Importance of Sensors in Engineering

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Questions and Answers

What is a characteristic of sensors used in nuclear reactors?

They can be easily replaced if they fail.

They are designed to provide output in a linear manner.

They must operate effectively under severe conditions without replacement. (correct)

They measure only temperature variations.

Which of the following physical properties can sensors measure?

Nutritional value

Contamination/particulates (correct)

Emotional response

Cognitive load

Which physical phenomenon is NOT typically used in sensors for generating an output?

Thermodynamics in chemical reactions (correct)

Capacitance in distance measurements

Magnetic field strength in angle measurements

Resistance changes in strain gauges

What type of measurements can use IR radiation?

Distance measurements Signup and view all the answers

In sensors, how may the output relate to the input?

It may be either linear or non-linear. Signup and view all the answers

Which of the following is used to measure flow velocity or pressure?

Heat transfer Signup and view all the answers

What is a common application for sensors measuring sound intensity?

Environmental detection Signup and view all the answers

Which type of sensors detects ionising radiation?

Smoke detectors Signup and view all the answers

What is the primary purpose of a sensor as defined in the content?

To detect or measure a physical phenomenon. Signup and view all the answers

Which of the following factors must be considered when selecting a sensor for a specific purpose?

Accessibility, budget, and availability. Signup and view all the answers

What type of output do most sensors generate in response to a physical phenomenon?

Electronic output like volts or mA. Signup and view all the answers

Which additional components might be needed to effectively use a sensor?

Power supplies, controllers, and amplifiers. Signup and view all the answers

What is the aim for the students by the end of the lecture on sensors?

To be familiar with sensor terminology and different sensors. Signup and view all the answers

Which of the following best describes a potentiometer in the context of sensors?

It is an example of a sensor that has already been used. Signup and view all the answers

Why is it important for engineers to understand sensor outputs?

To understand measurements for design, validation, and control. Signup and view all the answers

What characteristic should a sensor possess related to generating outputs?

It must provide measurable output in response to phenomena. Signup and view all the answers

What does a sensor's signal voltage typically range from?

0-5V Signup and view all the answers

Which term refers to a device that transmits a signal, commonly in a 4-20mA current?

Transmitter Signup and view all the answers

What is a significant characteristic of the sensor mentioned in the content?

It is ratiometric. Signup and view all the answers

What range of physical measurement does the sensor possess?

0-280 degrees Signup and view all the answers

Why are sensors critical in manufacturing and production environments?

They contribute to durability, reliability, and stability. Signup and view all the answers

Which of the following is NOT a typical use of sensors?

Generating false signals Signup and view all the answers

What is a common issue with sensor signals in critical systems?

Generation of false warnings. Signup and view all the answers

Which type of device is a transducer specifically referring to?

A device that converts energy from one form to another. Signup and view all the answers

What is the minimum measurable pressure for most pressure sensors?

-15psi Signup and view all the answers

Why is a 1000kg load cell preferred for a 100kg variation on a 500kg mass?

It can handle total loads better. Signup and view all the answers

What are the different units used for measuring pressure?

Pa, kPa, mmHg Signup and view all the answers

What is the significance of Common Mode pressure when selecting a pressure sensor?

It can damage low-rated transducers. Signup and view all the answers

How many different pressure sensors are available on digikey.com?

Over 8700 Signup and view all the answers

What can happen if you use a transducer rated too low for background pressure?

It may get destroyed. Signup and view all the answers

When visiting a manufacturer's website, what terminology might you encounter regarding sensors?

Basic, compensated, amplified Signup and view all the answers

Which statement is true regarding pressure measurement at high background pressures?

It requires special transducers capable of handling the pressure. Signup and view all the answers

What is the output voltage range of a pressure sensor measuring +/- 2000Pa?

0.5V to 4.5V Signup and view all the answers

What is a major advantage of digital sensors over analog sensors?

Conversion of analog voltage to digital signal Signup and view all the answers

What kind of output voltage do thermocouples produce at temperatures less than 0C?

Negative output voltage Signup and view all the answers

What is a common challenge faced by voltage-based sensors?

