Showing posts from December, 2018

what is an LVDT ( Linear variable differential transformer) or Differential transformer? Working, advantages and disadvantages|

Linear variable differential transformer (LVDT) - LVDT is a passive inductive transducer and is commonly used employed to measure force( or weight, pressure and acceleration etc. Which depend on  force) in terms of the amount and direction of displacement of an object.
Construction -Refer fig.b
It consists of one primary winding and two secondary winding (S1 and S2) which are placed on either side of the primary mounted on the same magnet core. The magnetic core is free to move axially inside the coil assembly and the motion being measured is mechanically coupled to it.the two secondaries S1 and S2 have equal number of turns are bat are connected in series opposition  so that e.m.f ( E1 and E2) induced in them are 180 digree out of phase with each other and hence , cancel each other out. Fig.CWorking principle -When the core is n the center ( called reference position) the induced voltages E1 and E2  are equal and opposite. Hence they cancel out and the output voltage Vo is Zero.When th…

What is Cathode Ray Oscilloscope ( C.R.O ) and C.R.T ? C.R.O working and Applications of C.R.O |

CATHODE RAY OSCILLOSCOPE (C.R.O) -A cathode-ray oscilloscope is an instrument which presents signal wave- forms visually it is also useful for comparing two signal in phase, frequency or amplitude. A C.R.O can operate up to 50 MHz, can allow viewing of signals within a time span of a few nano seconds and can provide a number of wave form displays simultaneously on the screen. It also has the ability to hold the displays for a short or long time ( or many hours ) so that original signal may be compared with one coming on later.                                  A block diagram of cathode ray oscilloscope is show in fig.  

Cathode Ray Tube- A cathode ray tube is the 'Heart' of a oscilloscope and is very similar to the picture tube in a television set. Fig.b shows the cross - sectional view of a general-purpose electrostatic C.R.T it has the following four major components : 1. An electronic gun -  It produces a stream of electrons. 2. Focusing and accelerating anodes- they produce a …

what is the Yagi Uda Antenna in hindi ? or applications

Yagi- Uda antenna 

Reflector का प्रयोग एक Particular  Direction  मे Directivity Gain प्रदान करता है| Driven element मे wire को feed wire से connect किया जाता है | reflector की लम्बाई Dipole से 5 % अधिक रखी जाती है | तथा Direction की लम्बाई 5 % कम रखी जाती है | तथा फिर अगले Director ( Director -4 )  की लम्बाई Director -3 से 5 % कम रखी जाती है |                        reflector का कार्य ,  λ/2  dipole element के back side  की radiate Energy को कम करके लगभग उतनी energy (front -side ) मे radiate energy को बढ़ाना है | reflector dipole के Forward की signal strength मे लगभग 5 dB की वृद्धि करता है | जबकि back side की signal power को 15 dB  कम करता है | इस एक reflector से 20 dB front to back power अनुपात प्रदान करता है |                      yagi Uda antenna मे reflector और Director का प्रयोग Directivity तथा gain बढ़ाने मे किया जाता है |    Notes-  It s also called s super  gain antenna.It has a moderate gain in the vicinity of 7 dB.It is mostly used as a UHF television receiving antenna.reflector …

what is the pulse code modulation in hindi ? with block diagram |

Pulse code modulation ( PCM )
1. low pass filter Low pass filter , low frequency को पास करता है | और high frequency को ब्लॉक कर देता है |  2. Sampling -
sampling मैं  साइन वेव को पल्स के रूप मे  परिवर्तन अर्थात जिस तरह यह  साइन वेव ( इनपुट ) Fig. जा रही है | इसका pulse  के रूप मे  modulating  करना sampling  कहलाता है | 3. Quantizer -
quantizer मे  pulse को  Near about valueदेना  quantizer कहलाता है |   Fig.C 4. Encoder-  Encoder, Near  about value को Binary  मे convert करता है |  5. Decoder -Decoder, Binary को अपने original  signal  मे convert  करता है |                          

what is the carbon microphone ? working principle ? advantages and disadvantages |

