100+ Instrument Engineer Interview Questions and Answers

Questions related to general working ranges, temperature sensors, and purpose of instruments for Instrumentation Engineer position.

• General current and voltage working ranges of instruments depend on the type of instrument and its application.

• Temperature sensors types include thermocouples, RTDs, thermistors, and infrared sensors.

• Thermocouples work on the principle of Seebeck effect, while RTDs work on the principle of change in resistance with temperature.

• Instruments may or m...read more

Transmitters are devices that convert physical variables into electrical signals. 3-wire and 4-wire transmitters differ in their wiring configurations.

• Transmitters are used to measure and transmit physical variables such as temperature, pressure, and flow rate.

• 3-wire transmitters have one common wire and two signal wires, while 4-wire transmitters have two common wires and two signal wires.

• 3-wire transmitters are less accurate than 4-wire transmitters due to the voltage drop ...read more

Digital and analog inputs and outputs are used in PLCs to receive and send signals. Digital signals are binary, while analog signals are continuous.

• Digital inputs and outputs use binary signals to communicate with other devices.

• Analog inputs and outputs use continuous signals to measure and control variables such as temperature, pressure, and flow.

• Digital signals are either on or off, while analog signals can have a range of values.

• PLCs use digital and analog inputs and outpu...read more

The fire and gas protection system familiar to me is the Fire and Gas Detection System (FGDS).

• FGDS is designed to detect and mitigate the risks of fire and gas hazards in industrial facilities.

• It consists of various sensors, alarms, and control panels to monitor and respond to potential fire and gas incidents.

• The system can detect smoke, heat, gas leaks, and other hazardous conditions.

• Once a hazard is detected, the system triggers alarms, activates fire suppression systems, a...read more

The level state system in a Power Plant is responsible for monitoring and controlling the level of fluids in various tanks and vessels.

• The level state system uses sensors to measure the level of fluids in tanks.

• These sensors can be ultrasonic, radar, or pressure-based.

• The measured level is then transmitted to a control system.

• The control system compares the measured level with the desired level and takes appropriate actions.

• Actions may include opening or closing valves, start...read more

UUC and CSU are two different methods of calibration used for instruments.

• UUC stands for Universal Use Calibrator and is a portable device used for calibration of instruments.

• CSU stands for Centralized Standards Unit and is a fixed device used for calibration of instruments.

• UUC is used for field calibration while CSU is used for laboratory calibration.

• UUC is less accurate than CSU but is more convenient to use.

• CSU is more accurate than UUC but is more expensive and requires s...read more

Correct temperature indication by RTD can be verified using multimeter.

• Check the resistance value of RTD using multimeter and compare it with the standard resistance-temperature chart.

• Ensure that the RTD is properly connected to the measuring instrument and there are no loose connections.

• Perform a calibration check periodically to ensure accurate temperature measurement.

• Use a reference thermometer to cross-check the temperature reading.

• Verify the RTD for any physical damage o...read more

The range of pressure transmitter used in our plant is between 0-1000 psi.

• The pressure transmitter range is determined by the process requirements.

• The range can vary depending on the type of equipment and application.

• The transmitter range is usually specified by the manufacturer.

• The range can be adjusted or calibrated as needed.

• In our plant, the pressure transmitter range is between 0-1000 psi.

• This range is suitable for our process requirements.

Solenoids are electromechanical devices that convert electrical energy into linear motion.

• Solenoids use the principle of electromagnetic induction to create a magnetic field that moves a plunger or rod.

• They are used in various applications such as door locks, valves, and starter motors.

• Solenoids can be either push-type or pull-type depending on the direction of the linear motion.

• They are commonly used in automation and control systems.

• The strength of the magnetic field can be...read more

I can troubleshoot various control valves used in instrumentation engineering.

• I can troubleshoot globe valves, butterfly valves, ball valves, and plug valves.

• I am familiar with different types of actuators used in control valves such as pneumatic, hydraulic, and electric actuators.

• I can diagnose and fix issues related to valve positioners, solenoid valves, and valve controllers.

• I have experience troubleshooting control valve problems like leakage, improper response, sticking,...read more

NABL requirements and detailed calibration procedures for measuring instruments, flow meters, onsite calibration requirements.

• NABL accreditation is essential for calibration procedures to ensure accuracy and reliability.

