# Instrumentation **URL:** https://forumautomation.com/c/interview-questions-and-answers/instrumentation/35.md [Latest](https://forumautomation.com/latest.md) · [Categories](https://forumautomation.com/categories.md) · [Tags](https://forumautomation.com/tags.md) --- ## [About the Instrumentation category](https://forumautomation.com/t/about-the-instrumentation-category/1312)
**Author:** [@Administrator](https://forumautomation.com/u/Administrator)\ **Replies:** 0
Instrumentation Interview Questions and Answers --- ## [What is the purpose of an instrument index?](https://forumautomation.com/t/what-is-the-purpose-of-an-instrument-index/14282)
**Author:** [@Instrument\_Engineer](https://forumautomation.com/u/Instrument_Engineer)\ **Replies:** 1\ **Last updated:** [July 30, 2026, 4:37am UTC](https://forumautomation.com/t/what-is-the-purpose-of-an-instrument-index/14282 "2026-07-30T04:37:39Z")
What is the purpose of an instrument index? --- ## [What is the difference between ISO 13849 and IEC 61511?](https://forumautomation.com/t/what-is-the-difference-between-iso-13849-and-iec-61511/13956)
**Author:** [@Instrument\_Engineer](https://forumautomation.com/u/Instrument_Engineer)\ **Replies:** 1\ **Last updated:** [March 20, 2026, 4:01pm UTC](https://forumautomation.com/t/what-is-the-difference-between-iso-13849-and-iec-61511/13956 "2026-03-20T16:01:40Z")
What is the difference between ISO 13849 and IEC 61511? --- ## [Instrumentation Interview question : Vortex meters are used in which services?](https://forumautomation.com/t/instrumentation-interview-question-vortex-meters-are-used-in-which-services/267)
**Author:** [@automate](https://forumautomation.com/u/automate)\ **Replies:** 1\ **Last updated:** [November 27, 2025, 8:15am UTC](https://forumautomation.com/t/instrumentation-interview-question-vortex-meters-are-used-in-which-services/267 "2025-11-27T08:15:48Z")
Vortex meters are commonly used in following services 1.Steam 2.Cooling water 3.Process water 4.Light hydrocarbons where large turndown is required. 5.Gas flow where large turndown is required --- ## [What is the difference between zero trim and sensor trim?](https://forumautomation.com/t/what-is-the-difference-between-zero-trim-and-sensor-trim/13362)
**Author:** [@Instrument\_Engineer](https://forumautomation.com/u/Instrument_Engineer)\ **Replies:** 1\ **Last updated:** [July 19, 2025, 5:37am UTC](https://forumautomation.com/t/what-is-the-difference-between-zero-trim-and-sensor-trim/13362 "2025-07-19T05:37:00Z")
What is the difference between zero trim and sensor trim? --- ## [How do you use maintenance KPIs to improve decision-making?](https://forumautomation.com/t/how-do-you-use-maintenance-kpis-to-improve-decision-making/13284)
**Author:** [@Instrument\_Engineer](https://forumautomation.com/u/Instrument_Engineer)\ **Replies:** 1\ **Last updated:** [June 11, 2025, 10:01am UTC](https://forumautomation.com/t/how-do-you-use-maintenance-kpis-to-improve-decision-making/13284 "2025-06-11T10:01:46Z")
How do you use maintenance KPIs to improve decision-making? --- ## [Advantages and Limitations of Magnetic Flow Meters for Water and Wastewater Treatment Applications](https://forumautomation.com/t/advantages-and-limitations-of-magnetic-flow-meters-for-water-and-wastewater-treatment-applications/13168)
**Author:** [@ARTang](https://forumautomation.com/u/ARTang)\ **Replies:** 0\ **Last updated:** [April 18, 2025, 1:03am UTC](https://forumautomation.com/t/advantages-and-limitations-of-magnetic-flow-meters-for-water-and-wastewater-treatment-applications/13168 "2025-04-18T01:03:08Z")
Advantages in Water & Wastewater High Accuracy & Reliability ±0.5% accuracy for conductive liquids like drinking water, sewage, and industrial effluent. Unaffected by changes in density, viscosity, or temperature (as l… --- ## [Selection Principle of Electromagnetic Flowmeter?](https://forumautomation.com/t/selection-principle-of-electromagnetic-flowmeter/13167)
**Author:** [@ARTang](https://forumautomation.com/u/ARTang)\ **Replies:** 0\ **Last updated:** [April 18, 2025, 1:02am UTC](https://forumautomation.com/t/selection-principle-of-electromagnetic-flowmeter/13167 "2025-04-18T01:02:54Z")
Selecting an Electromagnetic Flowmeter (EMF) requires considering several factors to ensure accurate measurement, long-term reliability, and cost-effectiveness. Here are the key selection principles: Medium Characteris… --- ## [What are the best testing and measuring instruments for accurate readings in the manufacturing industry?](https://forumautomation.com/t/what-are-the-best-testing-and-measuring-instruments-for-accurate-readings-in-the-manufacturing-industry/12778)
