The first vacuum tubes, or radio tubes as they are sometimes called, were very similar to electric incandescent lamps (see Light sources). They had transparent glass balloons of the same shape, and their filaments glowed brightly.
At the end of the last century, the famous American inventor TL Edison discovered that the incandescent filament of an ordinary lamp emits, "throws out" a large amount of free electrons. This phenomenon, called thermionic emission, is widely used in all vacuum tubes.
Any electronic lamp is a metal, glass or ceramic balloon, inside which electrodes are fixed (see Fig.). A strong rarefaction of air (vacuum) is created in the cylinder, which is necessary so that the gases do not interfere with the movement of electrons in the lamp and so that the electrodes last longer. The cathode - the negative electrode - is the source of electrons. In some lamps, the filament serves as the cathode; in others, the filament serves as a miniature hot plate that heats the tubular cathode. The anode - the positive electrode - usually has the shape of a cylinder or box with no two walls and surrounds the cathode.
All names for vacuum tubes are associated with the number of electrodes: a diode has two electrodes, a triode has three, a tetrode has four, a pentode has five, etc.
The principle of operation of the first electronic tube, the diode, invented by the Englishman Fleming in 1904, has remained unchanged to this day. The main elements of this simplest lamp are the cathode and the anode. Electrons fly out of the hot cathode and form an electron "cloud" around it. If the cathode is connected to the “minus” of the power source, and the “plus” is applied to the anode, a current arises inside the diode (the anode will begin to attract electrons from the “cloud”). If we apply “minus” to the anode and “plus” to the cathode, the current in the diode circuit will stop. Thus, in a two-electrode lamp - a diode, the current can go only in one direction - from the cathode to the anode, that is, the diode has one-sided current conductivity.
The diode was used to rectify alternating current (see Electric current). In 1906, the American engineer Lee de Forest proposed to introduce another electrode between the anode and cathode of the diode lamp - a grid. A new tube appeared - a triode, which immeasurably expanded the field of use of electronic tubes (see Fig.).
The work of a triode, like any electronic tube, is based on the existence of an electron flow between the cathode and the anode. The grid - the third electrode - looks like a wire spiral. It is closer to the cathode than to the anode. If a small negative voltage is applied to the grid, it will repel some of the electrons flying from the cathode to the anode, and the strength of the anode current will decrease. With a large negative voltage, the grid becomes an insurmountable barrier for electrons. They are retained in the space between the cathode and the grid, despite the fact that the "minus" is applied to the cathode, and the "plus" of the power supply is applied to the anode. With a positive voltage on the grid, it will increase the anode current. Thus, by applying different voltages to the grid, it is possible to control the strength of the anode current of the lamp. Even small changes in the voltage between the grid and the cathode will lead to a significant change in the strength of the anode current, and therefore to a change in the voltage across the load (for example, a resistor) included in the anode circuit. If an alternating voltage is applied to the grid, then due to the energy of the power source, the lamp will increase this voltage. This happens because with an alternating voltage between the grid and the cathode, the direct current in the lamp load changes in time with this voltage, and to a much greater extent than the voltage on the grid changes. If this current is passed through a high-pass filter (see Electric filter), then an alternating current with a greater amplitude of oscillations will flow at its output, and a greater alternating voltage will appear on the load.
In the future, the designs of electronic tubes developed very quickly - lamps appeared containing not one, but several grids: tetrodes (lamps with two grids) and pentodes (lamps with three grids). They made it possible to obtain greater signal amplification.
Triodes, tetrodes and pentodes are universal vacuum tubes. They are used to amplify the voltage of alternating and direct currents, to work as detectors and as generators of electrical oscillations.
Combined lamps have become widespread, in cylinders of which there are two or even three vacuum tubes. These are, for example, diode-pentode, double triode, triode-pentode. They can, in particular, work as a detector (diode) and simultaneously amplify the voltage (pentode).
Vacuum tubes for low power equipment (radios, televisions, etc.) are small in size. There are even subminiature lamps that are no more than the thickness of a pencil. The complete opposite of miniature lamps are lamps used in high-power amplifiers for radio stations or radio transmitters. These vacuum tubes can generate high-frequency oscillations with a power of hundreds of kilowatts and can reach significant dimensions.
Due to the huge amount of heat generated, it is necessary to use air or water cooling of these lamps (see Fig.).
Electric lamp
Russian export radio tube 6550C
Electric lamp, radio tube- an electrovacuum device (more precisely, a vacuum electronic device), which works by controlling the intensity of the flow of electrons moving in a vacuum or rarefied gas between the electrodes.
Radio tubes were widely used in the twentieth century as active elements of electronic equipment (amplifiers, generators, detectors, switches, etc.). Currently, they are almost completely superseded by semiconductor devices. Sometimes they are also used in powerful high-frequency transmitters, high-quality audio equipment.
Electronic lamps intended for lighting (flash lamps, xenon lamps, and sodium lamps) are not called radio tubes and usually belong to the class of lighting fixtures.
Operating principle
Electronic tube RCA "808"
Heated Cathode Vacuum Tube
- As a result of thermionic emission, electrons leave the cathode surface.
- Under the influence of the potential difference between the anode and cathode, the electrons reach the anode and form an anode current in the external circuit.
- With the help of additional electrodes (grids), the electron flow is controlled by applying an electric potential to these electrodes.