• Calibration procedures should be detailed and documented to meet NABL requirements.

• Flow meters should be calibrated regularly to maintain accuracy.

• Onsite calibration may be necessary for instruments that cannot be easily transported.

• Calibration certificates sh...read more

To troubleshoot and rectify a faulty field instrument, I follow a systematic approach involving inspection, testing, and repair.

• Start by visually inspecting the instrument for any visible damage or loose connections.

• Check the instrument's power supply and ensure it is properly connected and functioning.

• Use appropriate testing equipment like multimeters or signal generators to measure and verify the instrument's output signals.

• Refer to the instrument's documentation or manuals...read more

Yes, I have experience in Bently Nevada system.

• I have worked with Bently Nevada system for 3 years.

• I am familiar with the various components and functionalities of the system.

• I have successfully implemented Bently Nevada system in a project for monitoring and controlling industrial processes.

• I have conducted troubleshooting and maintenance tasks on Bently Nevada system.

• I have attended training sessions and workshops to enhance my knowledge and skills in using Bently Nevada sy...read more

Different types of level instruments can be used in different applications depending on the requirements.

• For continuous level measurement, ultrasonic level sensors can be used.

• For point level detection, capacitance level switches can be used.

• For high-temperature applications, guided wave radar level sensors can be used.

• For corrosive or aggressive liquids, magnetic level gauges can be used.

• For level measurement in open tanks, radar level sensors can be used.

Power cable tray and instruments cable tray are used to distribute power and instrument cables respectively.

• Power cable tray is designed to support and protect power cables, ensuring safe and efficient power distribution.

• Instruments cable tray is specifically designed to support and protect instrument cables, which carry signals for measurement and control purposes.

• Both cable trays are typically made of metal or non-metallic materials and are installed in industrial plants, r...read more

Instrumentation engineering is the branch of engineering that deals with the design, development, installation, and maintenance of instruments and control systems used in various industries.

• Instrumentation engineers design and develop instruments and control systems for various industries such as oil and gas, chemical, pharmaceutical, and manufacturing.

• They are responsible for selecting the appropriate instruments, sensors, and control systems to measure and control various p...read more

A control valve is calibrated by adjusting its position to achieve the desired flow rate or pressure drop.

• Determine the desired flow rate or pressure drop

• Connect the valve to a calibration rig

• Adjust the valve position until the desired flow rate or pressure drop is achieved

• Record the valve position and corresponding flow rate or pressure drop

• Repeat the process at different setpoints to create a calibration curve

RTD measures temperature using resistance while thermocouple uses voltage difference.

• RTD has higher accuracy and stability than thermocouple.

• RTD is more expensive than thermocouple.

• RTD is suitable for precise temperature measurement while thermocouple is better for high temperature measurement.

• RTD has a linear relationship between resistance and temperature while thermocouple has a non-linear relationship.

• Examples of RTD include platinum, nickel, and copper while examples of ...read more

Efficiency of a pump can be calculated by dividing the output power by the input power.

• Efficiency = Output Power / Input Power

• Output Power = Flow Rate x Head x Density x Gravity

• Input Power = Flow Rate x Head x Density x Gravity / Efficiency

• Efficiency can also be calculated by measuring the actual flow rate and head against the design flow rate and head.

• Efficiency can be affected by factors such as impeller design, pump speed, and fluid viscosity.

No, normal copper wire cannot be used in place of thermocouple compensating wire due to different composition and temperature range.

• Thermocouple compensating wire is specifically designed to match the thermal properties of the thermocouple material.

• Normal copper wire does not have the same composition as compensating wire, leading to inaccurate temperature readings.

• Compensating wire can withstand higher temperatures compared to normal copper wire.

• Using normal copper wire can ...read more

Tubing fitting size and installation work

• The tubing fitting size should match the size of the tubing being used

• Proper installation techniques should be followed to ensure a secure and leak-free connection

• Common types of tubing fittings include compression, flare, and push-to-connect fittings

The assembly system of a boiler involves the installation of various components to create a functional heating system.

• The assembly system includes components such as the boiler itself, piping, valves, pumps, and controls.

• The boiler is the central component that heats water or generates steam.

• Piping is used to transport the heated water or steam to the desired location.

• Valves are used to control the flow of water or steam.

