Sensors are used in almost all industrial processes capacitive sensors and inductive sensors are some of the capacitive sensors for this case detect- The Filling level of the liquid. while the inductive sensor detects if the containers are covered. let’s take a closer look at how the different types of capacitive and inductive sensors work and some of the ways these sensors are used in automation.
inductive proximity sensor:-
let’s see about the inductive proximity sensor. an inductive sensor is an electronic device that can detect ferrous metal objects at a given distance without physical contact. Some inductive sensors can detect non-ferrous metal objects such as brass aluminum and copper. although the detection range or distance of an inductive sensor on non-ferrous material objects decreases the sensing distance depending on the object’s material. it can be found data sheet sheet of the sensor. although this distance is not more than 80 millimeters. the four main external parts of an inductive sensor are the sensor face, the sensor body, the indicator light, and the connecting wires inside the sensor body. it is where the circuitry that makes the sensor work is located in it.
we find a coil an oscillator the trigger circuit and the output circuit. the current oscillator allows the coil to generate an electromagnetic field in this way when the metal object enters the electromagnetic field an induction current or Cold current flows in the metal object. due to electromagnetic induction as the object approaches the sensor. the induction current flow increases causing the load on the oscillation circuit to increase.
then the oscillation Fades or stops. the sensor detects this change ge in the oscillation state with the amplitude detection circuit. a detection signal in this way it works by detecting the metal lid of the container in the process. when choosing a sensor we must take hysteresis into account but what i? it? when the metallic object approaches the sensor, it reaches a point where it is detected and the sensor sends an activation signal.
when the object moves away from the sensor will continue to detect it up to a certain distance. which we will call the deactivation or switching distance. when moving away so the interval between these two points is known as hysteresis. which we must take into account when placing the sensor and the object to be detected. hysteresis is important because it prevents bouncing between the two operating states of the sensor. inductive sensors are available in many different configurations. they can be shielded or sunshiny eluded a sensor. shielded if its inner coil has a metallic h field, here we can see the internal configuration of the sensor in a cross-section this Shield is lineshape and covers the entire Contour of the sensor coil, in this way the detection of the object is limited only to the front of the sensor. whereas an unshielded sensor has a protruding face and inside the coil does not have a metal shield around it, therefore it has a much larger census area.
there is also another set where a sensor can be normally open or normally closed. if a metallic object approaches the normally open sensor, it detects the object and closes its contact. Send a high-level level signal to its output. if a metallic object approaches the normally closed sensor the sensor detects the object and opens its contact sending a low-level signal to its output.
another configuration in the sensors is that it is NPN . for this case, I am considering sensors that are powered by a direct current voltage but there are also alternating current ones they usually have three cables the brown wire connects to the positive power supply, the blue or light blue wire connects to zero volts or negative power, and the black wire is where we get the signal from the sensor which connects to the load. which can be a relay a PLC or any other controller. we will detail the connections that need to be made in another blog. I will leave the links here as published.
the capacitive sensor, its external appearance is very similar to the inductive sensor since it consists of the same parts, but the difference is that it not only detects ferrous metal objects, but it can also detect any other objects like plastic, minerals, glass wood papers, letting etc. as we can see one of the applications is that it is used to detect the level of the liquid contained in a glass container. capacitive proximity sensors react to alteration ns in the electrostatic Field.
since these are based on dielectric principles of capacitance to establish a detection field near the face of the sensor, that creates a detection Zone. it must be remembered that the inductive sensors that were previously seen react to changes in magnetic fields internally. the sensor consists of dielectric plates with a certain capacitance on the detector face which is responsible for emitting an electrostatic field. the other important part of the sensor is the oscillator which is responsible for generating waves at a certain frequency. the trigger circuit which is activated when it detects the object and finally the output which is where the signal is digitized. when an object approaches the sensor it produces changes in capacitance. which Alters the sensor’s electrostatic field. the oscillator for its part remains inactive when the object is outside the electrostatic field produced by the dielectric plates. but if an object gets closer then the oscillator moves at maximum frequency and amplitude. if the object moves away the oscillator returns to its default state. the detection distance depends on several faincludingnclude the material of the object to be detected. the application environment and the distance from which the detection is to be performed. although most sensors come with an adjustment Bolt. for example, if the liquid in the container is not detected then the bolt must be rotated to adjust the detection distance of the material or object. capacitive sensors just like inductive sensors are also available in many different configurations among them, we can see that they can be normally open and normally closed in addition to being PNP configuration and NPN configuration. there are also shielded and unshielded sensors.
differences between these two types of sensors:-
let’s look at the features similarities and differences between these two types of sensors. inductive sensor detects only metallic objects relatively low range. which will vary depending on the nature of the alloy robust and resistant in hostile environments, unalterable against shocks and vibrations dust Etc. relatively High switching frequency, which makes it possible to control the passage of parts at high speed even in rota with time, with no moving Parts. subject to a where capacitive sensor detects ferrous metals and any other type of material they can detect objects through non-metallic walls alterable against humidity and dense Vapors. widespread use for level sensing for example through plastic bottles and for short-range sensing of transparent materials. absence of mechanical wear and long useful life.
post Written :- Dattakumar