I received an email from a reader with a question about different kinds of reports and certificates dealing with calibration—a subject that I comment on from time to time. After thinking about his question, I realized that, while most of the mis-statements and—in some cases—outright misrepresentation on reports of fifteen years ago are not as prevalent today, some of it is still out there.
Most companies with good quality systems have sorted these matters out to ensure they get what they expect in the way of documentation on calibration work. But not everyone in their company may be up to speed in this regard. Purchasing and engineering departments often come up short in specifying or comparing suppliers promising a ‘cert’ is included in their price. When price is the main consideration it often turns out that the cheapest price wins the order but while the quality folks want a calibration report, they get a piece of paper called a certificate which can mean anything—or nothing. I hope the following explanations will help you avoid such problems.
In the purest sense these documents outline what was calibrated and the results that were obtained. How much work is done can vary so that you may be expecting three readings on a dimension but receive only one. Or it may indicate only that the item was calibrated and is good to go.
Certificates can attest to anything with or without calibration data. Often, they contain verbiage that leaves the organization that issued it wide open for a lawsuit and provides little real information of benefit to the recipient.
The ISO 17025 laboratory standard allows calibration certificates to be issued that declare an item meets a specific standard after calibration BUT the data this decision was based on must be made available by the lab on request if it is not on the document.
In their crudest form (the no-charge ones), it may simply say the item was calibrated following certain procedures by their highly skilled inspectors, blah, blah, blah. Some may add references to standards to make them look better than they are.
CERTIFICATE OF CALIBRATION
This will usually state the item was calibrated and little more.
LONG FORM/SHORTFORM CERTS
I believe these were created by the gage making industry but I know that’s where you’re likely to encounter them. There are so many features on something like a thread gage that the cost of calibrating them all would send users of them into a state of rage. So, a shortened form of calibration is done where one or two features only are measured and reported. The long form version usually provides data on more features.
CERTIFICATES OF COMPLIANCE
The original purpose of these certificates was to provide assurance that a process or treatment of the item in question was followed when that fact is not usually verifiable after manufacture. These documents are sometimes used as substitutes for actual calibration reports and some quality auditors will accept them. They are usually offered at no charge because they are not worth much.
These are reports issued by labs that have not obtained proper accreditation. Also, they can be issued by accredited labs when the item calibrated is not on their scope of accreditation or it could be just outside the range shown on their scope for similar items. The lab will usually obtain customer approval of this situation before calibration and note it on the report.
GETTING WHAT YOU WANT
The simplest way to get what you want is to spell it out to your calibration source. Use the ISO 17025 standard for what a proper calibration report should include in the way of basic information and ask for data on the report. Some industries have additional requirements, some of which are of no practical use but they are part of a given industry so you have to specify them as well. Another way to get things right is to ask the lab you are using to give you sample reports for the type of items you want them to calibrate for you.
There you have it! Don’t let fancy graphics and creative writing mess up your system.