Question & its Answer

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1 Iportant Instructions to exainers: 1) The answers should be exained by keywords and not as word-to-word as given in the odel answer schee. 2) The odel answer and the answer written by candidate ay vary but the exainer ay try to assess the understanding level of the candidate. 3) The language errors such as graatical, spelling errors should not be given ore Iportance. (Not applicable subject English and Counication Skills.) 4) While assessing figures, exainer ay give credit principal coponents indicated in the figure. The figures drawn by candidate and odel answer ay vary. The exainer ay give credit any equivalent figure drawn. 5) Credits ay be given step wise nuerical probles. In soe cases, the assued constant values ay vary and there ay be soe difference in the candidate s answers and odel answer. 6) In case of soe questions credit ay be given by judgeent on part of exainer of relevant answer based on candidate s understanding. 7) For prograing language papers, credit ay be given to any other progra based on equivalent concept. Q. No. Question & its Answer Re Total Marks Q.1A Attept any six 12 a) Define Resolution and Dead Zone. Ans. Resolution: - Resolution is the least increental value of input or output that can be detected, caused or otherwise discriinated by the easuring device 01 OR It is the sallest change in the easured value to which the instruent will respond. Dead Zone: - The largest range of values of a easured variable to which the instruent does not respond. 01 b) What is loading effect of ultirange volteter? Ans. When selecting a eter a certain voltage easureent, it is iportant to consider the sensitivity of a dc volteter. A low sensitivity eter gives a correct reading when easuring voltages in a s low resistance circuit, but it is certain to produce unreliable readings in a high resistance circuit. A volteter when connected across two points in a highly resistive circuits, acts as a shunt that portion of the circuit, reducing the total equivalent resistance of that portion. The Page 1 of 36

2 eter then indicates a lower reading than what existed bee the eter was connected. This is called the loading effect of an instruent. c) State any two advantages of digital instruents over analog instruents. Ans. advantages of digital instruents over analog instruents: 1. They are having high input ipedance, so there is no loading effect 2. They are having higher accuracy 3. An unabiguous reading is obtained 01 each ( any two ) 4. The output can be interfaced with external equipent 5. They are available in saller size d) Define Accuracy in Digital Meters. Ans. Accuracy - It is the degree of closeness with which an instruent reading approaches the true value of the quantity being easured. s e) State the function of delay line in CRO Ans. The delay line is used in CRO to delay the signal soe tie in the vertical sections. As horizontal channel consists of trigger circuit and tie based generator. this causes ore tie to reach signal to horizontal plates than vertical plates. For synchronization of reaching input signal at sae tie to both the plates in CRT. s f) Define deflection sensitivity and deflection factor of a CRT Ans. Deflection sensitivity: - The deflection sensitivity (S) of CRT is defined as the deflection on the screen (in eters) per volt of deflection voltage. 01 Deflection factor: - The reciprocal of deflection sensitivity is called as the deflection factor (G) of CRT. 01 g) State the need of signal generators Ans. The generation of signals is an iportant activity of electronic developent and troubleshooting. Theree a signal generator is a vital electronic instruent in laboratory test setup which provides signals general test purposes. It is used to provide known test conditions the perance evaluation of various electronic systes s Page 2 of 36

3 and replacing issing signals in systes being analyzed repair. h) Define wave analyzer Ans. Definition: Wave analyzer is an instruent which is used to easure the agnitude of the various haronics of a coplex wave. It is an instruent that is designed to easure the relative aplitudes of single frequency coponents in a coplex or distorted wave. s definiti on OR (Any other relevant definition shall be considered.) B Attept any two 08 a) Define unit and give any two exaples each of base, suppleentary and derived units. Ans. Unit: - The result of a easureent of a physical quantity ust be defined both in kind and agnitude. The standard easure of each kind of physical quantity is called a Unit. (Any two relevant exaples). Sr. No Exaples of Base units Unit Nae Sybol 01 Length Meter M Mass Kilogra Kg 03 Tie Second S s (01 each units) Intensity of electric current Apere A Exaples of Suppleentary units 01 Plane angle radian rad Solid angle steradian sr Exaples of Derived units Page 3 of 36

