# CRO and Electronic Measurements

 Question 1
A $10\frac{1}{2}$ digit timer counter possesses a base clock of frequency 100 MHz. When measuring a particular input, the reading obtained is the same in: (i) Frequency mode of operation with a gating time of one second and (ii) Period mode of operation (in the x 10 ns scale). The frequency of the unknown input (reading obtained) in Hz is _______.
 A 100 B 1000 C 10000 D 100000
GATE EE 2017-SET-2   Electrical and Electronic Measurements
Question 1 Explanation:
$1.\;\;10\frac{1}{2}$ digital time counter:
Frequency mode of operation: $f=\frac{n}{t}$

Let f = frequency of input signal
n = number of cycles of repetitive signal
$\Rightarrow \;\;100 \times 10^6$
Let $t \Rightarrow$ Gate time $\Rightarrow \;t=1 sec.$
$f=\frac{100 \times 10^6}{1 sec}=10^8 Hz$
$\;\;=10^8 cycles/sec$
On $10\frac{1}{2}$ digit display
$100000000.00Hz$

$2.\;\; \text{Period mode of operation:}$
$P=\frac{1}{f}=\frac{t}{n}=\frac{1sec}{100 \times 10^6}$
Let P=Period of input signal
$P=0.01 \times 10^{-6}$
$\;\;=10 \times 10^{-9}$
$\;\;=1 \times 10n-sec$
$\;\;=10.000000000 n-sec$
 Question 2
A stationary closed Lissajous pattern on an oscilloscope has 3 horizontal tangencies and 2 vertical tangencies for a horizontal input with frequency 3 kHZ. The frequency of the vertical input is
 A 1.5kHz B 2kHz C 3kHz D 4.5kHz
GATE EE 2017-SET-2   Electrical and Electronic Measurements
Question 2 Explanation:
\begin{aligned} \frac{f_y}{f_x} &= \frac{\text{Horizontal Tangencies}}{\text{VerticalTangencies}}\\ \Rightarrow \; \frac{f_y}{3} &=\frac{3 }{2}\\ \Rightarrow \; f_y&= 4.5kHz \end{aligned}

 Question 3
The slope and level detector circuit in a CRO has a delay of 100 ns. The start-stop sweep generator has a response time of 50 ns. In order to display correctly, a delay line of
 A 150 ns has to be inserted into the y-channel B 150 ns has to be inserted into the x-channel C 150 ns has to be inserted into both x and y channels D 100 ns has to be inserted into both x and y channels
GATE EE 2017-SET-1   Electrical and Electronic Measurements
Question 3 Explanation:
A delay line of 150ns has to be inserted into the y-channel to get synchronous between sweep signal applied to x-plate and test signal applied to y-plate.
 Question 4
The two signals S1 and S2, shown in figure, are applied to Y and X deflection plates of an oscilloscope. The waveform displayed on the screen is A A B B C C D D
GATE EE 2014-SET-3   Electrical and Electronic Measurements
Question 4 Explanation:
The waveform pattern appearing on the screen of CRO is shown below. Here, $S_1$ is applied to vertical deflecting plate and $S_2$ to horizontal deflecting plate. Question 5
In an oscilloscope screen, linear sweep is applied at the
 A vertical axis B horizontal axis C origin D both horizontal and vertical axis
GATE EE 2014-SET-1   Electrical and Electronic Measurements
Question 5 Explanation:
A CRO uses a horizontal input voltage which is an internally generated ramp voltage (i.e. linear sweep voltage) called "Time base of CRO". An oscilloscope is used to disply waveform which varies as a function of time. To reproduce the waveform accurately, the beam must have a constant horizontal velocity i.e. the deflecting voltage must increase linearly with time. This voltage is called a ramp voltage. Thus , a sawtooth waveform also called linear sweep voltage is applied to the horizontal deflection system ( or horizontal axis) which provides a time base to CRO.

There are 5 questions to complete.