Friday, 25 September 2015



The oscilloscope is a remarkably wide range of electronic measuring instruments. It can invisible electrical signal is converted into a visible image, the change process easier for people to study a variety of electrical phenomena. Oscilloscope use a narrow, high-speed electrons from the electron beam hitting phosphor coated screen surface, can produce tiny points of light (which is the traditional analog oscilloscope works.

Under the influence of the measured signal, the electron beam is like the tip of a pen, can depict the change in the instantaneous value of the measured signal curve in the screen surface. Oscilloscope can observe a variety of different signal amplitude versus time waveform graph, you can also use it to test a variety of power, such as voltage, current, frequency, phase, amplitude modulation, and so on.
The instrument used to measure the shape of the wave alternating current or pulsed current, the tube amplifier, sweep oscillator, a cathode ray tube and other components. In addition to observing current waveform, but can also be measured frequency, voltage strength. Where can become electrical effects of periodic physical processes can be observed with an oscilloscope

Analog oscilloscope uses an analog circuit (CRT, which is based on the electron gun) the electron gun to the screen emit electrons, emitted electrons formed by electron beam focusing, and hit the screen. The inner surface of the screen is coated with a fluorescent material, so that the electron beam hit the spot will shine.

Digital oscilloscope is a series of technical data collection, A / D conversion, software programming and other manufactured high-performance oscilloscope. Digital oscilloscope works by analog converter (ADC) to the measured voltage is converted to digital information. Digital oscilloscope captured waveform is a series of samples, and the samples are stored, the storage limit is determined whether the accumulated waveform sample value can be depicted so far, then, digital oscilloscope waveform reconstruction. Digital oscilloscopes can be divided into digital storage oscilloscope (DSO), digital phosphor oscilloscope (DPO) and sampling oscilloscopes.

Friday, 18 September 2015

Very High Frequency VHF

Very High Frequency

VHF Very high frequency (VHF) refers to the 30Mhz to 300MHz band radio waves. Lower than the VHF radio frequency is a high frequency (HF), higher than the VHF radio frequency is UHF (UHF).
Most are used as a VHF radio and television broadcasting, but it is also the aviation and maritime communication channels.

VHF primarily for relatively short-distance transmission, and high-frequency (HF) is different, usually not reflected VHF signal ionosphere, and VHF often affected by environmental factors (such as: topography) on its signal.

VHF omnidirectional range

VHF omnidirectional range (VHF Omni-directional Range, hereinafter referred to as VOR), is a method for aeronautical radio navigation system. Its operating band for the 108.00 MHz -117.95 MHz band is very high, so named. VOR signal transmitted by the transmitter has two: one is fixed phase reference signal; another signal phase angle around the circumference with the beacon is continuously changing, that phase of the signal emitted by each angle is different a. To 360 degrees (pointing to magnetic north) and the reference signal is transmitted in phase (phase difference is 0), and to 180 degrees (pointing to magnetic south pole) transmitted signal with a reference signal phase difference of 180 degrees. VOR receiver on the aircraft according to the phase difference between two signals received can be calculated in the signal itself beacon to which one angle emission. VOR usually rangefinder (DME) with the installation site, in the direction of information supplied to the aircraft, while also providing distance information to aircraft navigation station, the location of such aircraft can be determined only down.

Thursday, 10 September 2015

Ultra High Frequency UHF


 The UHF bandwidth, signal transmitted from the transmitter out of the ground and did not return by the ionosphere to the ground; they are always sent to the universe. Instead, the signal transmitted from the universe always penetrate the ionosphere to reach the ground. Lower frequency users are more familiar with the global "shortwave" UHF spread in not being understood. UHF troposphere can cause bending, pipes, and diffusion, will significantly expand the communication range of the visible range. Aurora, atmospheric scattering, and EME propagation can sometimes be observed, but these models cannot provide reliable communications, they are only interested in amateur radio enthusiasts only. In the upper part of the bandwidth, the wave can focus and calibration by suitably sized dish antenna.

UHF bandwidth can be widely used in satellite communications and broadcasting, cellular telephone and paging systems, as well as third-generation wireless range. Because of the high frequency and wide bandwidths (from low to high have 2.7GHz span), the broadband frequency modulation and spread very practical, channel and sub-band wireless-band super high frequency portion through the International Telecommunication Union (ITU) for distribution.

UHF therapy is the use of the human body without side effects of ultra-high-frequency current, directly on the skin lesions organizations, finely layered and produce complete gasification, an intuitive lesions can be removed. As the instrument precision coupled with the unique operator tactics and operational skills, which greatly reduces the damage to normal tissue, can inhibit scarring UHF mast cells and collagen fibers, and has a bactericidal, veridical, homeostasis anti-inflammatory effect, so to maintain normal tissue wound healing smooth, easy to produce scars.

UHF ultra heat treatment is the lesion tissue by vaporization, lesions in the skin requires what level to what level, so after treatment scab scab off a wound, in the meantime pay attention to the protection of the wound, not wet and a collision. After the scab off the tender skin to prevent ultraviolet radiation, skin care more appropriate diet containing foods rich in vitamins. Dermis lesions recovery needs with few physical scars scar prevention treatment.
As for efficacy, UHF technology overcomes high-frequency electric, laser, freezing, corrosion and other traditional methods of drug recur shortcomings scars, making the treatment of the skin lesion reaches perfection.

Friday, 4 September 2015

CCTV Cameras

CCTV Cameras

Closed Circuit Television (CCTV) an image communication systems. Its signal from the source is transmitted only to pre-arranged point in communication with the source of a particular television. Widely used in a number of different types of monitoring work, education, videoconferencing.

Working principle

CCTV is open television broadcasting stations relative. Broadcast radio and cable broadcasting sub-two, open broadcast television equivalent of radio broadcasting (users get the TV signal from the antenna), it is equivalent to a wired CCTV broadcast (TV mode: TV signal from a satellite transmission side transmitted via cable specify the user). It is the transmission of television signals through wires. It is mainly converts audio and video signals into a radio frequency signal (i.e., a channel), so as to transfer the CCTV system.
CCTV generally refers to television for other than broadcasting, such as television industry, military television, medical TV, underwater television.

Surveillance system

CCTV extremely wide range of applications, and are growing at an unprecedented rate, we can say in all sectors of the national economy, the use of modern technology where all are inseparable from CCTV.

CCTV security technology to prevent the system is an important component is an advanced, highly integrated system of prevention capabilities, it can by remote control cameras and auxiliary equipment (lenses, pan, etc.) is monitored directly Watch place all the circumstances, but also can be linked with other security technology to guard against running anti-theft alarm system and other systems to prevent the ability to be more powerful. Technical requirements CCTV systems are mainly: the camera's resolution, the transmission bandwidth of the system, the video signal to noise ratio, standard TV signals and cameras.

Saturday, 29 August 2015


Photodiode is a way to light according to use, into a current or voltage signal light detector.  Common conventional solar cells are through a large area of the photodiode to produce electricity.
Photodiode with the conventional semiconductor diodes are similar, but the photodiode can be directly exposed in the vicinity of the light source or through a transparent small window, optical fiber package, to allow light to reach the light-sensitive area of this device to detect light signals. Many used to design a photodiode using a PIN diode junction, rather than the general PN junction, to increase the response speed of the device on the signal. Photodiodes are often designed to operate in a reverse bias state.

Infrastructure is typically a photodiode PN junction or a PIN junction. When a photon with sufficient energy shock to the diode, it will excite an electron to produce free electrons and there is a positively charged holes. Such a mechanism is also known as photoconductivity. If the photon absorption occurs in the junction depletion layer, the internal electric field in the region will eliminate the barriers between them, so that the hole can move in the direction of the anode, cathode electrons toward the direction of motion, so the photocurrent arises. The actual dark current and photocurrent is integrated light generated current, and therefore the dark current must be minimized to improve device sensitivity to light.