4 01 Area Square eter 2 Volue Cubic eter 3 03 Frequency Hertz Hz Density Kilograe per cubic eter Kg/ 3 05 Velocity Meter per second /s 2 (Any other two relevant units each typy shall be considered). b) Define calibration and state its need. Ans. Calibration - It is a process of estiating the value of a quantity by coparing that quantity with a standard quantity. Need of calibration: - Calibration defines the accuracy and quality of easureent recorded using a piece of equipent. Over tie there is a tendency result and accuracy to drift particularly using easuring particular paraeters such as teperature and huidity. To be better result being easured there is an ongoing need to service and aintain the calibration of equipent throughout its lifetie reliable, accurate and repeatable easureent. The ai of calibration is to iniize any easureent uncertainty by ensuring the accuracy of test equipent. Marks Definiti on Marks need c) Draw neat electrical circuit diagra of analog ultieter. Ans. s diagra Page 4 of 36

5 Or Any other relevant diagra shall be consider Q. 2 Attept any four. 16 a) Explain types of errors. Ans. There are three types of error 01 Mark i. Gross Error ii. Systeatic Error types iii. Rando Error. Explanation: 1. Gross Error - These errors are ainly huan istakes in reading instruents and recording and calculating easureent results. As huan beings are involved, soe gross errors will definitely be coitted. Although coplete eliination of gross error is ipossible, one should try to anticipate and correct the. Soe gross error is easily detected while others ay be very difficult to detect. These errors cannot be atheatically treated. However can be avoided by great care should be taken in reading and recording the data and two, three or ore readings should be taken quantity under easureent. 2. Systeatic Error These types of error are divided into three categories 03 Marks explan ation (01 each type explan ation) a) Instruental Errors ii) Environental Error iii) Observational Error Instruental error is due to inherent shortcoings in the instruent, due to isuse of the instruent and due to loading effects of instruent. Environental errors are due to conditions external to the easuring device including conditions in the area surrounding the instruent. These ay be effect of teperature, pressure, huidity, dust, vibrations or of external agnetic or electrostatic fields. Observational error is Page 5 of 36

6 nothing but parallax error. As the pointer of analog easuring instruents rests slightly above the surface of scale it causes parallax error. To iniize parallax error eters are provided with irror. 3. Rando Error These errors are due to unknown causes which are not deterinable. Such errors those reain after gross and systeatic errors have been substantially reduced. b) Derive the relation of shunt resistance with internal resistance of eter to extend Aeter range. Ans. Marks Diagra Explanation: The current range of aeter is further extended by a nuber of shunts, selected by a range switch. Such eter is called a ultirange aeter. Figure shows a diagra of ultirange aeter. The circuit has four shunts R sh1, R sh2, R sh3 and R sh4 which can be put in parallel with the eter oveent to give four different current ranges I 1, I 2, I 3 and I 4. Let 1, 2, 3 and 4 are the shunt ultiplying powers currents I 1, I 2, I 3 and I 4 Theree R sh1 = R / ( 1-1) Marks explan ation R sh2 = R / ( 2-1) R sh3 = R / ( 3-1) R sh4 = R / ( 4-1) c) Draw the block diagra of CRO and state the function of each block. Page 6 of 36

7 Ans. Marks Diagra Fig shows a block diagra of general purpose CRO. It consist of the following ain coponents. 1. Cathode ray tube The CRT is the heart of oscilloscope, which generates sharply focused electrons bea, accelerates the bea to a very high velocity, deflects the bea to create the iage and contains the phosphor screen where the electron bea eventually becoes visible. To ake these tasks, various electrical signals and voltages are required as shown in figure. Marks explan ation 2. Power Supply It provides the voltages required by the CRT to generate and accelerate the electron bea as well as to supply the required operating voltages the other circuits of the oscilloscope. High voltages are required by the CRT acceleration and low voltage is the heater of the electron gun of the CRT, which eits electron. 3. Vertical Aplifier The input signal to be viewed on CRT screen is applied to the vertical aplifier, the push pull output of which is fed to the vertical deflection plates of CRT via delay line with sufficient power to drive the CRT spot in the vertical direction. 4. Tie base generator It develops a saw tooth wave that is used as the horizontal deflection voltage of the CRT. Page 7 of 36

