What are the basic concepts of industrial instrumentation?

Industrial instrumentation is a fundamental discipline in the process industry and production plants. It is possibly less well known than industrial automation, but there are technicians and engineers specialized only in this field.

In short, industrial instrumentation refers to a multi-disciplinary area that requires knowledge of electrical electronics, chemistry, mechanics microcontrollers and microprocessors, software language, process control. Also, such as the principles of pneumatics and hydraulics, and basics of industrial protocols, network communications.

Now, let’s know what is meant by instrumentation.

What is Instrumentation?

The process in which the set of various interconnected electrical, measurement, and control instruments measure, analyze, and control electrical and non-electric physical quantities is called Instrumentation.

There are various types of process instruments  

A) Electrical instruments

B)Electronic instruments

C)Mechanical instruments

Instrumentation is further classified into different types, such as

  1. Electrical instrumentation
  2. Industrial instrumentation
  3. Electronic instrumentation,
  4. Mechanical instrumentation

Purpose of industrial instrumentation

The process of measuring and controlling various quantities in production processes using various instruments or industrial elements is defined as “industrial instrumentation”.

To control any quantity, one must primarily measure that particular quantity. After measuring the desired quantity, the measured values are transmitted for indication, calculation, or control purposes, either with manual or automatic operation.

In an automatic control operation, the quantity can be controlled using the control signal sent by the CPU to the control devices.

In practice, the sensors read the different field data such as flow, pressure, displacement, vibrations, etc., and transmit them to the control systems that will regulate these variable quantities.

In industry, control is normally carried out by programmable logic controllers (PLC) or

Distributed control systems (DCS).

How industrial instrumentation works

Industrial instrumentation is considered a science of measurement and control of automated systems. Applications of this technology proliferated in technological research, industry, and everyday life.

From control systems for automobile engines to home thermostats, aircraft autopilots, pharmaceutical manufacturing, power plants, oil and gas, refineries, etc.

The first step in the operation of industrial instrumentation, as we have already mentioned, is measurement. If we can’t measure the process parameter,  It’s meaningless to try to control it.

This “something” typically takes one of the following forms in the industry:

  • Fluid flow
  • Fluid pressure
  • Temperature of an object
  • Volume of fluid stored in a container
  • Chemical concentration (pH, Conductivity, etc.,)
  • The machine’s vibration, displacement, motion, or acceleration
  • Voltage, current or electrical resistance, etc.

Once we measure the quantity of interest, we typically transmit a signal representing this quantity to a PLC/DCS system where human (manual) or automated action then takes place.

Therefore, the final control element sends a signal to PLC/DCS if the control action is automated.

Generally, the control devices are the control valve or electric motor. These instrumentation and control devices are connected to the measurement devices through a physical system called a “process”.

How does Industrial instrumentation work?

A practical example of industrial instrumentation.

The thermostat of the electric geyser is an example of a measurement and control system, in which the temperature of the water is the “Process” under control.

In this example, the thermostat typically has two functions. One is sensing and the other is control, while the heater coil adds heat to the water to increase the temperature. Input water from the overhead tank extracts heat from the geyser to decrease the temperature.

The job of this control system is to keep the water temperature at a comfortable level. Desired hot water temperature at desired value (called the set-point).

Characteristics of industrial instrumentation

The characteristics of industrial instrumentation in real-time applications are based on its sensors, transducers or input devices, controllers, processors, transmitters, and actuators (output devices).

Input instrumentation is used to measure, regulate physical quantities such as flow, level, pressure, temperature, and so on.

Output instrumentation includes control devices such as valves, regulators, switches, and relays. These are intended to control the desired output variable, providing remote or automatic control capabilities. They are considered final control devices or elements. The three main elements of industrial instrumentation are explained below.

Main elements of industrial instrumentation

1. Sensors

There are various sensors used as input devices in real-time control and instrumentation applications, but the most commonly used sensors are:

  • Pressure sensor
  • Flow sensor
  • Temperature sensor
  • Level sensor
  • Speed sensor
  • Photoelectric sensor
  • Pressure gauge
  • Thermistor
  • Thermocouple
  • Position and displacement sensor, among others.

2. Controllers

Most controllers or valves are generally implemented using mechanical or electronic systems. But recent industrial controllers in systems used in the industry rely on computers. Hence, it makes it easier to implement complex control algorithms.

The most used control systems in industrial instrumentation are

  1. PLC (Programmable Logic Controller)
  2. DCS (Distributed Control Systems)
  3. SCADA (Supervisory Control and Data Acquisition system)

3. Actuators

The actuator is used to control the mechanism or the system based on the signal given to it by converting the electrical signal into a large power action. The output signal from controllers or control systems like DCS, SCADA, or PLC used in industrial instrumentation is used to control the actuators.

Actuators are generally controlled by electrical current, fluid pressure, pneumatic pressure, and this energy is converted into mechanical energy or power.

There are different types of actuators to know:

  • Hydraulic actuator
  • Pneumatic actuator
  • Electrical actuator
  • Mechanical actuator

These actuators are used to control output devices such as valves, motors, relays, contactors, emergency lights, etc.

What does an industrial instrumentation technician do?

The industrial instrumentation technician is professionally trained, generally, in the areas of electronic engineering and or industrial engineering.

As a result of their training, they must have a solid foundation in electricity and electronics. For example, knowing how a vibration monitor works but also knowing how t handle measuring instruments (Voltmeter, Ammeter, and Oscilloscope, etc.).

In short, they work in the production plant facilities for the verification and calibration of sensors (pressure, temperature, humidity, tachometer, rotation, and speed), transmitters, and their detectors (pressure, temperature, and humidity).

In addition to controls, they are responsible for repairs and or replacement of devices and commissioning of measuring instruments. Also, they check the conformity of the installation following existing standards and current regulations before and during the production of the process.

Similarly, they carry out the verification and repairs of measuring instruments, sensors, and controllers by quality procedures defined with the manufacturer’s specifications or current standards.

The profiles of instrumentation technicians or engineers can be very varied.

An engineer can work in maintenance where he will be in charge of the maintenance of the control system and field instruments.

As well, the engineer can work in design, in this case, he will be in charge of the calibration of the sensors, the supervision of the installation, the programming of the control system, etc.,

Conclusions

All the operations related to real-time processes in the production plant have to be adequately controlled to achieve more economical, efficient, and reliable results.

Therefore, some devices are used to measure physical quantities like temperature, pressure, etc., which are called instrumentation.

Automation and industrial instrumentation are necessary to control various operations in industries. Author: Kireeti Samuel

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