Sensors Overview

Last modified by Microchip on 2023/11/09 09:03

Many system applications require the measurement of a physical or electrical condition or the presence or absence of a known physical, electrical, or chemical quantity. Analog sensors are typically used to monitor the environmental condition by generating a change in an electrical property as a result of a change in the environmental condition.

Typical phenomena that are measured:

  • Electrical signals and properties
  • Magnetic signals and properties
  • Temperature
  • Humidity
  • Force, weight, torque, and pressure
  • Motion and vibration
  • Flow
  • Fluid level and volume
  • Light and infrared
  • Chemistry

Typical sensor applications involve the monitoring of sensor parameters and controlling actuators. The sensor signal chain, as shown below, consists of analog and digital domains. Typical sensors output very low amplitude analog signals. These weak analog signals are amplified and filtered and converted to digital values using op amps, Analog-to-Digital Converters (ADC), or voltage-to-frequency converters, and are processed at the PIC® MCU. The analog sensor output typically needs proper signal conditioning before it gets converted to a digital signal.

signal chain control loop diagram

There are sensors that respond to these phenomena by producing the following electrical properties:

  • Voltage
  • Current
  • Resistance
  • Capacitance
  • Charge

These electrical properties are then conditioned by analog circuits before being driven to digital circuits. In this way, the environmental condition can be quantified and the system can make decisions based on the results.

The MCU controls the actuators and maintains the operation of the sensor signal conditioning circuits based on the condition of the signal detection. In the digital-to-analog feedback path, Digital-to-Analog Converter (DAC)digital potentiometer, and Pulse-Width-Modulator (PWM) devices are most commonly used. A MOSFET driver is commonly used for the interface between the feedback circuit and actuators, such as motors and valves. Microchip offers a large portfolio of devices for signal chain applications.

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Summary Of Common Physical Conditions and Related Sensor Types

This table provides an overview of typical phenomena, the type of sensor commonly used to measure the phenomena and electrical output of the sensor.

PhenomenaSensorElectrical Output
MagneticHall Effect
Magneto-Resistive
Voltage
Resistance
TemperatureThermocouple
RTD
Thermistor
IC
Infrared
Voltage
Resistance
Resistance
Voltage
HumidityCapacitive
Infrared
Capacitance
Current
Force, Weight, Torque, PressureStrain Gauge
Load Cell
Piezoelectric
Mechanical Transducer
Resistance/Voltage
Resistance
Voltage or Charge
Resistance, Voltage, Capacitance
Motion and VibrationLVDT
Piezoelectric
Microphone
Ultrasonic
Accelerometer
AC Voltage
Voltage or Charge
Voltage
Voltage, Resistive, Current
Voltage
FlowMagnetic Flowmeter
Mass Flowmeter
Ultrasound/Doppler
Hot-wire Anemometer
Mechanical Transducer (turbine)
Voltage
Resistance/Voltage
Frequency
Resistance
Voltage
Fluid Level and VolumeUltrasound
Mechanical Transducer
Capacitor
Switch
Thermal
Time Delay
Resistance/Voltage
Capacitance
On/Off
Voltage
TouchCapacitance
Inductance
Resistance
Voltage
Current
Frequency
ProximityCapacitance
Inductance
Resistance
Voltage, Frequency
Current, Frequency
Voltage, Current
LightPhotodiodeCurrent
ChemicalpH Electrode
Solution Conductivity
CO Sensor
Photodiode (turbidity, colorimeter)
Ion Sensor
Voltage
Resistance/Current
Voltage or Charge
Current
Current

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​Reference Materials

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