Carbon MicrophoneBasic Concept : The basic concept behind the carbon microphone is the fact that when carbon granules are compressed their resistance decreases. This occurs because the granules come into better contact with each other when they are pushed together by the higher pressure.The carbon microphone comprises carbon granules that are contained within a small contained that is covered with a thin metal diaphragm. A battery is also required to cause a current to flow through the microphone. When sound waves strike the carbon microphone diaphragm it vibrates, exerting a varying pressure onto the carbon. These varying pressure levels are translated into varying levels of resistance, which in turn vary the current passing through the microphone.The varying current can be passed through a transformer or a capacitor to enable it to be used within a telephone, or by some form of amplifier. The frequency response of the carbon microphone, however, is limited to a narrow range, and th…

what is the Crystal microphone ? Working principle | Construction | Applications

Crystal Microphone Principle : A crystal microphone is based on the principle of “Piezo electric effect” which is defined as “Difference of potential between the opposite faces of some crystals is produced when these are subjected to mechanical pressure”. The crystals which shows this effect are Quartz, Tourmaline, Rochelsalt and Ceramic.

Construction The constructional details of Crystal Microphone are shown in the above fig. a. The crystal is cut along certain planes to form a slice. Metallic foil electrodes are attached to the two surfaces to carry the potential differences to the output terminals. Two thin crystal slices suitably cut are placed in an insulating holder with an air space between them. A large number of such elements are combined and increase an emf. A diaphragm made of aluminium is attached to the crystal surface through a push rod. The whole unit is encases in a protective case. There is a protective cover over the diaphragm.
Working When there is a sound waves of co…

moving coil microphone/ dynamic microphone | working principle |

Moving coil microphoneBasic The moving coil microphone also called dynamic microphone. Dynamic microphone uses the principle of electromagnetic induction .when sounds pressure variation move a coil places in a magnetic field, there is a change of magnetic flux passing through the coil.
The main components of a moving coil microphone are a magnet, diaphragm and coil .these are shown in figure a .the magnet is a permanent magnet of pot type with a central pole piece ( south pole) and the peripheral pole piece ( north pole). Moving coil microphone consists of a magnet, and a diaphragm to which a coil is attached. The assembly is held in place by an outer casing and the coil can move freely over the magnet. Diaphragm is non - magnetic material and is light weight. A protective cover is used to save the delicate diaphragm and coil assembly from being mishandled. The electrical equivalent circuit for a moving coil microphone is show in figure b.

Principle of working When sound wa…

what is an inverter ? classification of invertor ? application of invertor |

D.C signal convert to A.C signal it is called inversion . and the device through which the process is edited that called inverter.

Classification of inverters-series  inverter.parallel  inverter.bridge inverters. 1. Series inverter-

It is inverter is called series because commutation components permanent connected in series with the load. series circuit must be under damped and current attain zero value due to nature  of series circuit.  it is also classified as self commutated inverter and load commutate inverter. It operate at high frequency 20 Hz to 100 GHz. three modes in series commutated  inverter.
The voltage DC voltage directly applies commutation components series circuit as soon as the SCR is turned on.  the polarity of capacitor  is show in the fig. B . Mode - 2
the load current become zero from point a to b as the SCR1 turns off in this time period . the SCR1 and SCR2 are turns off in this time duration and voltage across capacitor becomes equal to DC …

What is the UJT| UJT construction| Application of UJT|

UJT ( Uni junction transistor ) As  a show in figure it is a three terminals device. A uni junction transistor (UJT) is an electronic semiconductor device that has only one junction .

Construction of UJT
 It has three terminals an emitter (E) and two bases (B1and B2). The base is formed by lightly doped n-type bar of silicon. Two ohmic contacts B1 and B2 are attached at its ends. The emitter is of p-type and it is heavily doped. The resistance between B1 and B2, when the emitter is open-
circuit is called interbase resistance. The original UJT, is a simple device that is essentially a bar of N type semi-conductor material into which P type material has been diffused somewhere along its length.
RBB = RB1 + RB2
RB1= Resistance of base B1
RB2=Resistance of base B2
N- channel is lightly doped , therefore RBB is relatively high typical 5 to 10k ohm.

