ArulmiguMeenakshi Amman College of Engineering
Vadamavandal-604410.
Important questions and answers
MR3491-SENSORS AND INSTRUMENTATION
Prepared by
V.Umapathy,
Prof. /Mech.
S.No. Questions and answers
Unit-I
INTRODUCTION
2 – marks question and answers
1. What are sensor and its types?
Sensors come in a variety of types, including electronic, mechanical, optical, chemical, biological, and
thermal sensors. Each type of sensor is designed to detect specific physical or chemical properties and
convert them into signals that can be measured and interpreted.
2. Why are sensors important?
Sensors are central to industrial applications being used for process control, monitoring, and safety.
Sensors are also central to medicine being used for diagnostics, monitoring, critical care, and public health.
3. What is the classification of errors?
The definition of error is the difference between the actual measured value and the true predetermined
value. The classification of error in measurement features three main categories. These are systemic,
random, limiting, and gross errors.
4. What do you mean by error analysis?
, Error analysis is a quantitative approach to understanding the uncertainties and discrepancies that arise in
measurements, estimations, and numerical computations. It recognizes that most measurable quantities—
such as time, length, and temperature—are inherently inaccurate, and absolute values are rarely achievable.
5. What is the difference between static and dynamic characteristics of a sensor?
Static characteristics where the performance criteria for the measurement of quantities that remain
constant. Or vary only quite slowly. Dynamic characteristics on the other hand, show the relationship
between the system input and output when the measured quantity is varying rapidly.
6. How to measure sensor performance?
When assessing reproducibility, we compare a sensor with another one of the same kind. To determine
accuracy, we compare a sensor with a reference measurement. In both cases, we examine the agreement
between two variables, with higher agreement indicating better sensor performance.
7. How do you calibrate a sensor?
Direct Comparison: This method involves manually comparing the sensor's output to a known standard and
adjusting it accordingly. For example, in temperature calibration, the sensor might be placed in a controlled
environment where the temperature is known, and adjustments are made to ensure the sensor reads
correctly.
8. What is the output of a sensor?
Thus, a sensor responds to the stimulus and converts it into an electrical signal which is compatible with
electronic circuits. The sensor's output signal may be in a form of voltage, current, or charge.
9. What is the difference between analog and digital sensors?
Analog sensors create analog signals from the quantity that is sensed. In comparison, digital sensors
produce digital signals when performing a measurement. As mentioned previously, the most common
types of analog sensors include sound sensors, light sensors, temperature sensors, and pressure sensors.
10. What is PWM and why is it used?
, PWM is used to control the average value of a waveform over a switching period by controlling the pulse
width. The PWM generation methods can be classified into carrier-based and space vector modulation
(SVM) methods. Both of these methods provide high-quality output voltages and currents and good
transient response.
13 and 15 marks question and answers
11. Elaborate classification of errors in sensors.
, Sensor errors can be broadly classified into two main types: systematic errors and random
errors. Systematic errors are consistent and predictable, while random errors are unpredictable and
variable. Additionally, a third category, gross errors, can arise from human mistakes during measurement.
Here's a more detailed breakdown:
1. Systematic Errors:
These errors are consistent and predictable, meaning they tend to occur in the same direction (either always
too high or always too low).
They can be caused by factors like:
o Instrumental errors: Imperfections or biases in the sensor itself, such as calibration errors, or inherent
limitations in the sensor's design.
o Environmental errors: Changes in the surrounding environment (temperature, pressure, humidity, etc.)
that affect the sensor's readings.
o Bias: A consistent offset in the sensor's readings.
o Drift: A gradual change in the sensor's output over time.
2. Random Errors:
These errors are unpredictable and variable, meaning they fluctuate randomly and can be positive or
negative.
They are often caused by:
o Noise: Random fluctuations in the sensor's output due to electrical noise or other external factors.
o Resolution: The smallest change a sensor can detect.
o Variations in measurement conditions: Uncontrollable changes in the environment or the measurement
process.
