Sensors

ElectronicsResistive Sensors

Terry Sturtevant

Wilfrid Laurier University

May 31, 2017

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Introduction to transducers

convert one form of energy to anotherelectrical input transducer;output is some form of electrical property(i,v,r,c,l,nu, etc.)input transducer = sensoroutput transducer = actuator

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Introduction to transducers

convert one form of energy to another

electrical input transducer;output is some form of electrical property(i,v,r,c,l,nu, etc.)input transducer = sensoroutput transducer = actuator

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Introduction to transducers

convert one form of energy to anotherelectrical input transducer;

output is some form of electrical property(i,v,r,c,l,nu, etc.)input transducer = sensoroutput transducer = actuator

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Introduction to transducers

convert one form of energy to anotherelectrical input transducer;output is some form of electrical property

(i,v,r,c,l,nu, etc.)input transducer = sensoroutput transducer = actuator

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Introduction to transducers

convert one form of energy to anotherelectrical input transducer;output is some form of electrical property(i,v,r,c,l,nu, etc.)

input transducer = sensoroutput transducer = actuator

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Introduction to transducers

convert one form of energy to anotherelectrical input transducer;output is some form of electrical property(i,v,r,c,l,nu, etc.)input transducer = sensor

output transducer = actuator

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Introduction to transducers

convert one form of energy to anotherelectrical input transducer;output is some form of electrical property(i,v,r,c,l,nu, etc.)input transducer = sensoroutput transducer = actuator

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistive sensors

A resistive sensor is a resistor which changes according to somephysical change in its environment. Some examples would be:

Potentiometer; the resistance varies with physical movementPhotoresistor; the resistance varies with lightThermistor; the resistance varies with heatStrain gauge (or gage); the resistance varies with stress orcompressionForce-dependent resistor; the resistance varies with appliedpressure

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistive sensors

A resistive sensor is a resistor which changes according to somephysical change in its environment.

Some examples would be:Potentiometer; the resistance varies with physical movementPhotoresistor; the resistance varies with lightThermistor; the resistance varies with heatStrain gauge (or gage); the resistance varies with stress orcompressionForce-dependent resistor; the resistance varies with appliedpressure

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistive sensors

A resistive sensor is a resistor which changes according to somephysical change in its environment. Some examples would be:

Potentiometer; the resistance varies with physical movementPhotoresistor; the resistance varies with lightThermistor; the resistance varies with heatStrain gauge (or gage); the resistance varies with stress orcompressionForce-dependent resistor; the resistance varies with appliedpressure

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistive sensors

A resistive sensor is a resistor which changes according to somephysical change in its environment. Some examples would be:

Potentiometer;

the resistance varies with physical movementPhotoresistor; the resistance varies with lightThermistor; the resistance varies with heatStrain gauge (or gage); the resistance varies with stress orcompressionForce-dependent resistor; the resistance varies with appliedpressure

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistive sensors

A resistive sensor is a resistor which changes according to somephysical change in its environment. Some examples would be:

Potentiometer; the resistance varies with physical movement

Photoresistor; the resistance varies with lightThermistor; the resistance varies with heatStrain gauge (or gage); the resistance varies with stress orcompressionForce-dependent resistor; the resistance varies with appliedpressure

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistive sensors

A resistive sensor is a resistor which changes according to somephysical change in its environment. Some examples would be:

Potentiometer; the resistance varies with physical movementPhotoresistor;

the resistance varies with lightThermistor; the resistance varies with heatStrain gauge (or gage); the resistance varies with stress orcompressionForce-dependent resistor; the resistance varies with appliedpressure

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistive sensors

A resistive sensor is a resistor which changes according to somephysical change in its environment. Some examples would be:

Potentiometer; the resistance varies with physical movementPhotoresistor; the resistance varies with light

Thermistor; the resistance varies with heatStrain gauge (or gage); the resistance varies with stress orcompressionForce-dependent resistor; the resistance varies with appliedpressure