Photovoltaic mode

When the current bias is 0:00 photodiode in photovoltaic mode, then out of the photodiode is suppressed ends a potential difference accumulated to a certain value. (Solar cell)

Photoconductive mode

When operating in this mode, the photodiode is reverse biased often dramatically reduces the response time, but the noise had to increase the cost. At the same time, the width of the depletion layer is increased, thereby reducing the junction capacitance, also makes it possible to reduce the response time. Reverse bias will cause small amounts of current (saturation current), the current and the photocurrent in the same direction. For specific spectral distribution between the photocurrent and the incident light is linearly proportional to the luminance.

Other operating modes

 Conventional of avalanche photodiode having a structure similar to a photodiode, but requires much higher reverse bias voltage. This will allow the carriers of light generated by the avalanche breakdown substantial increase, resulting in internal gain in the photodiode inside, thereby further improving the response rate of the device.

Thursday, 27 August 2015

Magnetic-core memory

Magnetic-core memory

Magnetic-core memory (English: Magnetic Core Memory) is an early form of computer memory. Magnetic-core memory using memory-magnetic material, its principle is: the magnetic ring (core) with magnetic or non-magnetic properties of the state, to represent the 1 or 0 bit, a long string of 1 or 0 on behalf of the combination of information to be stored.

Magnetic-core memory is a random access memory (Random Access Memory), the computer can assume the role of main memory. Compared to the vacuum tube, the magnetic-core memory power, nor life issues vacuum tube. When the computer into the semiconductor era, there is still a considerable period of time, magnetic-core memory continued role as the main memory. Also, because the magnetic-core memory is non-volatile memory (Non-volatile Memory), one of its features are: Even when the machine or power outage, as long as there are no errors write signal occurs, still can retain its contents.

For magnetic-core memory have an important contribution to the Dr. Wang An, who is also the founder of Wang Laboratories. He invented a reading that is written (write-after-read cycle), to solve one of the important issues on the core body application that will be read at the same time can not erase the memory retains data problems, and later made the relevant patent.
Although the semiconductor memory used today has been a long, but sometimes still use the traditional name, also known as Memory Core, one obvious example is the Core Dump: In the program crashes and abort to save main memory contents up to for debugging purposes.

Sunday, 23 August 2015



Magnet can attract iron and its outer magnetic field is generated objects. Magnet means narrow magnetite ore products, broadly refers to the use of magnets to generate a magnetic field of an object or device. As a magnetic dipole magnet that attracts ferromagnetic materials such as iron, nickel and cobalt and other metals.  Poles are judged by a thread hanging magnet, called the finger pointing to the North Pole or N-pole, pointing to the South Pole as a guide pole or S pole. (If you want to become a big magnet Earth is currently Earth's magnetic north pole is S pole, the geomagnetic South Pole is the N pole.) Magnet is different poles attract, with the exclusion pole. And refers to the Arctic polar attraction guide, guide pole and guide poles repel, repel finger Arctic and Arctic finger.

Permanent magnets and magnet divided into non-permanent magnets. Natural, also known as lodestone permanent magnet, a permanent magnet may be manufactured by hand (the strongest magnets are neodymium magnets). Only non-permanent magnets have magnetic properties under certain conditions, usually in the form of electromagnets to produce, that is, the use of electric current to strengthen its field.

Non-magnetized magnet inside the magnetic molecules (molecular magnets theory) is randomly arranged, arranged in the magnetization process after the magnetic molecules have rules. In this case, N pole and S pole magnetic molecules will be facing in the same direction so that the magnet has a magnetic and become magnets. At the same time, the presence of the opposite poles of the magnetic poles and an equal amount on the same magnet.



Loudspeakers name suggests is the sound amplification, spread farther mean relatively speaker, microphone sound more penetrating.
Loudspeaker according to its size, usage and purpose can be divided into various types, each with their use advantage. Due to the shape and size of portable loudspeakers, speakers’ constraints, general power is only 3--8W. The wireless microphone wired microphone and volume sizes are various different purposes, and smaller size for teachers, tour guides used to hang at the waist, both hands to play more freely, its power is generally also 3W-8W. Bulky for outdoor activities, summer camps, extracurricular lectures and other high traffic areas, the power at 35W --- 95W. Lithium battery according to the type of loudspeaker is made using a classification. It solves the problem of pollution on the environment of traditional batteries, which is used mainly in the mobile phone supply lithium-ion technology to the loudspeaker.

Traditional loudspeakers, through universal, homogeneous competition in recent years, have brought the market price shopping, so that companies are increasingly emphasis on cost rather than quality. Blind pursuit of cost, not only contribute to sound quality cannot be improved, but also makes noise noise increases, to bring a certain degree of physical and mental damage to the user.

Poor sound quality, cannot meet the standard of living has been increasing gradually increasing consumer demand, the market needs to product upgrades. The new "sub-spreader" because the use of crossover broadcast technology to effectively solve the traditional loudspeaker sound rushed, fried, thick, shortcomings. You can enhance the soft and delicate, reduce noise, so sound quality is more stress. The audience does not cause dizziness, irritability, rapid heartbeat, high blood pressure, and entertainment at the same time to feel more pleasure, more physical and mental health. Sub-spreader enables high bass harmony echo, microphone input sound, but also can play a more realistic sound, so seize the audience, enhance the sense of affinity.

Wednesday, 19 August 2015

Hybrid integrated circuits

Hybrid integrated circuits

Hybrid integrated circuits are then integrated semiconductor integrated circuit external components, or said secondary integration. It is composed of a semiconductor integrated process and thick (thin) film technology combined and integrated circuits made of semiconductor integrated circuits, it is also one of the miniaturization of electronic equipment, the main way to achieve.

Hybrid integrated circuits including the thick-film, hybrid integrated circuits and thin film, thick-film hybrid integrated circuits. Thick-film hybrid integrated circuits is an insulating substrate (typically ceramic) as the substrate of the circuit, and the first conductor network resistance, capacitance and other components using serigraphy, plasma spraying and other craft printed on the substrate surface, then use the WB, TAB , FCB and reflow soldering and other processes, the other components (such as integrated circuits, sensors, other functional elements, etc.) assembled on a ceramic substrate, and then connect the output pin, and finally as a whole package, the formation of a fully functional circuit products. Known as a thick film integrated circuit or directly called thick.

Film hybrid integrated circuit is the use of thin-film vacuum deposition techniques, sputtering, photolithography and other basic process, the electronic components of the circuit in the form of film products in the production of circuits formed on an insulating substrate.

Tuesday, 18 August 2015

Programmable DC Electronic Load

programmable DC Electronic Load

Programmable DC Electronic Load is the principle of the flux guide or the control of the power MOSFET transistors (duty ratio of the size of the volume), the power dissipated by the power consumption of the power tube apparatus which can accurately detect the load voltage, load current precise adjustment, while analog load short-circuit, an analog resistive and inductive load is capacitive, capacitive load current rise time. Debugging detect general switching power supply is indispensable.

Programmable DC electronic load can simulate real-world loads (appliances). It has a constant current, constant resistance, constant voltage and constant power capabilities, as well as short circuit, over current, dynamic, etc., it should be said that all power manufacturers will be useful, but also must have. Electronic load into DC electronic load and AC electronic load, electronic load due to the application surface problem, this paper introduces the DC electronic loads.

1. Voltage, current and power of choice

According to the output characteristics of the device under test to select electronic load: voltage, current, power and accuracy of the testing requirements. Programmable DC Electronic Load Module can only work when tested alone or parallel operation, the series for the module is very dangerous. So ideal state is that all requirements are within the range single group, followed by multiple modules connected in parallel to achieve the selection. That is, when the voltage of the selected module must meet the test requirements. Individual modules or the full sum of the current and power box is installed to meet the testing requirements.

2. Accuracy and resolution choices

Accuracy and resolution is an important parameter index electronic load. Meaning accuracy of different representations of programmable DC electronic load.

Friday, 7 August 2015



Capacitor referred capacitors; it is also a major element of the electronic circuit components. It can store electrical energy, with the charge, discharge and through the exchange, DC-blocking properties. In a sense, a bit like a capacitor battery. Although both work in very different ways, but they can store energy.