Signal loss due to long wires Signup and view all the answers

What is a disadvantage of digital sensors compared to analog sensors?

Need for appropriate data bus access and hardware Signup and view all the answers

Which voltage range indicates a loadcell at zero load?

0V Signup and view all the answers

What factor limits the number of individual digital sensors that can be used simultaneously?

Limited addressing or data lines Signup and view all the answers

What type of output do loadcells exhibit when under tension?

Positive output voltage Signup and view all the answers

Study Notes

Why Sensors Are Important

Engineers need information to understand the physical world.
Sensors provide data for design, validation, control, and alerts.
Sensors are used to understand what's happening.
Sensors generate an output (usually electronic) in response to a physical phenomenon.
Engineers measure that output to understand what is being studied.

Sensor Definition

A sensor is a device that detects, measures, and records a physical phenomenon.
It generates a measurable output, typically an electronic signal.

Common Sensor Terminology

Transducer: Converts an input from one form (mechanical or physical) to another (electrical signal).
Transmitter: Transmits a signal, usually a 4-20mA current.
Sensor: A more generic term for a transducer.

Sensor Uses

Monitoring: To check process parameters and ensure standards, optimise performance, or maintain performance for safety.
Experiments: For research and testing purposes to gather data.

Monitoring Considerations

Durability, reliability, and stability are key factors in production and processing scenarios.
Redundancy is essential in critical systems for safety with multiple sensors measuring the same parameter.

Sensor Applications

Sensors measure many physical properties including pressure, force, temperature, velocity, position, distance, displacement, angle, sound intensity, light intensity, and contamination.

Sensor Physics

Sensors rely on various physical phenomena to generate an output.
Examples:
- Pressure acting on materials in pressure sensors
- Force acting on materials in force and acceleration sensors
- Magnetic field strength in distance and angle measurements
- EM radiation (IR for thermal measurements, IR laser for distance measurements, IR LED for pulse generation in encoders)
- Capacitance (C=εA/d) in distance and pressure measurements
- Eddy currents in distance measurements
- Induced voltages in LVDTs
- Heat transfer in flow velocity or pressure measurements
- Thermoelectric effects in temperature measurements
- Resistance changes in strain gauges, platinum RTD temperature sensors, hot wires, thermistors, and position sensors
- Ionising radiation in smoke detectors

Sensor Output

Sensor output can be linear or non-linear with respect to input.
Some devices offer both linear and non-linear options depending on configuration and internal electronics/processing.

Pressure Sensors

Pressure sensors come in various units, including Pa, kPa, psi, mbar, bar, inch H2O, and mmHg.
Pressure can be gauge or absolute.
Pressure sensors may have a minimum measurable pressure (vacuum) and a maximum pressure.
Pressure sensors are a significant category with over 8,700 different types available.

Common Mode Pressure

When measuring pressure differences at a high background pressure, the background pressure is considered a Common Mode pressure.
The Common Mode pressure must be considered when selecting a pressure sensor.
Using two transducers to measure the difference may not be appropriate in this context.

Sensor Terminology

Manufacturers often use terms like basic, compensated, and amplified when describing sensors.
Understanding these terms is essential.

Voltage Based Sensors

Many sensors generate a voltage output.
Pressure sensors may have outputs like 0-33mV, 0-50mV, 0-100mV, 0-5V, 1-6V, or 0.5-4.5V.
Voltages are easy to measure, but can be susceptible to signal loss over long wires or noise interference.

Digital Sensors

Digital sensors are becoming increasingly prevalent.
They convert analog voltages into digital signals, enabling data transfer over a data bus.
Digital sensors use various standards, including I2C, SPI, CanBUS, Wireless, and Bluetooth.

Limitations of Digital Sensors

Digital sensors require access to the appropriate data bus with suitable hardware for reading the output.
They are individually addressed, which limits the number of devices of the same type that can be used due to limited addresses or data lines.

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Description

This quiz will explore the critical role of sensors in engineering, covering their definitions, common terminology, and various uses. Understand how sensors provide the vital data required for design, control, and monitoring in engineering applications.