**Author:** [@Instrument\_Engineer](https://forumautomation.com/u/Instrument_Engineer)\ **Replies:** 1\ **Last updated:** [November 6, 2024, 4:22pm UTC](https://forumautomation.com/t/what-are-the-best-testing-and-measuring-instruments-for-accurate-readings-in-the-manufacturing-industry/12778 "2024-11-06T16:22:48Z")
What are the best testing and measuring instruments for accurate readings in the manufacturing industry? --- ## [Why 4-20 ma signal is used in Industrial instrumentation?](https://forumautomation.com/t/why-4-20-ma-signal-is-used-in-industrial-instrumentation/2248)
**Author:** [@denizen](https://forumautomation.com/u/denizen)\ **Replies:** 4\ **Last updated:** [September 4, 2024, 4:45pm UTC](https://forumautomation.com/t/why-4-20-ma-signal-is-used-in-industrial-instrumentation/2248 "2024-09-04T16:45:54Z")
4-20 ma Signal in Industrial Instrumentation Signal Flow from Instrument to Controller (PLC/DCS/Stand alone controller) - A physical signal(Temperature / Pressure / Level / Flow etc) measured by a sensor is converted t… --- ## [What is difference between IR sensor and ultrasonic sensor?](https://forumautomation.com/t/what-is-difference-between-ir-sensor-and-ultrasonic-sensor/12520)
**Author:** [@Instrument\_Engineer](https://forumautomation.com/u/Instrument_Engineer)\ **Replies:** 1\ **Last updated:** [September 4, 2024, 2:33pm UTC](https://forumautomation.com/t/what-is-difference-between-ir-sensor-and-ultrasonic-sensor/12520 "2024-09-04T14:33:48Z")
What is difference between IR sensor and ultrasonic sensor? --- ## [What is Loop checking? importance of Loop checking](https://forumautomation.com/t/what-is-loop-checking-importance-of-loop-checking/2346)
**Author:** [@sivaranjith](https://forumautomation.com/u/sivaranjith)\ **Replies:** 0\ **Last updated:** [September 26, 2017, 7:33am UTC](https://forumautomation.com/t/what-is-loop-checking-importance-of-loop-checking/2346 "2017-09-26T07:33:17Z")
What is a Loop check? Loop check is an operational check of a control loop. Intended to find out the deficiencies in control loop/ field interface/ HMI Loop checking is the is final stage of a project commissioning. We … --- ## [Top 10 Temperature Measurement Interview Questions](https://forumautomation.com/t/top-10-temperature-measurement-interview-questions/12007)
**Author:** [@Rabert](https://forumautomation.com/u/Rabert)\ **Replies:** 0\ **Last updated:** [April 25, 2024, 2:50pm UTC](https://forumautomation.com/t/top-10-temperature-measurement-interview-questions/12007 "2024-04-25T14:50:45Z")
1). What is PRT? PRT is expressed as Platinum Resistance Thermometer. 2). What is the most precise type of thermocouple? Type T thermocouples have an accuracy of ±1C, followed by types J and K (±1.7C) and type N (±2.… --- ## [How to adjust 20 psi air supply to a transmitter?](https://forumautomation.com/t/how-to-adjust-20-psi-air-supply-to-a-transmitter/11183)
**Author:** [@Sudha\_m](https://forumautomation.com/u/Sudha_m)\ **Replies:** 0\ **Last updated:** [May 22, 2023, 3:52pm UTC](https://forumautomation.com/t/how-to-adjust-20-psi-air-supply-to-a-transmitter/11183 "2023-05-22T15:52:51Z")
The general stages of adjusting a 20 psi (pounds per square inch) air supply to a transmitter are as follows: Determine the pressure adjustment mechanism: A pressure regulator or control valve are common pressure adju… --- ## [Instrumentation Interview Question : Pressure measurement](https://forumautomation.com/t/instrumentation-interview-question-pressure-measurement/350)
**Author:** [@automate](https://forumautomation.com/u/automate)\ **Replies:** 2\ **Last updated:** [March 25, 2023, 6:26am UTC](https://forumautomation.com/t/instrumentation-interview-question-pressure-measurement/350 "2023-03-25T06:26:01Z")
Q)What is pressure ? or Define pressure ? A)Pressure is the amount of force applied over a defined area. Q)The factors that will influence hydro static pressure ? A)Level of the liquid Density of the liquid Pressure o… --- ## [What is the difference between accuracy and precision in measurement?](https://forumautomation.com/t/what-is-the-difference-between-accuracy-and-precision-in-measurement/10882)
