Sensor is a type of gadget which converts physical quantities like pressure, temperature, weight into an electrical signal proportionally. Sensors are the base of automation.
There are multiple types of sensors are available. In this post, Proximity sensors are going to be discussed. Which includes its working mechanism, its connections & wiring diagram.
PROXIMITY SENSORS
Proximity – The state of being near to somebody/something in distance or time.Proximity sensor detects the presence of near by object or material without getting physically in contact with it & produces an electrical signal. All these things been done through the electronic circuitry present inside the proximity sensor. There are different types of proximity sensors having different working mechanism; which will be discuss ahead.
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WORKING MECHANISM OF PROXIMITY SENSORS
Generally, Proximity sensors are having three types:
- Inductive sensors
- Capacitive sensors
- Magnetic sensors.
All these three have different working mechanism Which are discussed next one by one.
1. Inductive sensors
As name suggests inductive, This sensor utilizes electromagnetic induction to detect the presence of metal around it. This sensor generates electromagnetic field around its face-front. Whenever a metal comes in the vicinity of this magnetic field, An eddy current get generated around that metal.
A power loss in the circuitry of sensor get happened due to the induction. Which is further been detected by the electronic circuitry of the sensor. At last, An electrical signal is generated by the electronic circuitry. These sensors can only detects the presence of ferromagnetic materials around it.
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2. Capacitive sensors
This sensor utilizes capacitor phenomenon for working. Capacitor is an element with parallel conductive plates & having dielectric material in between them. The capacitance value of the capacitor depend upon the size & distance between the plates.
In Capacitive sensor, Sensor’s front & Sensing object work as a capacitive plates. Due to the presence or size of the object, Capacitance in between the plates changes which is been detected by the electronic circuitry of the sensor which further produces an electrical signal.
Apart from metallic elements; These sensors can also detect liquids, plastic & powders.
3. Magnetic sensors
This sensor produces the signal in the vicinity of special objects which are producing magnetic field of particular type. These sensors are generally used in Door safety limits & pneumatic cylinders.
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CONNECTIONS & WIRING CONFIGURATION
As discussed, The types of proximity sensors based upon different working mechanism, But wiring configuration remains same for all three sensor types. Normally, DC supply voltage range for proximity sensors is 10to30VDC. On detection of the object, these sensors produces a signal which can be positive or negative or both.
These sensors are available in 2 wires, 3wires & in 4 wires. All these wires have particular color code & terminal description.
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In 2 wires sensors, load output & sensor are connected in series across the power supply. On detection, these sensors changes its contact NO or NC which is clearly shown in an GIF below:
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In 3 Wires sensors, 2 wires work as a supply wires while remaining single wire work as an output which can be positive or negative depending upon the type. The sensor which produces positive known as PNP while the another sensor which produces negative known as NPN sensor.
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Plug type proximity sensors
Apart from sensors with wires, These sensors are also available in Plug type connection. An image of plug type proximity sensor been shown in along with pin description.
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SUMMARY
- Proximity sensors detects the presence of near by object or material without getting physically in contact with it & produces an Electrical signal.
- Generally, Proximity sensors are having three types : Inductive sensors, Capacitive sensors & Magnetic sensors.
- All different types of proximity sensors based upon different working mechanism, But wiring configuration & color code almost remains the same for all sensor types.
- Normally DC supply voltage range for proximity sensors is 10to30VDC. On detection of the object, these sensors produces a signal which can be positive or negative or both.
- These sensors are available in 2,3 & 4 Wires.
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