VARDHAMAN COLLEGE OF ENGINEERING
(AUTONOMOUS)
Shamshabad – 501 218, Hyderabad
Department of Electronics and Communication Engineering
Four Year B. Tech V Semester Question Bank 2014 – 15 (Regulation: VCE R-11)
ELECTRONIC MEASUREMENTS AND INSTRUMENTATION
UNIT-III
Q1.what is secondary emission? How it is useful in a storage oscilloscope
Q2. Derive the bridge balance equation of the basic ac bridge.
Q3. What is meant by Q factor of coil?
Q4. Which bridge is preferred for measurement of high Q COIL?
Q5. List out the limitations of Wheat stone bridge
Q6. What are the different sources of errors occurred in ac bridges
Q7. a) What are the different problems associated with measurement of low resistance?
Explain the principle of working a Kelvin’s double bridge. Draw the circuit of a Kelvin’s
double bridge used for the measurement of low resistances. Write the condition for balance
b) If in fig the ratio of Ra to Rb is 1000𝜴, R1 is 5𝜴 and R1=0.5R2. What is value of Rx
Q8.a) what is the principle of Q meter and describe the Operation of a series connection of Q
meter. Derive the unknown resistance, inductance and capacitance
b) Find the series equivalent inductance and resistance of Hays Bridge with the following
bridges arm ω=3000rad/s, R2=10k 𝜴,R1=2K 𝜴 C1=1 µF R3=1K 𝜴
Q9.a) Draw and explain the block diagram of digital storage oscilloscope
b) State the advantages of digital storage oscilloscope
Q10. a) Describe the following storage techniques used in storage oscilloscopes:
i)
Mesh storage
ii)Phosphor storage
b) State the limitations of analog storage oscilloscopes.
Q11. a) Draw a neat schematic diagram of the Andersons Bridge. Deduce the equations when
the bridge is under balance condition.
b) An ac bridge has the following constants
Arm AB---capacitor of 0.5µF in parallel with 1K 𝜴 resistance
Arm AD---resistance of 2K 𝜴
Arm BC----capacitor of 0.5µF
Arm CD---unknown capacitor Cx and Rx in series
Frequency—1 KHz
Determine the unknown capacitance and dissipation factor using Sherings Bridge shown in
fig.
Q12. a) The sketches shown in fig.1 display Lissajous patterns for cases where voltages of same
frequency out of different phase are connected to Y and X plates of the oscilloscope. Find the
phase difference in each case. The spot generating the patterns moves in the anticlockwise
direction.
b) The Lissajous pattern obtained on the screen by applying horizontal signal of frequency 1 KHz
as shown in fig. determine the unknown frequency of vertical signal.
Q13.a) Draw the circuit diagram of Maxwell's bridge and derive the equation for determining
unknown quantities.
b) The four arms of a Maxwell's bridge are arranged as follows:
AB and CD are non reactive resistances of 250 𝜴 each; DA is a standard variable reactor L of
resistance 35.2 𝜴and CD comprises a standard variable resistor R in series with a coil of
unknown impedance. Balance is obtained when L=25.6mH and R=25 𝜴. Find the resistance
and inductance of the coil.
UNIT-IV
Q1. Give the classifications of transducers in instrumentation.
Q2. Mention the different types of strain gauges used for measurement of resistance.
Q3. Define the following and give one example
a) Transducer b) Inverse Transducer
Q4.Draw the following characteristics for thermistors
a) Resistance-temperature b) voltage-current
Q5. Are thermocouple act as active or passive transducer and draw the thermocouple output voltage
as a function of temperature for various thermocouple materials?
Q6. Mention the different criteria for selection of transducer for a particular application.
Q7. a) Sketch the deflection system for dual-trace oscilloscope. Explain its operation. Also, explain
the use of a system in chopped mode and in alternate mode with waveforms.
Q8. A resistance wire strain gauge uses a soft iron wire of small diameter. The gauge factor is ±4.2.
Neglecting the piezo resistive effects calculate passions ratio?
