Understanding Sensors

In the simplest of terms, sensors are objects which are purposed to detect changes in their environment and then provide corresponding outputs. Sensors are unique types of transducers and provide various outputs using optical or electrical signals.

Sensors respond to input from the physical environment. These inputs can be light, motion, heat, pressure apart from other environmental phenomena.

With giant leaps in the field of micro-machinery and micro-controllers, the use of sensors has expanded manifold. Sensors have a wide application area. They are used in everyday appliances such as elevator buttons and touch lamps for dimming and brightening the lights and in complex mechanical processes which require high precision.

A good sensor is able to work with the following parameters:

1. Being sensitive to the property that is measured.
2. Being insensitive to any other property which is likely to come in contact with the application.
3. Not influencing the property being measured.

Types of Sensors

Depending on their usage, sensors can be of different types.

These includes:

a. Pressure Sensor

pressure sensor

These measure pressure and generates a signal which is a function of the pressure induced.

b. Ultrasonic Sensor

Ultrasonic Sensor

These generate high-frequency sound waves and evaluate the echo received back. With the help of sound, these sensors accurately detect objects and measure distances.

c. Humidity Sensor

Humidity Sensor

These sensors analyse, measure and report the relative humidity in the air.

d. Gas Sensor

Gas Sensor

These sensors are mostly deployed as a part of the safety system. They measure the nearby gases in the environment and send out signals in case of leakage.

e. Acceleration Sensor

Acceleration Sensor

These sensors are specifically designed for enhancing functionality in low power applications of consumer electric devices in mobile phones.

f. Displacement Sensors

Displacement Sensors

These sensors measure distances moved by objects and are also used for measuring the height and width of an object.

Role of sensors in the SCADA units

Sensors play a crucial role in all components which are associated with SCADA units. They directly interface with the managed systems. The sensors use Remote Terminal Units or RTUs as local collection points for incoming reports and delivering the commands to the control relays.

In the master units, the sensors help in building up a human interface for the system for automatically regulating the managed system with respect to the inputs from sensors.

Working of Sensors

Typically, the sensors are installed on the field. Measurements from these units either in the analog or digital form are recorded by PLC units or RTUs. These signals are then transformed into digital data which is sent over to the master unit. When the master feedback is sent over by RTU, the electrical signals are applied to the relays and other instruments.

Application of Sensors

Sensors are highly versatile in their role and are regularly employed in a number of industries to facilitate the plant processes.

• Sensors are used in the remote fields to measure the pressure, temperature, viscosity, flow rate, etc. for fluids in pipelines.
• Displacement sensors are able to measure the thickness of layers, boards, plates, sheets, foils and so on. These are also able to measure the filling levels of the containers.
• Speed sensors are directly attached to shafts and are used to measure the speeds of compressors, revolutions and turbine gaps.
• Color sensors are able to sort products by their color and are used widely in the automation technology.


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