100+ Instrument Engineer Interview Questions and Answers

MOV (Metal Oxide Varistor) is used as a voltage protection device in electrical circuits.

• MOV is used to protect sensitive electronic devices from voltage surges or transients.

• It acts as a voltage-dependent resistor, limiting the voltage across the circuit.

• MOV absorbs excess voltage and diverts it away from the protected equipment.

• It has a high resistance at normal operating voltage and low resistance during voltage spikes.

• MOV is commonly used in power supplies, surge protecto...read more

Three element system at boiler is used to control the water level, steam flow, and feed water flow to maintain optimal boiler operation.

• Three element system monitors water level, steam flow, and feed water flow in a boiler.

• It helps in maintaining the water level within safe limits to prevent damage to the boiler.

• The system adjusts the feed water flow based on the steam flow to maintain a constant water level.

• It ensures efficient and safe operation of the boiler by controlling...read more

There are different types of calibration that can be done depending on the instrument being used.

• Zero calibration

• Span calibration

• Linearity calibration

• Sensitivity calibration

• Temperature calibration

• Humidity calibration

• Pressure calibration

AC drives use alternating current to control the speed of an electric motor, while DC drives use direct current for the same purpose.

• AC drives are more commonly used due to their ability to provide variable speed control and energy efficiency.

• DC drives are simpler in design and are often used in applications where precise speed control is required, such as in cranes or elevators.

• AC drives are typically more cost-effective and easier to maintain compared to DC drives.

• Examples ...read more

Inputs and outputs refer to the signals or data that are received and transmitted by a system or device.

• Inputs are the signals or data that are received by a system or device, which are then processed or used to produce an output.

• Outputs are the signals or data that are transmitted by a system or device, which are the result of processing the inputs.

• Examples of inputs and outputs include sensors and actuators in a control system, audio and video signals in a multimedia system...read more

Star/Delta starter is used to reduce the starting current of a motor.

• Star connection provides high starting torque but high starting current

• Delta connection provides low starting torque but low starting current

• Star/Delta starter uses both connections to reduce starting current and provide sufficient starting torque

• Used for large motors to prevent damage to motor and electrical system

Flame scanner detects the presence or absence of flame in a combustion chamber.

• Uses ultraviolet or infrared radiation to detect flame

• Sends signal to control system to adjust fuel and air flow

• Helps prevent explosions and improve efficiency

• Commonly used in boilers, furnaces, and gas turbines

Instrumentation is the science and art of measurement and control of process variables within a production or manufacturing area.

• Instrumentation involves the use of sensors, transmitters, controllers, and final control elements to monitor and control processes.

• Examples of instrumentation include pressure gauges, temperature sensors, flow meters, and control valves.

• Instrumentation plays a crucial role in ensuring the efficiency, safety, and quality of industrial processes.

Lead resistance is the resistance encountered in the electrical leads connecting a sensor or instrument to a measuring device.

• Lead resistance can affect the accuracy of measurements by introducing additional resistance in the circuit.

• It is important to account for lead resistance when designing and calibrating instrumentation systems.

• Lead resistance can be minimized by using high-quality, low-resistance leads.

• Examples of instruments where lead resistance is a concern include ...read more

Steam turbines are used to generate electricity by converting thermal energy into mechanical energy.

• There are two main types of steam turbines: impulse turbines and reaction turbines.

• Impulse turbines use high-pressure steam to rotate a set of blades, while reaction turbines use both high-pressure and low-pressure steam to rotate a set of blades.

• Steam turbines are commonly used in power plants to generate electricity.

• The largest steam turbine in the world is located in South K...read more

Level transmitters are instruments used to measure the level of a substance in a container or tank.

• Level transmitters use various technologies such as ultrasonic, radar, capacitance, and pressure to measure levels.

• They provide continuous level measurement and can be used in various industries like oil and gas, chemical, and water treatment.

• Level transmitters can be installed externally or directly in the substance being measured.

• They transmit the level data to a control syste...read more

RTD stands for Resistance Temperature Detector. It is a temperature sensor that operates on the principle that the resistance of a metal increases with temperature.

• RTD is commonly used in industrial applications for temperature measurement.

• Platinum is a popular material for RTDs due to its high accuracy and stability.

• RTDs are known for their high accuracy and repeatability compared to other temperature sensors.

