Introduction to Industrial Instrumentation

Instruments in measuring level
Table of Contents

What is Instrumentation?

What are Instrumentation basic concepts?

         Instruments are used in measuring the parameters and it is used to indicate, measure, and record physical values in any process.

List few uses of Instrumentation.

  • To research about various parts work and analyze the root of the system’s overall functionality.
  • To conduct a product test on a sample for quality assurance.
  • To identify useful components.
  • To create novel theories.
  • In the interest of health and safety, instruments are used to monitor the data.

How Industrial Instrumentation works?

         They operate in the production plant facilities for the calibration and verification of transmitters, sensors, and their detectors in pressure, temperature and level (including pressure, temperature, humidity, tachometer, rotation, and speed)

What is meant by IMS?

  • IMS stands for Industrial Measurement System.
  • With the aim of reducing errors and waste brought on by incorrect operation of instruments, the IMS specifies the criteria and requirements to be adopted by factories in order to ensure accuracy of measurement equipment used in all stages of production.

Which three components make up Industrial Instrumentation?

         The primary components of industrial instrumentation are sensors, transmitters and transducers which convert energy into measurable physical magnitudes for the control and maintenance of industrial processes.

What is an Instrumentation role in an Industrial process?

  • The fundamental goal of instrumentation in an industry is to maximize output while consuming the least amount of resources, including labor, raw materials, time, and energy.
  • The requirement for continuous measurement of pressure, temperature, level, and flow arose with the expansion of continuous manufacturing.

What are the parameters to be measured in Industry?

The Parameters to be measured in industries are

  • Pressure
  • Level
  • Flow
  • Temperature
  • Quality of intermediate and finished products
  • Speed/vibration/displacements for rotary machines

Classification of Instruments

1. Automatic and Manual Instruments

  • Hg-in-glass thermometer: Automatic instruments
  • Resistance thermometer: Manual instruments since Wheatstone bridge was added to the circuit

2. Self-generating (Active) and Power-operated instruments (Passive)

Ative: Includes an HG-in-Glass thermometer, a dial indicator, a BG, a PT, etc.

Passive: Some instruments need an external power source, such as electricity, hydraulic pressure, or compressed air, to operate. These instruments are externally powered (Passive). The input signals only contribute a negligible amount of the output power. Example:

  • LVDT – Pressure, Force, and Displacement
  • Light to resistance information for photo-conductive transducers
  • Wheatstone bridge is used with a strain gauge load cell.
  • Thermistors and resistance thermometers

3. Remote and self-contained indication Instruments

         A self-contained instrument is one that contains all of the necessary physical components, such as a mercury-in-glass thermometer or an analogue ammeter.

         A remote indicating instrument has primary and secondary elements. Sensor acts as primary element and indicating devices is secondary elements. They both are separated by a transmitting element but connected.

4. Instruments with Deflection and Null Output

         For instance, dial indications and spring balance, Wheatstone bridge circuit, Pan Balance

5. Instruments that is analogue and digital

Analog: With an analogue unit, the signals change continuously and can have an infinite number of values. Examples include a speedometer, fuel gauge, ammeter, and voltmeters.

Digital: Signals that change in discrete steps and can take a limited number of possible values within a defined range are said to be digital. A measured analogue value is transformed into a digital quantity that is shown numerically by the digital equipment. At each succeeding input increment, the output might either be a digit (pulse or step). Digital multimeter and speedometer are two examples.

6. Absolute and Secondary Instruments

Without the need for conversion, an absolute instrument measures a process variable directly from the process. They don’t need to be compared to any standards. It is necessary to calibrate secondary instruments in relation to the reference instrument.

7. Instruments that are mechanical, electrical, and electronic

  • Mechanical
    • Easy to build and design.
    • No further power source is needed.
    • Unable to indicate remotely.
    • Cause commotion and produce inaccurate results
  • Electric
    • A faster indication
    • Involves translating an electrical amount into mechanical motion on a scale.
  • Electronic
    • Quickly react to changing and dynamic conditions.
    • Lightweight, small, using little electricity, and very reliable.
    • Possess excellent sensitivity, adaptability, and the capability of distant indication.
    • It is also feasible to measure without making contact.

8. Instruments of the Contacting and Non-Contacting Type

         Non-contact types don’t actually make any kind of physical touch with the thing that’s being monitored, while Contact type instruments has contact with parameters to be measured

Characteristics of Measuring Instruments

Static Characteristics

         A system with static characteristics measures constant or slowly changing quantities. Example: Boiler temperature, the measured parameter may change abruptly (thermometer shoved into hot liquid) and the signal may fluctuate fast.

