250+ TOP MCQs on Data Conversion – 1 and Answers

Avionics Multiple Choice Questions on “Data Conversion – 1”.

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

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

Answer: b
Clarification: 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. 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

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

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

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

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

6. 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

Answer: d
Clarification: 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. 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

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

8. 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

9. 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

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

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

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

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

Answer: b
Clarification: The Digital to analog converter takes the binary number as an input and produces the analog voltage proportional to the binary number. These analog voltages represent specific analog voltage levels and have stairstep characters.