Deemed University 2011 B.Tech Electronics and Communications Engineering University: Lingayas University Term: V Title of the : Electronic Measurement and Instrumentation - Question Paper
Roll No. ..
Lingayas University
B.Tech. 2nd Year (Term V)
Examination Feb 2011
Electronic Measurement and Instrumentation (EC - 204)
[Time: 3 Hours] [Max. Marks: 100]
Before answering the question, candidate should ensure that they have been supplied the correct and complete question paper. No complaint in this regard, will be entertained after examination.
Note: Attempt five questions in all. All questions carry equal marks. Question no. 1 (Section A) is compulsory. Select two questions from Section B and two questions from Section C.
Section A
Q-1. Part A
Select the correct answer of the following multiple choice questions. [10x1=10]
(i) In circuits of RF voltmeters
(a) Vacuum tube diodes are used
(b) PN junction diodes are used
(c) Point contact type diodes are used
(d) All of the above
(ii) Electronic voltmeters which use rectifiers employ negative feedback. This is done
(a) To increase overall gain
(b) To improve stability
(c) To overcome nonlinearity of diodes
(d) None of the above
(iii) The input impedance of a CRO is nearly
(a) Zero (b) Around 10 W
(c) Around 100 W (d) Around one M W
(iv) Among the voltages to various electrodes in a CRT, voltage is highest on
(a) Focusing anode (b) Deflection plates
(c) PD anode (d) None of above
(v) A nixie tube requires
(a) 10 cathodes (b) 14 cathodes
(c) 15 cathodes (d) 20 cathodes
(vi) The switching time of LED is of the order
(a) 1 s (b) 1 ms
(c) 1 ms (d) 1 ns
(vii) Radiation pyrometers are used in the temperature range of
(a) 0-5000C (b) 500-10000C
(c) -250-5000C (d) 1200-25000C
(viii) A thermocouple
(a) Has low time constant when it is base
(b) Has low time constant when provided with sheath
(c) Has same time constant when it is bare or provided with sheath
(d) None of above
(ix) Time division multiplexing requires
(a) Constant data transmission
(b) Transmission of data samples
(c) Transmission of data at random
(d) Transmission of data of only one measurand
(x) A half effect transducer can be used for measurement of
(a) Power (b) Current
(c) Displacement (d) All of the above
Part B
(a) Describe the advantages of LED.
(b) Describe the properties of materials used for piezo-electric transducers. [2x5=10]
Section B
Q-2. (a) Explain the working principle and operation of sampling oscilloscopes.
(b) Explain the principle of operation of a digital storage oscilloscope. [2x10=20]
Q-3. (a) Draw and explain the block diagram of a function generator.
(b) Explain the working of a Harmonic analyzer. [2x10=20]
Q-4. (a) What is a data acquisition system? How is it incorporated?
(b) Describe dc signal conditioning system. What is major draw back of this system? [2x10=20]
Section C
Q-5. (a) A pulse in applied to a piezo-electric transducer for a time T. Prove that in order to keep the undershoot to a value within 5%, the value of time constant should be approximately 20T.
(b) A parallel plate capacitive transducer uses plates of area 500 mm2 which are separated by a distance 0.2 mm. Calculate the value of capacitance when dielectric is air having permittivity of 8.85x10-12 F/m. Calculate change in capacitance if linear displacement reduces the distance to 0.18 mm between plates. [2x10=20]
Q-6. (a) The electronic voltmeter has following data: Rs = 50 kW, rd = 100kW, gm = 0.005 mho A 50W ammeter with full scale deflection current of 1 mA is used. If input voltage is1V. What will be the calibration resistance to produce full scale current?
(b) A circuit consisting of a coil, a resistance and a variable capacitor connected in series is tuned to resonance using a Q-meter. If frequency is 500 kHz, resistance is 0.5W and variable capacitor set to 350 pf. Calculate effective inductance and resistance of coil if Q-meter indicates 90. [2x10=20]
Q-7. (a) A 
digit
voltmeter is used for measuring voltage
(i) Find resolution of instrument.
(ii) How would a voltage of 14.53 be displayed on 10 V scale and 100 V scale.
(b) Write short note on A/D converter. [2x10=20]
Q-8. (a) A 3 digits display counter selected for frequency measurement is provided with gating periods of 1 s, 100 ms, 10 ms and 1 ms. Gating period selected for measurement of unknown frequency is 10 ms. If reading found is 052
(i) What is frequency?
(ii) How can the validity of result be checked?
(b) The gap of reproducing head in a tape recorder is 6.4 mm. Determine the minimum speed of the tape for satisfactory response at 50 kHz. Assume wave length on the tape is greater than 2.5 times gap length. [2x10=20]
| Earning: Approval pending. |