8 5. Horizontal Aplifier The saw tooth voltage is fed to the horizontal aplifier which includes a phase inverter and produces two siultaneous output wave. The positive going saw tooth is applied to the right hand horizontal deflection plate of CRT and the negative going saw tooth to the left hand horizontal deflection plate. These voltages cause the electron bea to be swept across the CRT screen, fro left to right. 6. Trigger Circuit The trigger circuit is used to convert the incoing signal into trigger pulses so that the input signal and the sweep frequency can be synchronized. d) A basic d Arsonval eter with an internal resistance R = 100 Ω and a full scale current of I = 1 A, is to be converted into a d.c. volteter with range of 0-10 V. Find the values of series resistance. Ans. Given Data: Vin = 10 V, Ifsd = 1 A, R = 100 Ω Rs = (Vin / Ifsd) R Theree Rs = (10 / 1* 10-3 ) 100 Rs = 9900 Ω = 9.9 K Ω Marks (conside r s steps) e) Describe Lissajous pattern phase easureent. Ans. Lissajous pattern phase easureent: When two signals are applied siultaneously to an oscilloscope Marks without internal sweep, one to the horizontal channel and the other to descript ion the vertical channel, the resulting pattern is a Lissajous figure that shows a phase difference between the two signals. Such patterns result fro the sweeping of one signal by the other. Figure shows the test setup phase easureent by eans of Lissajous figures. Page 8 of 36

9 Depending on the phase shift between the two signals, the shape of the Lissajous pattern will go on changing 1. The Lissajous pattern will be an ellipse if the sine waves of equal frequency but phase shift θ between 0 0 and 90 0 are applied to the two channels of CRO. The phase shift is given by, Marks pattern ( any two) θ = sin -1 (A/B) 2. For phase difference above 90 0 and less than 180 0, the ellipse appears. The phase shift is θ = sin -1 (A/B) 3. If the two sine waves are of sae frequency are in phase, then Lissajous pattern will be a diagonal line aking an angle of 45 0 with X- axis 4. If the phase angle θ = 90 0, frequency is identical and aplitudes are equal of the two input sinusoidal signals, the Lissajous pattern Page 9 of 36

10 will be a circle f) Explain digital frequency eter with neat block diagra Ans. Marks Diagra Explanation: The signal ay be aplified bee being applied to the Schitt trigger. The Schitt trigger converts the input signal into a square wave with fast rise and fall ties, which is then differentiated and clipped. As a result the output fro the Schitt trigger is a train of pulses, one pulse each cycle of the signal. The output pulses fro the Schitt trigger are fed to a START / STOP gate. When this gate is enabled, the input pulses pass through this gate and are fed directly to the counter which counts the nuber of pulses. When gate is disabled the counter stops counting the incoing pulses. The counter displays the nuber of pulses that have passed through it in the tie interval between start and stop. If this interval is known the pulse rate and hence the frequency of the input signal cab be known. If f is the frequency of unknown signal, N is the nuber of counts displayed by counter and t is the tie interval between start and stop gate then, frequency of unknown signal is, Marks explan ation f = N / t Q. 3 Attept any four 16 a) Define standards and give their classification. Page 10 of 36

11 Definition: Standard is the physical representation of unit of easureent. Or A known accurate easure of physical quantity is tered as Standard. 01 Definiti on Standards are classified as, 1) International Standard 2) Priary Standard 3) Secondary Standard 4) Working Standard 03 classifi cation. b) Derive torque equation PMMC instruents. (Diagr a is optiona l) Construction Of PMMC Instruents Consider length of coil be l eter and width of coil be d eter. Assuing I is aount of current flowing in the coil having N turns, B is the flux density in the air gap and A is effective area of coil then, Page 11 of 36

12 F=BIL (N). Torque developed on each side of coil=f*(d/2) Total torque=2[bil(n)*(d/2)] For a given instruent B L d and N are constant thus, Td= G* I= B* A*I*N Td Equati on Controlling torque Tc= C* Ө As developed echanical torque is counterbalanced by electroagnetic torque, Td=Tc= G* I = C* Ө The deflection of pointer( Ө) varies directly with current passed through coil ( I) Tc Equati on c) Draw a neat and labeled diagra of internal structure of CRT s diagra d) Calculate ratio of vertical and horizontal frequencies an oscilloscope which displays the following Lissajous figures shown in fig, Page 12 of 36

