5 Mistakes When Using a Calibration Certificate that You Need to Correct

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During my time as a calibration engineer managing an in-house calibration lab, I have collected different types of calibration certificates coming from different users inside the company where I observed each one of it has different formats and contents.

And one day, one of the calibration certificates we have gives us a non-conformance because it is not an accredited certificate or not from an accredited calibration lab. The company I belong that time is manufacturing parts for automotive so an accredited lab is a requirement.

Have you ever encountered the same problems regarding the use of your calibration certificates? Do you review a calibration certificate and document the necessary details that suit your requirements?

In this post, I have presented the following:

  1. What is the purpose of a calibration certificate,
  2. Why there are different content of a calibration certificate?
  3. 3 types of calibration certificates that you need to be aware of.
  4. What are the advantages of having an accredited calibration certificate?
  5. 5 mistakes when using a calibration certificate



What is the Purpose of a Calibration Certificate?

It seems that is a very simple question that has a very simple answer ( in which it is). The simple and very basic answer is to show that a specific instrument is calibrated and within a calibration period.

But if you truly understand the content of a calibration certificate, you will realize that it is not a simple question.

In order to fully benefit the importance of calibration certificate and if you are making measurements regularly using the calibrated instrument, you should always consult the calibration certificate for the following:

  1. The error and correction factor
  2. The uncertainty results
  3. As found and as left data
  4. The tolerance

And if you are monitoring quality and compliance, you should review the following:

  1. Calibration interval
  2. As found and as left
  3. Written remarks
  4. Traceability information
  5. Details like correct information
  6. Compliance to specifications

Check out the related post in this link>How to read a calibration certificate



Why Are Calibration Certificates Have  Different Contents?

Many users are not aware of the different types of calibration certificate until they are audited and have a non-conformance.

Calibration labs have different calibration certificate formats or content for some reasons. These reasons are:

  1. They are not an accredited calibration lab and therefore does not follow the ISO 17025 calibration certificate requirements. See the requirements here
  2. The lab is following a customer requirement on what to reflect only in the calibration certificates as per their application.
  3. Other labs are following different formats and requirements as per the standard they are using like ANSI/NCSL Z540 in the US.
  4. Some other reasons which are related to the cost of calibration are to reduce the calibration price and at the same time limiting the test points and other information on the calibration certificate.

In order to prevent or avoid any problems, make sure to be aware of the different types of calibration certificates that you will receive and use including your requirements and internal policy or procedure about 3rd party certificates, and as much as possible, get the service only to an accredited laboratory under ISO 17025.


3 Types of Calibration Certificates That You Need To Be Aware Of.

Being aware of the different types of calibration certificates will immediately prompt you to take immediate action once you notice a different format of the calibration certificate you receive. This is why a review of calibration certificate after receipt is important.

If you are not aware of this and you receive their certificate, this will become a potential problem for you during audits.

In order to prevent this, I will share below different types of calibration certificates:

1. Accredited calibration certificates – this certificate follows the format of ISO 17025 requirements and it is the required calibration certificates if the lab is accredited under ISO 17025.  Check this link to view the full requirements

Accredited Certificate with accreditation body logo

          The main difference that is included here are:

  • The LOGO of the accreditation body
  • The  measurement uncertainty results
  • The statement of conformity with requirements or specification
  • Results of before and after adjustments or repair
  • Opinions and Interpretations if applicable
  • Traceability Information

Plus all of the contents of other calibration certificates are included here if applicable and required by the user.

2. Non-Accredited Calibration Certificates – as the name implies, this is the calibration certificates provided by a lab that is not accredited under ISO 17025. And therefore does not follow its requirements.

Original Equipment Manufacturer Calibration Certificate
  • You will easily determine that a calibration certificate is not accredited under ISO 17025 even though they follow its format if there is no LOGO  of the accreditation body.
  • This type of certificate is used by the Original Equipment Manufacturer, also known as Traceable calibration certificate. They use this for the instruments they manufacture. Most OEM certificates have less information compared to an accredited certificate.








3. Conformance  Certificate– this type of certificate has limited or no measurement data results. It only details specific information and the functionality of the instruments and certifying that the instruments have passed or meets the quality check on product performance.

  • This is mostly used by OEM for certifying the quality of a batch produced instruments.
  • You do not need this type of certificate if your purpose is in the accuracy of measurement results because it will not show the performance of the instruments and therefore it is not a valid calibration report.
Conformance Certificate



For more details you may check these articles:

Fluke Calibration Certificates

Types of  calibration certificates

What are the Advantages of an Accredited Calibration Certificate?

As we can see, there are different types of calibration certificates that we need to be aware of. Below are some of the reasons why we need to use or have an accredited calibration certificate:

  1. It has uncertainty results that you can use for your in-house calibration lab.
  2. There is high assurance that the calibration results are properly checked and monitored since technical competency is verified during the accreditation.
  3. Traceability to National or International Standards is assured which is the main requirement of ISO 9001 under clause 7.1.5.2.
  4. With the calibration certificate, format/content stated under ISO 17025 will ensure that customer requirement (and auditors requirements) are met.
  5. Customer support is highly expected when problems arise involving the calibration results.


5 Mistakes When Using a Calibration Certificate

Most users that I observed only use the calibration certificate to record the cal date and due date. Another is just a  show off in case an auditor will ask for its calibration details. Certificates are used as a display only.