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistive sensors

A resistive sensor is a resistor which changes according to somephysical change in its environment. Some examples would be:

Potentiometer; the resistance varies with physical movementPhotoresistor; the resistance varies with lightThermistor;

the resistance varies with heatStrain gauge (or gage); the resistance varies with stress orcompressionForce-dependent resistor; the resistance varies with appliedpressure

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistive sensors

A resistive sensor is a resistor which changes according to somephysical change in its environment. Some examples would be:

Potentiometer; the resistance varies with physical movementPhotoresistor; the resistance varies with lightThermistor; the resistance varies with heat

Strain gauge (or gage); the resistance varies with stress orcompressionForce-dependent resistor; the resistance varies with appliedpressure

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistive sensors

A resistive sensor is a resistor which changes according to somephysical change in its environment. Some examples would be:

Potentiometer; the resistance varies with physical movementPhotoresistor; the resistance varies with lightThermistor; the resistance varies with heatStrain gauge (or gage);

the resistance varies with stress orcompressionForce-dependent resistor; the resistance varies with appliedpressure

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistive sensors

A resistive sensor is a resistor which changes according to somephysical change in its environment. Some examples would be:

Potentiometer; the resistance varies with physical movementPhotoresistor; the resistance varies with lightThermistor; the resistance varies with heatStrain gauge (or gage); the resistance varies with stress orcompression

Force-dependent resistor; the resistance varies with appliedpressure

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistive sensors

A resistive sensor is a resistor which changes according to somephysical change in its environment. Some examples would be:

Potentiometer; the resistance varies with physical movementPhotoresistor; the resistance varies with lightThermistor; the resistance varies with heatStrain gauge (or gage); the resistance varies with stress orcompressionForce-dependent resistor;

the resistance varies with appliedpressure

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistive sensors

A resistive sensor is a resistor which changes according to somephysical change in its environment. Some examples would be:

Potentiometer; the resistance varies with physical movementPhotoresistor; the resistance varies with lightThermistor; the resistance varies with heatStrain gauge (or gage); the resistance varies with stress orcompressionForce-dependent resistor; the resistance varies with appliedpressure

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Here’s an example of how a strain gauge works.

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistance

R = ρ LA

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistance

6

?

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistance

6

?

R ′ = ρ (L−∆L)(A+∆A) < R

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistance

R = ρ LA

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistance -?

6

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistance -?

6

R ′ = ρ (L+∆L)(A−∆A) > R

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Thermistors

Resistance

(Ω)

Temperature (C)

This is the resistance/temperature curve for a thermistor.

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Thermistors

Resistance

(Ω)

Temperature (C)

(High temperature; Rmin)

This is the resistance/temperature curve for a thermistor.

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Thermistors

Resistance

(Ω)

Temperature (C)

(High temperature; Rmin)

(Low temperature; Rmax )

This is the resistance/temperature curve for a thermistor.

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

Resistive sensors in voltage dividers

R1 I

R2 I

Vin

Vout = Vin(

R2R1+R2

)

True if Iout ≡ 0

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

If we want to put a variable resistor in a voltage divider, thenwe need to choose the other resistor.

To make the output vary over as large a range as possible asthe variable resistor goes from Rmin to Rmax , it turns out wewant to choose the other resistor, R so thatR =

√Rmin × Rmax

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

If we want to put a variable resistor in a voltage divider, thenwe need to choose the other resistor.To make the output vary over as large a range as possible asthe variable resistor goes from Rmin to Rmax , it turns out wewant to choose the other resistor, R so that

R =√

Rmin × Rmax

Terry Sturtevant Electronics Resistive Sensors

Sensors Resistive sensorsResistive sensors in voltage dividers

If we want to put a variable resistor in a voltage divider, thenwe need to choose the other resistor.To make the output vary over as large a range as possible asthe variable resistor goes from Rmin to Rmax , it turns out wewant to choose the other resistor, R so thatR =

√Rmin × Rmax

Terry Sturtevant Electronics Resistive Sensors