In vacuum electronic tubes, the presence of gas degrades the characteristics of the tube.
Gas-filled vacuum tubes
The main for this class of devices is the flow of ions and electrons in the gas filling the lamp. The flow can be created, as in vacuum devices, by thermionic emission, or it can be created by the formation of an electric discharge in a gas due to the strength of the electric field.
Story
According to the heating method, the cathodes are subdivided into cathodes of direct and indirect heating.
Directly heated cathode is a metal filament. Direct-incandescent lamps consume less power and warm up faster, however, they usually have a shorter service life, when used in signal circuits, they require a direct current supply of the filament, and in a number of circuits they are inapplicable due to the effect of the potential difference in different parts of the cathode on the operation of the lamp.
The indirectly heated cathode is a cylinder with a filament (heater) inside. Such lamps are called indirect incandescent lamps.
The cathodes of the lamps are activated with metals having a low work function. In direct incandescent lamps, thorium is usually used for this, in indirect incandescent lamps - barium. Despite the presence of thorium in the cathode, direct-incandescent lamps do not pose a danger to the user, since its radiation does not go beyond the cylinder.
Anode
Vacuum tube anode
Positive electrode. It is made in the form of a plate, more often a box in the form of a cylinder or parallelepiped. It is usually made from nickel or molybdenum, sometimes from tantalum and graphite.
Net
Grids are located between the cathode and anode, which serve to control the flow of electrons and eliminate side effects that arise when electrons move from the cathode to the anode.
The mesh is a lattice made of thin wire or, more often, it is made in the form of a wire spiral wound on several supporting posts (traverses). In rod lamps, the role of grids is played by a system of several thin rods parallel to the cathode and anode, and the physics of their operation is different than in the traditional design.
According to their purpose, the meshes are subdivided into the following types:
Depending on the purpose of the lamp, it can have up to seven grids. In some variants of switching on multigrid lamps, individual grids can act as an anode. For example, in a generator according to Schembel's scheme on a tetrode or pentode, the actual generator is a "virtual" triode formed by a cathode, a control grid and a screening grid as an anode.
Balloon
Basic types
Small-sized ("finger") radio tubes
The main types of electronic vacuum tubes:
- Diodes (easily made for high voltages, see kenotron)
- beam tetrodes and pentodes (as varieties of these types)
- combination lamps (actually include 2 or more lamps in one bottle)
Modern applications
Air-cooled metal-ceramic generator triode GS-9B (USSR)
High frequency and high voltage power technology
- In high-power broadcasting transmitters (from 100 W to units of megawatts), powerful and super-powerful lamps with air or water cooling of the anode and a high (more than 100 A) filament current are used in the output stages. Magnetrons, klystrons, so-called. Traveling wave radio tubes provide a combination of high frequencies, power and acceptable cost (and often just the fundamental possibility of existence) of the element base.
- The magnetron can be found not only in the radar, but also in any microwave oven.
- If it is necessary to rectify or quickly switch several tens of kV, which cannot be done with mechanical keys, it is necessary to use radio tubes. So, the kenotron provides acceptable dynamics at voltages up to a million volts.
Military industry
Due to the principle of operation, electronic lamps are devices that are much more resistant to damaging factors such as an electromagnetic pulse. For information: a single device can have several hundred lamps. In the USSR, for use in on-board military equipment in the 1950s, rod lamps were developed, which were distinguished by their small size and high mechanical strength.
Miniature lamp of the "acorn" type (pentode 6Ж1Ж, USSR, 1955)
Space technology
Radiation degradation of semiconductor materials and the presence of a natural vacuum in the interplanetary medium make the use of certain types of lamps a means of increasing the reliability and durability of spacecraft. The use of transistors in AMC Luna-3 was associated with a great risk.
Increased ambient temperature and radiation
Lamp equipment can be designed for a wider temperature and radiation range of conditions than semiconductor equipment.
High quality sound equipment
According to the subjective opinion of most music lovers, the "tube" sound is fundamentally different from the "transistor" sound. There are several versions of the explanation for these differences, both based on scientific research and frankly unscientific reasoning. One of the main explanations for the differences between tube and transistor sound is the "natural" sound of tube equipment. Tube sound is "surround" (some call it "holographic"), as opposed to "flat" transistor sound. The tube amplifier clearly conveys the emotions, energy of the performer, "drive" (for which guitarists adore them). Transistor amplifiers have a hard time coping with these tasks. Often, designers of transistor amplifiers use circuitry similar to lamps (operating mode in class A, transformers, lack of general negative feedback). The overall result of these ideas was the return of tube technology to the high-performance amplifier field. The objective (scientific) reason for this situation is the high linearity (but not ideal) of the lamp, primarily the triode. A transistor, primarily a bipolar one, is generally non-linear, and as a rule cannot work without linearization measures.
The advantages of tube amplifiers:
Simplicity of circuits. Its parameters depend little on external factors. As a result, a tube amplifier typically has fewer parts than a semiconductor amplifier.
The parameters of the lamps are less dependent on temperature than the parameters of the transistor. Lamps are insensitive to electrical overload. The small number of parts also greatly contributes to the reliability and reduction of distortion introduced by the amplifier. The transistor amplifier has problems with "thermal" distortion.
