Importance of Sensors in Engineering

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.

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.