• RTDs are commonly used in industries such as oil and gas, chemical...read more

Yes, 0-10 V can be used in PLC as an analog input or output signal.

• PLCs typically have analog input and output modules that can handle 0-10 V signals.

• The signal can be used to measure or control variables such as temperature, pressure, or flow.

• The resolution and accuracy of the signal depend on the PLC and the analog module used.

• Some PLCs may require additional scaling or conversion of the signal to match the desired range or units.

• Examples of PLCs that can use 0-10 V signals...read more

I am proficient in ladder logic programming for PLCs.

• Proficient in ladder logic programming for PLCs

• Experience with other PLC programming languages such as Function Block Diagram (FBD) and Structured Text (ST)

• Knowledge of industry standards for PLC programming

• Ability to troubleshoot and debug PLC programs

• Examples: Allen-Bradley RSLogix, Siemens TIA Portal, Mitsubishi GX Works

Control valve maintenance involves regular inspection, testing, and calibration to ensure optimal performance.

• Regularly inspect control valves for leaks, corrosion, or damage

• Perform testing to check for proper functioning and response time

• Calibrate control valves to ensure accurate control of flow rates

• Replace worn out parts or components as needed

• Keep detailed records of maintenance activities for future reference

Various types of communication protocols include Modbus, Profibus, HART, Foundation Fieldbus, and Ethernet/IP.

• Modbus - commonly used in industrial automation

• Profibus - used in process automation

• HART - for smart field devices

• Foundation Fieldbus - for process control

• Ethernet/IP - for industrial Ethernet communication

Instrumentation skill refers to the ability to design, install, maintain, and troubleshoot various types of instruments used in industrial processes.

• Understanding of different types of instruments such as sensors, transmitters, controllers, and final control elements

• Knowledge of calibration procedures and techniques

• Ability to read and interpret P&IDs (Piping and Instrumentation Diagrams)

• Proficiency in using software tools for data analysis and visualization

• Troubleshooting ski...read more

Different types of flow include laminar, turbulent, transitional, compressible, incompressible, steady, and unsteady.

• Laminar flow: smooth and orderly flow with no turbulence

• Turbulent flow: chaotic and irregular flow with eddies and swirls

• Transitional flow: a mix of laminar and turbulent flow

• Compressible flow: flow where the density changes due to pressure changes

• Incompressible flow: flow where the density remains constant

• Steady flow: flow where the velocity and other properti...read more

Mass flow meter measures the mass flow rate of a fluid in a pipe or duct.

• Works on the principle of Coriolis effect or thermal dispersion

• Fluid flows through a vibrating tube or a heated element

• Measures the change in frequency or temperature to determine mass flow rate

• Used in industries like chemical, food and beverage, and oil and gas

• Examples include Coriolis mass flow meter and thermal mass flow meter

Hydraulic pressure is the force exerted by a fluid in a closed system, while pneumatic pressure is the force exerted by a gas in a closed system.

• Hydraulic pressure is generated by the movement of a liquid, such as oil, in a confined space.

• Pneumatic pressure is created by the compression of a gas, such as air, in a closed system.

• Both types of pressure are used in various industrial applications, such as in hydraulic systems for heavy machinery or pneumatic systems for air tool...read more

Pressure, temperature, flow, and level are key parameters in instrumentation engineering.

• Pressure is the force exerted by a fluid on its container, measured in units like psi or bar.

• Temperature is the degree of hotness or coldness of a substance, measured in units like Celsius or Fahrenheit.

• Flow is the rate at which a fluid passes through a system, measured in units like liters per minute.

• Level is the height of a substance in a container, measured in units like meters or feet...read more

Standard maintenance procedures for instruments involve regular inspections, calibrations, and repairs to ensure optimal performance.

• Regularly inspect instruments for any signs of wear or damage

• Calibrate instruments according to manufacturer's guidelines

• Perform routine maintenance tasks such as cleaning and lubricating

• Keep detailed records of maintenance activities for each instrument

• Train staff on proper instrument maintenance procedures

• Schedule preventive maintenance to avo...read more

Interacting systems have feedback loops and can influence each other's behavior, while non-interacting systems operate independently.

• Interacting systems have mutual dependencies and can affect each other's inputs, outputs, or behavior.

