# Mechatronics Questions and Answers – Force Sensors

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This set of Mechatronics Multiple Choice Questions & Answers (MCQs) focuses on “Force Sensors”.

1. Which is the most common load cell used in the force sensors?

Explanation: Strain-Gauge based load cells are the most common load cell used in the force sensors. It is a transducer that is used for sensing the force, it converts the applied force into electrical signals which is used for sensing the amount of load that is applied.

2. What is the standard capacity of tension load cells to measure load?
a) 25,000 to 100,000 lbs
b) 25,00 to 10,000 lbs
c) 25,000 to 100,000 Kg
d) 25,00 to 10,000 Kg

Explanation: The standard capacity of tension cells to measure load ranges from 25,000 to 100,000 lbs. Tension cells calculate the applied force based upon the tension applied on beams or cables. Though this range can be exceeded in the custom ones.

3. Which force sensor is not a strain gauge type force sensor?
b) Shear beams

Explanation: ALC annular load cell sensor is not a strain gauge type force sensor. It is a capacitive load cell or a capacitive based load sensor. Other all the remaining are stress gauge type force sensors which are used to measure tension or sheer forces.

4. Which transducer does not require any external power supply for working?
a) Strain gauge transducer
b) Piezoelectric Crystals
c) Hydraulic transducer
d) Pneumatic transducer

Explanation: Piezoelectric Crystals does not require any external power supply for working. They generate a voltage when an external force is applied on it which is directly proportional to the external applied force. These sensors need special indicators for measuring that voltage change.

5. RFI (Radio frequency interference), moisture and temperature cannot interfere with the signals sent by the load cells.
a) True
b) False

Explanation: RFI (Radio frequency interference), moisture and temperature can interfere with the signals sent by the load cells. RFI acts as electrical noise to the force transducer’s signal. Moisture can wick itself the cables and can create a difference in capacitance between the signal lines. Temperature affects the resistance of the cables and thus can create an interference in the original signal.

a) True
b) False

Explanation: Higher capacitive load cells can ensure Wind loading and shock loading. Wind and shock waves can affect the actual measurement of weight or force calculated. Using higher capacitive load cells will eliminate the very small changes caused by these external factors and only give the correct ones in the output.

7. RFI is electrical noise to load cells. What does RFI stand for?
c) Relay Frequency Interference
d) Relay Frequency Interface

Explanation: RFI stand for Radio Frequency Interference. Radio frequency interference is also called as Electromagnetic interference (EMI). It is electrical noise to the load cell signal sent from the sensor.

8. What causes the problem of 60-hertz hum?
a) In-appropriate voltage supply
b) Absence of digital to analog converter
c) In-appropriate current supply
d) Absence of analog to digital converter

Explanation: Absence of analog to digital converter can causes the problem of 60-hertz hum. The controllers is advised to have a digital to analog converter which can be synchronised with the 60 Hz frequency signals in the power supply lines.

9. What is the phenomenon (principle) on which magnetoelastic force sensors work?
a) Villari effect
b) Hall effect
c) Lenz law
d) Mutual Induction

Explanation: Magnetoelastic force sensors work on “Villari effect” also known as the magnetoelastic effect. It was named after an Italian physicist who discovered it. This effect states that when a ferromagnetic material is subjected to stress then there is change in the magnetic flux. This effect is known as the “Villari effect”.

10. Which is an example of force sensor?
a) MSP430G2ET
b) CMCP793V-500
c) SLB700A/06VA
d) L298N

Explanation: SLB700A/06VA is an example of force sensor. It is a strain transducer that converts the strain to electrical signals. MSP430G2ET is a development board manufactured by the “TEXAS INSTRUMENTS”, CMCP793V-500 is a velocity sensor and L298N is a motor driver.

11. What is the value of force measured by a force sensor lying on a plane ground if a block of mass 3 kg is kept on it and a normal upward tensile force of 5 Newton is applied on the block? (Take acceleration due to gravity=10m/s2)
a) 15 Newton
b) 25 Newton
c) 30 Newton
d) 24 Newton

Explanation: Given:
Mass of block=3kg
Normal upward force=5Newton
Net force due to block=Force due to mass of block-Normal upward force
Force due to mass of block=mass*acceleration (here acceleration due to gravity)
Force due to mass of block=3*10=>30N
Net force due to block=30N-5N=>25N

12. What is the value of force measured by a force sensor lying on a plane ground if a block of mass 2 kg is kept on it and a normal upward tensile force of 4 Newton is applied on the block? (Take acceleration due to gravity=10m/s2)
a) 15 Newton
b) 20 Newton
c) 16 Newton
d) 24 Newton

Explanation: Given:
Mass of block=2kg
Normal upward force=4 Newton
Net force due to block=Force due to mass of block-Normal upward force
Force due to mass of block=mass*acceleration (here acceleration due to gravity)
Force due to mass of block=2*10=>20N
Net force due to block=20N-4N=>16N

13. What is the value of force, measured by a force sensor placed on the wall; if a rigid block of mass 3kg is smashed against the wall with an acceleration of 5m/s2? (Take acceleration due to gravity=10m/s2)
a) 15 Newton
b) 20 Newton
c) 16 Newton
d) 0 Newton

Explanation: Given:
Mass of block = 3 kg
Acceleration of block=5m/s2
Force experienced by sensor=mass*acceleration
Force experienced by sensor=3*5=>15 N

14. What should be the acceleration of a rigid body of mass 5kg; if a force sensor measures a normal collision impact force of 15N? (Ignore acceleration due to gravity)
a) 5 m/s2
b) 13 m/s2
c) 6 m/s2
d) 3 m/s2

Explanation: Given:
Mass of block=5 kg
Force measured by the force sensor=15N
Force experienced by sensor=mass of body*acceleration of body
Acceleration of body=Force experienced by sensor/mass
Acceleration of body=15N/5kg=>3m/s2

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