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Sport Engineering > Sensor - Intro, working mechanism, latest > Flashcards

Sensor - Intro, working mechanism, latest Flashcards

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1
Q

Sensors Definition

A

A sensor transforms a stimulus into a measurable signal, which can subsequently be converted into an observable output for further processing.

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2
Q

Sensors System Design

A
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3
Q

Sensor Classifications, 4 types? and examples of each

A
  • Mechanical: strain gage, displacement, accelerometer, force, pressure, etc
  • Thermal: thermal couple
  • Optical: camera, infrared sensor
  • Chemical: moisture sensor, pH sensor
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4
Q

Resistor sensor equation

A
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5
Q

Capacitance sensor equation

A
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6
Q

Inductance sensor equation

A
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7
Q

Classification based on sensor placement 2 types?

A
  • Contact sensors.
  • Non-contact sensors
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8
Q

Passive sensor definition

A

Passive sensor: response to its environment so does not require a power source

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9
Q

Active sensor definition

A

Active sensor: requires a power source to emit a signal that is scatter back to the sensor

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10
Q

What are the Sensor Specifications, 10 types?

A
  • Sensitivity
  • Linearity
  • Hysteresis
  • Environmental Effects
  • Drift
  • Accuracy
  • Precision (Repeatability)
  • Threshold
  • Range
  • Resolution
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11
Q

Calibration

A

The calibration procedure involves the comparison of the output from the sensor with a known measurement system.

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12
Q

Sensitivity

A
  • Sensitivity is a measure of the change in output of a sensor for a unit change in input.
  • Sensitivity can be obtained from the gradient of a graph of output as a function of input
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13
Q

Linearity

A

A sensor is linear if the output is linearly proportional to the input i.e. corresponding values of input and output lie on a straight line and sensitivity is constant across the input range
* This is considered desirable!
* The sensitivity of a non-linear sensor varies across part or all of the input range

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14
Q

Hysteresis

A

For a given input, the output from the sensor varies depending on whether the input stimulus is increasing or decreasing at the time
* Hysteresis is normally expressed as a percentage of the full scale output reading

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15
Q

Environmental Effects? 3 things

A

Sensitivity drift defines the amount by which the sensitivity of a sensor varies with environmental conditions.
In general, the output of a sensor depends not only on the input but on environmental conditions, such as
* Ambient temperature
* Atmospheric pressure
* Relative humidity etc.

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16
Q

Accuracy
Precision (Repeatability)

A

Accuracy is a measure of how close the measured value (the output from the system) is to the ‘true’ value (the input)
Repeatability is a measure of the similarity of output values when the same input is applied repetitively (it is NOT an indication of accuracy!)

17
Q

What are the two types of Measurement errors?

A

System errors: imperfect design of the measurement setup and the approximation.
Random errors: variations due to uncontrolled variables. Can be reduced by averaging.

18
Q

Threshold
Range or span
Resolution

A
  • Threshold is the smallest input that will produce a detectable change in the output of a sensor
  • The range of a sensor defines the minimum and maximum values of a quantity that the sensor is designed to measure
  • Resolution is the smallest change in input that will produce a detectable change in the output of a sensor at a particular point in its active range
19
Q

Temperature Sensors - three mechanisms to gain or lose heat

A
  • Conduction - The transfer of heat within a substance, or between substances through molecular interaction
  • Convection - Heat transfer within a fluid by the movement of heated molecules from one place to another
  • Radiation – heat transfer in the form of electromagnetic waves, generally in the infra-red region of the electromagnetic spectrum
20
Q

3 types of Contact Temperature Sensors?

A

Thermocouples - It utilise the thermoelectric effect where a small voltage is generated at the join between two metals. It have quick response times, and they can operate over the widest temperature range.
Thermistor - It contain a material in which a large changes in electrical resistance is produced by a small changes in temperature (High accuracy).
Resistance thermometer - RTDs materials have a positive temperature coefficient (the resistance of a metal increases with temperature). RTDs typically have higher thermal mass, and therefore they usually respond slower to temperature changes than thermocouple temperature sensors

21
Q

Non-Contact Temperature Sensors

A

Thermographic camera - It contains a sensor capable of non- contact detecting infrared radiation emitted from a surface.

