Brief About Instrumentation

Instrumentation is defined as the art and science of measurement and control of process variables within a production or manufacturing area. The process variables used in industries are Level, Pressure, Temperature, Humidity, Flow, pH, Force, Speed etc.


Instrumentation deals with,
1) Measurement and monitoring of process and operation
2) Control of processes and operation

Instrumentation divided into its sub parts which are listed below,
1) Instrumentation and control
2) Mechatronics
3) Automation and control
4) Control system
5) Process control and automation
6) Bio-medical engineering

Before covering all these points first we have to know what is instrumentation and what parameters coming into it?...

Measurement

                  Instrumentation is used to measure many parameters (physical values). These parameter includes,

1. Pressure (either differential or static)
2. Flow
3. Temperature
4. Level
5. Density
6. Viscosity
7. Properties of ionizing radiation
8. Frequency
9. Current
10. Voltage
11. Inductance
12. Capacitance
13. Resistivity
14. Chemical composition
15. Chemical properties
16. Properties of light
17. Vibration
18. Weight

Sensors and transducers

          A sensor is a device which senses physical parameter primarily with or without contacting to it. A transducer is a device that converts one form of energy to another form of energy.

          Energy types includes (but are not limited to) electrical, mechanical, electromagnetic (including light), chemical, acoustic, and thermal energy. An actuator is a transducer that accepts energy and produces the kinetic energy of movement (action).

          The energy supplied to an actuator might be electrical or mechanical (pneumatic, hydraulic, etc.). An electric motor and a hydraulic cylinder are both actuators, converting electrical energy and fluid power into motion for different purposes.

Control

             Instrumentation control system(ICS) is a general term that encompasses several types of control systems used in industrial production, including supervisory control and data acquisition (SCADA) systems, distributed control systems (DCS), and other smaller control system configurations such as programmable logic controllers (PLC) often found in the industrial sectors and critical infrastructures.

Distributed control system (DCS)

          DCSs are used to control industrial processes such as electric power generation, oil and gas refineries, water and wastewater treatment, and chemical, food, and automotive production. DCSs are integrated as a control architecture containing a supervisory level of control, overseeing multiple integrated sub-systems that are responsible for controlling the details of a localized process.

          Product and process control are usually achieved by deploying feedback or feed forward control loops whereby key product and/or process conditions are automatically maintained around a desired set point. To accomplish the desired product and/or process tolerance around a specified set point, only specific programmable controllers are used.

DCS Setup with HIS and ENG workstations

Programmable logic controller (PLC)

Industrial PLC's network

          PLC's provide Boolean logic operations, timers, and (in some models) continuous control. The proportional, integral, and/or differential gains of the PLC continuous control feature may be tuned to provide the desired tolerance as well as the rate of self-correction during process upsets. PLC's are used extensively in process-based industries. 

          PLC's are computer-based solid-state devices that control industrial equipment and processes. While PLC's can control system components used throughout SCADA and DCS systems, they are often the primary components in smaller control system configurations. They are used to provide regulatory control of discrete processes such as automobile assembly lines and power plant soot blower controls and are used extensively in almost all industrial processes.

Allen Bradley Micrologix 1200C

SCADA

          SCADA (supervisory control and data acquisition) is a system operating with coded signals over communication channels so as to provide control of remote equipment (using typically one communication channel per remote station). 

          The control system may be combined with a data acquisition system by adding the use of coded signals over communication channels to acquire information about the status of the remote equipment for display or for recording functions.

SCADA mimic

Types of processes using process control

 In practice, processes can be characterized as one or more of the following forms:

1. Discrete:- Found in many manufacturing, motion and packaging applications. Robotic assembly, such as that found in automotive production, can be characterized as discrete process control. Most discrete manufacturing involves the production of discrete pieces of product, such as metal stamping.
2. Batch:- Some applications require that specific quantities of raw materials be combined in specific ways for particular duration's to produce an intermediate or end result. One example is the production of adhesives and glues, which normally require the mixing of raw materials in a heated vessel for a period of time to form a quantity of end product. Other important examples are the production of food, beverages and medicine. Batch processes are generally used to produce a relatively low to intermediate quantity of product per year (a few pounds to millions of pounds).
3. Continuous:- Often, a physical system is represented through variables that are smooth and uninterrupted in time. The control of the water temperature in a heating jacket, for example, is an example of continuous process control. Some important continuous processes are the production of fuels, chemicals and plastics. Continuous processes in manufacturing are used to produce very large quantities of product per year (millions to billions of pounds).