13 Fig. 1 Ans Fv= no.of horizontal tangents. Fx= no.of vertical tangents. a) Fv/Fx= 1/2 b) Fv/Fx=2/1 01 each ratio c) Fv/Fx= 3/2 d) Fv/Fx= 2/3 e) State principle of operation of function generator with neat block diagra s Diagra Block diagra of function Generator Page 13 of 36

14 OR (Any Other relevant diagra should be considered) Principle of operation of function generator: Function generator operates to produce different waves such as sine, square, triangular of adjustable frequency which is used to test functionality of various electronic circuits. This has capability of phase lock with other function generator or to a frequency standard and its output waves will have sae accuracy and stability as standard source. In operation, frequency is controlled by varying the agnitude of current which drives the integrator. The frequency controlled voltage regulates two current sources. the upper current source supplies constant current to the integrator whose output voltage increases linearly with tie. Voltage coparator ultivibrator changes states at a predeterined axiu level of the integrator output voltage. This change cuts off the upper current supply and switch on lower current supply. The lower current source supplies a reverse current to integrator so that] its output decreases linearly with tie. When output reaches predeterined iniu level, voltage coparator again change state and switch on the upper current source. The output of integrator is triangular wave whose frequency is deterined by the agnitude of current supplied by constant current sources. For Explan ation f) Draw a neat block diagra of pulse generator Block diagra of pulse generator: Page 14 of 36

15 s correct diagra Q. 4 Attept any four 16 a) Explain with neat circuit diagra how full wave rectifier type analog AC volteter is used to easure unknown voltage. Diagra with wavefo r Bridge rectifier type AC volteter Or Page 15 of 36

16 For Explan ation Explanation: General rectifier type AC volteter Wave In full wave bridge rectifier the output voltage is double that of half wave rectifier. If we assue diode has zero ward resistance and infinite reverse resistance then, Page 16 of 36

17 OR (Any other relevant explanation shall be considered). Page 17 of 36

18 b) Describe working principle of PMMC instruent with neat construction diagra Diagra OR (Any other relevant diagra shall be considered) Working principle of PMMC: 1.The working principle of PMMC is based on basic eter oveent known as D Arsonval principle stated as when current passes through the coil a deflecting torque is produced due to interaction between agnetic field produced by peranent agnet and agnetic filed produced by oving coil. 2.Due to this torque coil deflects and this deflection is proportional to the current flowing through the coil. 3.The pointer attached with coil indicates the agnitude of quantity being easured. For workin g princip le 4.Another torque is developed by spring known as controlling torque.t Page 18 of 36

19 his torque helps to stabilize the pointer 5. When controlling torque becoes equal to deflecting torque then pointer attached with scale becoe stable at equilibriu. c) Give the classification of analog aeter and volteter. Ans The classification of Analog instruents( aeter and volteter) are as follows, 1) Peranent Magnet Moving Coil Instruent(PMMC) 2) Electro dynaoeter type instruents. 3) Moving iron type instruents (a)attraction type oving iron instruents. (b) Repulsion type oving iron instruents. 4) Therocouple Instruents 5)Electrostatic Instruents 6) Induction Instruents 7) Hot wire instruents O4 s classifi cation (Any four) d) Describe tie base generator to produce waves on CRO. Ans. The otion of spot on CRT screen fro left to right is called sweep. The generator which generates signals to ove bea spot on screen horizontally is called tie base or sweep generator. s diagra Tie base Generator using UJT Page 19 of 36

20 Explanation: The tie base convert given signal into sawtooth wave. As shown in figure which deflect the bea in the horizontal direction. Diagra: s explan ation The wave is divided into two parts i.e. sweep tie and retrace tie. During sweep tie t s the bea oves left to right horizontally. The bea is deflected towards right by increasing aplitude of rap voltage and the fact that positive voltage attracts the negative electrons. During retrace tie or flyback tie T r the bea returns quickly to the left side of screen. The control grid is generally gated OFF which back out the bea during retrace tie and prevent an undesirable retrace pattern fro appearing on the screen. The base generator pers the task of producing such repetitive and synchronized voltage signal. OR The tie base generator is shown in figure. Page 20 of 36