Intrinsic stand of ration;

what is the SCR | operation of SCR | SCR working principle |

SCR fill name silicon controlled rectifier. A silicon controlled rectifier is a semiconductor device that alts as a true electronic switch. It can be change alternating current and at the same time can control the amount of power fed to the load. SCR combines the features of a rectifier and a transistor. CONSTRUCTION
As show in figure it is a four layer three terminal device, layer being alternately p- type and N- type silicon junction are marked J1, J2, J3 where as terminals are anode , cathode and gate. Principle of operation of SCR Three modes of operation; 1. forward blocking region. 2. forward conduction region. 3. reverse blocking region.
1. Forward blocking region; In this mode of operation, the anode (+) is given a positive voltage while the cathode (−) is given a negative voltage, keeping the gate at zero (0) potential i.e. disconnected. In this case junction J1 and J3 are forward-biased, while J2 is reverse-biased, due to which only a sm…

what is the chopper ? chopper types | classification of chopper |

chopperPrinciple of chopper : Chopper is a static device then convert constant DC voltage to variable DC output voltage. Classification of Chopper ; 1. step down chopper. 2. step up chopper. 1. Step down chopper ; Vo < Vs
    where Vs = input voltage. Vo = output voltage.
When the average output voltage(Vs) is less then the input voltage called step down  chopper. for R L load
Vs = Vt + Vo
                                                            Vo = Vs - Vt

    T= cycle time period or chopping
 when chopper is ON load voltage = source voltage when is chopper OFF                                                         Vo = 0                                                        Is = Vs/Rl                                                       Vo = Vs x Ton / T Step up chopper
OR Vo = VsThe average output(Vo) greater then input voltage(Vs) is called step up chopper.when chopper is ON ;
                                                    VL = Vs when chopper is OFF ;

What is a TRAIC ? traic principle | traic advantage and disadvantages .

TRIAC  The triac is a member of the thyristor family. Basically, a triac can be thought as two SCR connected in parallel and in opposite directions witha common gate terminal. Unlike the SCR, the traic can conduct current in either direction when it is triggered on, depending on the polarity of the voltage across its A1 and A2 terminals. The triac is a bi- directional semi- controlled devices.

        Fig. (a) and (c) show the circuit symbol and schematic cross section of a triac respective. As  the Triac can conduct in both the directions the terms “anode” and “cathode” are not used for Triacs. The three terminals are marked as MT1 (Main Terminal 1), MT2 (Main Terminal 2) and the gate by G. As shown in Fig (b) the gate terminal is near MT1 and is connected to both  N3 and P2 regions by metallic contact. Similarly MT1 is connected to N2 and P2 regions while MT2 is connected to N4 and P1 regions.  The following TRIAC may be operate in four types-

Mode 1 ; MT2 positive with respect to MT…

What is a Avalanche photo diode (APD) ? Advantages and disadvantages.

APD ( Avalanche photo diode): One of the main working parts of any optical receivers the photo detector . Avalanche photo diode device that transform optical signal to electrical signal.                          An avalanche photo diode (APD) is a highly sensitive semiconductor electron devices that exploits the photo electric effect to convert light to electricity.
The avalanche photo diode possesses a similar structure to that of the PN or PIN photo diode. An avalanche diode structure similar to that of a Schottky photo diode may also be used but the use of this version is much less common.
The main difference of the avalanche photo diode to other forms of photo diode is that it operates under a high reverse bias condition. This enables avalanche multiplication of the holes and electrons created by the photon / light impact.     In APD an extremely high electric field region is created ~ 3×10 the 5 v cm-1. Avalanche photo diode advantages and disadvantages
Avalanche photo diodes poss…

What is a amplifier? Classification of Amplifier.

Amplifier An amplifier circuit amplifier it's A.C input into D.C output.             The process, in which a larger output is obtained for a smaller input signal, is termed as amplification. The device which performs this function is called amplifier.

In this fig increase the amplitude of its input signal without changing the other signal characteristics . The amplifier must be supplied with D.C operating power . Although the source of this is not shown.
Example of amplifier use are given below:

The amplification of the small signal normally generated by oscillator. Classification of amplifier According to the function: 1. Voltage amplifier  2. Power amplifier 3. Current amplifier According to the frequency to be amplified: 1. Audio frequency (A.F). 2. Radio frequency ( R.F). 3. D.C amplifier. According to the operating conditions i.e on the grid bias value; 1. Class A 2. Class B 3. Class AB 4. Class C  According to coupling method. 1. R.C coupled  2. Impedance coupled  3. Transf…