Calibration, verification, and validation are always used or read in every measurement related topic.
When I was just starting out in this calibration environment, I was always confused on how or when to use each term.
There were so many helpful articles that I read and review, and still afterward, when I needed to use each term, sometimes I still get confused.
I believe this also happens to most of you out there, whether reading or understanding a certain procedure or instructions.
In this post, I will present with you the:
- differences between each term,
- its applications in our measurement process (calibration Process)
- the ISO standards that require each to term to be performed
- some examples to illustrate each term
That I hope will help you to understand and interpret each requirement for managing our calibration process.
Definitions of Calibration, Verification, and Validation as per JCGM 200:2012
Below are the definitions that I directly copied from the International vocabulary of metrology or VIM for short.
The operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties and, in a second step, use this information to establish a relation for obtaining a measurement result from an indication
provision of objective evidence that a given item fulfills specified requirements
verification, where the specified requirements are adequate for an intended use
Understanding the differences in Calibration, Verification, and Validation as applicable to Calibration Management
Calibration, verification, and validation are mostly used interchangeably if you are not aware of their differences and true meaning.
For the purpose of simplicity, I will focus this presentation in relation to measuring instruments as applied to the calibration process.
Given the definitions above, which is very technical, I will provide a more detailed and simple explanation in order to make it clear and more meaningful (I hope so), based on what I understand and experience in applying its concept in the calibration field.
As with most simple definitions that I read, calibration is simply the “comparison” of the unknown reading of a UUC to a known reading of a Reference Standard, also known as the Master.
Based on a reference standard, you are comparing the performance of the unit under calibration (UUC). Through comparison, you can determine the accuracy and error or how far is the reading to the true value.
But the process does not end here, During calibration, we also consider:
- The traceability, the unbroken chain of comparison linking to the highest level (International standard like NIST)
- computed Measurement Uncertainty
Without these two, we cannot call it calibration; we are just performing a simple verification.
Also, in Calibration:
- you may or may not include adjustment or repair
- based on the result, pass or failed decisions are decided by the user as per their process acceptance criteria.
Your objective in performing calibration is guided by:
- customer requirements and regulatory authorities
- calibration procedures based on standard methods (from national, international or technical organizations)- also known as standard methods
- non-standard method – a validated laboratory-developed methods
- procedures from manufacturers or OEM
During calibration, we
- choose the required calibration procedure to be used
- compare to a reference standard (full-range or as per customer test point)
- determine the error
- adjust if capable
- check the traceability
- estimate measurement uncertainty
- record results to a calibration certificate
Verification is a process of “confirming” that a given specification is fulfilled.
It is a simple check to confirm that a certain instrument or equipment meets the intended output basing it to the requirements of certain specifications, not a comparison to a higher standard.
Your objective is guided by specifications from:
- a legal or regulatory body, examples are ASTM and ISO
- Manufacturer requirements.
- process or user requirements
Unlike Calibration where decisions are made based on how far or close the reading of the instrument in comparison to the provided results of the reference standard.
In verification, you are:
- Confirming the performance of the instrument based on given specifications or requirements.
- Ensuring that the instrument is working correctly for its intended purpose.
- Not checking the entire range. Just only to ensure that it is acceptable on its working or intended range
- Directly deciding what to do base on the verification result. These decisions are either:
- to recalibrate
- to adjust,
- extend usability
- scrap or make obsolete
Note that, we perform verification after calibration.
The activities where verification is involved in a calibration lab are:
- Intermediate check, which is used
- Before and after onsite calibration
- During the acceptance of newly purchased standards
- Once a reference standard has arrived from a third party calibration
- Preventive maintenance
- Receiving process of instruments for calibration
Validation is for “ensuring” the acceptability of the implemented measurement process.
It is the combined effect of calibration and verification but the final result is in the final output of the process.
The application in the calibration field is more on the development (design and development) of a calibration procedure in order to meet certain requirements.
A non-standard method can be used In a calibration laboratory, considering that it is validated before use.
