Engineering Questions with Answers - Multiple Choice Questions

# MCQs on Data Conversion – 1

1 - Question

What is the main role of an ADC?
a) Amplify
b) Convert analog to digital
c) Reduce noise
d) Increase range

b
Explanation: ADC corresponds to Analog to Digital Converter which is used to convert an analog signal into a digital. Digital signal can be processed and manipulated.

2 - Question

The process of converting a continuous analog signal to a discrete digital signal is called?
a) Discretisation
b) Sampling
c) Preemphasis
d) Reduction

b
Explanation: An analog signal is continuous and hence contains an infinite number of points. The process in which this continuous signal is discretized is called as sampling. The sampling period determines the accuracy of conversion.

3 - Question

What is the minimum frequency of sampling so that the analog waveform is adequately expressed?
a) Minimum sampling rate
b) Minimum sampling frequency
c) Nyquist frequency
d) Conversion rate

c
Explanation: The minimum frequency at which an analog wave should be sampled is given by Nyquist frequency. If the sampling frequency is below this limit then the analog waveform is not fully represented and leads to data loss.

4 - Question

What is the minimum rate at which an analog signal of frequency 6000Hz is sampled?
a) 6000Hz
b) 60Hz
c) 120Hz
d) 12000Hz

d
Explanation: Minimum sampling frequency= Nyquist frequency = 2x(frequency of analog waveform)
= 2x 6000Hz = 12000Hz.

5 - Question

What is the number of voltage increments that can be represented in an 8-bit system?
a) 255
b) 256
c) 215
d) 126

a
Explanation: The number of voltage increments that can be in an N bit system is given by 2N-1 = 28-1 =255.

6 - Question

What is the error that occurs when the number of bits is not sufficient enough to represent the analog voltages?
a) Data error
b) Sampling error
c) Acquisition error
d) Quantization error

d
Explanation: When the number of bits is not sufficient enough to represent the analog voltage levels, quantization error occurs. The greater the number of bits, the greater the number of increments over the analog range and the smaller the quantizing error.

7 - Question

What is the maximum amount of quantization error that can occur in a 10bit system in the input analog voltage is from 0V to 6V?
a) 10mV
b) 6mV
c) 0.5mV
d) 1mV

b
Explanation: The minimum voltage step input is 6/(2N-1) = 6/1023 =5.865mV ≈6mV. This is the maximum error that can occur during the conversion process.

8 - Question

What is the rms noise voltage if the weight of the LSB is 0.005865?
a) 5mV
b) 1mV
c) 1.7mV
d) 0.7mV

c
Explanation: 9 - Question

What is the signal frequency if the rectangular digital wave has a time period of 71.4μs?
a) 14,006Hz
b) 15,036Hz
c) 14Hz
d) 21,436Hz

a
Explanation: Signal frequency = 1/ time period of the wave = 1/71.4μs = 14,006Hz.

10 - Question

What is the 5th harmonic of the rectangular digital wave if the frequency is 14kHz?
a) 21kHz
b) 45kHz
c) 25kHz
d) 70kHz

d
Explanation: Fifth harmonic = 5 x signal frequency = 5 x 14kHz = 70kHz.

11 - Question

What is the output of a digital to analog converter?
a) Smooth continuous wave
b) Stairstep wave
c) Triangular waves
d) Circular waves