• Pumps are used to circulate the water or steam through ...read more

Salary deductions are common in CTC structures due to various components like PF, gratuity, taxes, etc.

• CTC includes various components like basic salary, HRA, PF, gratuity, etc.

• Deductions are made for PF, professional tax, income tax, etc.

• Net salary received is after deducting these components.

• Employers may also offer additional benefits like insurance, bonuses, etc.

Installing and commissioning new field instruments involves several steps and considerations.

• Review the instrument datasheet and specifications to understand its requirements

• Prepare the installation location and ensure it meets the necessary conditions

• Mount the instrument securely and connect it to the process or control system

• Configure the instrument settings and parameters according to the application

• Perform calibration and testing to ensure accurate measurements

• Document th...read more

To edit a rung in AB PLC software RS Logix, follow these steps:

• Open the RS Logix software and select the project

• Navigate to the ladder logic editor and locate the rung to be edited

• Double-click on the rung to open the rung editor

• Make the necessary changes to the rung

• Save the changes and download the updated program to the PLC

To install an ultrasonic flowmeter in big size lines, especially in flare service, proper planning and coordination with other disciplines is essential.

• Ensure the flowmeter is suitable for the size of the line and the conditions of the flare service.

• Coordinate with piping and instrumentation departments to determine the best location for installation.

• Consider factors such as accessibility for maintenance and calibration.

• Ensure proper grounding and electrical connections are i...read more

Glycol is used in the impulse tube of level transmitter to prevent freezing and ensure accurate measurement.

• Glycol has a lower freezing point than water, preventing the impulse tube from freezing in cold temperatures.

• Glycol also helps to prevent bacterial growth and corrosion in the impulse tube.

• The use of glycol ensures accurate measurement by maintaining a consistent fluid density in the impulse tube.

• Common glycols used include ethylene glycol and propylene glycol.

• The conce...read more

DI, DO, AI, AO loop wiring diagram is a schematic representation of the connections between input/output devices and controllers.

• DI (Digital Input) devices are connected to the controller through a digital input module.

• DO (Digital Output) devices are connected to the controller through a digital output module.

• AI (Analog Input) devices are connected to the controller through an analog input module.

• AO (Analog Output) devices are connected to the controller through an analog out...read more

Calibration of instruments ensures accuracy and reliability of measurements.

• Ensures accuracy and reliability of measurements

• Helps in maintaining quality standards

• Prevents errors in readings

• Increases instrument lifespan

• Compliance with regulations and standards

• Examples: calibrating a thermometer for accurate temperature readings, calibrating a pressure gauge for precise pressure measurements

3Wire RTD is preferred over 2Wire RTD due to better accuracy and noise reduction.

• 3Wire RTD compensates for lead wire resistance, resulting in more accurate temperature measurements.

• 3Wire RTD provides better noise reduction compared to 2Wire RTD.

• 3Wire RTD allows for easier implementation of temperature compensation techniques.

• 2Wire RTD is more susceptible to lead wire resistance errors and noise interference.

Yes, I have worked with Vibration Monitoring Systems.

• I have experience in installing and configuring vibration monitoring systems.

• I have conducted regular inspections and maintenance of vibration monitoring equipment.

• I have analyzed vibration data to identify potential issues and recommend corrective actions.

• I have worked with various types of vibration sensors and transducers.

• I have collaborated with other engineers and technicians to troubleshoot vibration-related problems....read more

Bromine manufacturing involves extraction from brine, purification, and electrolysis.

• Extraction of bromine from brine through evaporation and oxidation

• Purification of bromine using distillation or solvent extraction methods

• Electrolysis of purified bromine to obtain elemental bromine

• Byproducts such as hydrogen gas and sodium hydroxide may also be produced

There are various types of instruments used in different industries for measurement and control purposes.

• Some common types of instruments include pressure gauges, thermometers, flow meters, level sensors, and control valves.

• Working principles of instruments vary depending on their type and application.

• Examples of instrument makes and models include Rosemount pressure transmitters, Yokogawa flow meters, and Honeywell temperature controllers.

The cable laying for a 50x50 cable tray depends on the specific requirements and types of cables being used.

• The cable tray should be properly sized and designed to accommodate the cables.

• Consider the type and size of cables to be laid, such as power cables, control cables, or communication cables.

• Ensure proper segregation and separation of different types of cables to avoid interference.

