been preset to 3.0V, the first gate voltage VG1K has been preset to 2.1V, the rejection voltage VG2A has been preset to 5.2V, and the second gate voltage has been preset to 30V. Press The corresponding button will display the corresponding preset value.

5) To change the preset value, press the “∧” or “∨” key. If you press the “<” or “>” key, the number of digits of the preset value is changed, moving forward or backward. One.

6) In general, you can change the preset value according to the best value on the nameplate, then press the “set” button and the “>” button at the same time (or press the “set” button without pressing the “>” button) , the four voltages of the filament voltage, the first grid voltage, the second grid voltage and the rejection voltage are loaded onto the electron tube according to the preset value, and the “loading” indicator light is illuminated at this time. Note: only when four voltages are loaded, this The light is always on.

7) To load the filament voltage separately, one of the three voltages, such as the first gate voltage and the repellent voltage, press the “set” button and the corresponding voltage button at the same time. After the voltage is loaded, “load” The indicator light should flash.

8) After the four groups of voltages are loaded, the experiment can be carried out by preheating for ten minutes or more.

9) In manual mode experiment, the filament voltage should be kept, the first gate voltage and the repellent voltage are unchanged, and the second gate voltage starts from 0 (if it is not 0 volts, please adjust to 0 volts first), change to 85V, step size is 0.2V to 1V. Preset a second gate voltage value (automatic loading), record the voltage value and the corresponding current value. Work out the VG2K-IA curve by hand.

10) On the VG2K-IA curve, find the voltage value corresponding to each peak, and find the first excitation potential of the argon atom by the difference method and compare it with the accepted value of 11.5V (again, 13.5V). Relative error.

11) Recommendation: Experiments in manual mode are performed in automatic mode:

In the automatic mode, set the auto scan speed to “Low” (or “Medium”). At this time, each time a voltage value is scanned, there is enough time to record the current value (the voltage value is not recorded), which makes the manual operation become Very simple.

12) After the experiment is completed, press the “set” button + “<” button to unload (remove) the four groups of voltages.

Automatic mode experiment step

1) Connect the experiment connection manually. Press the “set” button + “ > ” button to load the four groups of voltages. At this time, the load light is on.

2) After loading for 10 minutes, press the “Auto/Manual” button, and the “Auto” light will be on.

3) At this time, the second gate voltage starts to scan automatically from 0V to 85.3V, a total of 512 steps, each step has 6 steps, and a step value is 0.166V (10 digits and display) The bit is displayed as the original value, and the 6 steps of one digit after the decimal point are displayed as 0.0, 0.2, 0.3, 0.5, 0.7, and 0.8). When scanning automatically, the reading of the ammeter should be constantly changing.

4) Adjust the amplitude of the oscilloscope and scan the knob to make the waveform stable. When the second gate voltage is automatically scanned, the six peaks generated in real time can be observed on the oscilloscope. After the automatic scanning is completed, the six peaks are still stable. Displayed on the screen, to clear these six peaks, press the “set” button + “auto/manual” button in manual mode.

5) In the automatic scanning, press the “set” button + “10-6” button to change the scanning speed. The scanning speed is divided into three levels: low, medium and high. The default setting is high.

6) To perform the next automatic scan, press the “Auto/Manual” button to go to the manual mode, then press the “set” button + “Auto/Manual” button to clear the data from the last scan, and then press “Auto”. /Manual" button to go to automatic scanning.

7) Summary of key functions:

"Auto / Manual" button: automatic / manual conversion.

“10-9”, “10-8”, “10-7” and “10-6”: current range conversion.

"filament voltage", "VG1K", "VG2A", "VG2k": four sets of voltage display conversion.

“set” + “filament voltage”: filament voltage loading.

"set" + "VG1K": first gate voltage loading.

"set" + "VG2A": Reject voltage loading.

“set” + “>”: all four voltages are loaded.

“set” + “<”: All four voltages are unloaded (cleared).

“set” + “∨”: If the displayed climbing curve is too large and folds, press this key combination one or two times under manual operation, and restore it in the third time.

“set” + “auto/manual”: clears the climb curve.

“set” + “10-6”: The scan rate is changed when the second gate voltage is automatically scanned.

“∧”, “∨”: The voltage is adjusted up and down, it is valid after loading.

“<” , “ > ”: Shift left and right during voltage adjustment.

Note: When the keyboard is locked, please press the “Reset” button to return to the original test state without affecting the following measurements. In the automatic operation, except the “Auto/Manual” button and the “set” + “10-6” button. Other keys are blocked.