• Non-interacting systems operate independently and do not have any influence on each other.

• Interacting systems often involve feedback loops where the output of one system affects the input of another.

• Non-interacting systems can be considered as s...read more

VFD stands for Variable Frequency Drive, used to control the speed of an AC motor by varying the frequency and voltage supplied to the motor.

• VFD consists of three main components: rectifier, DC bus, and inverter.

• Rectifier converts AC power to DC power.

• DC bus stores the converted DC power.

• Inverter converts DC power back to AC power with variable frequency and voltage.

• VFD allows for precise control of motor speed, reducing energy consumption and wear on the motor.

• Example: VFDs ...read more

Automation is the use of technology to control and monitor processes, reducing human intervention.

• Automation involves the use of control systems to operate equipment and machinery.

• It aims to increase efficiency, productivity, and safety by minimizing human error.

• Examples include automated manufacturing processes, smart home systems, and self-driving cars.

Instruments that power AI voltage include sensors, transducers, and signal conditioners.

• Sensors convert physical parameters into electrical signals.

• Transducers convert one form of energy into another.

• Signal conditioners amplify, filter, and convert signals for processing.

• Examples include thermocouples, pressure sensors, and strain gauges.

The PLC used in our plant is Siemens S7-1200.

• Siemens S7-1200 is a popular choice for industrial automation due to its reliability and flexibility

• It offers a wide range of communication options and programming capabilities

• The PLC is used for controlling various processes and equipment in the plant

I am good at process control systems

• Experienced in designing and implementing control systems for industrial processes

• Skilled in programming PLCs and SCADA systems

• Knowledgeable in instrumentation devices such as sensors, transmitters, and control valves

Process variable measurements are essential for monitoring and controlling industrial processes.

• Process variables include temperature, pressure, flow rate, level, pH, conductivity, etc.

• Measurements are typically done using sensors and transmitters.

• Accurate measurements are crucial for ensuring process efficiency and safety.

• Examples of instrumentation used for measurement include thermocouples, pressure transducers, flow meters, level sensors, etc.

To prepare a Transmitter Datasheet, include key specifications like range, accuracy, output signal, process connection, etc.

• Include key specifications such as range, accuracy, output signal, process connection, etc.

• Provide details on power supply requirements and environmental conditions.

• Specify any special features or certifications required for the application.

• Include information on calibration procedures and maintenance requirements.

• Ensure all necessary dimensions and moun...read more

Control valve function is to regulate the flow of fluid in a process system by varying the size of the flow passage.

• Regulates flow of fluid by adjusting flow passage size

• Controls pressure, temperature, level, or flow rate in a process system

• Can be operated manually or automatically

• Examples: globe valve, butterfly valve, ball valve

Process variable is the measured parameter in a system, while control system is the mechanism used to regulate the process variable.

• Process variable is the input to the control system

• Control system uses feedback to adjust the process variable

• Examples of process variables include temperature, pressure, flow rate

• Examples of control systems include PID controllers, PLCs, DCSs

Network topology types refer to the layout of a computer network and how different devices are connected.

• Common types include star, bus, ring, mesh, and hybrid topologies

• Star topology has a central hub with all devices connected to it

• Bus topology uses a single cable to connect all devices in a linear fashion

• Ring topology connects devices in a circular manner

• Mesh topology has each device connected to every other device

• Hybrid topology is a combination of two or more different t...read more

Field instruments are devices used to measure and control process variables in industrial settings.

• Working principles include pressure, temperature, level, flow, and analytical measurements

• Examples include pressure transmitters, thermocouples, level switches, flow meters, and gas chromatographs

• Instruments can be analog or digital, and may use various communication protocols such as HART or Modbus

A hook drawing for DP level transmitters is a diagram that illustrates the installation and connection of the transmitter in a process system.

• The hook drawing typically includes details such as the location of the transmitter, the process connections, and the electrical connections.

• It may also include information about the type of transmitter, the range, and any additional accessories or components.

• The hook drawing helps ensure proper installation and connection of the DP lev...read more

Turbine protection system is a safety system that protects the turbine from damage during abnormal conditions.

• It monitors various parameters like temperature, pressure, vibration, and speed.

• It triggers alarms and trips the turbine if any parameter exceeds the safe limit.