Dynamic Characteristics

They apply to systems with “time-varying process variables.” They quantify an instrument’s time-sensitive input-output relationship.

Application of Instrumentation

1) Controlling trade: Measuring instrument is used to calculate the length, volume, and mass in terms of standard units.

2) For surveillance: Measuring information enables us to take appropriate prescribed action.For instance, temperature monitoring in vaccine storage enables us to choose whether or not to speed up cooling. Applicable to controlling a process in industry or our daily lives within the context of an autonomous feedback control system

3) Automatic Feedback Control System

Feedback control System

Pressure Measurements

Pressure is defined as the applied force per unit area. Pressure is typically expressed in pounds per square inch (psi), inches of water column (WC), bars, or kilo gram per square centimeter (kg/cm2). It is

Terminologies used in Pressure measurements

  • Static pressure: The pressure of a fluid at rest is known as static pressure.
  • Dynamic Pressure: While a fluid is moving, its pressure will change depending on how quickly the fluid is flowing is termed as dynamic pressure
  • Absolute pressure: Atmospheric pressure is 14.7 psi (also written as 1 bar or 100 kPa) at sea level, although it changes by 0.5 psi for every 1000 feet of elevation. Absolute pressure is calculated relative to hover (Zero pressure). In other words, atmospheric pressure, or absolute pressure, is pressure measured in relation to a full vacuum (1 bar).
  • Gauge Pressure: The indicative pressure in gauge without atmospheric pressure is termed as “gauge pressure”.

Instruments and techniques for measuring pressure

         There are several different ways to measure pressure, including manometers, bourdon tubes, bellows, and diaphragms.

Pressure Measuring Instruments

         The pressure measuring instruments used are Pressure Gauge, Pressure transmitter and Pressure Switch

Pressure measurement

Temperature Measurements

         An instrument can be used to measure the degree of hotness or coolness that is present. It also expresses the rate of motion of a substance’s atoms and molecules. The Fahrenheit, Celsius, and Kelvin thermometers measure temperature in degrees.

Terminologies used in Temperature measurements

  • Ambient temperature: The ambient air temperature that is surrounding a sensor or instrument, expressed as an average or mean value.
  • Ambient temperature compensation: An automatic adjustment that shields a sensor or instrument’s reading from changes in the surrounding temperature
  • Temperature measuring technique and instruments: Based on the physical features, which are temperature dependent there are generally four different types of temperature sensors.

Measuring Principles for Temperature

  • Expansion of a substance with temperature (TG)
  • Temperature-dependent change in electrical resistance (RTD)
  • Variation in contact potential with temperature between different metals (TC)
  • Radiated energy variations with temperature (Radiation Pyrometer)
Temperature measuring instruments

Level Measurement

         A device that is used for measuring the height of materials, usually fluid inside a tank.

Level Measurement Techniques

                  There are basically 6 methods for measuring and monitoring level of fluids.

  • Float Level Transmitter
  • Ultrasonic Level Transmitter
  • Radar Level Transmitter
  • Capacitance Level transmitter
  • Differential pressure Transmitter
  • Load cells
Level measurement Instrument

Flow Measurement

         The quantification of bulk material (fluid) movement is known as flow measurement.

Principles of Flow Measurement

  • Volumetric flow: The most popular way to measure fluid flow past a specific place per unit of time is by volumetric flow
  • Mass flow: Mass flow is the amount of fluid passing a specific spot in one unit of time.
  • Inferential method: Putting a barrier in the flow channel causes the velocity to increase and the pressure to drop. This pressure difference in the pipe can be utilised to measure the flow rate. The most typical type of aperture employed in this procedure
  • Velocity methods: Magnetic flow meters work on the premise that when a conductor (the flowing fluid) moves in the presence of a magnetic field, a voltage is created in the conductor that is proportional to the fluid’s velocity. Examples: Vortex, turbine, and ultrasonic

Techniques used in Flow Measurement

  • Mechanical type Flow meter
  • Pressure type Flow meter
  • Thermal Flow meter
  • Vortex Flow meter
  • Electromagnetic Flow meter
  • Ultrasonic Flow meter
  • Coriolis Mass Flow meter

