Code: A-12 Subject: INSTRUMENTATION AND MEASUREMENTS
Time: 3 Hours Max. Marks: 100
NOTE: There are 11 Questions in all.
Question
1 is compulsory and carries 16 marks. Answer to Q. 1. must be written in the
space provided for it in the answer book supplied and nowhere else.
Answer
any THREE Questions each from Part I and Part II. Each of these questions
carries 14 marks.
Any
required data not explicitly given, may be suitably assumed and stated.
Q.1 Choose
the correct or best alternative in the following: (2x8)
a. If in a Wien bridge circuit the resistors are each equal to 50 K
and the
capacitors are each equal to 0.02
then the resonant frequency is nearly
_________.
(A) 159.2 Hz. (B) 512.5 Hz.
(C) 178.3 Hz. (D) 234.5 Hz.
b. The purpose of the trigger circuit in a CRO is ___________
(A) to generate an electronic beam from a heated cathode.
(B) to increase the potential of the input signal to the required
level.
(C) to synchronize the horizontal deflection with the vertical input.
(D)
to switch from the vertical channel to
the horizontal channel.
c. The circuit diagram given in Fig.1 is that of _______________
(A) an A/D converter. (B) an analog multiplexer.
(C) a
digital multiplexer. (D) a D/A converter.
d. The principle of a frequency counter is that of __________.
(A) enabling the input signal to
appear at the output when the gate pulse appears.
(B) generating an output frequency
which is proportional to the analog input.
(C) passing several independent
signals through a common circuit.
(D) facilitating gating of input
frequency into the counter for a predetermined time.
e. Considering the radio receiver characteristics, the ability to reject unwanted signals is indicated by the parameter namely ____________.
(A)
noise
figure. (B) selectivity.
(C) image response. (D) sensitivity.
f. In the op-amp circuit of Fig.2 the value of
the capacitor that is required for the voltage 
to be a ramp of 40 V/sec is______________.
(A) 12.5 
. (B) 5.0 m sec.
(C) 2.5 
. (D) 4.8 m sec.
g. The desirable characteristics of a wire type
of strain gauge are ________ and _________.
(A)
high
gauge factor, high temperature coefficient.
(B)
high
gauge factor, low temperature coefficient.
(C) low gauge factor, high
temperature coefficient.
(D) low gauge factor, low
temperature coefficient.
h. A comparison of a square wave generator and a pulse generator shows that the former has a duty cycle which is ________ and also ________.
(A)
higher,
variable. (B) lower, constant.
(C) lower, variable. (D) higher, constant.
PART I
Answer
any THREE Questions. Each question carries 14 marks.
Q.2 a. List out the various dynamic characteristics
of a measuring system. Explain the
terms : bandwidth, speed of response and settling time. (6)
b. Distinguish between the following pairs of
transducers :
(i) Active and
Passive. (ii) Piezoelectric and Photoelectric.
(iii)
Inductive and Capacitive. (iv) Input and Output. (8)
Q.3 a. Give the block diagram of a sweep frequency
generator and the circuit diagram of a typical linearizing circuit used with
it. (6)
b. Explain how the hysteresis loop of a material
is obtained under AC operating conditions. (8)
Q.4 a. Define
dissipation factor and power factor of a series RC combination, also
describe the special features of a Schering bridge. Derive the balance equation for this bridge. (6)
b. The bridge shown in Fig.3 is balanced at 1000
Hz. Determine R and C or L constants of
arm C D, considered as a series circuit.
The given data is : arm AB, R = 2010 
is parallel with C =
0.048
, arm BC, R = 1020 
in series with C =0.5
, arm DA, R = 290 
in parallel with 0.1
. (8)
Q.5 a. Explain the words acquisition time, aperture time and holding
time as applied to a sample and hold circuit. (6)
b. Give the voltage vs time
diagram of a successive approximation A/D converter, explain how it is to be
interpreted. (8)
Q.6 a. Give the block diagram of a general purpose
CRO and identify the various parts.
Briefly describe their important features. (8)
b. A CRT has parallel deflecting plates 3.6 cm long and 0.36 mm apart. If the screen is 60 cms from the centre of the deflecting plates, accelerating voltage is 270 V and the deflection on the screen 25 cms, determine the deflection voltage and deflection factor. Derive any formula used. (6)
PART II
Answer
any THREE Questions. Each question carries 14 marks.
Q.7 a. Give the block diagram of a ramp type DVM;
compare its features with the stair
case ramp DVM. (6)
b. Describe the
various measurement methods that are presently adopted in measurement systems. (8)
Q.8 a. List out the various methods for measurement
of R.F. power and describe in detail the method that involves a thermal sensor. (8)
b. What are the features of a bolometer element
and its support? (6)
Q.9 a. Describe the AM alignment and FM receiver
alignment for radio receivers. (7)
b. Give the set up for the quieting method and
explain the related steps. (7)
Q.10 a. Explain what is meant by harmonic
distortion. Also with the help of a block diagram explain the features of a
harmonic distortion analyser. (6)
b. A resistance strain gauge with a gauge factor
of 2.2 is fastened to a steel member which is subjected to stress. If the Youngs modulus of elasticity of
steel is 
change in resistance
per unit of resistance 
of the strain gage is
0.12%, determine the stress in 
of the steel member. (8)
Q.11 Write notes on any TWO
of the following:
(i)
Time
base error in frequency and time measurements.
(ii)
Storage
oscilloscope.
(iii)
Hall
effect transducers. (
)