Good matching of the input of the tube amplifier with the load. Tube stages have a very high input impedance, which reduces losses and helps to reduce the number of active elements in the radio device. - Ease of maintenance. If, for example, a concert amplifier's lamp breaks down during a performance, then it is much easier to replace it than a burnt-out transistor or microcircuit. But no one does this at concerts anyway. Amplifiers at concerts are always in stock, and tube amplifiers are always in double stock (because, oddly enough, tube amplifiers break down much more often).
The absence of some types of distortion inherent in transistor stages, which has a beneficial effect on the sound.
With the proper use of the advantages of lamps, it is possible to create amplifiers that surpass transistor ones in sound quality within certain price categories.
Subjectively vintage appearance when creating image samples of equipment.
Insensitive to radiation up to very high levels.
Disadvantages of tube amplifiers:
In addition to powering the anodes, lamps require additional power consumption for heating. Hence the low efficiency, and as a result - strong heating.
Lamp equipment cannot be instantly ready for use. Pre-heating of the lamps is required for several tens of seconds. The exception is direct incandescent lamps, which start working immediately.
The output tube stages must be matched to the load using transformers. As a result - the complexity of the design and poor weight and dimensions due to transformers.
Lamps require the use of high supply voltages of hundreds (and in powerful amplifiers - thousands) of volts. This imposes certain restrictions in terms of safety in the operation of such amplifiers. Also, high voltage pickup almost always requires a step-down output transformer. At the same time, any transformer is a nonlinear device in a wide frequency range, which causes the introduction of nonlinear distortions into the sound at a level close to 1% in the best models of tube amplifiers (for comparison: the nonlinear distortions of the best transistor amplifiers are so small that they cannot be measured). For a tube amplifier, distortion of 2-3% can be considered normal. The nature and spectrum of these distortions differs from those of a transistor amplifier. On subjective perception, this usually does not affect in any way. The transformer is of course a non-linear element. But it is very often used at the DAC output, where it provides galvanic isolation (prevents the penetration of noise from the DAC), plays the role of a band-limiting filter, and apparently ensures the correct "alignment" of the signal phases. As a result, despite all the disadvantages (first of all, the high cost), the sound only wins. Also, transformers are often used with success in transistor amplifiers.
Lamps have a limited lifespan. Over time, the parameters of the lamps change, the cathodes lose their emission (the ability to emit electrons), and the filament can burn out (most lamps work to failure for 200-1000 hours, the transistors are three orders of magnitude more). Transistors can also degrade over time.
The fragility of classic glass bulb lamps. One of the solutions to this problem was the development in the 40s of the last century of lamps with metal-ceramic balloons, which have great strength, but such lamps were not widely used.
Some features of tube amplifiers:
According to the subjective opinion of audiophiles, the sound of electric guitars is transmitted much better, deeper and more "musical" by tube amplifiers. Some people attribute this to the non-linearity of the output node and the introduced distortion, which are "appreciated" by fans of electric guitars. This is actually not the case. Guitarists use effects associated with increasing distortion, but for this, the corresponding changes are made to the circuit on purpose.
The obvious disadvantages of a tube amplifier are fragility, greater energy consumption than a transistor one, shorter lamp life, large distortions (this is usually remembered when reading technical specifications, due to a serious imperfection in measuring the main parameters of amplifiers, many manufacturers do not provide such data , or in other words - two completely identical, in terms of the measured parameters, amplifiers can sound completely different), large dimensions and weight of the equipment, as well as the cost, which is higher than that of transistor and integral equipment. The power consumption of a high-quality transistor amplifier is also high, however, its dimensions and weight can be comparable to a tube amplifier. In general, there is such a pattern that the "louder", "more musical", etc., the amplifier, the greater its dimensions and power consumption, and the lower the efficiency. Of course, a Class D amplifier can be very compact and can be as efficient as 90%. Just what to do with the sound? If you are planning a struggle to save electricity, then of course, the tube amplifier is not an assistant in this matter.
Classification by name
USSR / Russia markings
Markings in other countries
In Europe in the 30s, the leading manufacturers of radio tubes adopted the Unified European Alphanumeric Marking System:
- The first letter characterizes the filament voltage or its current:
A - heating voltage 4 V;
V - filament current 180 mA;
C - filament current 200 mA;
D - heating voltage up to 1.4 V;
E - filament voltage 6.3 V;
F - filament voltage 12.6 V;
G - heating voltage 5 V;
H - filament current 150 mA;
K - heating voltage 2 V;
P - filament current 300 mA;
U - filament current 100 mA;
V - filament current 50 mA;
X - filament current 600 mA.
- The second and subsequent letters in the designation determine the type of lamps:
B - double diodes (with a common cathode);
C - triodes (except for weekends);
D - output triodes;
E - tetrodes (except weekends);
F - pentodes (except weekends);
L - output pentodes and tetrodes;
H - hexodes or heptodes (hexodic type);
K - octodes or heptodes (octode type);
M - electronic light indicators of the setting;
P - secondary emission amplifying lamps;
Y - half-wave kenotrons;
Z - full-wave kenotrons.