Basics of field instrumentations & Terminologies

  • Transducer: The term “transducer” refers to a device that changes one physical quantity into an analogue representation of the first.
  • Sensor: A sensor is just a transducer that detects physical quantities (such as objects, temperatures, etc.).
  • Transmitter: After receiving a signal from a sensing device (transducer), a transmitter is a signal processing device that converts the signal to 4 to 20 mA or 0 to 10 v for transmission to control or display devices.
  • Digital Signals: Digital signals are the signals that travel from one field to another and have two states: ON and OFF. The common voltages for digital signals include 24V DC, 230V AC, and 110V AC.
  • Analogue signals: Any continuous signal that has a time-varying feature (variable) that represents another time-varying quantity is referred to as an analogue or analogue signal. Little changes in the signal have significance, unlike with a digital signal. The two most popular analogue signals are 0-10V and 4-20mA.
  • Protocols: An established method for transferring data between two devices is known as a protocol. The following is determined by the protocol:
    • What kind of error checking should be used method of data compression, if any
    • How the sending device will signal when a message has been sent
    • How the receiving device will signal when a message has been received

Field Instruments Connections

Connection of Field Instruments


         An actuator is a device that transmits a control signal to move or control a body or mechanism in a linear or rotational direction.

Types of Actuators

Actuators can be classified into two types

  • Linear Actuator
  • Rotary Actuator

Further classified based on Power Source

  • Pneumatic
  • Hydraulic
  • Electric
  • Magnetic
  • Mechanical

List the basic Instruments that were used to build the Process Automation Industries.

The fundamental major instruments used in the process automation construction industries are as follows:

  • Sensors: Sensors are instruments that gauge the physical characteristics of things like temperature, pressure, flow rate, and level. They give feedback to the automation system, which makes use of it to regulate the process.
  • Actuators: Actuators are instruments that regulate physical actions like opening and closing valves, changing motor speed, and adjusting the position of robotic arms. They use the output signals they receive from the automation system to control the process.
  • Control Valves: Control valves are used in industrial processes to regulate the flow of fluids, gases, or other materials. When necessary, they change the flow after receiving signals from the automation system.
  • VFD: VFDs, or variable frequency drives, are devices that regulate the speed of electric motors so they can operate more effectively and use less energy. As necessary, they alter the motor speed after receiving signals from the automation system.
  • PLC: These specialized computers, known as PLCs (programmable logic controllers), automate the management of industrial processes. They take data from sensors and other devices, transmit output signals to actuators that control the process, and receive input from other devices as well.
  • HMI: Operators can monitor and manage industrial processes using a graphical user interface known as a human machine interface (HMI). It enables operators to make necessary modifications by displaying real-time data, alarms, and other crucial information.
  • SCADA & DCS: SCADA (Supervisory Control and Data Acquisition) systems are used to remotely operate and observe machinery and other activities from a central location. The control and monitoring of intricate industrial processes, such as those in the oil and gas, power generating, and chemical sectors, is done using Distributed Control Systems (DCS). They cooperate with one another to regulate the process and comprise sensors, PLCs, HMIs, and other gadgets.
  • Safety Systems: Systems for ensuring the safety of people, property, and the environment include safety systems, which keep an eye on important safety indicators like temperature, pressure, and gas levels and take appropriate action as necessary.
  • Communication networks:  It includes Ethernet, DeviceNet, and Profibus, connect all the various parts of the automation system and allow them to communicate with one another.
  • Industrial Robots:  These are machines that automate tasks like assembly, painting, and welding. They respond to commands from the automation system and carry out duties precisely and repeatedly.

What kinds of Instruments are employed in various Industries?

         Depending on the particular application and industries there are numerous distinct kinds of instruments used in various industries. Below are some typical instrument types used in different industries:

  • Pressure gauges is used in a variety of applications to measure the pressure of gases and liquids.
  • The measurement of temperature, which is essential in many industrial operations, is done with thermometers.
  • Measures the rate at which fluids, such as water, gases, or chemicals, flow.
  • pH meters are used to assess a solution’s acidity or alkalinity.
  • Measures a solution’s capacity to conduct electricity using conductivity meters.
  • Tachometers: These devices are used to gauge the speed of rotating equipment such motors, fans, and pumps.
  • Analytical balances: Used in laboratories to precisely quantify the weight of chemicals and other items.
  • The components of complicated mixtures, such as petroleum products, can be separated and analyzed using gas chromatographs.
  • Spectrophotometers devices assess how much light is absorbed and transmitted by a sample, allowing for chemical analysis of the material.
  • Flow resistance of liquids and semi-solids, such as paints and adhesives, is measured with viscometers.
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