22
Q

Contact Vs non-contact Temperature Sensor

A
23
Q

What is a force sensor?

A

A Force sensor is defined as a transducer that converts an input mechanical load, weight, tension, compression or pressure into an electrical output signal.
Examples
* Piezoelectric force sensor
* Strain Gauge
* Resistive force sensor

24
Q

Piezoelectric force sensor?
Strain Gauge?

A
  • Piezoelectric materials generate an electrical potential (output voltage) when subjected to a force.
  • The electrical resistance of a length of wire varies in direct proportion to the change in any strain applied to it.
25
Q

Sources of error in strain gauge measurements, 5 things?

A
  • Bonding faults – a good bond is vital to ensure strain in the specimen is fully transmitted to the gauge element
  • Hysteresis – resistance values are slightly higher when unloading than loading
  • Cross-sensitivity – strain gauge response to strain at right angles to the main measurement axis
  • Moisture – strain gauges are susceptible to moisture and need to be encased in a damp-proof coating
  • Temperature – temperature influences strain gauge resistance, and can cause expansion of the gauge and the specimen which
    will all affect the output
26
Q

SPORTTECH

A

These high-functional and smart textiles are increasingly adding value to the sports and leisure industry by combining utilitarian functions with wearing comfort that leads to achieving high level of performance.

27
Q

What is a Smart Textile?

A

Smart Textile or Electronic Textile (E-textiles) can be defined as the materials and structures which can sense the environmental/human body changes. These stimuli could be thermal, chemical, mechanical, electric, magnetic or from other source.
Smart Clothes can monitor body functions eg:
* Heart Rate
* Breathing Rate
* Muscle Fatigue
* Movement
* Sweat

28
Q

Nanotechnology

A

Nanotechnology is the understanding and control of matter at dimensions of roughly 1 to 100 nanometres, where unique phenomena enable novel applications.

29
Q

Gore-Tex?

A

Gore-Tex is a waterproof/breathable fabric that is manufactured from PTFE into a laminated membrane
* Properties: breathable, lightweight, waterproof. When worn Gore-Tex releases water vapour(sweat) from the body but stops raindrops entering

30
Q

Nano/Micro-encapsulated fibre/fabrics

A

Microencapsulated textiles describes fabric which has microcapsules embedding in the fibres, which can be controlled to bleed due to a environmental change e.g friction, pressure or gradually by diffusion or during the process of biodegradation.

31
Q

Advantages of nanomaterial in sports equipment, 7 things?

A
32
Q

Examples where Nanotechnology is in sports?

A

Tennis and Golf: Nanomaterials in racket frames and clubheads improve strength and reduce weight, leading to better control and distance in shots.
* Cycling: Nanomaterials in bike frames enhance strength and aerodynamics, making bikes more efficient.
* Hockey: Sticks with nanomaterials offer improved power and precision, while protective gear enhances safety.
* Swimming: Competitive swimwear uses nanomaterials to reduce water drag, leading to faster times.
* Skiing and Snowboarding: Nanomaterial coatings on equipment improve performance and durability.
* Athletic Footwear: Nanomaterials enhance cushioning, flexibility, and durability for better comfort and support.
* Sports Balls: Nanomaterial coatings optimize aerodynamics, durability, and performance.
* Safety Equipment: Helmets and protective gear incorporate nanomaterials for better impact resistance and safety.
* Wearable sensors: flexible, breathable, lightweight and unobtrusive monitoring.

33
Q

Sustainability issues with nanotechnology

A
34
Q

Challenges with nanotechnology? 3 things

A
  • Rigid connections
  • Poor stability
  • Weak mechanical performance

Sport Engineering (5 decks)

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