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Miriam Boudreaux


What do Calibration and Approved Suppliers Have in Common?

Take a look into your purchasing procedures and supply chain and find out

Published: Monday, October 19, 2009 - 15:27

When you think about equipment that is used for measuring and test activities, you think about important equipment that is used to pass or fail product but may not necessarily see its correlation with a supply chain. However, this very equipment—whether it is calibrated in-house or off-site—does involve a supply chain one way or the other and therefore adherence to suppliers and supply-chain requirements is imperative.

If you outsource your calibration, you know that your calibration partners are your vendors. But when equipment is calibrated in-house, you may think there are no suppliers involved. However, even in this case, you probably still have to send the standard used for calibration to an outside calibration company that can provide traceability to National Institute of Standards and Technology (NIST) standards. So whether the calibration is done in-house or by an external company, calibration requires a thorough look into purchasing procedures and the supply chain.

Supply chain

When you send equipment out for calibration, the calibrating company becomes your supplier and is therefore subject to all the controls set forth in your supply chain or supplier approval procedures.  If your procedure is laid out correctly, then you will find most of the controls familiar. In fact, if you segregate your suppliers, in most cases calibration companies will fall under your top tier or critical suppliers, because you depend on them to calibrate the equipment that determines the quality of your product. Because the equipment you use will actually pass or fail your product, you want to make sure the companies who calibrate your equipment are good, reputable suppliers.

The first issue you want to ensure is that the calibration company or companies you use are part of your approved supplier list (ASL) or approved vendor list (AVL). Unless they were grandfathered in—that is, those suppliers existed before you put in place your supply chain approval procedures—then you need to be able to demonstrate that the calibration companies were approved following your calibration procedures. For example, if you require that all your prospect suppliers fill out a survey before approval, then you should have a completed survey on hand for your calibration suppliers. Likewise, if you require a ISO 17025 or ISO 9001 certificate in lieu of a survey or on-site audit as a method for approval, then you should have that certificate on-hand.  Whether it's  a survey or a certification, you must ensure that the current calibration suppliers meet all the requirements set forth in your procedures.

ISO 9001 requires that suppliers be re-evaluated, and you should have a process already in place for that. Because your calibration partners are suppliers, you have to make sure you re-evaluate them using the same procedures, whether that entails periodic audits, periodic surveys, supplier corrective action requests (SCAR), or corrective action statistics, etc.  If you feel that the current process in place is too cumbersome or not adequate for your calibration suppliers, you should modify your process and corresponding procedures to accommodate them. The idea is to make sure that these companies are subject to the supply chain requirements and that there are records to prove they are meeting those requirements.


Believe it or not, when you send equipment out for calibration you are outsourcing your calibration process, and therefore you need to apply extensive controls to your calibration partners to ensure that they are performing the assigned duties based on your requirements. 

When issuing purchase orders to a calibration company, one of the main steps is to establish the requirements for how you want the calibration to be done. For example some companies issue purchase orders with reference to their internal calibration procedures. Other may specify on the purchase order the parameters required to calibrate the equipment, such as:

  • Methods or protocol
  • Accuracy and  tolerance
  • Items to include in calibration certificate, etc.


If the accuracy, tolerances, method, etc. is contained within your procedure, then you need only reference that procedure. Otherwise, you need to convey to the calibration company how you want this equipment to be calibrated. If you require calibration according to a procedure, then you should e-mail the procedure, attach it to the purchase order, etc. 

You also have to pay close attention to the revision dates. For example, if you issued a purchase order last year to a calibration company and referenced your calibration procedure dated last year, that was great for last year.  But if you issue a purchase order this year, you should now see if there is a new revision of the procedure and ensure that the calibration partner has that particular version.  Some companies adopt a blanket statement such as:

“Calibrate to the latest revision of procedure ABC-XXX”

If you follow this statement, then you have to discuss this with your calibration partner to make sure they read your purchase order and always request the latest copy of ABC-XXX.

Whichever way you go, your purchasing group, your supply chain group, and your calibration vendor have to be knowledgeable of what is required and expected of them. 

Maintaining control

Overall control over your calibration partners is necessary to ensure they are meeting your requirements. Just telling them you want a piece of equipment to be calibrated is not sufficient. Likewise, assuming that your purchasing department (supply chain group, logistics, etc.) know and understand those requirements, is not prudent.  Be certain they recognize the implications of dealing with and ordering from calibration suppliers. With good processes and procedures in place, and thorough training, you should expect excellent results in your calibration purchases and ultimately be confident that your product and processes are being inspected and tested with fully compliant equipment.


About The Author

Miriam Boudreaux’s picture

Miriam Boudreaux

Miriam Boudreaux is the CEO and founder of Mireaux Management Solutions, a technology and consulting firm headquartered in Houston, Texas. Mireaux’s products and services encompass international standards ISO and API consulting, training, auditing, document control and implementation of Web QMS software platform. Mireaux’s 6,500 square foot headquarters, located in the northwest area of Houston, houses their main offices as well as their state-of-the art training center. Mireaux itself is certified to ISO 9001:2015 and ISO 27001:2013. To get in touch with Miriam Boudreaux, please contact her at info@mireauxms.com.


Approved Calibration Suppliers

Two comments:
1) ISO9001 certification alone is not sufficient evidence to approve a calibration supplier.
2) The #1 bullet regarding parameters identified on a purchase order should be: "Traceability to SI Units"

Calibration Supplier Controls

What controls do you put in place for calibration suppliers?  How do you treat calibration equipment you purchase from a supplier vs. a calibration supplier that actually does the calibration of that equipment after it's been purchased?  What risk level do each of these provide?