Electrical Engineering

 Transmission-Media Transmission Media or Communications media  are the paths, or physical channels, is that, over which information travels from one place to another. A key aspect of communication is the movement of information electronically from one place to another. It may be as simple as sending information from one office to another in the same building, or it may be as far- reaching as sending information around the word. Whatever the case, information/signal must travel over some path from its source to its destination. What are the types of Transmission media? Signals are usually transmitted over some transmission media that are broadly classified in to two categories. Guided Media/bounded : These are those that provide a conduit from one device to another that include twisted-pair, coaxial cable and fiber-optic cable. A signal traveling along any of these media is directed and is contained by the physical limits of the medium. Twisted-pair and coaxial c...

Band Limited Signal   A signal is said to be a band limited signal if all of its frequency components are zero above a certain finite frequency. i.e it's power spectral density should be zero above the finite frequency. Figure 1 shows a signal g(t) that is band limited. Bandwidth requirements (communications) The channel bandwidths needed to transmit various types of signals, using various processing schemes. Every signal observed in practice can be expressed as a sum (discrete or over a frequency continuum) of sinusoidal components of various frequencies. The plot of the amplitude versus frequency constitutes one feature of the frequency spectrum (the other being the phase versus frequency). The difference between the highest and the lowest frequencies of the frequency components of significant amplitudes in the spectrum is called the bandwidth of the signal, expressed in the unit of frequency, hertz. Every communication medium (also called channel) is c...

The superhet radio or to give it its full name the super heterodyne receiver is one of the  most popular forms of receiver in use today. Virtually all broadcast radios, televisions  and many more types of receiver use the superhet or super heterodyne principle. First developed at the end of the First World War, with its invention credited to the American Edwin Armstrong, the use of the superhet has grown ever since the concept was first discovered. 

Modulating signal and carrier Wave   Modulated wave   Frequency spectrum of AM wave   If the equation of modulating signal is

  Voltage to Time A/D converter (Ramp type) Any digital voltmeter has a fundamental cycle sequence which involves sampling, display, and reset sequence. The application of input voltage initiates the measurement cycle. The oscillator is automatically switched with the operator and its output consists of pulses which are counted by an electronic counter. A units counter is first actuated. This units counter provides a carry pulse to the tens counter on using the counter input pulse. In turn, the tens counter provides its own carry pulse after it has counted 10 carry pulses from the units counter. If excess input voltage is being measured, it provides its own carry pulse which switches on a warning lamp. Each decade counter unit in a DVM is counted as a D to A converter. Outputs of a D to A convertor are connected in parallel which build up a comparison voltage. At the instant when the comparison section senses that the input voltage and comparison voltages ar...

  Why we need temperature Measurement ?    

  Introduction   • The last stage of instrumentation & measurement is display devices & recorders. Because the results of a measurement system are meaningful, they must be displayed for instant observation of for storage for observation at a later stage. The first device is called a “ display device ” and the second a “recorder” . The data presentation devices may be called as output devices.