- A two-digit or three-digit number indicates the external design of the lamp and the serial number of this type, with the first digit usually characterizing the type of base or leg, for example:
1-9 - glass lamps with a lamellar base ("red series")
1x - lamps with an eight-pin base ("11-series")
3x - lamps in a glass bottle with an octal base;
5x - lamps with a local base;
6x and 7x - glass subminiature lamps;
8x and from 180 to 189 - miniature glass with a nine-pin stem;
9x - miniature glass with a seven-pin stem.
see also
Discharge lamps
HID lamps typically use an inert gas discharge at low pressures. Examples of gas discharge vacuum tubes:
- Gas dischargers for high voltage protection (for example, on overhead communication lines, receivers of powerful radars, etc.)
- Thyratrons (three-electrode lamps - gas-discharge triodes, four-electrode - gas-discharge tetrodes)
- Xenon, neon and other gas-discharge light sources.
see also
- AOpen AX4B-533 Tube - Intel 845 Sk478 motherboard with tube audio amplifier
- AOpen AX4GE Tube-G - Motherboard on Intel 845GE Sk478 with tube audio amplifier
- AOpen VIA VT8188A - Motherboard based on VIA K8T400M Sk754 chipset With 6-channel tube audio amplifier.
- Hanwas X-Tube USB Dongle is a DTS-enabled USB sound card for laptops that simulates the appearance of a vacuum tube.
Notes (edit)
Links
- Handbook on domestic and foreign radio tubes. More than 14000 radio tubes
- Tube handbooks and all the information you need
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Ecology of cognition. Science and technology: The key to a fuel-free source of electricity is to generate electricity directly from a conventional tube-type pentode triode in unusual modes of operation
Valery Dudyshev has solved the mystery of Nikola Tesla about his source of electricity in his electric car.
An energy revolution is brewing in the field of alternative energy
Nikola Tesla actually demonstrated a fuel-free electric car in operation back in 1931 in Bufallo (USA). The electric power in the car's electric motor came from a mysterious box with radio tubes. But until now, this mystery of the source of electricity for an electric car remained unsolved.
The key is to obtain electricity directly from a conventional tube-type pentode triode in unusual operating modes. It is only necessary to provide explosive electron emission from its cathode. As a result, it is possible to get from the tube triode into an electrical load connected to it in parallel - as much electricity as we want (well, of course, within reason: say, with a source output power of 5-10 kW). Explosive electron emission is the discovery of academician G. Mesyats used in this invention. - achieved in the triode by supplying a series of short duration high-voltage high voltage pulses to the control grid of the triode.
Explosive electron emission from the cathode surface leads to the formation of an avalanche of electrons accelerated by the control grid and hitting the anode of the triode
As a result, this avalanche of electrons from the anode enters the electrical load and through it again to the anode of the triode. This is how a free electric current arises and is maintained in the "triode - load" circuit. In other words, in this mode, a conventional tube triode with a strong el. the field on the control grid becomes a free source of electricity.
Calculations show that a conventional vacuum tube triode in this operating mode allows one to obtain powerful electron emission in a tube triode and, after some refinement of the triode, to obtain free electricity from a conventional tube triode, moreover, when the cathode and anode are cooled, from one radio tube to 10 kW - that's such miracles!
A very rational technical solution is the combination of a Tesla resonant transformer with a vacuum tube. In this case, the explosive electronic ejection from the cathode of the vacuum tube is provided by the Tesla transformer itself.
Powerful field emission from the output winding of the Tesla transformer
A variant of the device using a Tesla transformer
Fig. 1 Block diagram of the design of the source of gratuitous electrical energy. This device is made on the basis of combining a Tesla transformer and a spherical vacuum tube with a needle cathode.
Brief description of the design of the source of free electricity
A vacuum electronic lamp of an original design (circled by a dotted line) contains a spherical anode 1 in the form of an outer metal hollow evacuated sphere, inside which a spherical cathode 2 with external needles is placed. The outer sphere anode 1 is placed in the center of a cubic housing 3 with internal electrical insulation. 4 Metal rods 5 are rigidly attached to the anode and cathode, which through holes 6 go outside the housing 3 and are electrically connected through keys K2,3,4, respectively, to the output of the Tesla transformer 7 and electrical load 8, connected to the ground electrode 9. Tesla transformer 7 is connected at the input with the key K1 to the primary low-power source of electricity 11 (for example, the battery "Krona"). A voltage converter 10 is connected in parallel to the output electrical load 8 through the key K4.
The device works as follows: First, using the key K1 (12) connect the primary source of electricity 11 to the Tesla transformer 7. The output high-voltage voltage from its output is fed through the key K2 to a spherical needle electrode - cathode 2, which forms a powerful electron emission from its needles. The flow of electrons torn out from the needles of the cathode 2 reaches the anode 1 and settles on its inner surface.
As a result, the outer surface of the spherical hollow anode 1 acquires an excess electric charge, i.e. electrically charged to high voltages. Then, after charging the spherical anode 1. it is connected electrically through the output rod electrode 5 with the key K3 to the electrical load 8 and the electric charge from the anode 1 begins to drain through the load 8 into the ground electrode 9 and through it to the Earth, i.e. in the electrical load 8, a useful electric current arises and useful electrical energy is generated. If it is necessary to obtain standard parameters in other payloads of electricity, a voltage converter is provided to turn on the K4 key.
Excess electricity in the load 8 compared to the consumption of electricity from the primary source 12 for the operation of the Tesla transformer 7 is due to the avalanche powerful field emission of electrons under the influence of the huge electric forces of the electric field created by the secondary winding of the Tesla transformer on the needles of the spherical cathode 2
Tesla transformer - a source of powerful electron emission. By means of a conventional vacuum tube (lamp diode), this stream of electrons can be converted into useful electrical energy. More details in the article TESLA TRANSFORMER AS A SOURCE OF FREE ELECTRIC POWER.
