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Question

Answer 1

6.1

Open motor speed control system :

A control system in which the control action is totally independent of output of the system then it is called open loop control system.

The system the control is totally independent of output of the system becasue open motor speed system has no feed back.

Sketch the diagram for open motor speed control system :

In this circuits the speed varied based on the load.

If the load of the circuit changes then the speed of the motor changed.

Example :

Automatic washing machines :

In the automatic washing machine, the machine runs according to the pre-set time.

Washing machines is turn off when the pre-set time is completed but it not considered washing is completed or not.

Answer 2

6.2.1

Diagram for the characteristic curve of the Triac :

 

Characteristics of a triac are shown in figure.

The triac has on and off state characteristics similar to SCR.

Characteristic is applicable to both positive and negative voltages.

Triac consists of two SCR connected in parallel but opposite in directions.

Answer 3

6.2.2

Diagram for the characteristic curve of the SCR :

SCR is a four-layer device.

SCR consist of three terminals anode cathode and the gate.

When the anode is made positive with respect to the cathode, junctions J₁ and J₃ are forward biased and junction J₂ is reverse-biased.

Leakage current will flow through the device. The SCR is then said to be in the forward blocking state or in the forward mode or off state.

Answer 4

6.2.3

Diagram for the characteristic curve of the Diac :

The diac acts as open-circuit until its switching or breakover voltage is exceeded.

The diac, because of its peculiar construction, does not switch sharply into a low voltage condition at a low current level like the SCR or triac.

Once diac goes into conduction, the diac maintains an almost continuous negative resistance characteristic, voltage decreases with the increase in current.

Answer 5

7.1.1

IEC symbol of photo diode :

The photodiode symbol shows the light in the form of arrows striking the diode junction, the arrows are in the opposite direct to that of a light emitting diode where they emanate from the device.

Factors including in photodiode are noise, reverse bias constraints, gain, wavelength, and more all play a part.

Answer 6

3.7.2

IEC symbol of photo diode :

A phototransistor is a bipolar device that is made of semi-conductor material.

Phototransistor is dependent on light energy.

Phototransistors are generally encased in an opaque or clear container in order to enhance light as it travels through it and allow the light to reach the phototransistor’s sensitive parts.

Answer 7

• The output of the integrator is a triangular wave whose frequency depends on the current supplied by the constant current supply sources.
• The comparator output provides a square wave of the same frequency as output.
• The resistance diode network changes the slope of the triangular wave as its amplitude changes and produces a sinusoidal wave with less than 1% distortion.

 

- See more at: http://www.mycircuits9.com/2012/11/function-generator-working-with-block.html#sthash.keza0iyc.dpuf

• The output of the integrator is a triangular wave whose frequency depends on the current supplied by the constant current supply sources.
• The comparator output provides a square wave of the same frequency as output.
• The resistance diode network changes the slope of the triangular wave as its amplitude changes and produces a sinusoidal wave with less than 1% distortion.

 

- See more at: http://www.mycircuits9.com/2012/11/function-generator-working-with-block.html#sthash.keza0iyc.dpuf

8.1

Block diagram of a basic function generator :

 

• The output of the integrator is a triangular wave whose frequency depends on the current supplied by the constant current supply sources.
• The comparator output provides a square wave of the same frequency as output.
• The resistance diode network changes the slope of the triangular wave as its amplitude changes and produces a sinusoidal wave with less than 1% distortion.

 

- See more at: http://www.mycircuits9.com/2012/11/function-generator-working-with-block.html#sthash.keza0iyc.dpuf

he output of the integrator is a triangular wave whose frequency depends on the current supplied by the constant current supply sources. - See more at: http://www.mycircuits9.com/2012/11/function-generator-working-with-block.html#sthash.keza0iyc.dpuf

• The output of the integrator is a triangular wave whose frequency depends on the current supplied by the constant current supply sources.
• The comparator output provides a square wave of the same frequency as output.
• The resistance diode network changes the slope of the triangular wave as its amplitude changes and produces a sinusoidal wave with less than 1% distortion.

 

- See more at: http://www.mycircuits9.com/2012/11/function-generator-working-with-block.html#sthash.keza0iyc.dpuf

In this instrument the frequency is controlled by varying the magnitude of current that drives the integrator.

A typical function generator can provide frequencies up to 20 MHz.

This instrument provides different types of waveforms, such as sinusoidal, triangular and square waves.

Answer 8

7.2

Transducers :

A transducer is a device that converts energy from one form to another.

Four types of transducers :

(1) Piezoelectric Transducer :

Piezoelectric transducers convert mechanical energy into electrical energy and similarly, electrical energy can be converted into mechanical energy.

Application of Piezoelectric Transducer :

This is used  for the detection of muscle movements which can be termed as acceleromyography.

 

(2) Pressure Transducer :

Pressure transducer can be defined as a special type of pressure sensor that converts the pressure imposed into electrical signals. Pressure transducers are also termed as pressure indicators, transmitters, manometers, piezometers, and pressure sensors. 

Application of Pressure Transducer :

Pressure transducers are specially used for measuring the pressure of the particular quantity such as gas or liquid by converting the pressure into electrical energy.

 

(3) Temperature Transducer :

Temperature transducer can be defined as a device that converts temperature of a system or device into other form electrical energy or mechanical energy or pressure.

Application of Temperature Transducer :

Temperature transducers are majorly used for measuring air temperature such that to control the temperature of many control systems such as heating, air-conditioning, ventilation, and so on.

 

(4) Ultrasonic Transducer :

The transducers that convert ultrasound waves to electrical signals and similarly, electrical signals to ultrasound waves are called as ultrasonic transducers. These types of transducers are also termed as piezoelectric or capacitive transducers.

Application of Ultrasonic Transducer :

The ultrasonic transducer can be used for measuring distance based on reflection of sound.

Answer 9

8.2

Purpose of time base generators in oscilloscope :

A time base generator is a special type of function generator, an electronic circuit that generates a varying voltage to produce a particular waveform.

Time base generators produce very high frequency sawtooth waves specifically designed to deflect the beam in cathode ray tube smoothly across the face of the tube and then return it to its starting position.

In CRO, output signal voltage of the vertical amplifier is fed to the vertical plates of CRT (to amplify the signal) and some of its portion is used for triggering the time base generator circuit, whose output is supplied to the horizontal deflection plates through horizontal amplifier.

The time base generator is used to generate waveform in the order of 100 ns.

So the input signal of the vertical deflection plates of a CRT is to be delayed by at least the same or little more amount of time to allow the operator to see the leading edge of the signal waveform on the screen.