During the validation of a calibration procedure, our objective is to determine:
- if the components introduced is capable for its intended use,
- relevant to customers’ needs
- consistent with the specifications of the instruments.
Another application of validation is qualifying a group of measuring devices that function as a system.
An example is a pressure transmitter, it consists of a pressure sensor and a transducer to convert a pressure signal to a current (4-20 mA) parameter in order to feed into a PLC display that performs a specific control and monitoring.
Moreover, we are focusing on validating the system as a whole, not just the instrument that is installed.
All parameters should be calibrated and verified before it can be used as a whole.
In Other words, In order to validate a process or procedure, you need to perform a calibration and verification.
The final output of validation is documented in a validation report where all results are recorded with a final decision for its suitability to be used in its intended purpose. It will also include the signatures of the persons who will approve the performed validation.
Techniques Used For Method Validation as per ISO 17025:
- calibration or evaluation of bias and precision using reference standards or reference materials;
- systematic assessment of the factors influencing the result;
- testing method robustness through variation of controlled parameters, such as incubator temperature, volume dispensed;
- comparison of results achieved with other validated methods;
- interlaboratory comparisons;
- the evaluation of measurement uncertainty of the results based on an understanding of the theoretical principles of the method and practical experience of the performance of the sampling or test method.
As per the above techniques, we can see that every validation technique is a process in itself.
For a specific example on how to use these terms, visit my other post in this link: How to differentiate calibration, verification, and validation?
You may also want to learn about the Differences Between Accuracy, Error, Tolerance, and Uncertainty in a Calibration Results
Why do we perform calibration, verification, and validation?
We are performing each activity to ensure quality in our measurement process and to comply as per the requirements of a standard.
These standards are ISO 17025 and ISO 9001. I will present the clauses where each term is used.
As per ISO 9001:2015
Measurement traceability under Clause 188.8.131.52
When measurement traceability is a requirement or is considered by the organization to be an essential part of providing confidence in the validity of measurement results, measuring equipment shall be:
- calibrated or verified, or both, at specified intervals, or prior to use, against measurement standards traceable to international or national measurement standards; when no such standards exist, the basis used for calibration or verification shall be retained as documented information;
>> The above requirements show that calibration and verification are used in ensuring measurement traceability or confidence in the validity of measurement results.
>> Validation will be performed when no such standard exists, and the basis of validation is through calibration and verification,
We can either perform calibration or verification or both.
AS per ISO 17025:2017
Under Clause 6.2.6
The laboratory shall authorize personnel to perform specific laboratory activities, including but not limited to, the following:
- a) development, modification, verification and validation of methods;
Under Clause 6.4.13
Records shall be retained for equipment that can influence laboratory activities. The records shall include the following, where applicable:
- c) evidence of verification that equipment conforms with specified requirements;
Under Clause 7.1.7
The laboratory shall cooperate with customers or their representatives in clarifying the customer’s request and in monitoring the laboratory’s performance in relation to the work performed.
Such cooperation includes the preparation, packaging, and dispatch of items needed by the customer for verification purposes.
Under Clause 7.2
Selection, verification, and validation of methods
>>As per above requirements, we can see that verification and validation are applicable in terms of:
- Assigning authorize personnel performing verification and validation of methods;
- Records should be maintained for verification and validation performed
- Lab cooperation for customer verification purposes as part of customer service
- Selection, verification, and validation of methods used in calibration or testing activities.
Calibration, verification, and validation are the 3 terms that most of us used interchangeably. In this post, I have presented the difference of each term, the reason why we need to perform them, simple examples and the necessary requirements under the clauses of ISO 9001 and 17025 standard that requires the use of calibration, verification, and validation.
By having the knowledge and understanding regarding the meaning of each term, we can easily understand and interpret what the standards are requiring us to do.
Still confused and unclear between the differences in calibration, verification, and validation? Please feel free to comment.
You may also visit the specific example where these 3 terms are used in a Liquid Oxygen Tank System in this LINK.
For other important terms, check my other post: Differences Between Accuracy, Error, Tolerance, and Uncertainty in a Calibration Results
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