21 Explanation: UJT relaxation oscillator is ain part of tie base generator. It is used to produce sweep. When power is applied to UJT, initially it is off and the capacitor charge through R T. When voltage across capacitor reaches V P (peak voltage), then UJT turn ON. Then capacitor discharge rapidly through R 1 and turn OFF UJT. The cycle of charging and discharging repeats and sawtooth wave produced as shown in figure. e) It is desired to easure the voltage across a 50 K Ω resistor in a circuit shown in fig. 2. Two volteters are available this purpose: volteter A with a sensitivity of 1000 Ω/V and volteter B with sensitivity of Ω/V. Both eters have 0-30V range. Calculate the reading of each volteter Page 21 of 36

22 Fig. 2 Ans. voltet er A voltet er B Page 22 of 36

23 f) Design an Ayrton shunt to provide an aeter with current ranges 1A, 5A and 10A. A basic eter with an internal resistance of 50oh and full scale deflection current of 1A is to be used. Ans. 01 diagra To find values of R1,R2,R3 i. For 1A range, (I -I) (R1+R2+R3)=I.R ( ) * (R1+R2+R3)= 0.001*50 (R1+R2+R3)= 0.05/0.999=0.050 oh. ii. For 5A range, (I -I) (R2+R3)=I.(R+R1) ( ) * (R2+R3)= 0.001*(50+R1) 4.999*(R2+R3)= R1 Eq(1) Eq(2) 03 s ( 01 each R1, R2, R3) iii. For 10A range, (I -I) (R2+R3)=I.(R+R1+R2) ( ) * R3= 0.001*(50+R1+R2) 9.999*R3= R R2 Page 23 of 36

24 9.999*R3-0.05=0.001(R1 +R2) (R1 +R2) = 9999R3-50 Eq(3) Put value of (R1 +R2) in eq(1) we get, (R1+R2+R3)= R3-50+R3= R3= R3=50.05/10000 R3=5.005*10-3 oh Put value of R3 in equ (3) we get, (R1 +R2) = 9999R3-50 =9999*5.005* = R2= R1 eq(4) Put value of R2 & R3in eq(2) we get, 4.999*(R2+R3)= R ( R1 ) *5.005*10-3 = R1 o r1+0.50= r =4.999R R1 R1=3.998*10-2 Oh R1 = Oh Put value of R1 in eq(4) R2= R1 R2= *10-5 Page 24 of 36

25 Hence values are : R1= Oh = 0. Oh R2= Oh = 0.05 Oh R3=0.005 Oh R2= oh ( Values by rounding ay vary little shall be considered ) OR (Any other suitable ethod correct calculation shall be considered). Q.5 Attept any FOUR of following 16 a) Explain with neat block diagra the operation of single bea dual trace oscilloscope. Ans Diagra: diagra Page 25 of 36

26 Operation: Fig. illustrates construction of single bea dual trace oscilloscope. There are two separate vertical input channels A and B. They use separate attenuator & pre-aplifier stages. Theree the aplitude of each i/p as viewed on oscilloscope can be controlled individually. After copletion of both channels are applied to electronic switch. This switch will pass one channel at a tie to vertical aplifier via delay line. operati on There are two coon odes electronic switch called alternate & chop. In alternate ode electronic switch connects the two channels A & B alternately in successive cycles of sweep generator. The alternate ode can not be used displaying very low frequency signal. In Chop ode electronic switch will ake several transition fro one channel to the other channel during one sweep. The trigger selector switch S 2 allow the circuit to be triggered on either A or B channel on line frequency fro an external signal. Sweep wave is fed to horizontal aplifier via s/w S 1 & S 3 The X-Y ode eans, oscilloscope operates with channel A as the vertical signal & channel B as the horizontal signal. Accurate easureent can be done in thi ode. b) Explain with neat diagra the operation of vertical deflection syste Ans Diagra. diagra Page 26 of 36