Battery has two electrodes inside the battery, so that a chemical reaction to produce electron electrode, the other electrode of the electron absorption. The capacitor will have a much simpler, it does not produce electron - it just to store electrons. It is one of the indispensable basic elements of the extensive use of various types of electronic equipment. Various capacitors in the circuit can play different roles, such as coupling and DC blocking, bypass, rectifier filter, high-frequency filter, tuning, storage and division and so on. The capacitor should be selected according to the circuit voltage, frequency, waveform, AC and DC components of temperature and humidity conditions.
Capacitor, typically referred to its ability to hold a charge capacitance, denoted by the letter C.   Capacitors, by definition, is 'loaded container electricity', it is a device receiving the charge. English name: capacitor. Capacitor is one of a large number of electronic components used in electronic equipment; it is widely used in the circuit compartment straight cross-connection, coupling, bypass, filtering, tuning circuits, energy conversion and control.

The capacitance of the capacitor is different. Capacitance basic physical quantities, the symbol C, the unit is F (farad).

General formula C = Q / U parallel plate capacitor special formula: electric field strength between the plates E = U / d, the capacitor capacitance of the formula C = εS / 4πkd.

Thursday, 6 August 2015

Amplitude modulation

AM Signals

Amplitude modulation (AM) also referred to as amplitude, by varying the amplitude of the output signal, to achieve the purpose of transmitting information. General changes in the amplitude modulation of the high-frequency end of the output signal and the original signal into a certain function, demodulation end demodulates and outputs the original signal.

In fact, a function is generally proportional relationship. The greatest benefit of this modulation is the modulation and demodulation is very simple, just a diode and a capacitor can, of course, the biggest drawback is the relatively large distortion, while more sensitive to interference, relatively speaking, is a relatively old technology. But technology does not mean that the old applications are not widespread, there are still many areas of application, such as a radio (AM radio) and Aeronautical Radio, Especially in the field of aviation radio, the traveling speed of the aircraft very quickly, quicker fighter, for FM, the Doppler effect is too big, it will affect communications, and AM is not affected by the Doppler effect, it can not be replaced. At the same time there are some improvements AM techniques, such as single sideband modulation (also known as single sideband), residual sideband modulation (Vestigial Side Band, VSB), and amplitude modulation multiple variants such as the current amplitude is widely used in a mobile communication digital modulation.

Saturday, 1 August 2015

Dipole antenna

Dipole antenna

Dipole antenna used to transmit and receive signals of fixed frequency. Although the usual measurements are used in wideband antenna, but the venue and the measurement antenna attenuation coefficients are required to use a dipole antenna. Dipole antenna in the frequency range 30MHz ~ 4GHz. Which is a set of precise VHAP and UHAP dipole antenna is especially suitable for measuring site attenuation and antenna factor. Meanwhile, the antenna for the Japanese VCCI standards organizations designated only dedicated antenna anechoic chambers and open-field site attenuation measurement and the like. The antenna is used by many laboratories, as antenna standard laboratories.

Vertical antenna is actually a dipole antenna. Dipole antenna consists of two conductors, each 1/4 wavelength, i.e., the total length of a half wavelength of the antenna. So dipole antenna, also called half-wave dipole. The transducer can be a dipole antenna horizontal position, vertical position may be. Its pattern to the feeding point of symmetry. Feed point in the center of the half-wave vibrator. Feed point impedance is purely resistive, approximate 75Ω (approximately 73Ω). If the two 1/4 wavelength resonator extended and then folded back to the center, and joined together, then it became a folded dipole antenna, referred to as folded vibrator.

Folded dipole antenna impedance is purely resistive approximate 300Ω (about 290Ω), shows a high input impedance, high impedance transmission antenna feeder parallel constitute use in many occasions. The dipole antenna straight up, perpendicular to the ground, then a vertical antenna. If the "remove" the lower part of the 1 / 4λ oscillator, the asymmetrically vertical antenna. Common vertical antenna are asymmetric antenna, isotropic in the horizontal direction.
A special.This antenna has a special name called Marconi antenna. R7000 receiver and other antenna configurations belong to this antenna.

Wednesday, 29 July 2015



Battery, defined in a narrow sense is itself generally stored chemical energy into electrical energy device, broadly defined as pre-stored energy from the device into external power available. So, like solar conversion without storage function only means not a battery. Other names have batteries, batteries, and Chinese have storage tanks and bottles intended effect.
Historical battery can be traced back two thousand years ago in ancient Iraq era. In the capital Baghdad found unglazed clay pots. It is a copper and iron battery.
Type of Batteries

Chemical batteries, electrochemical cell means by an oxidation-reduction reaction, the positive electrode, a negative electrode active material of chemical energy, into electrical energy for a class of devices. Common redox reaction with different oxidation and reduction reactions that are carried out separately, the oxidation of the negative electrode, the reduction in the positive electrode, and the electron gains and losses is carried out by an external circuit, thus forming a current.

Dry and liquid batteries distinguish battery is limited to that period of early development. The first battery of a glass container filled with an electrolyte and two electrodes. Later we introduced to paste electrolyte-based batteries, also known as dry batteries.

Disposable batteries (Primary Battery), commonly known as "disposable" cell, because after their power runs out, can not be recharged using only discarded. Common disposable batteries include:
Manganese battery - voltage of about 1.5V, the battery capacity is low, the battery can output low, almost alkaline manganese batteries are replaced, except after long-term storage is not leaking harmful corrosive liquids, so still in use in low electricity requires long-term use of devices simultaneously, such as clock, infrared remote control and so on.
Alkaline manganese battery - voltage of about 1.5V, battery capacity and output of the battery than the zinc-manganese batteries is high, but less than nickel-metal hydride battery, after long-term storage of hazardous leaking corrosive liquids.

Other disposable batteries include zinc batteries, zinc-air battery, zinc-mercury batteries, mercury batteries, battery and magnesium hydroxide, manganese batteries.
Rechargeable batteries, also known as the secondary battery (Secondary battery), batteries. Rechargeable battery according to different production materials and workmanship, the advantage can be reused many times after it is charged, they can be full charged and discharged more than two times or even up to 2500, the rechargeable battery output current (load force) than large part disposable batteries is high. Common types are:

Lead-acid battery - voltage of about 12V, low capacity, but can output more power, battery, often used in automobiles for starting the engine to use, or for uninterruptible power system (UPS), radios, communications machine.

Friday, 24 July 2015

Avalanche diode

Avalanche diode

Avalanche diode negative resistance is generated solid microwave devices using semiconductor structure carrier impact ionization and the transit time of two physical effects.

PN junction one-way conductivity, resistivity is small, a large reverse resistance.

When the reverse voltage is increased to a certain value, reverse current suddenly increases. It is the reverse electrical breakdown. It points avalanche and Zener breakdown.

Avalanche breakdown PN junction reverse voltage is increased to a value, like an avalanche multiplication of carriers, as far and fast increase.

Take advantage of this feature is to make the crystal diode avalanche diode
Major domestic manufacturers have Haiou light OTRON brand.

Avalanche breakdown in the electric field, the carrier energy increases constantly collide with atoms in the crystal, so that a covalent bond is formed in the electron excitation of free electron - hole pairs. New carriers generated by the collision and free electron - hole pairs, which is a multiplier effect. 1 Health 2,2 Alive 4, the same increase as the avalanche of carriers.

Zener breakdown is completely different, at high reverse voltage, there is a strong electric field PN junction, which can directly destroy covalently bound electrons will be separated to form an electron - hole pair formed a large reverse current. Zener breakdown electric field strength required great!

Only in impurity concentration particularly large PN junction to do the job.
It is in the applied voltage can produce high-frequency oscillation of transistors. High-frequency oscillations generated works: the use of avalanche breakdown of the crystal injected carriers, because the wafer carrier transit will take some time, so its current lags the voltage, It is often used in the field of microwave oscillation circuit.

Tuesday, 21 July 2015



Ampere, referred to security, is the International System of Units in the current strength of the unit, the symbol is A. at the same time it is also one of the seven basic units of the International System of Units . Ampere is the French mathematician and physicist Andre - Marie Ampere named, in honor of his contribution in terms of classical electromagnetism.

The actual situation, ampere is a unit of time cross-sectional measure the amount of charge through a conductor. Within one second by the cross section of 1 coulomb charge (6.241 × 1018 electrons in the charge), the current size of 1 amp
small current can be expressed in mA, microamps and other units.

