Datasheet

3
Signal Chain Design Guide
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 indicate the magnitude or
change in the environmental condition, by reacting to the
condition and generating a change in an electrical property
as a result.
Typical phenomena that are measured are:
■ Electrical signal and properties
■ Magnetic signal and properties
■ Temperature
■ Humidity
■ Force, weight, torque and pressure
■ Motion and vibration
■ Flow
■ Fluid level and volume
■ Light and infrared
■ Chemistry/gas
Summary Of Common Physical Conditions and Related Sensor Types
Phenomena Sensor Electrical Output
Magnetic
Hall Effect Voltage
Magneto-Resistive Resistance
Temperature
Thermocouple Voltage
RTD Resistance
Thermistor Resistance
IC Voltage
Infrared Current
Humidity
Capacitive Capacitance
Infrared Current
Force, Weight, Torque, Pressure
Strain Gauge Resistance/Voltage
Load Cell Resistance
Piezoelectric Voltage or Charge
Mechanical Transducer Resistance, Voltage, Capacitance
Motion and Vibration
LVDT AC Voltage
Piezoelectric Voltage or Charge
Microphone Voltage
Ultrosonic Voltage, Resistive, Current
Accelerometer Voltage
Flow
Magnetic Flowmeter Voltage
Mass Flowmeter Resistance/Voltage
Ultrasound/Doppler Frequency
Hot-wire Anemometer Resistance
Mechanical Transducer (turbine) Voltage
Fluid Level and Volume
Ultrasound Time Delay
Mechanical Transducer Resistance/Voltage
Capacitor Capacitance
Switch On/Off
Thermal Voltage
Touch
Capacitance Voltage
Inductance Current
Resistance Frequency
Proximity
Capacitance Voltage, Frequency
Inductance Current, Frequency
Resistance Voltage, Current
Light Photodiode Current
Chemical
pH Electrode Voltage
Solution Conductivity Resistance/Current
CO Sensor Voltage or Charge
Photodiode (turbidity, colorimeter) Current
Ion Sensor Current
Sensor Overview
There are sensors that respond to these phenomena by
producing the following electrical properties:
■ Voltage
■ Current
■ Resistance
■ Capacitance
■ Charge
This electrical property is then conditioned by an analog
circuit before being driven to a digital circuit. In this way,
the environmental condition can be “measured” and the
system can make decisions based on the result.
The table below provides an overview of typical
phenomena, the type of sensor commonly used to measure
the phenomena and electrical output of the sensor.
For additional information, please refer to
Application Note AN990.