week 5

Question 1

how do you convert decimal no. (base 10) to binary no (base 2)?

Answer 1

Decimal numbers (base 10) can be converted to Binary numbers (base 2) by
simply dividing the decimal number successively by 2

Question 2

What happens if there is a remainder for decimal to binary conversion?

Answer 2

If there is a remainder, the digit is 1 and no remainder the division result is 0

Question 3

How do you convert binary to decimal?

Answer 3

Binary numbers are converted to decimal by multiplying each bit (0 or 1) by the
corresponding power of 2 and then adding the results together

Question 4

What is the low state of logic gates?

Answer 4

the low state is approximately zero volts (0 V)

Question 5

What is the high state of logic gates?

Answer 5

high state is approximately five volts positive (+5V)

Question 6

What is a NOT gate?

Answer 6

• NOT gate will make the output LOW if the input is HIGH or vice versa and
hence called an Inverter

Question 7

For a NOT gate when the input is high the output is??

Answer 7

Low

Question 8

What is an AND gate

Answer 8

AND gate will make the output HIGH ONLY if all inputs are HIGH. All
other input combinations will make the output LOW

Question 9

What is an OR gate?

Answer 9

OR gate will make the output HIGH if any of the inputs is HIGH

Question 10

What is an NAND gate?

Answer 10

NAND gate is the reverse of an AND gate. It will make the output LOW ONLY if
all inputs are HIGH. All other input combinations will make the output HIGH

Question 11

What is a NOR gate?

Answer 11

NOR gate is the reverse of an OR gate. It will make the output high ONLY if all
inputs are LOW.

Question 12

What is the EX-OR gate?

Answer 12

EX-OR gate will make the output HIGH if ONLY ONE of the inputs is
HIGH.

Question 13

What are physical quantities?

Answer 13

Physical quantities such as temperature, pressure, stress, flow and displacement can be
measured using sensors. The sensors convert the change in the physical quantity into a
corresponding change in an electrical quantity

Question 14

What is signal conditioning?

Answer 14

Signal conditioning transforms the sensor output to an appropriate form

Question 15

What is the data acquisition system?

Answer 15

The conditioned signals are sent to the data acquisition system that periodically samples the
signal and converts to digital using an analog to digital converter (ADC)

Question 16

What is the process of the computer-based instrumentation system (CBIS)?

Answer 16

Physical system
CBIS
(
Sensor
Signal conditioning 
Data acquistion
{
Sampling
A/D conversion
}
)
General purpose computing

Question 17

What are sensors?

Answer 17

Sensor, also called a transducer, converts the physical variable to an
electrical variable

Question 18

What is an 2 examples for physical sensor?

Answer 18

Pressure sensor
Temperature sensor
Acoustic sensor

Question 19

What are some applications of pressure sensors? (4)

Answer 19

 measure the fuel pressure during fuel pumping
 measure the tire pressure in vehicle tires
 measure the air pressure outside an aircraft (using an aneroid barometer)
 measure blood pressure using a small sensor penetrated into blood vessels

Question 20

What is a pressure sensor

Answer 20

responds to the pressure applied to its sensing surface and

converts to an electrical signal

Question 21

What is a temperature sensor?

Answer 21

responds to the temperature and converts to an electrical

signal

Question 22

What are applications of temperature sensors? (3)

Answer 22

 measure the air temperature to control the air conditioning and heating systems
 measure the temperature inside the case of an computer to turn on the fan
 measure the food temperature in transport and storage in order to minimise the harmful bacterial growth

Question 23

What is an acoustic sensor?

Answer 23

converts to the sound energy into electrical energy

Question 24

What are applications of acoustic sensors? (2)

Answer 24

 These sensors help offshore exploration, reduce the impact of tsunami, aid in
navigation etc.
 Used in avalanche warning and research

Question 25

What are two most important signal conditioning functions?

Answer 25

amplification and filtering

Question 26

What is signal amplification?

Answer 26

Signal amplification increases the power of the signal received from the
sensor

Question 27

What is filtering?

Answer 27

Sensor signals may consist of interference from noise or undesired output.
Filtering of the output signal from the sensor is carried out to eliminate such
noise effects

Question 28

What is data acquisition?

Answer 28

Data acquisition is the process that converts the conditioned signals in to
digital numeric values that can be manipulated by a computer

Question 29

What does a data acquisition system consist of?

Answer 29

Data acquisition systems consist of an analog multiplexer (MUX), a buffer, a
sample/hold amplifier and an ADC

Question 30

What is a multiplexer (MUX)?

Answer 30

 The channel to be monitored is selected and applied to a sampler

Question 31

What does the multiplexer do in the data acquisition system? (3)

Answer 31

 The operational amplifier reduces the impact that two parts of a system may have on
each other
 The sampled output is converted to digital using the multiplexer that is controlled by
the control circuit, which simultaneously triggers the sampling circuit and the ADC
 The multiplexer then selects the next channel after the ADC completes the conversion
and sends an appropriate signal to the control circuit

Question 32

What are the two main steps in ADC (analog to digital conversion)?
(2)

Answer 32

 Sampling – sampled at regular time intervals to generate a discrete-time
signal
 Quantisation – the sampled signal is quantised and encoded in to a
binary signal

Question 33

What is the Nyquist rate?

Answer 33

 Sampling must be conducted at a rate higher than the
twice the highest frequency,
fH of the analog signal and
this rate is called the Nyquist rate, Fs greater than or equal to 2fH
 If
Fs greater than 2fH, the reconstruction of the sample values
cannot match the original analog signal and aliasing will occur

Question 34

As the number of quantisation levels increases…

Answer 34

the number of bits required to

represent those levels too increases

Question 35

What is Resolution?

Answer 35

 Resolution is defined as the maximum analog voltage range divided by the number of
quantisation intervals, (2n - 1) = (L-1)