For all real time process related operations in industries, the entire system has to be controlled properly for achieving more economical, efficient, and reliable operations. Hence, some devices are used for measuring the physical quantities such as temperature, pressure and so on , which are called as instruments. Industrial automation and industrial instrumentation are required to control various operations in industries. But, first of all, let us know about what is Instrumentation?
What is Instrumentation?
The process in which assembly of several electrical, measuring and control instruments interconnected for measuring, analyzing and controlling the electrical and non-electrical physical quantities is called as Instrumentation. Basically, there are different types of instruments such as electrical instruments, electronic instruments and mechanical instruments. Instrumentation is further classified into many types such as electrical instrumentation, industrial instrumentation, electronics instrumentation, mechanical instrumentation, and so on.
The process of measuring and controlling various quantities in industries by utilizing various industrial instruments is called as industrial instrumentation. For controlling any quantity, primarily that particular quantity has to be measured. The common quantities used in industries and which are considered for measurement include fluid pressure, fluid flow rate, temperature of a device, volume of fluid, motion or position or physical dimensions or acceleration of the machine, electrical current, electrical voltage and electrical resistance.
Thus, after measuring the desired quantity, the measured values are transmitted for indication or computation or controlling purpose either with manual operation or automatic operation. In an automatic- controlling operation the quantity can be controlled using the control signal sent by the computer to the controlling devices.
In general, controlling devices are electric motor, control valve and electric heater. These instrumentation and control devices are connected to the measuring devices by using some physical system referred to as “process”.
Most of the industries are automated for ease of operation for this purpose; the microcontroller and microprocessors are required for programmable switching. For example, in many industries, the industrial power schedule is automated using embedded systems.
Structure of Industrial Instrumentation in Real Time Applications
This can be easily analyzed with its simple structure as shown below. It majorly consists of sensors or transducers or input devices, controllers or processors, transmitters and actuators or output devices.
Input instrumentation is used for measuring, regulating physical quantities such as flow, level, pressure, temperature and so on.
Output instrumentation includes control devices such as valves, regulators, circuit breakers and relays. These are intended for controlling desired output variable, providing control capabilities either remotely or automatically. These are considered as final control devices or elements.
Three major elements in industrial instrumentation are explained in brief below.
There are many sensors used as input devices in real time electronics instrumentation and control applications, but frequently used sensors include temperature sensor, pressure sensor, optoelectronic sensor, flow sensor, level sensor, speed sensor, inductance coil pulse generator, manometer, optical pyrometer, orifice plate, thermistor, thermocouple, image sensor, position & displacement sensor, and so on.
The temperature sensor is used to detect the changes in temperature of a particular device or machine or system and such that gives the signal to the controllers in case of change in temperature limits. There are different types such as thermistor, thermostat, thermocouple and so on, specific sensor used based on the application.
Pressure sensor acts as a transducer and it is used to measure pressure of liquids or gases, it converts the pressure into electrical signals.
Thus, specified process which is intended to work in a particular manner is connected to a specific sensor to detect any changes in the operation, to sense the output and transmit it to the controllers for controlling or monitoring or operating the process in a predefined manner.
Most of the controllers or valves are generally implemented using mechanical systems or solid electronics. But the recent industrial controllers of industrial control systems depends on computers, which makes ease of implementation of complex control algorithms than using a mechanical system.
Frequently used control systems in instrumentation are PLC, DCS, SCADA systems.
Programmable Logic Controller (PLC)
The Programmable Logic Controller is a digital computer frequently used in several industries and machines for automation of industrial electromechanical processes. It is a real time system used to produce output within limited time as a response to changes in input conditions. The general relay control systems are replaced by PLCs.
The industrial instruments or machines such as electric motors, pneumatic or hydraulic cylinders, solenoids, etc. can be operated using PLCs.
Supervisory Control and Data Acquisition (SCADA)
The industries consist of equipments and instruments placed at remote locations, these can be controlled remotely using the SCADA. It is a type of industrial control system in which supervisory system is combined with data acquisition system for acquiring information about the remote instruments or equipment with coded signals over different communication channels like wireless communication for transferring data to control panel.
Distributed Control System (DCS)
In industries control elements are located in a central location and also at distributed locations throughout the industry. Thus, for controlling these distributed subsystems a control system is required to operate at distributed locations called as distributed control systems. DCS is used for the automation of processes in various processes using computerized control system.
It is used to monitor and control various processes in industries such as nuclear power plants, water management system, oil refining plants, chemical plants, petrochemical industries, etc.
The actuator is used to control the mechanism or system based on the signal given to it by converting the electrical signal into powerful action. The output signal of the controllers or control systems like DCS or SCADA or PLCs used in industrial instrumentation are used for controlling the actuators.
Actuators are generally operated by the electric current, fluid pressure pneumatic pressure and this energy is converted into mechanical energy.
There are different types of actuators namely hydraulic actuator, pneumatic actuator, electric actuator and mechanical actuators.
These actuators are used for controlling the output devices such as motors, lights, valves, relays, contactors, and so on.
The output of the PLC is used to close the Solenoid switch, resulting in switching on high currents, for example to switch on motor in industries.
The device used for controlling, regulating the flow of fluids by making open or close or partial obstruction of passageways or tubes. The flow of liquids or gases in industries can be controlled by using valves which can be controlled manually using handles or pedal or wheel and automatically driven according to the variations in pressure, flow and temperature.
The brief description regarding the industrial instrumentation is given in this article along with its major elements or processes. Do you want to know more information about the different instrumentation methods such as electronics instrumentation, mechanical instrumentation, electrical instrumentation? Then, post your queries to know about the advanced technologies in instrumentation by posting your comments below.