1 Amp (A) = 1000  (mA)

1 milliamperes (mA) = 1000 microamps (μA)

Ampere force law of proof in a parallel existence of two straight power-attraction or repulsion between wires. This force is used to formally defined amps:
Vacuum, in two parallel infinitely long straight conductor cross-section can be ignored, and the distance of one meter. Through the same size, the same constant current direction in the two wires, when the wire is attractive per meter by 2 × 10-7 Newton, the two wires of the current of one ampere.

Ampere was originally defined as a centimeter - tenth - second current unit abampere - grams. Its size is so determined to ensure the international system of units derived from other units ampere value obtained is appropriate.

"International ampere" is an older unit of electric current, defined as the silver nitrate solution to precipitate the current 0.001118000 grams of silver per second. After a more accurate measure found that the current is 0.99985 A.
This unit Ampere and Watt balance and Ohm's law in the unit volts, ohms linked.

Monday, 20 July 2015

Sound System measurements

Sound System measurements

First, the human ear any subjective feelings are "absolutely" objective measurements may be used to represent data, otherwise all the knowledge of cognitive psychology and the psychology of perception on all the deceptive; please do not doubt, even religion and love so complex ideas can be objectively measured, under relatively sound sense of hearing is so simple! But we may not know how the existing capacity measure, or someone else had found and we did not know.
The second, but not a simple physical phenomenon "objective measurement data," mostly psychological phenomenon. This is why the measurement data clearly incorrect, but the listener can feel good to hear, because of the psychological feelings and physical stimulation is not a linear relationship.

To take a simple example: Please find a white paper, starting from the middle of a half will completely blacked out. ok, then you will say, external physical stimuli is not just black and white two properties, what else? It really wrong ...... physiological phenomenon of human vision, through the so-called ZERO CROSSING conversion, you'll find close to the middle boundary, white, more white, black and more black; this is certainly no humans there will be a normal physiological and psychological phenomenon.

Therefore, if we only care about the qualitative and quantitative external physical stimuli, will never forgive restricted to physical stimuli only black and white, do not know the human psychological phenomenon is real, "especially from black to white and black to white and then to special"; Just watch see "only physical stimulation from outside" view of human senses, it is not limited and lost a lot of rich message.

Many people see here say: Behold! Objective measurements useless ...... The more outrageous mistake. Because, objectively measured "absolutely" helpful; you then can not see how there is absolutely subjective, "especially from black to white and black to white and then to special" feeling in a black paper; this feeling, though not on the physical stimulation, but it is absolutely linked to a specific physical stimulus. So the first point I would emphasize: "All the subjective feeling" absolutely "objective measurement data can be used to represent" the only question is: even if we find the correct physical measurement data, how do we "explain" to get corresponding psychological feelings.

Because of the psychological feelings and physical stimulation is not a linear relationship, so for the "physical measurement data" "correct interpretation" even more important than the "right measure." Any physical data are not directly correspond to any sense of hearing, all we need to "correct interpretation"; and this explanation is necessary is an objective, because everyone should all have similar physiological and psychological phenomenon. So, at first glance subjective psychological feelings, still reflects a variety of objective material or social factors, it will never be cool enough to hear so simple.

Thirdly, I hereby personally think: with objective physical measurement is the "basic", is "starting from scratch", is "self-growth start." Even if I did not play a sound people listen to music, I listen to music when I found into a bottleneck and intend to re-start, what to do? Return to the starting point, increasing the "voice" of the objective of the physical message from the start; so he began to desperately play sound.

Friday, 10 July 2015

Cassegrain antenna

Cassegrain antenna

Cassegrain antenna is another commonly used in microwave communication antennas, which evolved from a parabola. Cassegrain antenna consists of three parts, namely the main reflector, sub-reflector and the radiation source. In which a rotating parabolic main reflector, sub-reflector surface of the rotational hyperboloid. Structurally, the focus of a hyperbolic paraboloid focus coincides hyperboloid focal axis coincides with the axis paraboloid focus, and the focus of the radiation source is located on another double curved, as shown below. It was a reflection of the electromagnetic radiation emitted subreflector carried out, the electromagnetic wave reflection to the main reflector, and then after the main reflector reflected plane wave beam obtain directions to achieve directional transmission. Cassegrain antenna works as follows.

When the radiator located hyperboloid of revolution real focal point F1, the rays emitted from F1 after the reflected rays hyperboloid, the equivalent of the virtual focus hyperboloid emitted directly out of the rays. So as long as the focus of the hyperboloid virtual focus coincides with the paraboloid, the sub-reflecting surface can be the main ray reflecting surface is parabolic reflector in a plane wave radiated.

Cassegrain antenna with respect to a parabolic antenna is concerned, it will feed the radiation pattern from the feedforward parabolic manner changed after the feeding mode, which makes the structure of the antenna is more compact, making it more convenient. Also Cassegrain antenna is equivalent to a parabolic antenna with a long focal length, and this can be a long focal length to the distance from the antenna from the focal point of each aperture is nearly constant, thus space radiation attenuation effect on the feeder to be smaller so Cassegrain antenna efficiency is higher than the standard parabolic antenna.

Monday, 6 July 2015

Directional antenna

Directional antenna

Directional antenna refers to the transmitting and receiving electromagnetic waves is particularly strong on one or a few specific direction, while transmitting and receiving electromagnetic waves is zero or a minimum of an antenna in the other direction. Directional transmitting antenna is intended to increase the effective radiated power utilization, increase confidentiality; the main purpose of the use of directional receiving antenna to increase signal strength is enhanced anti-jamming capability.

Directional antenna used to cover a long street, and has the following advantages:

1, has a large forward gain

2, the signal, when the cell behind the cell it would potentially interfere with this feature is useful to inhibit later.

Also worth mentioning is the directional antenna can improve indoor coverage within the micro-cellular coverage in some buildings.
Directional antenna in the horizontal direction in Fig showed a range of angles of radiation, which is usually referred to directional. Like with omnidirectional antenna, beam width is smaller, the greater the gain. Directional antenna in a communication system generally used in communication distance, small-coverage, high target density, high frequency utilization environment.

We may also like this to think about the relationship between omnidirectional antennas and directional antennas: All will transmit a signal to the antenna in all directions around, you can receive the signals, directional antenna like antenna mask after a bowl-shaped reflective surface, signals can only be transmitted to the front, towards the back of the signal is blocked by the reflective surface and is reflected to the front, reinforced front signal strength.

Saturday, 4 July 2015



Ohm meter (ohmmeter), also known as resistance table, is a specialized instrument for measuring electrical resistance. Electromechanical components impede the flow of current nature, called the resistance in ohms. Milliohm meter special measuring small resistance; and megohms meter, also known as Megaohmmeter, or high table, the special measure very great resistance.

Ohmmeter original design, with a small battery voltage is applied to the resistor, and, with a modified galvanometer (galvanometer) to measure the current flowing through the resistor. Galvanometer scale marked change in ohms. Due to the constant voltage applied to the battery to ensure that the current will be inversely proportional to the resistance. So, know the current, you can get resistance.

As shown right ohmmeter scale representation from zero to infinity. When in contact with the two probes, the resistance is zero; when separated, the resistance is infinite. The majority of the number of domains between the two numbers to a logarithmic scale mode of expression. So, assuming the battery of emf 6 \ volt \, \!, You want to set current 4 \ mA \, \!, The internal resistance must be adjusted to 1.5 \ k \ Omega \, \!. When two probe together, the total resistance is 1.5 \ k \ Omega \, \!, Current is 4 \ mA \, \!, Ohm meter display shows the resistance to needle 0 \ k \ Omega \, \! .

When displaying the needle in the middle of zero and infinity, the current is 2 \ mA \, \!. So, the total resistance is 3 \ k \ Omega \, \!, The measured resistance is 1.5 \ k \ Omega \, \!.
When displaying the needle in the middle between zero and 1.5 \ k \ Omega \, \! When current is 3 \ mA \, \!. So, the total resistance is 2 \ k \ Omega \, \!, The measured resistance is 500 \ \ Omega \, \!.
When the display needle 1.5 \ k \ Omega \, \! In the middle with the infinite, the current is 1 \ mA \, \!. So, the total resistance is 6 \ k \ Omega \, \!, The measured resistance is 4.5 \ k \ Omega \, \!.