• Follow industry standards and guidelines for cable laying, such as NEC, IEC, or IEEE.

• Use a...read more

Capacitors store energy and inductors resist changes in current, causing transients in DC supply.

• Capacitors store energy and can discharge quickly, causing voltage spikes or dips in the DC supply.

• Inductors resist changes in current, causing voltage spikes or dips in the DC supply when the current changes rapidly.

• Transients can be mitigated by adding resistors or diodes to the circuit.

• Examples of transients include switching on or off a load, or sudden changes in current deman...read more

PLC stands for Programmable Logic Controller and SCADA stands for Supervisory Control and Data Acquisition.

• PLC is a digital computer used for automation of electromechanical processes.

• It is programmed to control machinery and processes in industries.

• SCADA is a system used to monitor and control industrial processes.

• It collects and analyzes real-time data from various sensors and devices.

• PLC and SCADA systems work together to automate and optimize industrial operations.

• PLC pro...read more

Half duplex communication allows data to be transmitted in both directions, but not simultaneously.

• Data can be sent and received, but not at the same time

• Common examples include walkie-talkies and CB radios

• Requires a switch between sending and receiving modes

Gas analyzer block diagram consists of sample inlet, gas sensor, signal processing unit, and display.

• Gas sample is drawn into the analyzer through a sample inlet.

• The gas sensor detects the presence of specific gases in the sample.

• The signal processing unit processes the sensor data and calculates the gas concentration.

• The results are displayed on a screen for the user to read.

• Examples of gas analyzers include infrared gas analyzers, paramagnetic gas analyzers, and electrochem...read more

I have 5 years of experience in PLC and DCS systems.

• 5 years of hands-on experience in programming and troubleshooting PLCs and DCS systems

• Proficient in designing control logic, implementing HMI interfaces, and integrating various sensors and actuators

• Experience with major PLC brands such as Siemens, Allen-Bradley, and Schneider Electric

• Implemented PID control loops, alarm management, and data logging functionalities

• Worked on projects involving process automation and optimizat...read more

Maintenance of a transformer involves regular inspections, cleaning, testing, and preventive measures.

• Regularly inspect the transformer for any signs of damage or overheating.

• Clean the transformer and its components to remove dust, dirt, and debris.

• Perform routine testing to ensure proper functioning and identify any potential issues.

• Check and maintain the oil level and quality in oil-filled transformers.

• Inspect and tighten electrical connections to prevent loose connections ...read more

PLCs are used for automation of industrial processes, such as controlling machinery and equipment.

• PLCs are used to automate processes in industries such as manufacturing, automotive, and food processing.

• They can control machinery, equipment, and processes by receiving input from sensors and other devices.

• PLCs can be programmed to perform specific tasks, such as turning on/off motors, regulating temperature, and monitoring production lines.

• They help improve efficiency, reduce ...read more

F&G detectors detect fire and gas hazards. They work based on different principles and selection criteria.

• F&G detectors are used to detect fire and gas hazards in industrial settings.

• There are different types of F&G detectors such as flame detectors, gas detectors, smoke detectors, etc.

• Flame detectors work based on the principle of detecting the UV or IR radiation emitted by flames.

• Gas detectors work based on the principle of detecting the presence of specific gases in the ai...read more

Close loops in CFBC boiler operation are used for controlling various parameters.

• Close loop for controlling bed temperature

• Close loop for controlling air flow rate

• Close loop for controlling fuel feed rate

• Close loop for controlling steam pressure

• Close loop for controlling flue gas temperature

Dry wiring refers to wiring without any external protection, while wet wiring involves the use of protective coatings or materials.

• Dry wiring is typically used in low-risk environments where there is no chance of moisture or other contaminants damaging the wiring.

• Wet wiring is used in high-risk environments where moisture or other contaminants are present, such as in chemical plants or outdoor installations.

• Examples of wet wiring materials include heat shrink tubing, silicone...read more

There are numerous sensor types available for various applications.

• There are sensors for temperature, pressure, humidity, motion, light, sound, and more.

• Some examples include thermocouples, pressure transducers, accelerometers, photodiodes, and microphones.

• Sensor types can also be categorized as analog or digital, active or passive, and contact or non-contact.

• The number of sensor types is constantly growing as technology advances and new applications are discovered.

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