Conclusion
The idea of free electricity from a triode is that it is quite possible to use a conventional tube triode as a source of electricity, provided that significant electron emission from the cathode is obtained!
To obtain electricity in a conventional tube triode, you just need to apply a high voltage between the cathode and the accelerating grid, with c + on the grid, and then, with the appearance of a stream of electron emission, from the cathode and its acceleration + on the triode grid - to the anode of the triode - from the cathode will rush the flow of electrons is an electric current, which we will close through the load to the cathode.
The greater the magnitude of the accelerating electric field between the cathode and the grid, the greater the electron emission from the cathode (up to explosive electronic emission), which means that the more useful electric current from the anode - el. load current.
So, if you create elementary normal conditions for the operation of a tube triode in such a free mode (after all, there is a huge amount of electrons in the cathode material and will last for many years of work), then we will completely get free electricity in e-mail. load at the ends of the triode - parallel to it. The effect is most easily obtained on a tube triode, because there is a vacuum in it. Consequently, electronic emission and even more explosive email. emission in it will arise most simply and especially efficiently, in the presence of a large electric potential on the grid of a conventional triode with a vacuum inside its glass bulb. published by
We are now used to compact electronic devices and ultra-thin laptops. And a little over a hundred years ago, a device appeared that made it a reality and made a real revolution in the development of electronics. It's about a radio tube.
Tube intro
In circuitry, lamps were widely used before, the first electronic devices were built with their use. The golden time of radio tubes fell on the first half of the 20th century. For our grandfathers and great-grandfathers, giant computers were much more familiar, occupying an entire room and warming themselves like hellish heat. You can't watch a serial on such a car.
Then there was a time when Soviet microcircuits became the largest in the world. But that's another story, which began after the advent of semiconductor devices. As you can imagine, this article is about the operation of the vacuum tube and its modern use.
Vacuum devices
Vacuum is the absence of matter. More precisely, its almost complete absence. In physics, high, medium and low vacuum are distinguished. It is clear that there can be no electric current in a vacuum, since the current is the directed movement (of particles) of charge carriers, which have nowhere to come from in a vacuum.
But so nowhere? Metals emit electrons when heated. This is the so-called thermionic emission. The work of electronic vacuum devices is based on it.
Thermionic emission was discovered by Thomas Edison. More precisely, the scientist found out that when the filament is heated and there is a second electrode in the vacuum flask, the vacuum conducts a current. Then Edison did not fully appreciate the significance of his discovery, but just in case he patented it. Conclusion: in any incomprehensible situation, patent!
Vacuum devices - hermetically sealed cylinders with electrodes inside. Cylinders are made of glass, metal or ceramics, after evacuating air from them.
In addition to vacuum tubes, there are the following vacuum devices:
- microwave devices, magnetrons, klystrons;
- CRTs, cathode ray tubes;
- x-ray tubes.
The principle of operation of a vacuum tube
A vacuum tube is an electronic vacuum device that works by controlling the rate of flow of electrons between electrodes.
The simplest type of lamp is a diode. Instead of reading the definitions, let's take a look at it.
Any lamp has a cathode, from which electrons fly out, and an anode, to which they fly. If "minus" is applied to the cathode, and "plus" to the anode, the electrons emitted from the hot cathode will begin to move towards the anode. A current will flow in the lamp.
By the way! If you need to calculate a diode amplifier, our readers now have a 10% discount on
The diode has one-sided conductivity. This means that if a plus is applied to the cathode and a minus to the anode, there will be no current in the circuit.
In addition to these two electrodes, lamps may have others.
All names for vacuum tubes are associated with the number of electrodes. Diode - two, triode - three, tetrode - four, pentode - five, etc.
Let's take a triode. This is a diode to which an additional electrode is added - a control grid. Such a lamp with three electrodes can already work as a current amplifier.
If there is a small negative voltage on the grid, it will delay some of the electrons flying towards the anode, and the current will decrease. With a large negative voltage, the grid "inhibits" the lamp, and the current in it will stop. And if a positive voltage is applied to the grid, the anode current will increase.
A small change in voltage across the grid, which is installed near the cathode, significantly affects the current between the cathode and anode. The principle of amplification is based on this.
Application of vacuum tubes
Almost everywhere the lamp has been replaced by a semiconductor transistor. However, in some industries, lamps have taken their place and remain indispensable.
For example, in space. Lamp equipment withstands a wider temperature range and background radiation, therefore it is used in the manufacture of spacecraft.
Air- or water-cooled lamps are also used in high-power radio transmitters.
Of course, it's hard to imagine modern musical equipment without tube circuits.
Tube sound: truth or fiction?
Amplifiers of low frequency or simply amplifiers of sound are the most famous modern application of radio tubes, which also causes a lot of controversy.
It comes down to the "holivars" between the adepts of tube and transistor sound. The tube sound, as they say, is more “soulful” and “softer”, it is pleasant to listen to it. While the transistor sound is “soulless” and “cold”.
Nothing happens just like that, and it is unlikely that such disputes and opinions arose out of nowhere. At one time, scientists became interested in the question of whether tube sound is really more pleasant to the ear. Quite a lot of research has been done on the differences between a lamp and a transistor.