This ohmmeter has an important drawback is that it requires a very stable battery voltage. After a period of use, the voltage will gradually decrease. This will make ohm meter lose accuracy. When in contact with the two probes, the display no longer needle will point 0 \ k \ Omega \, \!, And will point to the growing resistance.

Sunday, 28 June 2015



Diode is a kind of asymmetrical double electrode conductance electronic components. Ideal diode in the forward conductive between its two electrodes (anode and cathode) have infinitely small resistance, and the reverse when there are infinite resistance, ie, the current is allowed to flow from a single direction only through the diode.

Diode having an anode and a cathode two terminals, current can only flow to a single direction. That is, the cathode current may flow from the anode, and not from the cathode to the anode. To diode possess one-way nature of such applications, often called "rectification" function. In the vacuum tube, with a voltage applied between the electrodes so that hot electrons can reach the anode from the cathode, thus rectifying effect. The alternating current into direct current, comprising a radio receiver for a radio signal modulation, are accomplished by the rectifier.

Reverse circulation because of its forward blocking characteristics, diode can be thought of as an electronic version of a check valve. However, in practice, diodes and do not exhibit such a perfect switch resistance, but showing a more complex non-linear electrical characteristics - which are determined by the specific type of diode technology. In general, only in the forward reaches the threshold voltage, the diode will start to work (this state is called forward bias) A change in the voltage drop across the diode is forward biased only to do with current, and is a function of temperature. Therefore, this feature can be used to the temperature sensor or reference voltage.
Semiconductor diode non-linear current - voltage characteristics, thereby forming an impurity may be different depending on the selected semiconductor material and a semiconductor doped with different impurities to alter.

Diode characteristics after the change in the use of switches used in addition to the way, there are many other features, such as: used to adjust the voltage (Zener diode), thereby limiting the high-voltage protection circuit (APD), radio tuner (varactor), generating a radio frequency oscillation (tunnel diode, Gunn diode, IMPATT diode) and generate light (light emitting diode).

Semiconductor diode, there is the use of P-type and N-type joints PN junction of two semiconductor effect, but also the type of Schottky rectifying action to achieve the effect produced by the use of a metal-semiconductor bonding. If the PN junction type diode, the P-type anode side is, N-type side is a cathode.

Saturday, 27 June 2015

Power Supply

Power Supply

Power Supply  usually it refers to the source of electricity. It could be a system or device for supplying electric power, or other device capable of providing energy to the load output of the power supply.

Power supply to other forms of energy into electrical energy device called a power supply.
Generator can convert mechanical energy into electrical energy, batteries can convert chemical energy into electrical energy generator battery itself is not charged, its positive and negative charges respectively poles, positive and negative charge generated by the voltage (current voltage is under the effect of the charge directional movement formed), there would have been in charge of the conductor to produce current only voltage can, when the battery is connected to the conductor to generate electricity poles and the release of positive and negative charge out, when the charge is dissipated, also do you charge flow (pressure) disappeared. batteries and other known power supply. Through the transformer and rectifier, the alternating current into direct current power supply device called a rectifier power. To provide an electronic device called a signal source. Transistor can be amplified signal sent, again amplified signal is transmitted to the back of the circuit to go. Transistor on the back of the circuit can also be seen as a signal source. Rectifier power supply, sometimes called the power supply source.

Friday, 26 June 2015



LED-backlit LCD TV is the use of light-emitting diodes (LED) as a liquid crystal display backlight TV. this does not mean that television use light-emitting diodes for image display With the light-emitting diode TVs increasingly competitive market, coupled with the light emitting diode applications matures, various TV manufacturers have actively into the light-emitting diode-backlit LCD TV, an attempt at a home television on the occasion of regime change can come out on top.

Types of light-emitting diode backlight technology;

LED back-light technology can be divided into direct type (direct back-lit or full LED array back-lit) and side-illuminated (edge LED back-lit) are two, and light-emitting diodes which are used in direct-divided into white light diode and red, green and blue light-emitting diode two kinds.

1-Direct type light-emitting diode backlight technology;

Direct type LED back-light technology is the more pieces of light-emitting diodes arranged in an array, placed behind the LCD diffuser and directly illuminated LCD. Thus, the direct type can comply with different parts of the screen brightness changes quickly fine-tune the brightness of the light-emitting diode, greatly improve the level of dynamic contrast ratio to the plasma display. The disadvantage is the need to use a large number of light-emitting diodes, and higher prices.
Had a direct type LED back-light use white LED, also used red, green and blue color LEDs (RGB LED) using RGB LED can have a wider spectrum of light, that have a wider color field.

2-Side-light emitting diode backlight technology;

Side-light emitting diode backlight technology is to white light emitting diodes on four sides of the LCD, LCD size with the LCD after a close reflective film, light emitting diodes LCD with photos from the gap between the reflective film inside, reflective film on a specially designed micro LED lighting pattern can come back after the LCD according to the light for 90 ° reflection. These reflective sheet was fine in the case without astigmatism sheet also enables the average light-emitting diode light distribution to shine LCD back.

Conventional side-illuminated light-emitting diode backlight brightness compliance can not quickly adjust brightness change different parts of the screen, but recent changes in vendor compliance screen success with the side illuminated LED technology limited quickly adjust brightness.

Tuesday, 23 June 2015

LED or light emitting diode


LED is a light emitting diode (Light Emitting Diode, LED) for short, also known as light-emitting diodes, the semiconductor component is generally used as the indicator, a display panel, which not only can efficiently direct contact Mitutoyo photovoltaic electrical energy into light energy, while the operating voltage is low (some only a little over volts).

And have the most up to tens of thousands of hours to 100,000 hours of life, but have not as conventional bulbs fragile, and the advantages of energy saving.

It is a semiconductor diode that can put energy into light energy; often abbreviated is an LED. Like ordinary diode emitting diode is a PN junction composed, also with unidirectional conductivity. When coupled to the light emitting diode forward voltage, injected into the holes from the P region and the N zone area by the N electrons injected into the P region, near the PN junction within a few microns were empty and Electronics and P region of the N region Point complex, resulting in the spontaneous emission of fluorescence. Energy states of electrons and holes which are different in different semiconductor materials. When an electron and hole recombination energy released somewhat different, more energy released, the shorter the wavelength of light is emitted. Commonly used hair red, green or yellow light diode.

Friday, 19 June 2015

Liquid crystal display LCD


Liquid Crystal Display, abbreviations: LCD flat thin display device, by a number of color or monochrome pixel composition, placed in front of the light source or reflector side. Low-power liquid crystal display, so much favored by engineers, for battery of electronic equipment.

Each pixel of the liquid crystal display consists of the following parts: two layers of liquid crystal molecules suspended in a transparent electrode (indium tin oxide) between a columns outside on both sides with two mutually perpendicular polarization directions of the polarizing filters. If there is no liquid crystal between the electrodes, wherein the light through a polarizing filter whose polarization direction of the sheet, and the second polarizer perfectly vertical, and therefore is completely blocked. However, if the polarization direction of light through a polarizing filter sheet is rotating LCD, then it can be filtered through another polarizing sheet. Liquid crystal rotates the polarization direction of the light can be controlled by an electrostatic field, in order to achieve light control.

Liquid crystal molecules are easily affected by the induced charge arising from the applied electric field. A small amount of electric charge is applied to the transparent electrode of each pixel or sub-pixel to produce an electrostatic field, the liquid crystal molecules are induced by the electrostatic field induced charge and static torque, leaving the liquid crystal molecules are originally aligned to produce a rotating change, so also changed by rotating the amplitude of light. Changing the certain angle, it is possible through the polarization filters.

Before the charge applied to the transparent electrodes, the liquid crystal molecules are arranged to determine the alignment of the electrode surface, chemical surface electrode may be used as seed crystals. In the most common TN liquid crystal, the liquid crystal vertically aligned upper and lower electrodes. Liquid crystal molecules are spirally arranged, through a polarization filters rotated polarization direction of the light after passing through the LC panel, thereby through another polarizer. In this process, a small portion of the light blocked by the polarizer from the outside appears to be gray. After the charge is applied to the transparent electrodes, the liquid crystal molecules almost completely along the field direction are arranged in parallel, and therefore the direction of polarization of light through a polarizing filter sheet is not rotating, and therefore the light is completely blocked.

