Instrumentation Questions

Mastering the Instrument Calibration Interview: Essential Questions and Answers

Mastering the Instrument Calibration Interview: Essential Questions and Answers 1

Calibration Interview Questions and Answers

What is Calibration?

  •  Calibration pertains to the meticulous procedure of comparing measurements from one instrument with those obtained from another instrument that has undergone calibration and is referenced to known parameters.
  • The reference equipment should be able to be traced back to equipment that has been calibrated in accordance with the national standard

Why is Calibration important for Measuring Instruments?

  •  Calibration holds paramount significance as the precision of measuring instruments tends to degrade over time due to a multitude of factors, including wear and tear and the environmental conditions they are subjected to. 
  •  Calibration serves as an imperative process to enhance the accuracy of these measuring devices, thereby instilling unwavering confidence in the integrity of measurement outcomes.

What is adjustment, and How Does it Differ from Calibration?

  • Adjustment, in essence, represents a meticulous process through which an instrument is meticulously fine-tuned to minimize deviations in measurement from the desired setpoint value. 
  • The measurement instrument is permanently modified throughout the adjustment process.
  • This calibration-adjacent procedure is executed within the confines of predefined tolerances. 
  • Notably, the process of adjustment brings about a permanent transformation in the instrument.

What is Traceability, and Why is it important in Calibration?

  • Traceability serves as a fundamental pillar in the calibration process, signifying the capacity to trace a measurement’s value back to national standards. 
  • This traceable lineage is established through a series of methodical comparisons, thereby affording the assurance of consistency and reliability in measurement results.

What is the Purpose of Calibration According to the International Laboratory Accreditation Cooperation (ILAC)?

  • The main objective of calibration, according to the International Laboratory Accreditation Cooperation (ILAC), is to determine the level of uncertainty that can be achieved with a measuring instrument and to confirm the accuracy of the measuring instrument. 
  • The calibration process improves the calculation of discrepancies between reference values and actual measurements while also revealing the uncertainty associated with these deviations when the instrument is in use.

How can you verify if equipment has been Calibrated?

  • Equipment calibrated at calibration laboratories or centers is always accompanied by a calibration certificate. 
  • When it is practical, the calibration date and serial number are printed on a sticker that is applied to the equipment with each calibrated item.
  • The sticker is attached to the box for small objects like transducers that don’t have enough room for them. 
  • The sticker is given along with the printed certificate if neither a specific box nor an open space is available on the equipment.

Why should a new Instrument be Calibrated, Even if it is directly from the factory?

  • The calibration of new instruments, even if they emerge directly from the manufacturing facility, is imperative for a constellation of compelling reasons. Notably, it may be mandated by legal stipulations. 
  • Furthermore, it establishes a trail of calibration data commencing from the point of initial acquisition. 
  • This chronological recordation enables the systematic comparison of measurement results over the course of the instrument’s operational life.

Is it adequate to send Instruments for Calibration every two years?

  • It is dependent on the level of accuracy that you require. When compared to equipment that is utilized on a less frequent basis, such as once a month, a daily-used piece of machinery will have a shorter calibration cycle.
  •  calibration on an annual basis is strongly suggested for all devices in order to reduce the likelihood of obtaining uncertain readings.

When should an Instrument be recalibrated?

  • It is advised that a calibration history be started from the very first day, and that it be re-calibrated once a year (or as per the plant philosophy). This enables the results of measurements to be compared over the course of time.

What’s the difference between an accredited calibration and a traceable one?

  • Traceable calibration adheres to the same standards as accredited calibration but is not granted explicit approval by an official governing organization. 
  • Accredited calibration, on the other hand, has been granted approval by both national and international authorities such as the ILAC.

What makes accredited calibration preferable? Isn’t it sufficient to have calibration that can be traced?

  • If you or your clients want to make the results of the measurements public or complete requirements in quality processes like getting ISO certification, accredited calibration is required.
  • The certificate received through accredited calibration can also be utilized as legally acceptable documentation.

Is using a Calibrator alone sufficient for Calibration?

  • While a calibrator serves as a valuable tool for the immediate pre- and post-measurement verification process in the field, it does not serve as a comprehensive substitute for periodic  calibration conducted within the controlled confines of a certified laboratory.

What is required for a Calibration Laboratory to achieve accreditation?

  • The attainment of accreditation status by a calibration laboratory necessitates the meticulous establishment of a comprehensive quality policy that meticulously aligns with the stringent dictates of ISO 17025 standards. 
  • This includes the location of the actual premises as well as the technique, protocols, traceability, technical skills, and record documentation.

What does it mean to have Traceability in Calibration?

  • Traceability of calibration requires that the results on the certificate of calibration for the instrument be traceable to the standard that was used for the calibration, and that the results on the certificate of calibration for the standard be traceable to the standard that was used for the calibration of the standard. 
  • This gives confidence that the calibration results are correct and reliable.
  • Because the calibration interval is determined by a variety of factors, including the measured quantity, the allowable tolerance range, the stress to which the equipment is subjected, the stability of the equipment’s previous calibrations, the required measuring accuracy, and the quality assurance requirements, there is no one answer that is definitively correct to this question.
  • In most cases, the recommended calibration interval is from one to three years; however, the client can make exceptions to this rule by specifying them in the purchase order and delivery note.

What is the key distinction between calibrating and verifying an Instrument?

  • The calibration process applies a correction in order to compensate for any lack of trueness, whereas the verification process ensures that the measurement error is less than the maximum amount of error that the user has determined to be acceptable.

Is it required to record the data “as found/as left” in the calibration certificate?

  • Even though the collection of measurement data isn’t strictly necessary for most quality programmes, doing so is strongly encouraged.
  • As found/as left data helps to determine where within tolerance requirements the instrument was located and returned to the customer.
  •  It also helps analyze the impact of out-of-tolerance readings on processes and evaluates the performance of the instrument in order to determine the adequate calibration interval.

For more automation interview questions, refer the industrial automation questions and answers.

For more instrumentation interview questions, refer the instrumentation interview Questions and answers 

For more about industrial instrumentation calibration process  refer Basic Safety and General Consideration While Executing Calibration Process in process industries

Sundareswaran Iyalunaidu

With over 24 years of dedicated experience, I am a seasoned professional specializing in the commissioning, maintenance, and installation of Electrical, Instrumentation and Control systems. My expertise extends across a spectrum of industries, including Power stations, Oil and Gas, Aluminium, Utilities, Steel and Continuous process industries. Tweet me @sundareshinfohe

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