Download Experiment 4 Cathode Ray Oscilloscope and Multimeter

Experiment 4
Cathode Ray Oscilloscope and Multimeter
Nana Siddharth
16 October 2008
Aim:To gain familiarity with the Multimeter and the understanding already obtained.
Cathode Ray Oscilloscope by performing various
experiments such as studying the charecteristic of
Theory:The Cathode Ray Oscilloscope is used to
ciruits like the LR and the RC circuits and observing analyse the characteristics of circuits such as the LR
the various Lissajous figures observed.
and the RC circuits. These circuits upon input of
a varying voltage show a complex “resistance” with
Apparatus:The functions of the galvanome- the resultant qantity called an impedance customarter,ammeter and the voltmeter are combined into ily called Z given by Eq.1.
p
a single instrument,the implementation of these
(1)
Z = R2 + (Xc − Xl )2
features and some other common lab tasks is represented in a single instrument called the Multimeter.
Though the tolerance of the multimeter is no match
The rectances of the Inductor and the Capacitor
for the tolerances of these instruments in their solo
are given by Eq.(2a) and Eq.(2b) respectively.
form; It suffices for everyday laboratory purposes.
The Cathode Ray Oscilloscope is an indispensable
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Xc =
(2a)
tool in studying time-variant inputs, such as alterCω
nating current,modulated signals etc..itconsists of an
Xl = Lω
(2b)
electron beam which when incident on the phosphor
screen produces a glowing dot.When a transverse
The Multimeter is used to verify the data collected
Electric field is applied the dot moves; when the field
is proportional to the input then it moves in such a from the oscilloscope. Care is taken to note whether
the rms or the peak parameters are collected.
fashion as to depict the variation in the input.
The signal generators are then connected to the
The Cathode Ray Oscilloscope has among its
arsenal,a screen which is marked as a grid and inputs of the Cathode Ray Oscilloscope.The electron
various circuits to vary the proportionality be- beam is then subjected to SHM in two dimensions
tween the input signal and the movement of the and has a trajectory which is referred to as a
dot.Thus allowing for a “zooming” of the plot or a Lissajous figure.When the the frequencies match,
“contraction” , it also allows for the timescale to the figure is a conic (an ellipse if the amplitudes are
be varied.The Cathode Ray Oscilloscope however, distinct or a circle if otherwise).
allows for a simultaneous plot of more than one
input, allowing the variation to have more than one
Procedure: The RC circuit (Fig.1) is set up
degree of freedom.The Cathode Ray Oscilloscope as shown and the data obtained tabulated.The
is thus another way to obtain information of the same is repeated to with the LR circuit(Fig.2).The
circuit being studied and adds a new dimension to bread-board is utilised for realising the circuit as
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the current is of the order of a milli-ampere.The
Lissajous figures are then observed and the output
depicted.
Figure 1: An RC Circuit.
Figure 3: A plot of LR Data
Table 2: Data gathered for an RC Circuit.
S.No
1.
2.
3.
4.
Figure 2: An LR Circuit.
Frequency(KHz)
0.098
0.088
0.09
0.196
Voltage(V)
0.016
0.018
0.017
0.008
Observations:
Table 1: Data gathered for an LR Circuit.
S.No
1.
2.
3.
4.
5.
Frequency(KHz)
0.099
0.071
0.08
0.09
0.135
XL (×10−5 Ω)
8.79
6.15
6.23
9.43
14.47
Here both XL and Xc are calculated using Ohm’s
Law and noting that the observed current is 10−3 A
( VRr ).
The data is plotted and a least squares fit is performed to yield the capacitance to be 999.68 mF and
the inductance to be 5.141×10−3 H.
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Figure 5: A plot of observed Lissajous Figures.
Figure 4: A plot of RC Data
The Lissajous Figures observed are depicted in
Fig.5
Result:The characteristics of the RC and LR circuits are observed and the functions of the Cathode
Ray Oscilloscope and the the Multimeter noted.
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