• It also includes emergency shutdown systems to prevent catastrophic failures.

• Examples of protection systems include overspeed protection, low oil pressure protection, and high exhaust temperature protection.

PLC HMI is a crucial component in ensuring the proper functioning of instruments in industrial settings.

• PLC HMI (Programmable Logic Controller Human Machine Interface) allows operators to monitor and control the instrument's working conditions.

• It provides real-time data, alarms, and notifications to ensure smooth operation.

• Examples of working condition instruments include temperature sensors, pressure gauges, flow meters, etc.

Control valve sizing requires accurate input data to ensure proper valve selection and performance.

• Process fluid properties such as density, viscosity, and pressure drop

• Flow rate and flow characteristics

• Piping and valve specifications

• Control system requirements

• Environmental factors such as temperature and altitude

• Consideration of safety and reliability

• Examples of input data include P&ID diagrams, process data sheets, and equipment specifications

Different flow characteristics of pump include centrifugal, positive displacement, axial, and mixed flow.

• Centrifugal pumps are commonly used for low viscosity fluids and high flow rates.

• Positive displacement pumps are suitable for high viscosity fluids and low flow rates.

• Axial flow pumps are used for high flow rates and low head applications.

• Mixed flow pumps combine features of both centrifugal and axial flow pumps.

A control valve CV is a device used to control the flow of fluid in a system by varying the size of the flow passage.

• Control valves are commonly used in industries such as oil and gas, chemical, and power plants.

• They can be operated manually or automatically using an actuator.

• Control valves can regulate variables such as flow rate, pressure, temperature, and level in a process system.

• Examples of control valve manufacturers include Fisher, Emerson, and Valtek.

Control valves include globe, butterfly, ball, and plug valves. Transmitters include pressure, temperature, level, and flow transmitters.

• Types of control valves: globe, butterfly, ball, plug

• Types of transmitters: pressure, temperature, level, flow

• Examples: Globe valve, Pressure transmitter

SPI modules are communication interfaces used to transfer data between microcontrollers and peripheral devices.

• SPI stands for Serial Peripheral Interface

• It is a synchronous communication protocol

• SPI modules have a master-slave architecture

• Data is transferred in full duplex mode

• Commonly used in microcontroller-based systems for communication with sensors, displays, and memory devices

CV calculation of control valve involves determining the valve's flow coefficient.

• CV is calculated using the formula: CV = Q / (SG * sqrt(dP))

• Q is the flow rate, SG is the specific gravity of the fluid, and dP is the pressure drop across the valve.

• CV is used to select the appropriate valve size for a given application.

• Factors such as valve type, trim size, and pressure drop affect the CV value.

• CV calculation is important for ensuring proper control of fluid flow in industrial...read more

Three element drum level control is a method of controlling the water level in a steam drum using three inputs.

• The three inputs are steam flow, feedwater flow, and drum level.

• The steam flow and feedwater flow are used to calculate the rate of change of drum level.

• The drum level is then adjusted based on the calculated rate of change.

• This method provides better control than single or two element control.

• It can prevent boiler damage due to low water levels or carryover of water...read more

The three element method of boiler is a control strategy that uses three variables to maintain water level and steam flow.

• The three variables are steam flow, water flow, and drum level.

• The steam flow and water flow are measured by flow meters.

• The drum level is measured by a level transmitter.

• The controller compares the steam flow and water flow to maintain a balance.

• If the drum level drops, the controller increases the water flow to maintain the level.

• If the steam flow increa...read more

Boilers are vessels that heat water or other fluids to generate steam or hot water for various applications.

• Fire-tube boilers: hot gases from combustion pass through tubes submerged in water

• Water-tube boilers: water flows through tubes and hot gases from combustion surround them

• Electric boilers: use electricity to generate heat and produce steam or hot water

• Condensing boilers: extract additional heat from the exhaust gases to increase efficiency

DP type LT stands for Differential Pressure type Level Transmitter used for measuring level in tanks or vessels.

• DP type LT measures level by detecting the pressure difference between two points in a vessel.

• It consists of two pressure sensors connected to the top and bottom of the tank.

• The configuration involves setting the zero and span points to calibrate the transmitter.

• Commonly used in industries like oil & gas, chemical, and water treatment.

• Example: Rosemount 3051S DP Lev...read more