GROUP MEMBERS : MANSUR IYLIA MOHAMED RAZIP 2010515951 FAIZ BIN ISMAIL 2010369245 AQILAH BINTI ABDUL SAMAD 2010964679 HASMIDA BINTI MUDA @ NORUDDIN 2009127055

ELE663 ASSIGNMENT 1CAPACITIVE SENSOR

WHAT IS CAPACITIVE SENSOR

A device or sensor that design to detecting change in capacitance or anything related to capacitor effect such as electrical field between the capacitive sensor and the intended target.

can sense both metallic as well as non-metallic can vary by a change in the plate distance, the

effective plate surface or the dielectric. For non-conducting materials, the changes in

dielectric are use for the sensor concept and for conducting material functions used the change in plate distance concept.

CAPACITOR COMPONENT AND IT SYMBOL’S

insulator

conductor

conductor

conductor conductor

insulator

conductor

conductor

insulator

HOW CAPACITOR CAN BE CONSTRUCTED

•A capacitor can be constructed by having two conducting plate with two dielectric layers and rolling them up.

•The rolling part can make the capacitor build in compact size.

CONT…

Apply a potential difference across the two plate of the capacitor

electrical field will start to built up between the conducting plates

It will start to store electrical energy until the potential difference across capacitor is equal to the power supply

CHARGE OF CAPACITOR

ELECTRIC FIELD

Two plate of capacitors put side by side.

The potential difference is applied to the two plate of capacitor, electrical field exists.

FACTORS THAT INFLUENCE CAPACITANCE

C is the capacitance in Farads (F) ε product of permittivity of dielectric

and permittivity of free space d distance between two conducting

plates A is the surface area of each plate.

DISTANCE

•The distance between two plates of capacitor is inversely proportional to the capacitance value.

•Which means decrease in capacitance will make increase in capacitance value.

EFFECTS OF VARYING DISTANCE

Crash Airbag System

EFFECT OF DIELECTRIC

Dielectric is an insulator between the two conducting plate.

Electrical field exist when dielectric have different potential value.

Electric charges can be stored.

CONT…

Dielectric constant is directly proportional to the capacitance value.

Materials with higher dielectric constant value are easy to sense.

APPLICATION ( WATER LEVEL INDICATOR )

When the water level increase, the dielectric of water will increase.

But dielectric of air or gas decrease.

The dielectric is directly proportional to capacitance value.

CONT…

There are two types of material that gives different value of capacitance.

1. conductive material2. non-conductive material

CONT…

CONDUCTIVE NON-CONCDUCTIVE

• Conductive material will

counter the electrical field

• When the distance

increase, the electric field

decrease and the

capacitance decrease.

• Act as an insulator between

the plate of

capacitors.

• The capacitance value was

change because of changes

value in dielectric constant.

PROXIMITY SENSOR

As non-conductive material go through the electrical field, it will be seen as an insulator (dielectric) which change the capacitance value of the capacitive sensor, thus the non-conductive material presence can be detected.

CONT…

Affected by two things: 1) The distance between the probe and a grounded surface 2) The dielectric constant of the material between the probe and the grounded surface.

ADVANTAGES

More reliable than mechanical sensor No moving part- there is no wear or tear Less expensive Can detect metal and non-metal 

DISADVANTAGES

Dirty or wet environment Large gap between sensor and target is

required Very sensitive to environment and

noise.

CONCLUSION

Capacitive sensors are widely used especially in industry.

Capacitive sensor can detect anything change in capacitance or anything related to capacitor effect.

Capacitive sensor more reliable than mechanical button

Less expensive Have 3 effect that influence capacitance value.

1. dielectric2. distance3. area

THE END