According to one of them, tube amplifiers add even harmonics to the signal, which are subjectively perceived by people as “warm”, “pleasant” and “cozy”. True, how many people, so many opinions, so disputes are still ongoing.
Arguing is often a waste of time. Student service, on the other hand, will help save valuable man-hours. Please contact our experts for quality assistance in any area of expertise.
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St. Petersburg
Introduction. ... ... ... ... ... ... ... ... ... ... 3
1. General part
1.1. Description of the subject area. ... ... ... ... ... 4
1.1.1. Electronic lamps. ... ... ... ... ... ... 4
1.1.2. Calculation formulas. ... ... ... ... ... ... eleven
1.2. Analysis of solution methods. ... ... ... ... ... ... thirteen
1.3. Overview of software. ... ... ... ... ... 14
1.4. Description of the selected programming language. ... ... ... sixteen
2. Special part
2.1. Formulation of the problem. ... ... ... ... ... ... ... 23
2.1.1. Basis for development. ... ... ... ... ... 23
2.1.2. Purpose of the program. ... ... ... ... ... 23
2.1.3. Technical and mathematical description of the problem. ... ... ... 23
2.1.4. Requirements for the program. ... ... ... ... ... 24
2.1.4.1. Requirements for functional characteristics. ... 24
2.1.4.2. Reliability requirements. ... ... ... ... ... 25
2.1.4.3. Requirements for technical means. ... ... ... 25
2.2. Description of the scheme of the program. ... ... ... ... ... ... 26
2.2.1. Description of the scheme of the main program. ... ... ... 26
2.2.2. Description of the scheme of the module for calculating thermal stresses in the anode MHP 26
2.2.3. Description of the diagram of the plotting module. ... ... 27
2.3. Program text. ... ... ... ... ... ... ... 28
2.4. Program description. ... ... ... ... ... ... ... 33
2.4.1. General information. ... ... ... ... ... ... 33
2.4.2. Functional purpose. ... ... ... ... 33
2.4.3. Description of the logical structure. ... ... ... ... 33
2.5. Description of the program debugging process. ... ... ... ... 34
2.6. An example of the results of the program. ... ... ... ... 35
3. Economic justification of the projected program. ... ... ... 36
4. Measures to ensure the safety of life. ... ... 40
4.1. The effect of electric current on the human body
4.2. Grounding devices
Conclusion. ... ... ... ... ... ... ... ... ... ... 42
Bibliography. ... ... ... ... ... ... ... ... ... 43
Appendix 1. Scheme of the program. ... ... ... 44
Appendix 2. Screen forms. ... ... ... 47
Appendix 3. Examples of errors. ... ... ... 51
Over the past few years, the word "computer" has been used more and more often. If earlier computers were owned only by world-renowned firms, and programs were written in low-level languages, today there is a computer in almost every apartment, and programs are written in high-level languages. More than a million computers are sold in Russia every year. Modern computers have great capabilities: they make numerical calculations, prepare books for printing, create drawings, films, music on them, manage factories and spaceships. The computer is a versatile and fairly simple tool for processing all types of information used by humans.
This diploma assignment will allow employees of factories and design bureaus to reduce the number and cost of models of the designed devices. The developed program will provide the calculation of the temperature field in the body of the MHP anode during heating after turning on the device, as well as the thermal stresses arising in this case, which have a destructive effect on the anode material. The results of the work of this program will give the necessary initial information for the analysis of temperature stresses in the anode body and the choice of operating modes that preserve the service life and ensure high reliability and durability of the devices.
A COMMON PART
Description of the subject area
Electronic tubes
Vacuum tubes are used to generate, amplify, or convert electrical oscillations in various fields of science and technology.
The principle of operation of electronic tubes
The principle of operation of all radio tubes is based on the phenomenon thermionic emission- this is an increase in the speed of electrons to such that they fly out of the metal with a negative charge and can move directionally between the electrodes, creating an electric current. This also requires that they do not encounter obstacles such as air molecules - which is why a high vacuum is created in the lamps. To obtain thermionic emission, the metal must be heated to about 2000 o K. It is most convenient to heat the metal filament electric current ( filament current) as in lighting lamps. Not every metal can withstand such a high temperature, most melts, because of this, pure tungsten filaments were used in the first samples of electronic lamps, which glowed to a white glow, hence the name "lamp". But such brightness is very expensive - a strong current is needed (half an ampere for the receiving lamp). But soon a way was found to reduce the filament current. Studies have shown that if tungsten is coated with some other metals or their oxides (barium, strontium and calcium), then the release of electrons is facilitated (the so-called "work function" decreases). The output requires less energy, and hence a lower temperature. Modern oxidized filaments operate at temperatures of about 700-900 ° C, in this regard, it is possible to reduce the filament current by about 10-20 times.
It should be noted that the control of all electron flows in the lamp is carried out by means of electric fields generated around the electrodes with different charges.