Q9. a) What is piezo resistive effect? Explain with diagrams of bonded and unbounded types of strain
gauges?
b) Explain the construction and working of a linear voltage differential transformer. Explain how
the magnitude and direction of the displacement of core of an L.V.D.T detected.
Q10. a) What are thermistors, Explain their different forms of constructions. Draw their resistivity
versus temperature characteristics
b) The output of an LVDT is connected to a 5v voltmeter through an amplifier (amplification
factor is 250) an output of 2mv appears across the terminals of LVDT when the core moves a
distance of 0.5mm. Calculate the sensitivity of the LVDT
Q11. a) Describe the working and construction of resistance thermometer. Sketch the typical
characteristics with the materials used for RTD
b) A Quartz piezo electric crystal having a thickness 2mm and voltage sensitivity of 0.055 v-m/N
is subjected to a pressure of 1.5 MN/m2. Calculate the voltage output if the permittivity of
quartz is 40.6×1012F/m. calculate its charge sensitivity.
Q12.a) Explain the construction and principle of working linear voltage differential transformer
b) A resistance strain gauge with a gauge factor of 2 is cemented to a steel member who is
subjected to strain of 1×10-6. If the original resistance of gauge is 130𝜴, calculate the change in
resistance.
Q13. a) What is the principle of piezo electric transducer? Derive the equation for voltage sensitivity
(g) and charge sensitivity (d) of a crystal.
b) State the advantages and limitations of thermocouple
UNIT-V
Q1. What are the uses of Data Acquisition Systems?
Q2. What is the principle used for measuring Vacuum using Ionization type vacuum gauge.
Q3. What are the uses of Recorders in digital data acquisition systems?
Q4.What are the secondary transducers used for the measurement of pressure
Q5.What are the different types of microphones used for sound measurement
Q6.Name 4 types of electric pressure transducers and describe one application of each type?
Q7. a) What is pH value? Describe the working of a pH meter with neat sketch
b) Mention the different quantities involved in vibration measurement
Q8. a) Why ballast circuit cannot be used for the measurement of static strain? Why the null method
of Wheatstone bridge is unsuitable for the measurement of dynamic strain
b) A single strain gauge having a resistance of 500Ω, gauge factor of 2 and a temperature
coefficient of 1x10-5 per 0c at room temperature is mounted on the bam and connected in the
arm AB of the bridge for measuring a strain in a cantilever beam. The other three arms BC, CD
and DA of the bridge have resistance of 100,100 and 500 Ωs respectively. The detector
connected across terminals A and C of the bridge has a resistance of 100 Ω and sensitivity 5mm
per μA. Determine the detector deflection for gauge strain of 0.002. Also determine the change
in effective strain indicated for an increase of 200c in room temperature. Supply to the bridge is
of 12v.
Q9. a) Explain different methods used for measurement of Torque?
b) Define PLC? Explain a program sequence executed by a PLC?
Q10. a) Explain the following methods of measurement of torque
i) Digital method
ii) Magnetostrictive method
b) A strain gauge has a resistance of 120 𝜴 & gauge factor 2, this strain gauge in series with a
ballast resistance of 120 𝜴 across a 6V supply.
Determine i) voltage sensitivity ii) change in output voltage
Taken pressure of 240MN/m2, modulus of elasticity is 200×109 N/m
Q11. a) Explain the working of transducers for the measurement of acceleration
b) Explain with the diagram the PLC structure and define Scan time and response time?
Q12. a) Draw the block diagram of analog data acquisition system and explain each block in brief
b) A strain gauge has two fixed resistors R3 & R4 of 150 𝜴 each and a variable resistor R2 which
is 110 𝜴 at zero strain & 110.75 𝜴 with the strain. The gauge factor is 2.54 determine strain.
Q13. Draw the architecture of the IEEE 488 interfacing Bus and explain it?
Q14. a) What is data acquisition system? Explain the working of multichannel analog multiplexed
DAS.
b) Where are sample and hold circuit used? Sketch the circuit arrangement along with the
output waveform and discuss briefly the operation of the circuit