2, GT4507A microcomputer type Franck-Hertz tester

The GT4507A microcomputer-based Frank-Hertz tester has all the functions of the GT4507 intelligent Franck-Hertz tester. The manual and automatic test steps are the same as those of the GT4507. At this time, the experimenter is connected to the oscilloscope. Also connected to a computer's serial port.

1) Description of the experimental software

Menu Item

The menu items are divided into four main menus: "File", "Settings", "Database" and "Help".

"File" is divided into "Open", "Save", "Print Graphic" and "Exit". "Save" is to save the existing climbing curve on the hard disk, the file name is selected by itself, and the file extension is dat. "Open" is to display the existing climbing curve and display it on the screen. "Printing graphics" actually prints the entire screen.

“Settings” include “working mode” and “scanning rate”. “Working mode” has two types: “self-defending” and “normal operation”. The scanning rate is divided into three types: “high”, “medium” and “low”. The provincial value is "high".

During the “self-test” operation, click “send” and then click “painting” to display a small climbing curve on the screen. It is the pre-generated data of the single-chip microcomputer. If there is a curve, it indicates that the experiment instrument communicates with the computer. normal.

For "normal operation", click "send" and then click "paint" to display the actual captured climbing curve on the screen. It should be basically the same as the curve displayed on the oscilloscope.

To change the scan rate, click on one of “High”, “Medium”, “Low”, and then click “Send”, the scan rate of the second gate voltage changes, and the scan period is 6 minutes and 38 seconds respectively. , 22 minutes and 26 seconds, 38 minutes and 16 seconds.

“Database” includes four items: “Add”, “Update”, “Delete” and “Browse”. It is MSACCESS type, named db1.mdb. Click “Browse” to browse the database, then click to hide the database. Note: “ When adding "," "update", the "number" should not be repeated. The fields of the database include: "number", "name", "class", "storage file name", "description", "date" and "sample value" And the results".

The Help menu contains instructions for using the lab and experimental instructions.

Test button

"Example": automatically generates a climbing curve.

"Send": Send a command to the experimenter.

“Drawing”: After receiving the command sent by the computer, the experimenter sends the data collected in real time to the computer to draw a curve on the computer and display the data of VG2K and IA in characters.

"Erase": Clear the graphic display in the picture.

"Print Screen": Send the entire screen to the printer for printing.

"Magnifying glass": a magnifying glass tool that calls the operating system.

“Manual calculation”: On the climbing curve, click the six peaks on the curve from left to right with the mouse, and then click “Manual calculation”, then display in the lower part of the screen and “sample value and result” Automatically calculated results.

"Clear sample value": Clear the content displayed in the "sample value and result" text box.

Button

“Zoom in”: The collected data is enlarged in the vertical direction (Y direction) and displayed again.

"Zoom out": The collected data is reduced in the vertical direction (Y direction) and displayed again.

Serial port selection

Optional serial port 1 or serial port 2, the default value is serial port 1.

2) Preparation before the test

First of all, the Franck-Hertz experiment software should be installed on the hard disk of the PC.

Requirements for PC: CPU above P200, memory above 128M, free hard disk space above 5OM, with one or two free serial ports, color display above 15 inches, resolution is set at 800×600 or above. Installed with win98, win2000 or winXP operating system.

The program installation is very convenient, execute Setup.exe on the CD with the random tape, and then follow the prompts. After the program is installed, execute the “Frank-Hertz Experimenter” program to enter the experiment screen.

3) Operation steps

In the "automatic" test, the second gate voltage value is automatically scanned from 0V to 85.3V, at which time the current representation number is constantly changing regularly, and when "Settings" → "Working mode" → "Self-test" is clicked A small curve appears on the screen, indicating that the Franck-Hertz experiment is working normally.

Click “Settings” → “Working Mode” → “Normal Operation”, then click “Send”, then click “Draw”, then the actual collected climbing curve will appear on the screen. If the climbing curve Not ideal, can be "zoomed in" or "zoom out" operations, these operations do not affect the measurement of the first excitation potential of argon atoms.

On the climbing curve, click on the six peaks (or valleys) from left to right, and then click on “Manual Calculation”. The calculation results are immediately displayed in the “Sampling Values ​​and Results” on the lower and right sides of the screen.

Select one of the three files "High", "Medium", and "Low" in "Settings" → "Working Method" → "Scan Rate", and then click "Send" to change the scanning rate of the second gate voltage.

You can save the captured climbing curve (should take a name: xxx.dat) or recall it from the hard disk. You can print the entire screen.

In addition, you can also perform various operations on the database, such as changing the "number", "name", adding records, etc. In particular, you can add various text descriptions in the text box of "sampled values ​​and results". You can also enter MSACCESS and then The database operates.

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