Wednesday, 10 June 2015



Multimeter  is a multi-purpose electronic measuring instruments, mainly used to measure the field of physical, electrical, electronic, etc., generally contain ammeter (ammeter), a voltage meter (voltmeter), resistance meter (ohmmeter) and other functions , also known as universal design, multi-meter, multimeters, multimeter or multimeter.

Pointer multimeter known as VOM (Volt-Ohm meter, volt - ohm meter) in English, but this name is not usually used for digital multimeter.

Multimeter with a portable device used for basic troubleshooting, but also a desktop device is placed in a factory or laboratory workbench.

Some meter resolution can reach seven or eight digits; such a device, it often occurs in the laboratory is used as a reference voltage or resistance, or to adjust the standard multi-function performance.

Basic measurement functions:
Current, voltage and resistance measurements, generally regarded as the universal plan of basic functions. Early multimeter manufacturers AVO brand name of these three is the unit of measurement device capable of measuring the abbreviation: Ampere (Ampere), V (Volt), ohms (Ohm)

Generally we have a basic multimeter measurement functions:

DC voltage (DCV)

DC current (DCmA, DCA)

AC voltage (ACV)

Resistance (Ω, KΩ, MΩ)

AC current (ACmA, ACA) not all multimeters have, especially low-level multimeter.
Pointers and digital multimeter:

Pointer multimeter, using a magnetic field deflecting pointer dial, this watch head and the same classic galvanometer; digital multimeter is used to display LCD, vacuum fluorescent display (VFD), LED, OLED, etc. In addition, it also uses digital tube early.

Pointer multimeter on the new and second-hand market are hard to find. But because zero and accurate readings from the instrument panel are prone to error, and difficult to scale subdivision restrictions in accuracy and resolution are not as digital meters. And the digital meter voltage profile with a high input impedance, and can immediately read the number, the pointer meter unless there are marked directly refers to the value of large-scale , It shall be observed and counted within the meaning of the small-scale relations with neighboring large measure, it read really value. However, in some cases, such as speed of response header, easy to quickly outline that value, or the value of the response in terms of jitter, etc., remain some of the advantages, and the internal circuit is simple, easy to learn measuring circuit theory, therefore, part of the some situations or circumstances are still in use. In addition, some digital meters have reacted faster than the number of changes strip show, emulate pointer effects to quickly grasp the changes in the value of the benefit.

In order to improve pointer multimeter input impedance voltage profile and reduce the impact of treatment of the circuit under test, and some high-end pointer multimeter uses vacuum tubes to amplify the input signal, this design is also known as vacuum multimeter voltmeter (VTVM, Vacuum Tube Volt Meters) or vacuum multimeter (VTMM, Vacuum Tube Multimeters). Such as the use FET to amplify the input signal, it is FETVM.

Digital multimeter with digital meter based and is specifically called a digital multimeter (DMM, Digital MultiMeter). In this device, the measured signal is converted into a digital voltage and digital pre-amplifier, and then by the digital display directly display the value; thus avoiding parallax when reading the error caused.

Similarly, better systems and electronic circuit technology, but also to improve the measurement accuracy. General basic accuracy pointer instrument (DC voltage range) between 2% to 5%, the common basic accuracy of 3 to 4%. Digital portable digital multimeter common portable type basic accuracy of 0.5% to 1%, advanced models, it can reach ± 0.025%, and the table device as much as one millionth of accuracy.

Monday, 8 June 2015

Resistor or Resistance

Resistor color code

In electromagnetism, the resistance is the ability of an object to hinder current through to the equation is defined as

R= v/r

Wherein, R is the resistance, V is the voltage across the object, I is the current through the object.
Assuming that the object has a uniform cross-sectional area, the resistance and resistivity, proportional to the length, and inversely proportional to the cross-sectional area.

SI units, the resistance in ohms (Ω, Ohm). Resistance reciprocal conductance in siemens (S).
The temperature is assumed constant, many substances will abide by Ohm's law, objects consisting of these substances, the resistance is constant, not with the current or voltage. These substances referred to as "ohm substance"; failure to comply with Ohm's law matter is "non-ohmic material." R circuit symbol often used to represent, for example: R1, R02, R100 and so on.

Wire like a class of objects, having a low resistance, can be very efficient current transfer, such objects called "conductor." Usually by conductor such as copper, gold and silver-metal manufacturing has excellent conductive properties, or inferior conductive properties of aluminum.

The resistor is a circuit element having a specific resistance. Raw materials used in the preparation of the resistor there are many; what materials should be used, depending on the specified resistance, energy dissipation, and so accurate, and cost factors.

Suppose wire conducting a high frequency alternating current, since the skin effect, the effective cross-sectional area of the wire decreases. Assume several parallel wires together, due to the proximity effect, the effective resistance of each wire will be greater than the resistance of a single wire. For ordinary household AC power, since the frequency is low, the effect is very small, you can ignore these effects.

Friday, 5 June 2015

Direct current

Direct current

Direct Current, DC is the unidirectional flow of electric charge. DC current, by batteries, thermocouples, solar cells or commutator motor generator. Direct current can flow through the conductor such as wire, but may flow through the semiconductor, insulator, or even capable of electron or ion beam shape by vacuum. DC current is constant direction, and thus distinguished from alternating current (AC).

DC current can be called from by using rectifiers, which includes electronic components (usually) or electromechanical components  a current is supplied only on alternating current electric current switching apparatus of the flow in one direction. DC current can be made into an alternating current of the inverter or the motor generator.

The first commercial power transmission (by Thomas Edison in the late nineteenth century, the development of) the use of direct current. Since the DC current significant advantages over alternate transformation and transmission, and today almost all of the AC power distribution. In the mid-1950s, HVDC transmission, is now an option, rather than the long-distance high-voltage AC power system. For applications such as DC third rail power system, AC was assigned to a substation, which uses a rectifier power is converted to direct current.

DC current to charge the battery, and in almost all electronic systems as a power source. A very large number of DC power for the production of aluminum and other electrochemical processes. DC Some railway propulsion, especially in urban areas, is used to transmit large amounts of electricity HVDC on the remote site or an AC power grid interconnection.

Alternating Current

Alternating Current

 Alternating Current, abbreviations: AC refers to the size and direction of the current varies cyclically, running average over a cycle is zero. Unlike direct current does not change direction over time.

Generally sinusoidal waveform. AC can effectively transmit electricity. But in fact there are other applications of waveform, such as triangular wave, square wave. Mains life is having to use the AC sinusoidal waveform.

Once discovered electromagnetic induction, the method generates an alternating current was known. Early finished by the British Michael Faraday (Michael Faraday) developed with the French Hippolyte Pike Xi (Hippolyte Pixii) at all.
In 1882, the British electrician James Gordon built a large two-phase alternators. Lord Kelvin and Sebastian Fei Landi (Sebastian Ziani de Ferranti) developed early alternators, frequency between 100 Hz to 300 Hz.

In 1891, Nikola Tesla made "high frequency" (15,000 Hz) of the alternator patents.
In 1891, the multi-phase AC generator is used to supply current, alternating current frequency thereafter alternator usually designed Hz to 100 Hz in 16 rooms, with an arc lamp, incandescent lamp or electric motor use.

According to the law of electromagnetic induction, when the magnetic field around the conductor changes, the induced current in the conductor. Normally, rotating magnet called the rotor conductor wound on the core of the coil fixed group, called the stator, a magnetic field when it is over, they generate electricity. It called basic machine to generate AC alternator.

Thursday, 4 June 2015

Power Capacitors

Power Capacitors

Power capacitors for power systems and electric equipment capacitors. Any two metallic conductors separated by a dielectric medium, constitute a capacitor. The size of the capacitance of a capacitor, its dielectric properties and geometry between the two plates to decide. When the capacitor is used in the AC voltage.

