PRESENTATION GROUP 10

GROUP’S MEMBERS :1)FATIN MUNIRAH BINTI ZULKAFLI (UK33721)

2)MARIA FAZIRA BINTI MOHD FEKERI (UK34068)3)NORFATIHAH BINTI MARZUKI (UK34825)

4)SITI NURLIYANA AUNI BINTI EZANI (UK35831)5)MUHAMAD SYAIZWADI BIN SHAIFUDIN (UK34287)

6)MUHAMMAD IMRAN FIRDAUS BIN KAMARDAN(UK34413)

7)NOOR SYAZWAN BIN JAFRI (UK34671)8)SHAHRULNIZAM BIN HASSAN (UK36220)

CAPACITANCE SENSOR

APPLICATION : PROXIMITY CAPACITIVE

SENSOR

What Is Capacitance Sensor ?

• A capacitive sensor is a sensor that detects nearby objects by their effect on the electrical field created by the sensor.

• Capacitive sensors can sense conducting and non-conducting materials in solid or liquid form.

• Acts as detecting the inner material

APPLICATION

CAPACITIVE PROXIMITY SENSOR

CAPACITIVE PROXIMITY SENSING

DIAGRAM 1 : capacitive sensor components

• The sensor consists of : -A capacitive probe plate -An oscillator -A signal level detector -A solid-state output switching device -An adjustment potentiometer

• Similar in size, shape, generate electrostatic field and reacts to changes in capacitance caused when a target enters the electrostatic field.

• The oscillator is inactive when target is outside the electrostatic field

• Target approaches, capacitive coupling develops between target and capacitive probe

• Oscillator is activated when capacitance reaches specified threshold, triggering the output circuit to switch states between ON and OFF

DIAGRAM 2 : capacitive proximity operation

• Factors of ability to detect : -target’s size -dielectric constant -distance from the sensor

• The higher the target’s size, the stronger the capacitive coupling between probe and target

• The higher the dielectric constant, the easier to detect the target. The shorter the distance, the stronger the capacitive coupling

How it works ?• With shielded capacitive sensor -shielded sensors have a metal band surrounding

the probe

-shielded construction allows sensor to be mounted flush in surrounding material without causing false trigger

-this shielded sensors are best suited for sensing materials with low dielectric constants (difficult to sense) as a result of their highly concentrated electrostatic fields.

DIAGRAM 3 : shielded capacitive sensors

• With unshielded capacitive sensors -unshielded sensors do not have a metal band

-it is more suitable compared than shielded types for use with plastic sensor wells

-this unshielded sensors are well suited for detecting high dielectric constant (easy to sense) materials

- Unshielded capacitive proximity sensors have longer sensing distances than shielded versions.

-this sensors more suitable than shielded types for use with plastic sensor (for liquid level applications) wells

-unshielded models equipped with a compensation probe are able to ignore mist, dust, small amounts of dirt and fine droplets of oil or water accumulating on sensor

-materials with high dielectric constants may be sensed through the walls of containers made with materials with lower dielectric constant

-an example is the detection of alcohol or flour through a glass wall

DIAGRAM 4 : Capacitive sensing through a tank

-The alcohol would be detected through the glass while the flour would not

• Environmental Considerations

-any material entering a capacitive sensor’s electrostatic field can cause an output signal

-function of the compensation electrodes in the probe helps to stabilize an unshielded sensor

-when contaminants lie directly on the sensor face, both fields are affected.

-when a target approaches the sensor, the sensing field is affected

DIAGRAM 5 : unshielded capacitive sensors

The use of capacitive sensor• Liquid level sensingSensing through a sight glass to watch liquid level, such as batter for food processing or ink for printing applications

• Product filling linesBottling applications, full-case detection to ensure that container has the required number of products and checking

material levels

• Plastic parts detectionPlastics on product packages

• Irregularly shaped productsObjects randomly oriented on conveyor belt and highly textured object

DIAGRAM 6 : level sensing in a hopper can be either through a window or embedded in material

DIAGRAM 7 : product sensing through packaging

Detection materials

SUMMARY

• Detect most nearby objects• Involved electric field• Sensed materials in electric field• Shielded capacitive sensor• Unshielded capacitive sensor