Vadamavandal-604410.
Important questions and answers
MR3491-SENSORS AND INSTRUMENTATION
Prepared by
V.Umapathy,
Prof. /Mech.
S.No. Questions and answers
Unit-I
INTRODUCTION
2 – marks question and answers
1. What are sensor and its types?
Sensors come in a variety of types, including electronic, mechanical, optical, chemical, biological, and
thermal sensors. Each type of sensor is designed to detect specific physical or chemical properties and
convert them into signals that can be measured and interpreted.
2. Why are sensors important?
Sensors are central to industrial applications being used for process control, monitoring, and safety.
Sensors are also central to medicine being used for diagnostics, monitoring, critical care, and public health.
3. What is the classification of errors?
The definition of error is the difference between the actual measured value and the true predetermined
value. The classification of error in measurement features three main categories. These are systemic,
random, limiting, and gross errors.
4. What do you mean by error analysis?
, Error analysis is a quantitative approach to understanding the uncertainties and discrepancies that arise in
measurements, estimations, and numerical computations. It recognizes that most measurable quantities—
such as time, length, and temperature—are inherently inaccurate, and absolute values are rarely achievable.
5. What is the difference between static and dynamic characteristics of a sensor?
Static characteristics where the performance criteria for the measurement of quantities that remain
constant. Or vary only quite slowly. Dynamic characteristics on the other hand, show the relationship
between the system input and output when the measured quantity is varying rapidly.
6. How to measure sensor performance?
When assessing reproducibility, we compare a sensor with another one of the same kind. To determine
accuracy, we compare a sensor with a reference measurement. In both cases, we examine the agreement
between two variables, with higher agreement indicating better sensor performance.
7. How do you calibrate a sensor?
Direct Comparison: This method involves manually comparing the sensor's output to a known standard and
adjusting it accordingly. For example, in temperature calibration, the sensor might be placed in a controlled
environment where the temperature is known, and adjustments are made to ensure the sensor reads
correctly.
8. What is the output of a sensor?
Thus, a sensor responds to the stimulus and converts it into an electrical signal which is compatible with
electronic circuits. The sensor's output signal may be in a form of voltage, current, or charge.
9. What is the difference between analog and digital sensors?
Analog sensors create analog signals from the quantity that is sensed. In comparison, digital sensors
produce digital signals when performing a measurement. As mentioned previously, the most common
types of analog sensors include sound sensors, light sensors, temperature sensors, and pressure sensors.
10. What is PWM and why is it used?
, PWM is used to control the average value of a waveform over a switching period by controlling the pulse
width. The PWM generation methods can be classified into carrier-based and space vector modulation
(SVM) methods. Both of these methods provide high-quality output voltages and currents and good
transient response.
13 and 15 marks question and answers
11. Elaborate classification of errors in sensors.
, Sensor errors can be broadly classified into two main types: systematic errors and random
errors. Systematic errors are consistent and predictable, while random errors are unpredictable and
variable. Additionally, a third category, gross errors, can arise from human mistakes during measurement.
Here's a more detailed breakdown:
1. Systematic Errors:
These errors are consistent and predictable, meaning they tend to occur in the same direction (either always
too high or always too low).
They can be caused by factors like:
o Instrumental errors: Imperfections or biases in the sensor itself, such as calibration errors, or inherent
limitations in the sensor's design.
o Environmental errors: Changes in the surrounding environment (temperature, pressure, humidity, etc.)
that affect the sensor's readings.
o Bias: A consistent offset in the sensor's readings.
o Drift: A gradual change in the sensor's output over time.
2. Random Errors:
These errors are unpredictable and variable, meaning they fluctuate randomly and can be positive or
negative.
They are often caused by:
o Noise: Random fluctuations in the sensor's output due to electrical noise or other external factors.
o Resolution: The smallest change a sensor can detect.
o Variations in measurement conditions: Uncontrollable changes in the environment or the measurement
process.