Power capacitors use can be divided into eight kinds:

 01- shunt capacitor. Formerly known as phase shifting capacitors. Reactive power is mainly used to compensate the inductive load power system to improve power factor, improve voltage quality and reduce line losses.

02- series capacitor. Connected in series with the power frequency high voltage transmission and distribution lines to the distribution of the compensation circuit inductance, improving the system of static and dynamic stability, improve the quality of the line voltage, longer transmission distance and increasing transmission capacity.

03-coupling capacitor. HF communications are mainly used high-voltage power lines, measurement, control, protection, and as a member of extracting electrical energy use.

 04- Breaker capacitors. Formerly known as the equalizing capacitors. Parallel play equalizing effect on fracture in EHV breakers, the voltage between each fracture in the breaking process and even when disconnected, and to improve the extinguishing characteristics of the circuit breaker breaking capacity increase.

05- Electric capacitors. For the frequency range of 40 to 24,000 Hz electric equipment system to improve power factor, improve voltage or frequency circuit characteristics.

06- Pulse capacitors. Mainly from the energy storage effect, it is used as impulse voltage generator, the impact of current generators, test tank circuit breakers and other basic energy storage element.

 07- DC and filter capacitor. For HVDC devices and high-voltage rectifier filter device.

08- Standard capacitor. For high voltage measuring dielectric loss frequency circuit, a capacitor or used as a standard measurement of high voltage capacitor voltage dividing means.

Carved in the power system HV power capacitors (6KV above) and low-voltage power capacitors (400V)

Low Voltage Power Capacitor oil paper divided by nature self-healing power capacitors and power capacitors, power capacitors by function common and intelligent power capacitors do not repeat the general formula, focusing on intelligent power capacitor.

Monday, 1 June 2015



Microphone, also known as An electro-acoustic equipment, is a microphone, a sound transducer converts electrical voltage is generated by sound waves to the electro-acoustic components, and then converted to electricity. For a variety of public address equipment. Microphone wide range of simple circuit.

Analysis of the microphone circuit is mainly controlled by two things: (1) signal transmission loop analysis, relatively simple analysis of various microphone input jack circuits. (2) Analysis of the microphone amplifier, microphone amplifier is a low noise audio amplifier small-signal analysis mic level control circuit is not difficult

The microphone generates an electrical signal by the motion of the magnetic field conductor. Vibrating diaphragm driven by a coil so that the coil in a magnetic field generates an induced current. Features: Firm structure, stable performance, durability, low price; the frequency characteristics of a good, in the frequency range 50-15000Hz flat amplitude-frequency characteristic curve; good point; no DC voltage, easy to use, low noise.

Characteristics, amplitude-frequency characteristic curve flat in the audio frequency range, which is better than the dynamic microphones; non-directional; high sensitivity, low noise, sound soft; the output signal level is relatively large, low distortion, good transient response, this is less than the advantage of dynamic microphones; unstable operating characteristics, low frequency sensitivity with the increase in the use of time and decline, life is short, we need to create a DC power supply is inconvenient to use at work.

There condenser microphone preamplifier, of course you have to have a power supply, due to the volume relationship, the power supply is usually placed outside the microphone.
In addition to supplying the polarization voltage of the capacitor of the diaphragm, but also for the tube or transistor preamplifier supply voltage necessary. We call it the phantom power.

Integrated circuits

Integrated circuits

An integrated circuit (IC), also known as chip or microchip, is a structure of small dimensions of semiconductor material, a few square millimeters of area on which electronic circuits are generally manufactured by photolithography and which is secured in an encapsulated plastic or ceramic. The encapsulation has appropriate metallic conductors for connection between the IC and a printed circuit.

Integrated circuit is a pill or solid chip found in all or most of the necessary electronics embedded in a resin, to perform some function. These components are mostly transistors, although they also contain resistors, diodes, capacitors, etc.
Considering the level of integration (number of components) integrated circuits are classified as:

SSI (Small Scale Integration) small level: less than 12

MSI (Medium Scale Integration) means: 12-99

LSI (Large Scale Integration) Large: 100-9999

VLSI (Very Large Scale Integration) large: from 10 000 to 99 999

ULSI (Ultra Large Scale Integration) ultra large: not less than 100 000

As for the integrated functions, the circuits are classified into two groups:
Analog integrated circuits.
They can consist from simple encapsulated together without bonding between them until complete devices such as amplifiers, oscillators or even complete Radio receivers’ transistors.
Digital integrated circuits.

They can range from simple logic gates (AND, OR, NOT) to the most complicated as microprocessors.

Sunday, 31 May 2015



A transistor - Electronic component of a semiconductor material, usually with three terminals, allowing an input signal to control the current in the electrical circuit. Normally used to amplify, generation and transformation of electrical signals. In general, the transistor is any device that simulates the main feature of the transistor - the signal changes between two different states of the signal change at the gate electrode.

In the field, and current control of bipolar transistors in the output circuit is carried out by changing the input voltage or current. . A small change in the input quantities can lead to much greater change of the output voltage and current. This amplification properties of transistors used in analog technology (analog TV, radio, communication and so on. N.). Currently, analog technology is dominated by bipolar transistors (BT) (international term - BJT, bipolar junction transistor). Another important industry is the digital electronics equipment (logic, memory, processors, computers, digital communications, and so on. N.), Where, in contrast, bipolar transistors are almost entirely driven out of the field.

The first patents on the principle of the FETs were registered in Germany in 1928 (in Canada October 22, 1925) in the name of the Austro-Hungarian physicist Julius Edgar Lilienfeld. In 1934, German physicist Oskar Hile (Eng.) Russian. patented field-effect transistor. Field effect transistors (specifically MOSFETs) are based on a simple electrostatic field effect n physics it is much easier to bipolar transistors, and so they invented and patented long before the bipolar transistors. However, the first MOS transistor, forming the basis of the modern computing industry was made later of the bipolar transistor, 1960. Only in the 90s of XX century MOS technology has become dominate bipolar.

Below is the formal classification of current transistors, where the working fluid is a flow of charge carriers, and the states between which switching devices are determined by the magnitude of the signal: small signal - a big signal, the closed state - open state, which is implemented the binary logic of the transistor. Modern technology can operate not only the electric charge and magnetic moments, the spin of a single electron, phonon and light quanta, quantum states, in general.
The principle of operation and applications of transistors greatly depend on their type and internal structure, so the details of this attributable to appropriate


npn structure "reverse conduction."

pnp structure, "direct conductivity".

Saturday, 30 May 2015

Digital Cameras

Digital Cameras

Digital Camera  an electronic sensor to the optical image is converted into electronic data camera, unlike a conventional camera causes chemical changes on film by light to record an image. "Digital" is the English term originally Digital (digital) of Hong Kong-style translation, was brought to the mainland, and Taiwan use the "digital." According to different functions, structure and quality, currently more common digital camera can be divided into consumer digital camera (commonly known as fool the camera), class monocular digital cameras, digital SLR and mirror less interchangeable-lens camera four kinds. Also there are specific needs for highly specialized design of the digital medium format (120-format) camera.

In the digital camera, the light-sensitive charge-coupled device or a complementary metal oxide semiconductor sensor designed to replace traditional chemical photographic film camera function. The captured image data via integrated microprocessor after the adoption of certain coding algorithm stored in the camera's internal digital storage device (memory cards, micro hard disk, floppy disk or a rewritable disc) in. With the decline of flash memory and a substantial increase in prices, the vast majority of digital cameras are using flash memory as a storage solution.

Since the small, lightweight digital cameras, the film that has low cost, easy to save photos to share with post-editing and many other advantages, so that in a short time the rapid spread. Most digital cameras and has a recording, video recording motion pictures and other functions. In 2009, a total of digital cameras sold worldwide (including mobile phones with digital camera function) more than 900 million, while the traditional camera in the market has almost disappeared.

At present, more and more devices such as mobile phones, personal digital assistants, personal computers, terminals and tablet computers are integrated into the digital camera.


Bluetooth Signals

Bluetooth  a wireless technology standard, used to allow fixed and mobile devices, the exchange of information between the short distance to form a personal area network (PAN). The use of short-Porter high frequency (UHF) radio waves, via 2.4 and 2.485 GHz ISM band for communication. 1994 by the telecom provider Ericsson developed this technique. It was originally designed in the hope that the establishment of wireless communication alternative versions of a RS-232 data lines. It is possible to link a plurality of devices, to overcome the problem of synchronization.