27 Explanation: The ain function of vertical deflection syste is to provide an aplified signal of proper level to drive the vertical deflection plates without any distortion. The i/p stage of pre-aplifier, consists of FET source follower. The FET source follower has high ipedance. This ipedance FET aplifier fro attenuator. The FET source follower i/p stage is followed by BJT eitter follower. This is done in order to atch the ediu ipedance of FET aplifier with low i/p ipedance of phase inverter. Two antiphase o/p signals are provided by FET aplifier, in order to drive push-pull aplifier o/p. The push-pull o/p stage delivers equal signal voltage of opposite polarities to vertical deflecting plates of CRT. explan ation c) Describe with neat diagra the operation of AF signal generator. Ans Diagra: diagra OR (Any other relevant diagra shall be considered) Explanation: Fig. illustrates AF signal generator. It consist of RC wein bridge oscillator, Schitt trigger, Attenuator. explan Page 27 of 36

28 In AF signal generator, the variable frequency wein bridge oscillator produces the frequency of interest set by user. It is aplified & available at o/p as since function. The type of oscillator circuit used depends on range of frequencies which generator is designed. ation The o/p of wein bridge oscillator i.e. since wave applied to Schitt trigger. So the sae sine wave is converted to square by Schitt trigger(square wave shaper) and available at o/p as square function. d) Describe with neat block diagra the operation of frequency selective wave analyser Ans Diagra. diagra Explanation: The wave to be analysed in ters of its separate frequency coponents is applied to an i/p attenuator i.e. set by eter range switch on front panel. A driver aplifier feeds the attenuated wave to a high & active filter. The filter consists of a cascaded arrangeent of RC resonant sections & filter aplifiers. The passband of total filter section is converd in decade steps over entire audio range close-tolerance polystyrene capacitors are generally used selecting frequency ranges. A final aplifier stage supplies selected signal to eter circuit & unturned buffer aplifier. Buffer aplifier used to explan ation Page 28 of 36

29 drive recorder or electronic counter. The eter is driven by average type detector. e) Describe with neat block diagra the spectru analyser. Ans Diagra: diagra OR (Any other relevant diagra shall be considered) Explanation: The ain function of spectru analyzer is to be obtain the aplitude vs frequency plot fro the frequency spectru under test. They can be classified as scanning type & non-scanning type. The sawtooth generator generates the sawtooth wave. This sawtooth wave is applied to horizontal plates of CRO. The sawtooth signal also applied to voltage tuned local oscillator. This act as frequency controlled eleent of local oscillator. When sawtooth signal is applied to voltage tuned local oscillator its frequency changes fro Fin to Fax. explan ation The RF i/p signal is applied to the ixer. The o/p of voltage tuned oscillator is used to beat with i/p signal in order to produce interediate frequency. This, If coponent is produced when corresponding coponent is present in i/p signal. The resulting, if signal is applied to detector &video aplifier. The if coponent is aplified & delectected & then it is applied to vertical deflecting plates of CRO, producing a plot of aplitude vs frequency. Page 29 of 36

30 f) Describe the working principle of logic analyser with neat diagra Ans Diagra: diagra Explanation: Logic analyzer used to analyze digital signals. Logic analyzer deals with digital doain. This is basically ultichannel oscilloscope. The probes connect the logical analyzer to syste which is under test. The probes operates as voltage divides, the lowest possible s/w rate can be selected by dividing the i/p signal. The different logic failies i.e, TTL, CMOS,NMOS etc have different threshold voltage. Hence adjustable threshold coparators are used. Each signal is connected to each line of logic analyzer. The reference signal of each coparator is set to a voltage. The logic analyzer eory consists of a RAM. The clock signals I.e, internal or external clock i/p is connected to eory on receiving explan ation Page 30 of 36

31 clock signal, the logic analyzer saples the data present on i/p signals. These saples are stored in eory. For each i/p channel the analyzer can store fro 256 to 14 saples. When eory receives trigger signal then saples are stored in it & displayed on CRT. Q.6 Attept any FOUR 16 a) Copare analog instruent with digital instruents (any four points). Ans. Sr. No. Paraeter Analog instruent Digital instruent 01 Principle The instruent that displays analog signals is called as an analog instruent The instruent that displays digital signals is called as an digital instruent 01 each point (any 4 points) Accuracy Low High 03 Resolution Low High Power required Require ore power Require less power 05 Cost Cheap costly 06 Portability Portable Less 07 Observational error Considerable Observational error Free fro Observational error 08 exaples PMMC instruent, analog aeter, analog volteter. DMM, DVM Page 31 of 36