Types of vacuum tubes
Diode- a vacuum device that transmits an electric current in only one direction (Fig. 1a) and has two leads for inclusion in an electrical circuit (plus an incandescence lead, of course), a two-electrode lamp was invented in 1904 by physicist J. Fleming. Such an electronic lamp is a glass or metal balloon, from which air is pumped out, and two metal electrodes: a glowing cathode (-) and a cold anode (+). There are two types of cathode: direct heating and indirect heat... In the first case, the cathode is a tungsten filament (often covered with oxide), through which the current incandescent passes, and in the second, a cylinder covered with a metal layer with a low work function, inside which there is a filament, electrically isolated from the cathode. The action of the cathode as a source of electrons is based on thermionic emission... Figure 1a shows a vacuum diode device with a directly heated cathode. The disadvantage of directly heated cathodes is that they are not suitable for supplying them with alternating current, since when the current changes, the temperature of the filament has time to change, and the flux of emitted electrons pulsates with the frequency of the supply current, therefore, indirectly heated cathodes are now used.
The current-voltage characteristic of the diode (Fig. 1f) has a nonlinear character - this is explained by the accumulation of electrons at the cathode in a “cloud”. In the absence of anode voltage, electrons are not attracted to it, and the anode current is zero. Anode current occurs when a positive voltage is applied to the anode, as the voltage increases, the anode current will increase (faster on the AB curve). At a high voltage (at point B), the current reaches its maximum value - this is the saturation current. In a diode with an activated (oxide) cathode, there is no slowdown in the growth of the anode current, but when the anode current is above a certain limiting value, the cathode is destroyed. The properties of a diode are evaluated by the slope and internal resistance of the lamp.
If the outlet of the grid is connected to the cathode, then there will be no electric field between the grid and the cathode, and the turns of the grid will have a very weak effect on the electrons flying to the anode - it will be established in the anode circuit quiescent current... If you turn on a battery between the cathode and the grid so that the grid is charged negatively, then the latter will begin to repel electrons back to the cathode, and the anode current will decrease. With a significant negative potential of the grid, even the fastest electrons will not be able to overcome its repulsive effect, and the anode current will stop, i.e. the lamp will be locked. If the grid battery is connected so that the grid is positively charged relative to the cathode, then the resulting electric field will accelerate the movement of electrons. In this case, the measuring device in the anode circuit will show an increase in current.
The higher the grid potential, the higher the anode current becomes. In this case, some of the electrons are attracted to the grid, creating grid current, but with the correct design of the lamp, the number of these electrons is small. Only those electrons that are in the immediate vicinity of the turns of the grid will be attracted to it and create a current in the grid circuit - it will be insignificant.
The gain and power of the triodes are different. With a large anode current, the anodes undergo strong electron bombardment, which leads to their significant heating and even destruction, therefore the anodes are made massive, blackened, special cooling fins are welded or water cooling is used, which is described below. Water cooling is also used in the GI-11 (BM) pulse generator triode, which was recently developed by St. Petersburg scientists.
Shielded lamps can work well with low grid voltages, but sometimes when tetrodes are operating, secondary electrons knocked out of the anode reach the screen grid, creating a current and strong signal distortion - this phenomenon is called dinatron effect... Pentodes are the solution to this problem.
The way to eliminate the unpleasant consequences of the dinatron effect is obvious: it is necessary to prevent secondary electrons from reaching the screening grid. This can be done by introducing another grid into the lamp - the third in a row, which will be protective, so pentodes were obtained - from the Greek word "penta" - five (Fig. 1d). The third grid is located between the anode and the screening grid and is connected to the cathode, therefore, it turns out to be negatively charged with respect to the cathode. Therefore, the secondary electrons will be repelled by this grid back to the anode, but at the same time, being quite rare, this protective grid does not impede the electrons of the main anode current. In modern (for 1972) high-frequency pentodes, the gain reaches several thousand, and the grid-anode capacitance is measured in thousandths of a picofarad. This makes the pentode an excellent lamp for amplifying high frequency oscillations. But pentodes are also used with great success to amplify low (audio) frequencies, in particular in the final stages.
Low-frequency pentodes are structurally somewhat different from high-frequency ones. To amplify the low frequency, it is not necessary to have too large gains, but it is necessary to have a large straight-line section of the characteristic, since it is necessary to amplify large voltages, therefore, relatively rare screening grids are made. In this case, the gain does not turn out to be very large, and the entire characteristic is shifted to the left, so a larger part of it becomes usable. Low-frequency pentodes must deliver more power, therefore, they become massive and their anodes need to be cooled.
There are also Beam tetrodes- high-power low-frequency lamps without protective nets, in which the turns of the screening nets are located exactly behind the turns of the control nets. In this case, the flow of electrons is split into separate beams (rays) flying directly to the anode, and it is carried a little further and the secondary electrons knocked out of it cannot reach the screening grid, but are attracted by the anode back, without disrupting the normal operation of the lamp. The amplification factor of such lamps is several times higher than that of conventional tetrodes, because electrons from the cathode fly in direct beams between the turns of the grids and do not scatter, but are directed to the anode by the field of shielding plates located on the paths of possible leakage near the lamp anode, which are connected to the minus of the power supply through the cathode. With ray lamps, it is possible to create a very favorable shape of the characteristic, which allows you to obtain high output power with a low signal voltage on the grid.
