Calibration is the activity of checking, by comparison with a standard, the accuracy of a measuring instrument of any type. It may also include adjustment of the instrument to bring it into alignment with the standard.
There are three main reasons for having instruments calibrated:
1. To ensure readings from an instrument are consistent with the standard.
2. To determine the accuracy of the instrument readings.
3. To establish the reliability of the instrument.
✔Traceability: relating your measurements to others
✔Uncertainty: how accurate are your measurements?
✔Reliability: can I trust the instrument?
✔Achieving Traceability in your measurements
✔Adjustment: what a calibration is not
✔What a calibration certificate contains
By using a calibration laboratory that is accredited to international standard ISO/IEC 17025:2005. In Kenya, the Kenya Accreditation Service is the national certification body authorized to accredit laboratories to this standard among others. ISO/IEC 17025:2005 requires laboratories to demonstrate competence in both the technical aspects of the measurements and in the quality assurance aspects that ensure that you will get the service that you ask for if you have specific requirements, or will ensure that you get a useful and valid certificate and a sticker showing calibration date and the next recalibration date.
All measurements are used to help make decisions, and poor quality measurements result in poor quality decisions. The uncertainty in a measurement is a numerical estimate of the spread of values that could reasonably be attributed to the quantity. It is a measure of the quality of a measurement and provides the means to assess and minimize the risk and possible consequences of poor decisions.
Many measuring instruments have a specified accuracy greater than needed for most tasks. With such an instrument, where corrections and uncertainties are negligible, the user simply wants to know that the instrument is reliable. Reliability is judged primarily by the absence of any behavior that would indicate that the instrument is or may be faulty.
A calibration certificate will be issued only if an instrument is found to be reliable, and will satisfy its intended purpose.
✔Testing a new instrument
✔Testing an instrument after it has been repaired or modified
✔Periodic testing of instruments
✔Testing after the specific usage has elapsed
✔Prior to and/or after a critical measurement
✔When observations are not accurate or instrument indicators do not match the output of a surrogate instrument
✔After events such as:
✔An instrument has had a shock, vibration, or exposure to adverse conditions, which can put it out of calibration or damage it.
✔Sudden weather changes
✔ Safety procedure: In case of instruments involving perishable products such as food or thermometers with area of sensitive nature, uncalibrated instruments may cause potential safety hazards.
✔ Wastage: If the instrument is not perfectly calibrated, it might lead to potential wastage of resources and time consumed in the operations, resulting in an overall increase in expenses.
✔ Quality: If the instrument is not calibrated, this can result in poor quality products. Calibration helps maintain the quality in production at different stages, which gets compromised if any discrepancy arises.
✔ Fines or litigations: Customers who have incurred damage may return the product against a full refund, which is still alright; but if they go for litigation due to damages, you could be up for serious costs in terms of reputation and restitution payments.
✔ Increased downtime: Poor quality of finished goods is the first indicator of disrepair in your equipment. Regular calibration programs identify warning signs early, allowing you to take action before any further damage is caused.
The calibration interval is dependent on:
✔ The importance of the measurements to your product or service;
✔ The degree of wear and tear to the instrument
✔ Usage .In case the frequency of usage is very high, two calibrations per year may be necessary.
✔ The stability of the instrument itself and a review of the calibration records that already exist to determine whether adjustment has been needed previously.
For a calibration certificate to fulfill its intended purpose of supporting traceability, it must do the following:
✔ Establish the identity and credibility of the calibrating laboratory;
✔ Uniquely identify the instrument and its owner;
✔ Identify the measurements made; and
✔ Include a concise statement of the results, including an uncertainty statement.
✔Onsite calibration reduces instrument downtime and the need for additional equipment.
✔It has minimal interruptions to your processes that require use of the instrument.
✔Flexibility: You can have all your calibrations performed at once, or you can schedule your calibrations them throughout the year.
✔Onsite calibration eliminates transport costs and delays