Q. Why do I need to calibrate my instruments?
A. Any instrument that is used to measure a physical parameter has certain level of accuracy. Over a period of time it is possible to experience a certain amount of drift, which will result in erroneous readings if the instrument is used to measure this parameter. By calibrating your instruments at regular intervals ensures the most satisfactory method of ensuring top performance for any instrument, and a more accurate and reliable result.

Q. Who is N.P.L.?
A. Every Country has a government body that controls the measurement standards, and has in its possession the ultimate standards of physical parameters, such as dimensional parameters, electrical parameters, optical parameters etc. In the UK, N.P.L. (National Physics Laboratory) carries out the task. Ensuring that via correct calibration all similar instruments measure the same parameter producing the same reading within their capabilities. In the USA, for instance, N.I.S.T. (National Institute Of Standards and Technology) carries out this task

Q. Why is it necessary to recalibrate instruments at regular intervals?
A. If using an instrument regularly, its repeatability and accuracy may deteriorate, over time. In addition, as various parts of the instrument age differently many will need realigning and readjusting. Calibrating the instruments at regular intervals and retention of all the previous certificates ensures that all these trends are observed and that the behavior of the instrument remains predictable.

Q. Why do I need to calibrate a brand new instrument with a warranty?
A. Even though Instruments when purchased are reasonably accurate in their measurements, they are not certified and there is this doubt about the traceability of the measurements performed.

Q. Which Company should I choose to carry out my calibrations?
A. There are many companies from very small operations to Multinationals. Whatever the company, always look at their certificate and see how much detail you get. When comparing prices always compare like for like. A certificate that declares, “We certify that this instrument is OK” is not worth the paper it has been written on. Or you may have to pay a considerable amount more to get a reasonably detailed certificate, which add to the value of the instrument as they represent a history of the stability and accuracy.

Q. What are ISO 9000 series of Quality Assurance Programs?
A. In Europe towards the late seventies a movement started to ensure that standards were made uniform so that Germans could for example produce bolts to fit French nuts and that say British cars could use the German bolts and French nuts to assemble their cars. This gave rise to a system of paperwork and standards, that ensured a total traceability of the origins of not only the raw materials to final product, but also from a customer’s enquiry to final delivery. This system of paperwork is defined as ISO 9001 or ISO 9002 depending upon the type of Company, seeking the approval. These days in Europe many large manufacturers prefer to purchase from Companies with these ISO9000 approvals. One of the requirements of these programs is the regular calibration program of used instruments within the approved Company.

Q. What is meant by traceability?
A. When a company calibrates your instrument they use more accurate instrument than yours to verify the performance of your instrument. They also on a regular interval have to send their equipment to another Company who has in their possession a more accurate instrument than your supplier’s and so on. The chain carries on until the ultimate, which is N.P.L. If your instrument hasn’t got an N.P.L. traceable certificate there is no guarantee that the calibration is valid because the chain should never be a broken one.

Q. What should a Certificate of Calibration contain?
A. Name and address of Customer Instrument and the type Instrument Serial Number Date Of Test Date of next Test Equipment used to carry out the calibration and serial numbers Measurements Interpretations of the figures Statement of confidence probability Statement of traceability Ambient temperature at the time of calibration (If On Site) Signature of calibration Engineer

Allied Aerosystems Ltd has over 20 years

experience in calibration and repair. Though We

understand you may have questions regarding

your particular requirements, we have collated

some of our frequently asked questions. However;

feel free to contact us and we will be happy to

answer any queries you have.