Manish Kumar
The competition due to globalisation has resulted in better process control, optimum utilisation of resources and higher level of automation in all industry sectors. The demand for automation is increasing day by day. Growing requirement of control and computing has created a large space for “Research in Instrumentation”. To face these challenges, competent instrumentation engineers are required.
Automation or automatic control, is the use of various control systems for operating equipment such as machinery, processes in factories, boilers and heat treating ovens, switching in telephone networks, steering and stabilisation of ships, aircraft and other applications with minimal or reduced human intervention.
Instrumentation is defined as the art and science of measurement and control of process variables within a production or manufacturing area. An instrument is a device that measures a physical quantity such as flow, temperature, level, distance, angle, or pressure. Instruments may be as simple as direct reading thermometers or may be complex multi-variable process analysers.
Introduction of automation
Instruments attached to a control system may provide signals used to operate solenoids, valves, regulators, circuit breakers, or relays. These devices control a desired output variable, and provide either remote or automated control capabilities. These are often referred to as final control elements when controlled remotely or by a control system.
A transmitter is a device that produces an output signal, often in the form of a 4- 20 mA electrical current signal, although many other options using voltage, frequency, pressure or ethernet are possible. This signal can be used for informational purposes, or it can be sent to a PLC, DCS, SCADA system, LABVIEW or other type of computerized controller, where it can be interpreted into readable values and used to control other devices and processes in the system. Control instrumentation plays a significant role in both gathering information from the field and changing the field parameters, and as such are a key part of control loops.
In the early years of process control, process indicators and control elements such as valves were monitored by an operator that walked around the unit adjusting the valves to obtain the desired temperatures, pressures, and flows. As technology evolved pneumatic controllers were invented and mounted in the field that monitored the process and controlled the valves. This reduced the amount of time process operators were needed to monitor the process. Later years the actual controllers were moved to a central room and signals were sent into the control room to monitor the process and outputs signals were sent to the final control element such as a valve to adjust the process as needed. Each instrument company introduced their own standard instrumentation signal, causing confusion until the 4-20 mA range was used as the standard electronic instrument signal for transmitters and valves. This signal was eventually standardized as ANSI/ISA S50, “Compatibility of Analog Signals for Electronic Industrial Process Instruments”, in the 1970s. The transformation of instrumentation from mechanical pneumatic transmitters, controllers, and valves to electronic instruments reduced maintenance costs as electronic instruments were more dependable than mechanical instruments. This also increased efficiency and production due to their increase in accuracy.
Measurement instruments have three traditional classes of use: Monitoring of processes and operations, Control of processes and operations, Experimental engineering analysis, while these uses appear distinct, in practice they are less so. All measurements have the potential for decisions and control.
Practical Examples of Instrumentation
Digital cameras and wristwatches might technically meet the loose definition of instrumentation because they record and/or display sensed information. Under most circumstances neither would be called instrumentation, but when used to measure the elapsed time of a race and to document the winner at the finish line, both would be called instrumentation.
Household: A very simple example of an instrumentation system is a mechanical thermostat, used to control a household furnace and thus to control room temperature. A typical unit senses temperature with a bi-metallic strip. It displays temperature by a needle on the free end of the strip. It activates the furnace by a mercury switch. As the switch is rotated by the strip, the mercury makes physical (and thus electrical) contact between electrodes.
Automotive: Modern automobiles have complex instrumentation. In addition to displays of engine rotational speed and vehicle linear speed, there are also displays of battery voltage and current, fluid levels, fluid temperatures, distance travelled and feedbacks of various controls (turn signals, parking brake, headlights, transmission position). Cautions may be displayed for special problems (fuel low, check engine, tire pressure low, door ajar, seat belt unfastened). Navigation systems can provide voice commands to reach a destination. There may be independent airbag systems which contain sensors, logic and actuators. Anti-skid braking systems use sensors to control the brakes, while cruise control affects throttle position.
Aircraft: Early aircraft had a few sensors. “Steam gauges” converted air pressures into needle deflections that could be interpreted as altitude and airspeed. A magnetic compass provided a sense of direction. The displays to the pilot were as critical as the measurements. A modern aircraft has a far more sophisticated suite of sensors and displays, which are embedded into avionics systems. The aircraft may contain inertial navigation systems, global positioning systems, weather radar, autopilots, and aircraft stabilisation systems.
Scope of instrumentation engineering
Instrumentation engineering is the engineering specialisation focused on the principle and operation of measuring instruments that are used in design and configuration of automated systems in electrical, pneumatic domains etc. A highly interdisciplinary branch- Instrumentation engineering covers major aspects of chemical, mechanical and electrical and electronics fundamentals. The Instrumentation and Control Diploma / Degree Engineers get employment opportunities in both hardware and software industries. The options being Engineering design, Simulation, Development, Fabrication, Testing, Quality Control, and Marketing In Industries like Industrial Automation, Home Automation, Nuclear Power Stations, Aircraft Instrumentation and Controls, Refineries, Petrochemical, Chemical and Food Industries, Cement, Textile, Paper industries, Pharmaceutical, Engineering, Electrical and Electronic, Biomedical, Thermal Power Station, Automobile Industries, Fertiliser Industries, Wood processing, Mining, etc. with the goal of improving system productivity, reliability, safety, optimisation and stability.