**Author:** [@Instrument\_Engineer](https://forumautomation.com/u/Instrument_Engineer)\ **Replies:** 0\ **Last updated:** [February 16, 2023, 5:19am UTC](https://forumautomation.com/t/what-is-the-difference-between-accuracy-and-precision-in-measurement/10882 "2023-02-16T05:19:22Z")
In measurement and instrumentation, both accuracy and precision are important, but they mean different things. Accuracy is how close a measured value is to the real value of the thing being measured. In other words, it i… --- ## [200+ instrumentation interview Q&A](https://forumautomation.com/t/200-instrumentation-interview-q-a/10005)
**Author:** [@Ajmal\_ismail](https://forumautomation.com/u/Ajmal_ismail)\ **Replies:** 1\ **Last updated:** [November 22, 2021, 5:51am UTC](https://forumautomation.com/t/200-instrumentation-interview-q-a/10005 "2021-11-22T05:51:39Z")
1. What is Measurement? This is a function that compares the unknown quantity to the standard, resulting in the knowledge of the unknown quantity’s quantity based on the standard used for comparison. 2. What is a Th… --- ## [Common Interview Questions: Entry Level Instrumentation](https://forumautomation.com/t/common-interview-questions-entry-level-instrumentation/141)
**Author:** [@instrumen](https://forumautomation.com/u/instrumen)\ **Replies:** 4\ **Last updated:** [December 17, 2020, 9:44am UTC](https://forumautomation.com/t/common-interview-questions-entry-level-instrumentation/141 "2020-12-17T09:44:11Z")
Que. : Draw an electronic two wire system control loop. Que. : What are Intrinsically safe system ? Que. : What does a transmitter output start from 3-15 psi or (0.2 - 1 Kg/Cm2) or 4 - 20 ma. etc. ? Que. : What is force … --- ## [What is the difference between mass flow meter and volumetric flow meter?](https://forumautomation.com/t/what-is-the-difference-between-mass-flow-meter-and-volumetric-flow-meter/8694)
**Author:** [@denizen](https://forumautomation.com/u/denizen)\ **Replies:** 0\ **Last updated:** [October 19, 2020, 5:05pm UTC](https://forumautomation.com/t/what-is-the-difference-between-mass-flow-meter-and-volumetric-flow-meter/8694 "2020-10-19T17:05:13Z")
Density will vary in all flow and we will not consider the variation in case of volumetric measurement. That means flow measured with static density. In mass flow measurement we will consider the density,temperature,pre… --- ## [Saudi Aramco Interview questions: Instrument/DCS Engineer](https://forumautomation.com/t/saudi-aramco-interview-questions-instrument-dcs-engineer/193)
**Author:** [@instrumen](https://forumautomation.com/u/instrumen)\ **Replies:** 29\ **Last updated:** [August 7, 2019, 7:35pm UTC](https://forumautomation.com/t/saudi-aramco-interview-questions-instrument-dcs-engineer/193 "2019-08-07T19:35:00Z")
what is cascade loop and how it work and why it used instead of PID single loop? In cascade, Which loop is faster and slower? Please explain with loop drawing and example… --- ## [Interview Questions : Control Valve technician / Instrument Technician](https://forumautomation.com/t/interview-questions-control-valve-technician-instrument-technician/389)
**Author:** [@denizen](https://forumautomation.com/u/denizen)\ **Replies:** 1\ **Last updated:** [July 9, 2019, 8:02pm UTC](https://forumautomation.com/t/interview-questions-control-valve-technician-instrument-technician/389 "2019-07-09T20:02:51Z")
State the function of Valve 2.Describe the three types of Valve 3.List the four uses of pressure control valve 4.Describe two types of relief valve 5.State the difference in cracking pressure and full flow pressure 6.De… --- ## [Basic instrumentation engineering interview questions](https://forumautomation.com/t/basic-instrumentation-engineering-interview-questions/5615)
**Author:** [@sivaranjith](https://forumautomation.com/u/sivaranjith)\ **Replies:** 0\ **Last updated:** [December 31, 2018, 4:52pm UTC](https://forumautomation.com/t/basic-instrumentation-engineering-interview-questions/5615 "2018-12-31T16:52:05Z")
What are the process Variable? Flow Pressure Temperature Level Quality i. e. % O2, CO2, pH etc. Define all the process Variable and state their unit of measurement. ? Flow: Defined as volume per unit of time at … --- ## [What are the advantages of using an instrumentation amplifier over an ordinary differential amplifier?](https://forumautomation.com/t/what-are-the-advantages-of-using-an-instrumentation-amplifier-over-an-ordinary-differential-amplifier/4558)
