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Electronics and Communication Engineering - Measurements and Instrumentation

Exercise : Measurements and Instrumentation - Section 4
16.
The current passing through a resistance of 100 ± 0.2% Ω is 2 ± 0.5% A. The limiting error in computation of power will be
± 0.7%
± 0.9%
± 1.2%
± 0.3%
Answer: Option
Explanation:

Limiting error = 2 x 0.5 + 0.2 = ± 1.2% (we have to take 2 x 0.5 because power ∝ I2).

17.
If the secondary burden of a CT 15 VA and secondary current is 5 A, the load impedance of CT is
0.6 Ω
5 Ω
6 Ω
10 Ω
Answer: Option
Explanation:

.

18.
Consider the following instruments
  1. Tangent galvanometer
  2. Rayleigh current balance
  3. Household energy meter
  4. Hot wire ammeter
Out of above absolute instruments are
1, 2 and 3
1, 2 and 4
1 and 2
2, 3 and 4
Answer: Option
Explanation:

Only tangent galvanometer and Rayleigh Current balance are absolute instruments. Energy meter and ammeter are secondary instruments.

19.
A 0-150 voltmeter has a guaranteed accuracy of 1% of full scale reading. If actual reading is 83 V, the percentage error is
0.83%
1%
1.81%
none of the above
Answer: Option
Explanation:

.

20.
In a CRO, the frequency of output of time base generator
is only one constant value
is adjustable
varies automatically
either (a) or (c)
Answer: Option
Explanation:

Time base signal frequency is adjustable so that voltages of different frequencies can be measured.

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