Motion and Vibration Sensors

Motion and Vibration Sensors

• Accelerometer: measures vibration or acceleration of a structure, based on Newton's Second law of motion
• Capacitive MEMS Accelerometer: detects acceleration by exploiting the movement of a seismic mass, resulting in a capacitance change between parallel plates
  • Used mostly in mobile devices
• Piezoresistive Accelerometer: measures the resistance changed by the force applied on the material
  • Used in automotive crash testing, safety air-bags & traction control system testing, etc.
• Piezoelectric Accelerometer: contains a Piezoelectric quartz crystal which produces an electric charge or output under acceleration
  • Used in cell phones, vibration sensors, guitar pickups, etc.

Touch and Pressure Sensors

• Touch Sensor: a tactile sensor that is sensitive to touch, force or pressure
  • Mostly used in smartphones and robotics
  • Opens up a circuit which allows current to flow through when there is a contact or pressure on the sensor

Strain and Displacement Sensors

• Strain Gauge/Load Cell: measures deformation by changing electrical resistance
  • Load cells convert force into an electrical signal using strain gauges
  • Commonly used in weighing systems, force measurement, structural health monitoring, testing and quality control, prosthetics, and rehabilitation equipment
• Linear Variable Differential Transformer (LVDT): a type of electrical transformer used for measuring linear displacement (position)
  • Comprises a cylindrical coil assembly and a movable core
  • Used in industrial automation, aerospace, civil engineering, medical devices, and wind speed sensors

Flow and Level Sensors

• Water Flow Sensor: measures the rate of flow of liquids
  • Uses mechanical and electronic subsystems to measure fluid
  • Operation: water flows through a motor/turbine mechanism, rotations generate a voltage proportional to the flow rate
• Rain Sensor: used to notice water drops and rainfall
  • Includes two parts: a sensor pad and sensor module
  • Has two outputs: analog and digital
  • Operation: the rain sensor's sensing pad has copper traces acting as a variable resistor, water on the pad changes its resistance inversely to the amount present

Pressure Sensors

• Barometric Pressure Sensor: also known as pressure transducers, measure the pressure exerted by the atmosphere
  • Play a crucial role in various fields, including weather forecasting, navigation, and consumer electronics
• Manometer: a measuring instrument used to determine the pressure of a fluid, such as air or water
  • Consists of a tube connected to an indicator device that displays the pressure on a graduated scale
  • Precise monitoring and control of pressure to ensure proper and safe operation
  • Used in environmental studies, scientific research, educational laboratories, aviation, and industrial applications

Temperature Sensors

• Thermal Transducers: convert thermal energy into other physical quantities such as mechanical energy, pressure, electrical signals, etc.
• Resistance Temperature Detector (RTD): temperature sensors that operate on the principle of resistance change with temperature
  • Capitalizes on the fact that the electrical resistance of a material changes as its temperature changes
  • Widely used in industrial settings to monitor and control the temperature of processes, ensuring optimal operating conditions and safety
• Thermistor: also called as Thermally Sensitive Resistors
  • Temperature sensors that exhibit a significant change in resistance with a change in temperature
  • Cheaper than RTDs, but highly sensitive and nonlinear
• Thermocouple: the most commonly used type of temperature sensor
  • Popular due to simplicity, ease of use, and speed of response to changes in temperature
  • Have the widest temperature range of all the temperature sensors from below -200 degrees C to well over 2000 degrees C
  • Are thermoelectric sensors that consist of two junctions of dissimilar metals, such as copper and constantan that are welded or crimped together
• TEG/TEC (Thermoelectric Generator/Cooler): part of Thermoelectric modules
  • TEG is used for heat generation to produce electricity mainly used for power generation
  • TEC is used to transfer heat from one electronic device to another, mainly used for cooling and heating applications
• LM35 - Temperature Sensor: a temperature measuring device having an analog output voltage proportional to the temperature
  • Provides output voltage in Centigrade (Celsius)
  • Does not require any external calibration circuitry
  • The sensitivity of LM35 is 10 mV/degree Celsius
  • Used to measure surrounding temperature ranging from -55 °C to 150 °C
• Bimetallic Thermostat: a component made up of two strips of different metals that expand at different rates when heated
  • This unique property allows bimetallic strips to be used in various applications, including thermostats