32 (Any other relevant points should be considered) b) List the applications of DSO. Ans. Applications: 1. It can be used to easure AC as well as DC Vtg. Duty cycle etc. 2. It can be used to easure frequency, tie period. 3. It can be used to give visual representation target of radar. 4. It can be used tin edical field. 5. It can be used to save signals. 6. It can be used to deterine odulation characteristics. 7. It can be used to observe V-I characteristics of diode, transistors etc. 8. It can be used to observe B-H curves, P-V diagras. 9. It can be used to observe radiation pattern generated by transitting antenna. 10. In odern DSO it is possible to add, subtract the wave. 01 each point (any 4 points) c) How to connect aeters and volteters in electrical circuits? Give justification. Ans. Connections of Aeters: aeters are to be connected in series of circuits. 1. While connecting aeters across ef source always a series resistance should be used. This is necessary to liit the current passing through eter. 2. The polarity of the eter should be first observed & then it should be connected accordingly. The reverse polarity ay daage the pointer of eter. 3. While using the ulti range aeter, first use highest current range & then go on decreasing range until good upscale reading obtained. s Connections of Volteters: 1. The resistance of Volteter is very high & so while connecting a Volteter, care should be taken that the Volteter is connected across (parallel) the circuit or coponent. 2. Polarity should be observed & connections should be accordingly ade. 3. While using Volteter highest range should be used first & then range should be decreased. 4. Loading effect can be iniized by using high sensitivity s Page 32 of 36

33 Volteters. d) Explain operation of Integrating type digital volteter with neat block diagra. Ans. Diagra: s diagra s explan ation OR (Any other relevant points should be considered) Operation: At the start of easureent counter is reset to zero. So output of Flip-Flop is zero. This is applied to switch control. The switch control now connects input vtg. (V in ) to the integrator. Integrator now starts integrating the input vtg. that eans capacitor starts charging. Because of this output of integrator changes fro zero value. It causes zero detector to change its stage. It eans it provides a high signal to logic gate. Logic gate opened, no. of clock pulses are passed to counter. The counter will count these pulses a certain tie T 1. After this tie the counter is reached to 999. After this 1 is passed to Flip-Flop. The output of Flip-Flop is 1. This is connected to control logic. Now s/w changes position fro V in to V ref. so integrator will starts integrating this ref. voltage (-V ref ). This will cause capacitor starts discharging. It will take place tie period t 2. At this instant zero detector gets changed. This will cause Page 33 of 36

34 closing of logic gate & counting operation is copleted. Then data passed to digital readout. e) Explain digital ultieter with neat block diagra. Ans. Diagra: s diagra s explan ation Explanation: In order to easure unknown current, current to vtg. (I to V) converter is used. An unknown current applied to op-ap. I/P ipedance of opap is very high. So current passing through it is negligible. Thus I in = I Fb. This feedback current pass through resistance. This will cause a vtg. drop across resistance. This vtg. is applied to A to D converter & finally digital display is obtained. Thus o/p is directly proportional to unknown current. In order to easure unknown resistance; a constant current source is Page 34 of 36

35 used. The current fro this constant current source is allowed to pass through unknown resistance. Thus proportional vtg. is obtained. This o/p directly proportional to unknown resistance. To easure AC vtg, a rectifier & filter is used. This rectifier converts AC into DC signal & this DC signal is applied to A to D converter & to digital display. f) Explain working principle of Q eter with neat circuit diagra. Ans. Diagra: s diagra s explan ation OR (Any other relevant points should be considered) Explanation: The Q factor is called as quality factor or storage factor. Working principle of Q eter is based on characteristics that vtg. across the coil or capacitor is equal to applied vtg. ties the Q factor of the circuit. If a fixed vtg. is applied to the circuit, the volteters across the capacitor can be calibrated to read Q value directly. At resonant frequency, X L = X C The vtg. across capacitance, Ec = IXc = IX L = I W L (2) Dividing equation (2) by (1) Theree E = IR Theree E C /E = I W L/ IR = IX C = Q Q = WL/ R = E C /E E C = Q E Page 35 of 36

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