While this is not a mistake, we are not using the full importance that will provide greater benefits than just a displaying a calibration certificate.

Being exposed in an in-house and 3rd party calibration lab, below are 5 mistakes when using a calibration certificate that I observed and encountered.

1. Not reviewing the specific information once received. A review of calibration certificates should be included in the procedure regarding 3rd party calibration.  

  • This will ensure that correct details reflected in the calibration certificate. Wrong information like the “serial number” will invalidate the traceability of the calibrated instruments on its certificate.
  • Check for the traceability information – this is one of the main requirements of ISO 9001 as stated under advantages above. I have a read a good article which shows different formats and traceability statements in a calibration certificate.. measurement traceability
  • Other information that needs to be reviewed- Check my other post here.

2. Not using the correction factor.

  • Most of the results of the instruments that are calibrated and cannot be adjusted have a correction factor (CF) with it. This must be used every time you are making a measurement to compensate for the error.


To compute for the Correction Factor:
CF = true value-the actual value

Check my other post which I explained this in more detail in this link.. correction factor

3. Neglecting to review the necessary remarks.
This one is critical, in any case, that the instruments have a problem during the initial calibration, we can isolate immediately and perform assessments to the affected products where the instrument is used.

These remarks that we need to be aware of includes:

  • out-of-tolerance or failed
  • a limited calibration – not all range is covered during calibration.
  • Other important information that the lab wants you to know about the performance of the calibrated instrument, an example is “current function is defective”.
sample remarks

4. Not comparing the previous results from the latest
This is one of the requirements under ISO 9001 clause 7.1.5.2: which states that “The organization shall determine if the validity of previous measurement results has been adversely affected when measuring equipment is found to be unfit for its intended purpose, and shall take appropriate action as necessary”.

We will check here the “As found Data”  which is the result of calibration before any adjustment with the “As Left Data”, which is the result after the adjustment.

The benefits of recording and reviewing the data results are:

  1. Comparing this data will show you if there is out of tolerance found before the adjustment takes place.
  2. the long term trend can be seen and the performance of our instruments will be determined. You will observe here if it is going near the limits or readings are still stable.
  3. By recording the performance, this will show you if you need to adjust the calibration interval of your instruments. This is good evidence when you plan to extend the calibration interval of your instrument.

5. Using a calibration certificate that is not issued by an ISO 17025 accredited laboratory.
This happens if we are not aware of what calibration lab should we accept or there is an instance when there is no available calibration lab that is accredited under ISO 17025  to calibrate our instrument. Where the only options are:

  • To have it calibrated by a non-ISO 17025 accredited lab, or
  • To send it back to the Original Equipment Manufacturer (OEM) (most OEM are not ISO 17025 accredited).

Please don’t get me wrong here, it is not a mistake to use a calibration lab that is not accredited under ISO 17025, actually if you are following ISO 9001, the only requirements is to use a calibration lab with “measurement standards traceable to international or national measurement standards”.


But this will become a mistake if you are not aware of the requirements of your internal procedure or the certification bodies you applied for.

Most certification bodies have a policy regarding calibration service providers where  “it should be ISO 17025 accredited”, with this requirement, mistakes or non-conformance will occur unless below are implemented:

  • There should be evidence that the user has searched for an ISO 17025 accredited lab and none where found.
  • There should be evidence that the chosen lab have sufficient capabilities and traceability.

Check this article for more details>>calibration certificate content

Conclusion

A simple calibration certificate as we see can be a source of non-compliance or a process problem if not given time to understand and interpret the content. In this post, I have presented this article in order to help and guide us for some requirements and formats that we need to be aware of when required to review and use a calibration certificate.

I presented the following:

  1. What is the purpose of a calibration certificate,
  2. Why there are different content of a calibration certificate?
  3. 3 types of calibration certificates that you need to be aware of.
  4. What are the advantages of having an accredited calibration certificate?
  5. 5 mistakes when using a calibration certificate

Thank you for reading my post, Please comment and subscribe.

You can also connect with me on my Facebook page

Edwin

2 Responses

  1. Sonny D
    | Reply

    Edwin,

    I noticed Calibration Certificate recommends a 12 month calibration interval. It is difficult to understand the logic behind the 12 month interval, shouldn’t this depends on the number of usages ? It is probably making more sense with say a 12 month interval or 500 uses (ie. instrument uses 2 times/day for 52 weeks) recommendation, whichever comes first. This kind of recommendation makes life easier for management to budget funding. What is your thought on this subject? Thanks.

    Sonny D

    • edsponce
      | Reply

      Hi Mr. Sonny,
      Thank you for reading my post.
      Actually, as per ISO 17025 standard, it is not allowed to put a calibration due date in calibration certificates if unless communicated and agreed with the customer.
      This is also the reason why it is stated as” recommended “due date, not the actual due date.

      Most due dates are based on:
      1. Experience on the same type of instruments
      2. Manufacturer recommendation
      3. Calibration Laboratory recommendation

      You are correct; it depends on the number of usages the owner has acquired or how frequent it is being used. You should be implementing the best calibration interval that gives more sense to you as the tool owner.

      You can put in your procedure that, in every 500 uses, you will have it calibrated. And after 3 times in a row where the instrument is calibrated, and as you record and track the performance, you observe that it is still within limits or very stable, you can decide and increase it to 1000 uses before having it calibrated again. This is now your new calibration interval. This is just an example but it can be implemented in this principle.

      Hope this helps.
      Edwin

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