Sensors for Industrial Automation
Selecting sensor for particular application in industrial automation is a real choice to make .There would be plenty of sensors available in the market , each based on different principles of operation and different level of precision .
What is the first thing that comes to your mind when you hear the word 'sensor' ? It would most likely be the sense organs that we have eyes, nose, ears, tongue and skin. These are the natural sensors that we have. Based on the sensory organs, if we define sensor, then we can say that it is a device that allows us to sense objects around us, to see them, to smell the odor , to taste eatables, to feel the environment, etc. However .in general terms, a sensor can be define as a device that detects, measures and converts a physical quantity into a signal that can be read by an observer or an instrument. A sensor allows us to notice things and understand them easily.
The sense organs that we have are considered to be natural sensors and based on these sensors, we have many man made or artificial sensors that allow us to make our life easy day by day . The artificial sensors are hardware components that can allow a device to know its location, surrounding and many more things . These can be either wired or wireless.
Let us discuss these sensors in detail to determine their features and to understand their scope of use.
1. Proximity Sensor
Proximity sensors are such a device that detect the presence of an object without physical contact.
These solid-state electronic device are completely encapsulated to protect against excessive vibration , liquids, chemicals,and corrosive agents found in the industrial environment, proximity sensors are used when:
- The object being detected is too small, lightweight, or soft to operate a mechanical switch.
- Rapid response and high switching rates are required, as in counting or ejection control applications.
- An object has to be sensed through nonmetallic barriers such as glass, plastic, and paper cartons.
Proximity sensors have two types
1. Inductive Proximity Sensor
2. Capactive Proximity Sensor
1. Inductive Proximity Sensor
When application calls for noncontact metallic target sensing an inductive type proximity sensors are used. Inductive proximity sensors are used for detect both ferrous metals and nonferrous metals ( such as copper, aluminum and brass).
When application calls for noncontact metallic target sensing an inductive type proximity sensors are used. Inductive proximity sensors are used for detect both ferrous metals and nonferrous metals ( such as copper, aluminum and brass).
Inductive sensor work as following below:
- The oscillator circuit generates a high frequency electromagnetic field that radiates from the end of the sensor.
- When a metal object enter the field, eddy currents are induced in the surface of the object.
- The eddy currents on the object absorb some of the radiated energy from the sensor resulting in a loss of energy and change of strength of oscillator.
- The sensor's detection circuit monitors the oscillator's strength and triggers a solid state output at a specific level.
- Once the metal object leaves the sensing area, the oscillator returns to its initial value.