**Author:** [@rajeena](https://forumautomation.com/u/rajeena)\ **Replies:** 1\ **Last updated:** [April 26, 2019, 6:41am UTC](https://forumautomation.com/t/what-are-the-advantages-of-using-an-instrumentation-amplifier-over-an-ordinary-differential-amplifier/4558 "2019-04-26T06:41:48Z")
What are the advantages of using an instrumentation amplifier over an ordinary differential amplifier, in measuring low signals and voltages? What is the instrumentation amplifier? An instrumentation (or instrumentation)… --- ## [Instrumentation Interview Questions - Based on Temperature measurement](https://forumautomation.com/t/instrumentation-interview-questions-based-on-temperature-measurement/6266)
**Author:** [@sivaranjith](https://forumautomation.com/u/sivaranjith)\ **Replies:** 0\ **Last updated:** [April 18, 2019, 3:24pm UTC](https://forumautomation.com/t/instrumentation-interview-questions-based-on-temperature-measurement/6266 "2019-04-18T15:24:01Z")
1. What are the main reason for temperature measurement? Answer: The important reasons for temperature measurement are: To ensure the safety of personnel and equipment by maintaining temperatures within design limits. … --- ## [Power plant interview question](https://forumautomation.com/t/power-plant-interview-question/5810)
**Author:** [@sivaranjith](https://forumautomation.com/u/sivaranjith)\ **Replies:** 0\ **Last updated:** [January 28, 2019, 5:47pm UTC](https://forumautomation.com/t/power-plant-interview-question/5810 "2019-01-28T17:47:58Z")
What are the main circuits in the Thermal Power Plant? Feed water and steam flow circuit Coal and ash circuit Air and gas circuit Cooling water circuit On which cycle thermal power plant works? Thermal power plant work… --- ## [Study guide question : viscosity](https://forumautomation.com/t/study-guide-question-viscosity/5481)
**Author:** [@ernestoec4](https://forumautomation.com/u/ernestoec4)\ **Replies:** 0\ **Last updated:** [December 13, 2018, 8:24pm UTC](https://forumautomation.com/t/study-guide-question-viscosity/5481 "2018-12-13T20:24:00Z")
viscosity is analyzed in all of the following ways? --- ## [What are the types of Control Systems?](https://forumautomation.com/t/what-are-the-types-of-control-systems/4823)
**Author:** [@rajeena](https://forumautomation.com/u/rajeena)\ **Replies:** 0\ **Last updated:** [October 2, 2018, 3:30pm UTC](https://forumautomation.com/t/what-are-the-types-of-control-systems/4823 "2018-10-02T15:30:44Z")
What are the types of Control Systems? A control system can be functioned electrically, mechanically, pressure by fluid (gas or liquid), or it can be combination of these ways. Control systems are used to arrange and man… --- ## [What are Flanges? Types of Flanges](https://forumautomation.com/t/what-are-flanges-types-of-flanges/4590)
**Author:** [@sivaranjith](https://forumautomation.com/u/sivaranjith)\ **Replies:** 0\ **Last updated:** [September 8, 2018, 3:16pm UTC](https://forumautomation.com/t/what-are-flanges-types-of-flanges/4590 "2018-09-08T15:16:05Z")
What are Flanges? A flange is an external or internal rib used for connecting pipes, valves and other equipment to frame a piping system. A flange is to strength or attachment to another object, as the flange on the end … --- ## [Why Is Reduced Trim Required In Control Valves?](https://forumautomation.com/t/why-is-reduced-trim-required-in-control-valves/4557)
**Author:** [@rajeena](https://forumautomation.com/u/rajeena)\ **Replies:** 0\ **Last updated:** [September 5, 2018, 3:37pm UTC](https://forumautomation.com/t/why-is-reduced-trim-required-in-control-valves/4557 "2018-09-05T15:37:52Z")
Why Is Reduced Trim Required In Control Valves? What Is The Trim In A Control Valve? The trim of the control valve is the parts that are in direct contact with the fluid that is controlled. The edge of the valve consists… --- ## [What are the different problems in control valve?](https://forumautomation.com/t/what-are-the-different-problems-in-control-valve/2948)
**Author:** [@sivaranjith](https://forumautomation.com/u/sivaranjith)\ **Replies:** 0\ **Last updated:** [January 10, 2018, 8:16pm UTC](https://forumautomation.com/t/what-are-the-different-problems-in-control-valve/2948 "2018-01-10T20:16:52Z")
There are different common problems in control valves. Here we are going to discuss such problems: 1. Mechanical friction: Moving parts of control valves can be subjected to friction, primarily between the valve stem … [Next page](https://forumautomation.com/c/interview-questions-and-answers/instrumentation/35.md?page=1)