Mumbai University EXTC (Semester -III) 1 |www.brainheaters.in Solution for Electronic Instruments and Measurements May 2016 Index Q.1) a) …………………………………………………………………………. 2 b) …………………………………………………………………………. 3 c) …………………………………………………………………………. 4 -5 d) …………………………………………………………………………. 6 e) …………………………………………………………………………. 6 f) …………………………………………………………………………. 7 Q.2) a) …………………………………………………………………………. 7-10 b) …………………………………………………………………………. 10-11 Q.3) a) …………………………………………………………………………. 11-15 b) ………………………………………………………………………….16-18 Q.4) a) ………………………………………………………………………….18-20 b) …………………………………………………………………………. 20-22 Q.5) a) …………………………………………………………………………. N.A b) …………………………………………………………………………. 23-24 Q.6) a) …………………………………………………………………………. 24-25 b) …………………………………………………………………………. N.A c) …………………………………………………………………………. 26-28 d) …………………………………………………………………………. 28-29
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Solution for Electronic Instruments and Measurements · Solution for Electronic Instruments and Measurements ... Explain alternate mode and chop mode in a dual trace ... mode of operation
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Mumbai University EXTC (Semester -III)
1 |www.brainheaters.in
Solution for Electronic
Instruments and Measurements
May 2016
Index
Q.1)
a) …………………………………………………………………………. 2
b) …………………………………………………………………………. 3
c) …………………………………………………………………………. 4 -5
d) …………………………………………………………………………. 6
e) …………………………………………………………………………. 6
f) …………………………………………………………………………. 7
Q.2)
a) …………………………………………………………………………. 7-10
b) …………………………………………………………………………. 10-11
Q.3)
a) …………………………………………………………………………. 11-15
b) ………………………………………………………………………….16-18
Q.4)
a) ………………………………………………………………………….18-20
b) …………………………………………………………………………. 20-22
Q.5)
a) …………………………………………………………………………. N.A
b) …………………………………………………………………………. 23-24
Q.6)
a) …………………………………………………………………………. 24-25
b) …………………………………………………………………………. N.A
c) …………………………………………………………………………. 26-28
d) …………………………………………………………………………. 28-29
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Q1) Answer any four.
a) Explain alternate mode and chop mode in a dual trace
oscilloscope.
Ans: Alternate Mode : A display mode of operation in which the oscilloscope
completes tracing one channel before beginning to trace another channel.
Chop Mode : A display mode of operation in which small time segments
of each channel are traced sequentially so that more than one waveform
can appear on the screen simultaneously.
Alternate and Chop Display
On analogue scopes, multiple channels are displayed using either an alternate or
chop mode. (Digital oscilloscopes do not normally use chop or alternate mode.)
Alternate mode draws each channel alternately - the oscilloscope completes one
sweep on channel 1, then one sweep on channel 2, a second sweep on channel 1,
and so on. Use this mode with medium- to high-speed signals, when the sec/div
scale is set to 0.5 ms or faster.
Chop mode causes the oscilloscope to draw small parts of each signal by
switching back and forth between them. The switching rate is too fast for you to
notice, so the waveform looks whole. You typically use this mode with slow
signals requiring sweep speeds of 1 ms per division or less.
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b) What is cold junction compensation in thermocouples.
Ans:
Metal used for thermocouple
Copper-constantan alloy: 0-
200000 F
Iron-conatanatn alloy : 0-12000F
Platinum –Platinum/Rhodium
alloy: 0-30000 F
Chromel – Alumel alloy :0-9000 F
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c) Write a note on piezoelectric transducer .
Ans:
Different modes of piezoelectric transducer
Different arrangements of using the piezoelectric transducer are shown as
in above diagram
(a) (b)Equivalent circuit of the piezoelectric
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d) Which is fastest ADC and why?
Ans: Flash converters are extremely fast compared to many other types of
ADCs, which usually narrow in on the "correct" answer over a series of stages.
Compared to these, a flash converter is also quite simple and, apart from the
analogue comparators, only requires logic for the final conversion to binary.
For best accuracy, often a track-and-hold circuit is inserted in front of the ADC
input. This is needed for many ADC types (like successive approximation
ADC), but for flash ADCs there is no real need for this, because the
comparators are the sampling devices.
A flash converter requires a huge number of comparators compared to other
ADCs, especially as the precision increases. A flash converter
requires comparators for an n-bit conversion. The size, power consumption
and cost of all those comparators makes flash converters generally impractical
for precisions much greater than 8 bits (255 comparators). In place of these
comparators, most other ADCs substitute more complex logic and/or analogue
circuitry that can be scaled more easily for increased precision.
e) Define accuracy ,precision and sensitivity with suitable example.
Ans : a) Sensitivity: The sensitivity is defined as mV/mm . and it is typically 1
to 2 mV/0.01 mm for the LVDT Sensitivity should be as high as possible and
the typical value of LVDT sensitivity shows that it is a highly sensitive
transducer
b) Accuracy: It indicates the deviation of actual output from the theoretical
value. It depends on the accuracy of the resistors used in ladder and the
precision of the reference voltage used. It is also specified in terms of
percentage of full scale output e.g. If full scale output is 15V and accuracy is +
or – 0.1 % then the
maximum error =o.1x15/ 100 = 15mV
c) Precision: It is a measure of the responsibility of the measurement ,that is
given a fixed value of variable. Precision is a measure of the degree of which