Radio tube designs
For low-power equipment, such as a radio receiver, they tried to make the lamps as small as possible (finger lamps). They are often called amplifier tubes. There are also subminiature (pencil-thin) lamps with soft leads. In the powerful equipment of radio nodes and in radio transmitters, lamps of much larger sizes are used, which develop much higher power in the anode circuit. Such lamps have massive anodes with forced air or water cooling. For this, the anodes are made cone-shaped from copper or other heat-resistant metals, hollow fins or tubes are welded to them, through which chilled water is passed. Powerful lamps with copper anodes and water cooling, invented in 1923 by M. A. Bonch-Bruevich, are used in powerful radio transmitters all over the world (where semiconductor devices cannot be used).
There are several ways to cool the anode:
· Forced air;
· Forced water;
· Natural (scattering).
To reduce heating of the anode, it is often equipped with ribs or wings.
During the existence of radio tubes, their designs have undergone major changes. The first samples of receiving-amplifying lamps differed in rather significant dimensions and consumed a very high incandescence current. As the design and production technology improved, the size of the lamps decreased, the lamps became more durable, economical, and their quality improved. Receiving-amplifying tubes of our days are very little similar to the first radio tubes, although the basic principles of their operation have not changed.
Modern receiving and amplifying tubes are produced almost exclusively of the finger type (5-7 centimeters long). Internal fittings and leads of all electrodes are fixed directly on the flat glass bottom of the lamp and go out in the form of thin but strong pins, located asymmetrically. Each of the pins is connected to a lead of one of the lamp electrodes. The connection of the electrodes (pinout) of lamps of the same type is always exactly the same.
To ensure the correct insertion of the lamp pins into the socket, two methods are used: an asymmetrical arrangement of the pins and the creation guide key on a plinth made of plastic (Fig. 1e), which fits into the groove located on the panel.
In mass production, lamp anodes are cylindrical and made of copper or heat-resistant alloys. The developed program is intended to simplify and reduce the cost of modeling and production of such electronic tubes.
Designs and designations of electronic tubes on the diagrams
A) 
B) 
V) 
G) 
D) 
E) 
a) - diode with direct heating (two designs and schematic designation);
b) - circuit of a triode with indirect heating (with a third electrode - a grid);
c) - design and schematic designation of a directly heated tetrode.
d) - design and schematic designation of a directly heated pentode.
e) - the octal base of the radio tube with a guide (into the socket) protrusion.
f) is the anode volt-ampere characteristic of the vacuum diode.
Calculation formulas
The temperature distribution over the thickness of the anode wall is determined by solving the differential equation:
on the solution of which the boundary conditions are imposed:
On the inner (heated) surface:
(2)
On the outer (cooled) surface:
(3)
with the initial condition: T (r, 0) = T o = 300 о K. (4)
Equation (1) is integrated until the steady state is reached (heating is completed), i.e. the condition is satisfied 
.
In equation (3): ε is the emissivity of the surface; σ о = 5.67 * 10 -12 - Stefan-Boltzmann constant.
According to the results of integration of equation (1), the thermal voltage in the anode is calculated as:
(5)
T av. (r, t) is the average temperature of the anode in the section with the coordinate r.
The integral in equation (5) is calculated by the Simpson method:
Where is the number of splits n= 2m is even, and the step is h = b-a / 2m. M is the number of spatial intervals.
Formulas for calculating temperatures in the finite-difference representation:
Boundary conditions on the anode surfaces:
R int. : 
. (2’)
R out .: 
(3’)
Here: i, j - numbers of space and time intervals, k - outer wall;
Δr and Δ t are the steps of the space-time grid in coordinate and in time;
n is the number of spatial intervals within the thickness of the anode wall (R nar - R vn).
Designations accepted in the project:
R bunk, R int. - outer and inner radii of the anode (cm);
t - operating time after turning on the glow (sec);
r - coordinate in the cross section of the anode (cm); R int. ≤ r ≤ R bunk
T (r, t) - temperature in the section with the coordinate ‘r’ at the moment ‘t’;
λ - thermal conductivity of the anode material (W / cm * deg.);
α is the thermal diffusivity of the anode material (copper = 1.1);
E - modulus of elasticity (kg / cm²);
α t - coefficient of linear expansion (1 / deg);
ε – surface emissivity;
σ about = 5.67 * 10 -12 (W / cm 2 deg 4) - Stefan-Boltzmann constant;
q is the power supplied to the anode (W / cm²);
T 0 - ambient temperature (degrees K).
Analysis of solution methods
Differential equation (1) - (3), (4) can be solved in two ways: an implicit (absolutely convergent) method and an explicit (relatively convergent) finite-difference approximation method. The difference between these methods is that in the implicit method, the step Δt is set by any, and in the explicit method it is limited and taken very small.
This implies a difference in the conditions of stability of the schemes:.
In the explicit scheme ω<1/2, а в неявной схеме ω не ограничена. Это приводит к тому, что в явной схеме значение температуры в данный момент времени находится с помощью значения температуры в предыдущий момент времени, а в неявной схеме значение температуры в данный момент времени находится с помощью значения температуры в тот же момент времени.
The equation of the implicit scheme cannot be solved immediately, it is necessary to compose a system of equations, which greatly complicates the program scheme. The advantage of the implicit scheme is that by specifying the desired step, you can drastically reduce the number of iterations, while in the explicit method the number of iterations will be tens of thousands. However, given the modern speed of computers, the difference of several thousand iterations during program operation will not be even a second, and a simple and convenient algorithm contributes to better and faster writing and debugging of the program. Therefore, when developing this program, an explicit method of finite-difference approximation was used.