Bluetooth technology is by the Bluetooth SIG (SIG) is responsible for maintaining the technical standards, the alliance has more than 20,000 member companies, the distribution of its members on the field of telecommunications, computer, network and consumer electronic products. IEEE Bluetooth technology has been standardized as IEEE 802.15.1, but the standard is no longer continued to use.

Bluetooth technology was originally created by Ericsson. Ericsson's technology began in 1994 program, which is the study of low-power between mobile phones and other accessories, low cost method of wireless communication connection. The inventors hope to create a uniform set of rules (ISO protocol) for communications between devices, in order to resolve incompatible between users of mobile electronic devices. 1997 years ago, this concept contact Ericsson mobile device manufacturers, to discuss cooperation in the development of their projects, the results obtained support.
May 20, 1999, Sony Ericsson is easy, IBM, Intel, Nokia and Toshiba and other industry leading the creation of "special interest group" (Special Interest Group, SIG), a precursor of the Bluetooth SIG, the goal is to develop a cost low, high efficiency, the Bluetooth technology standard free wireless connections within a short distance.
Today Bluetooth is managed by the Bluetooth SIG (Bluetooth Special Interest Group, called SIG). Bluetooth technology alliance in the world with more than 25,000 member companies, which are distributed in the telecommunications, computer, networking, and consumer electronics such as multiple fields. IEEE Bluetooth technology as IEEE 802.15.1, but now is no longer to maintain the standard. The Bluetooth SIG oversees the development, management certification program the Bluetooth specification, and maintain trademark rights. Manufacturer's equipment must comply with the Bluetooth SIG standards in order in the name of "Bluetooth devices" into the market. Bluetooth technology has a patent network, issued to compliant devices.

Friday, 29 May 2015

Infrared (IR) WAVES

Infrared (IR) WAVES

The IR, or infrared radiation is electromagnetic radiation with wavelengths shorter than microwaves and terahertz radiation from the visible light but long. Infrared technology, which means that down the name adopted in Latin and consist of infra red English word meaning red and comes with the six-meaning red. Color red is the longest wavelength of visible light. The wavelength of the infrared radiation between 750 nano meters and 1 micrometer. In the normal human body temperature is around 10 micrometers made radiation.

Objects emit infrared radiation in wide spectra, but only because they can detect sensors for specific bandwidths are usually referred to the specific infrared bands. Therefore infrared band is divided into smaller subbands.
International Commission on Illumination (CIE) separating infrared radiation has 

proposed the following tape. 

IR-A: 700 nm-1400 nm

IR-B: 1400 nm to 3000 nm

IR-C: 3000 nm-1 mm

A partitioning format commonly used are as follows:
Near-infrared (NIR, IR-A DIN): 0.75-1.4 .mu.M between wavelengths. Because of the low amount of losses it is generally used in fiber optic communications. Night vision equipment is generally used at those wavelengths.

Redwell heats only the walls unlike conventional heaters warm the air. Walls are stored much longer than air and gives back slowly to room temperature environments. Therefore, it becomes impossible to disperse the walls and moisture stay dry. Another advantage is that the airflow does not pass to the movement of the powder is.

How to works Radio Waves

Symbol of radio waves

Radio waves music, speech,  and information may submit a seamless air millions of kilometers away, the thousands every day is a different way. Even if radio waves are invisible and cannot be touched by people, it has completely changed the history of humanity. Today, mobile phone, wireless phone and uses radio waves to communicate all of them if we are talking about thousands of wireless technologies such as these.
The few examples we use in daily life using radio waves are as follows:
• AM and FM radio broadcast
• Cordless home phones
• Wireless networks (the Internet)
• Remote-controlled toys
• Mobile Phones
• GPS receivers
• Satellite communications
The list goes on ... Although the radar and microwave ovens can barely stand to radio waves was unthinkable without NEVİGASYON and communications satellites and radio waves. Modern aviation and aircraft are using the dozens of different radio systems. The current fashion of today is wireless internet, which means it would be more convenient in the future.

Today all radio uses the sine waves to transmit data. The reason is the use of sine waves of many different people want to use radio waves and devices simultaneously. If there was a way to see the radio waves, you would see thousands of them in the form of sine wave is different. We have around your TV, radio, police-firefighters, satellite, mobile phone, radio wave devices such as GPS. Each has a different sine wave frequency of the radio waves, these waves determines how it spreads.
Any radio consists of two main parts:
1) Transmitter
2) Buyers

Transmitting any data (sound, pictures, etc.) Takes a message and converts the sine wave, respectively, by encoding it later if it transmits radio waves. The receiver receives and decrypts code that radio waves as a sine wave. It uses both the receiver and transmitter antennas to radiate and receive radio waves.

Thursday, 28 May 2015

Radio Transmitter

Radio Transmitter

Transmitters, generating high-frequency electromagnetic waves to be sent by way of the energy transmitted by the antenna are electronic devices. They are made in a variety of types according to their use of power and purpose. The main task of the transmitting antenna to provide power at a certain frequency, and to transmit information with the help of electromagnetic waves generated in this way. First time donors only could send high-frequency energy at a fixed frequency. Such transmitting continuous wave (CW Continuous wave) is called transmitters. With these information transmission is only possible in coded (such as Morse code)
Recently requested information (especially speech, music and video) of a carrier wave (Carrier Wave) is sent superimposed. This process is called modulation and such waves modulated continuous wave. MCW (Continious Wave Modulated) transmitter are divided into two main categories according to the modulation method.
1. Amplitude (Amplitude) modulated transmitters:
Double yanbantl full-makers carrier (DSB-Double side band).
Double-sideband suppressed carrier (DSB-SC = Double Side Band - Supressed Carrier)
2 Yanbantl single transmitter (SSB-Single Side Band)
Single-sideband suppressed carrier (SSB-SC = Single Side Band - Supressed Carrier)
Angle-modulated transmitters:
Frequency modulation transmitters (FM-freguency Modulation).
Phase modulation transmitters (AM-phase modulation).
Generally, three types of transmitters used in practice. These are:
AM transmitters.
FM transmitters.
SSB transmitters.
The simplest one AM transmitter consists of four main sections.

Oscillators solid.
Solid buffer (Buffer).
High Frequency (RF) power amplifier.
Modulator floor (this floor is not available in the CW transmitter).
Oscillator: This is the most important part of the transmitter. Radio Frequency (greater than 100 kHz) produces energy. The frequency of the energy generated must remain within certain limits here. Otherwise it cannot be monitored.
Modulator and audio frequency stage: the electrical signal obtained from the microphone is too small. Audio-frequency amplifier (solid) raises its desired level. The modulator is also an adaptive layer that transmits sound signals to the power stage. The power stage according to the intensity of the sound by influencing the frequency amplitude gain (amplitude) performs modulation.
A simple FM transmitter consists of the following layers:
Audio frequency amplifier and reactance modulator solid. (Reactance: Coil or alternating current resistance of the capacitor.)
Oscillators solid.
Solid bumper and the driver.
RF power amplifier solid.
Solid buffer (Buffer): Buffer solid, solid insulates power from the oscillator. Thus oscillator provides more stable work. If desired this layer may also remove two or three times the frequency of the oscillator, the frequency multiplier is called.
RF power level: This layer feeds in the desired signal power to the antenna; information from a modulator is superimposed on a carrier wherein the oscillator
The audio frequency amplifier and the reactance modulator: the signal from the microphone is applied to the reactance modulator raised to the desired level. Reactance modulator, the oscillator circuit capacitive or inductive reactance of the coil or remove it added. Thus, according to the intensity of sound frequencies by changing the oscillator frequency FM (Frequency Modulation) is provided.

Oscillator: generates radio-frequency energy within certain limits. (As standard FM radio channel is from the 85-108 MHz)

Buffer and driver: wherein the replication process is performed if both the frequency and the desired sealing action.

RF power amplifier: Frequency modulated signals from the antenna until the level rises will spread on the floor.