AMIETE – ET (NEW SCHEME)   –   Code: AE60

 

Subject: INSTRUMENTATION AND MEASUREMENTS

 

Flowchart: Alternate Process: DECEMBER 2009Time: 3 Hours                                                                                                     Max. Marks: 100

 

 

 

NOTE: There are 9 Questions in all.

·      Question 1 is compulsory and carries 20 marks. Answer to Q.1 must be written in the space provided for it in the answer book supplied and nowhere else.

·      Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.

·      Any required data not explicitly given, may be suitably assumed and stated.

 

 

Q.1       Choose the correct or the best alternative in the following:                                  (210)

       

             a.  A measure of the consistency or repeatability of measurements is called

 

                  (A) sensitivity                                        (B)  accuracy

                  (C) precision                                        (D)  resolution

 

             b. A 600 V voltmeter is specified to be accurate within  at full scale.  The limiting error when the instrument is used to measure a voltage of 250 V is

 

                  (A) 10%                                               (B) 7.5%

                  (C) 1.25%                                            (D) 4.8%

 

             c.  The DVM with the highest speed of conversion is   

 

                  (A) Successive approximation type       (B) Dual slope type

                  (C) Integrating type                               (D) Ramp type

                                                                             

             d.  Digital instruments have input impedance of the order

 

                  (A)                                                 (B)

                  (C)                                               (D)

       

             e.  Complex waveform are most accurately measured with an     

 

                  (A) Average responding voltmeter         (B) True RMS voltmeter

                  (C) Peak responding voltmeter              (D) None of the above

 

             f.   AC bridge circuits are commonly used for  

 

                  (A) phase shifting                                 

                  (B) providing feedback paths for oscillator

                  (C) filtering out undesirable signals        

                  (D) all of the above

 

             g. Maxwell’s bridge is used for inductance measurements of  

 

                  (A) low Q                                            (B) high Q

                  (C) both (A) and (B)                            (D) none of the above

 

             h.  Analog spectrum analysers are also called as   

 

(A)  Real time analysers                         (B)  Fourier analysers

                  (C) Digital analysers                              (D) None of the above

 

             i.   An example of a first order instrument is

 

                  (A) Potentiometer                                 (B) Mercury in glass thermometer

                  (C) Spring balance                                (D) None of the above

 

             j.   The resolution of a DVM with 4 digit display is  

 

                  (A)                                                 (B)

                  (C)                                         (D)

 

 

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

 

 

  Q.2     a.   Discuss the following types of static error of a measuring instrument

                   (i)   Gross errors                                  (ii)  Systematic errors                                  

                   (iii) Random errors                                                                                          (10)

                                      

         b.   Three resistors have the following ratings: , , .  Determine the magnitude and limiting error in ohm and in percent of the equivalent resistance of these resistances connected in series.                             (6)

 

  Q.3     a.   An unbalanced wheatstone bridge is given in the Fig.1.  Calculate the current through the galvanometer G.                                                              (6)
 

 


             b.   Derive the expression for dissipation factor in Schering’s Bridge.                         (5)    

 

             c.   An AC bridge has the following constants

                   Arm AB-capacitor of  in parallel with resistance.

                   Arm AD – resistance of 2

                   Arm BC – capacitor of

                   Arm CD – unknown capacitor  and  in series.

                   Frequency – 1kHz

                   Determine the unknown capacitance and dissipation factor.                                 (5)

                  

  Q.4     a.   Two different voltmeters are used to measure the voltage across  in the circuit of Fig.2.  The meters are as follows:

                   Meter 1: 

                   Meter2:                                                  

                   Calculate

                   (i)   Voltage across  without any meter across it.

                   (ii)  Voltage across  when Meter 1 is used.
 
                   (iii) Voltage across  when Meter 2 is used

                   (iv) Error in the voltmeter.                                                                                  (8)

 

 

 

 

 

 

 

 

             b.   Discuss the following:

                   (i)   AC voltmeter using fullwave Rectifier.

                   (ii)  Average responding voltmeter.                                                                     (8)

 

  Q.5     a.   Bring out the principle of Dual slope type DVM and prove that the accuracy of the measured voltage is independent of the integrator time constant.                                                      (10)

 

             b.   Discuss the salient features of Digital phase meter.                                               (6)

 

  Q.6     a.   Mention the front panel details of a AF signal generator.                                      (6)

 

             b.   Explain the following with reference to a CRO

                   (i)   Vertical amplifier.

                   (ii)  Horizontal Deflection system.                                                                     (10)

            

  Q.7     a.   What is the difference between a wave analyzer and a harmonic distortion analyzer?  Draw the circuit diagram and explain the working of heterodyne type wave analyzer.                                    (10)

 

             b.   How is the SWR measured using directional couplers?  Determine SWR if the maximum value of voltage is 8V and the minimum value of voltage is 2V in a standing wave pattern.                               (6)

       

  Q.8     a.   Write short notes on:

 

                   (i)  Potentiometric Recorders.

                   (ii) Digital Data Recording.                                                                            (62)

 

             b.   If the frequency of a signal to be recorded with a strip-chart recorder is 20Hz.  What must be the chart speed used to record one complete cycle on 5 mm of recording paper?                              (4)

 

  Q.9     a.   Describe the principle of operation of a pressure transducer employing each of the following principles

                   (i)    Inductive transducer

                   (ii)   Capacitive transducer                                                                               (10)

 

             b.   Explain the ratiometric conversion and logarithm compression w.r.t signal conditioning of the inputs.                                                                       (6)