Calibration—The Good, the Bad And the Ugly

by Jay L. Bucher

There are good, bad and ugly calibration programs. Before diving headfirst into particulars, let’s define what calibration is and what it is not.

Essentially, calibration is the comparison between test equipment with an unknown uncertainty to a standard with a known uncertainty.

Calibration is the comparison of a piece of test equipment and a standard, regardless of whether the standard is:

  • Kept by National Institute of Standards and Technology (NIST).
  • Used as the reference standard by a third party calibration lab.
  • Used as the working standard everyday by your local calibration technicians.

Calibration is a comparison. You need something to calibrate and a standard to compare it against. It has nothing to do with adjusting, repairing, aligning, zeroing or standardizing. All of these activities can be incorporated into the process at some point, depending on what the item is, how it is used and, in some cases, at what level it is being calibrated.

I’ve had ISO 9001 auditors tell me you cannot calibrate a thermometer because you cannot adjust it. Naturally, I was obligated to inform them of the error of their ways.

Calibration Everywhere?

There are some statements calibration technicians might make to describe how their jobs affect our quality of life. They might say:

  • The equipment I calibrate on a daily basis helps catch killers and rapists all across America.
  • My work was instrumental in helping to free the innocent from prison.
  • The accuracy of my work helps airlines reduce accidents and mishaps.
  • The highways and byways are safer because of the due diligence of our calibration program in automotive manufacturing.
  • The number of people helped by the medications we manufacture using calibrated systems and measurements is incalculable.
  • There are discoveries of more drugs and cures for the incurable than ever before, in part because of the repeatable readings and accuracy of our calibrated test equipment.

How is any of this possible? Quality calibration systems are the foundation for improving R&D, production and quality assurance arenas through accurate, reliable and traceable calibrations of test equipment. If quality calibration is not important, then why is it a requirement in industry, government and the private sector?

Calibration can be, and usually is, a critical component in any manufacturing company. But, like any other part of a quality system, calibration relies on truth—collecting the right information, recording it correctly and determining whether the test equipment is in or out of tolerance.

The people performing the calibration must have integrity in all aspects of their job performance. If they fudge the numbers, there might be several consequences such as:

  • Bad product is produced, and customers waste their money.
  • Bad product is produced, and customers are sickened or die.
  • Bad product is produced, and a company’s good reputation becomes irreparably damaged, resulting in employee layoffs.

Does this sound far-fetched or the figment of an overactive imagination? Not really, especially when public safety is part of any Food and Drug Administration inspection.

When producing drugs, medical devices or any other product that impacts people’s safety, it is imperative that standard operating procedures are followed and the truth about measurement and its results be correctly recorded.

A quality product starts in the mind of the R&D scientist and ends when a finished product is ready for purchase by the public. There are thousands of steps along the way that could impact the quality, quantity, size or value of that product. All it takes is one untruth to impact the final product.

One simple “Ah, this isn’t that important” attitude from a calibration technician (or any other person in the manufacturing process) can easily impact the final result.

Good, Bad and Ugly

So what is the difference between good, bad and ugly calibration systems? Here are some examples of each to clear up any misunderstanding.

Good calibration system: The calibration technicians are honest and ethical in their endeavors. The technicians:

  • Use written calibration procedures that fall under a quality documentation system.
  • Record what the standard reads, as well as both the “as found” and “as left” readings from the unit under calibration (UUC) when appropriate.
  • Compare the results and act on the difference.

When the UUC is found to be out of tolerance, there should be procedures in place to inform the user or customer, as well as a written process for evaluating whether the product or process was impacted by the test equipment found to be out of tolerance. This is only the tip of the iceberg of any quality calibration program.

At a minimum, a good calibration system will also have the following in place:

  • Traceability documentation.
  • Proper calibration labels.
  • Uncertainty budgets.
  • Calibration interval procedures.
  • Good scheduling practices.
  • Environmental conditions and parameters.
  • Calibration management software.
  • Documented training procedures.
  • Continuous process improvements.

Bad calibration system: Most of the parts are missing or misunderstood. Calibration records are either nonexistent or don’t contain the required items to make them usable or viable. There is no uncertainty budget or traceability paper trail to speak of. The only reason the company is not written up by an auditor might be because the audit is a “paperwork only” process, not a true inspection against a standard.

An FDA inspector would write up a bad calibration system without hesitation. It’s very easy to identify. The usual result is unreliable test equipment that cannot produce accurate measurements. The company is not required to adhere to any standard or regulation and cannot compare itself to its competition.

Ugly calibration system: This is a horse of a different color. It has most, if not all, of the elements found in a good calibration system. The major difference comes in the lack of integrity and honesty of the calibration technicians, their supervisor and upper management. Other characteristics of an ugly system include:

  • Numbers are fudged on the calibration record and are difficult to find during an audit.
  • Calibration due dates are extended when the backlog starts to rise, and overdue calibrations are unacceptable (test equipment doesn’t really go bad over time, does it?).
  • Test equipment is said to be calibrated when in fact it isn’t.

By far, this last situation is the most common characteristic and is commonly referred to as “lick ’em and stick ’em,” “hot stamping” or “turn and burn.” These phrases denote placing a calibration label on equipment that has not been correctly, competently or actually calibrated. Or the equipment is out of tolerance, and the technician doesn’t want to follow the processes set in place.

Predictably, the company with an ugly calibration system produces inferior products but gets away with it by displaying ISO 9001 or current good manufacturing practice labels on the products. Eventually, the customer base goes away because of unreliable, nonrepeatable and substandard products. It is hoped that none of the company’s products cause illness or death.

It’s important to note that the vast majority of calibration technicians, supervisors and upper management with whom I have worked have had the highest integrity. Their ethics are beyond reproach, and a quality product is always on their minds. As with most things in life, the few bad apples get the attention. I would like to acknowledge the good apples here.

The diligent calibration technician, working under a quality calibration system, no matter whether private industry or government, continually produces a quality product in a timely manner.

Without their due diligence, our world would be a far worse place in which to live.

Defining Calibration

The following are primary and secondary definitions of the term “calibration,” according to The Quality Calibration Handbook:1

Calibration is a term that has many different but similar definitions. It is the process of verifying the capability and performance of an item of measuring and test equipment compared to traceable measurement standards.

Calibration is performed with the item being calibrated in its normal operating configuration—as the normal operator would use it. The calibration process uses traceable external stimuli, measurement standards or artifacts as needed to verify the performance. Calibration provides assurance that the instrument is capable of making measurements to its performance specification when it is correctly used.

The result of a calibration is a determination of the performance quality of the instrument with respect to the desired specifications. This might be in the form of making pass/fail decisions, determining or assigning one or more values, or determining one or more corrections.

The calibration process consists of comparing test equipment with specified tolerances of unverified accuracy, to a measurement system or device of specified capability and known uncertainty, to detect, report or minimize by adjustment any deviations from the tolerance limits or any other variation in the accuracy of the instrument being compared. Calibration is performed according to a specified documented calibration procedure, under a set of specified and controlled measurement conditions, and with a specified and controlled measurement system.

Many manufacturers, auditors and quality assurance inspectors incorrectly use the term calibration to refer to the process of alignment or adjustment of an item that is either newly manufactured, known to be out of tolerance, or otherwise in an indeterminate state. Many calibration procedures in manufacturers’ manuals are actually factory alignment procedures that only need to be performed if a unit under calibration is in an indeterminate state because it is being manufactured, is known to be out of tolerance, or has been repaired. When used this way, calibration means the same as alignment or adjustments, which are repair activities and excluded from the metrological definition of calibration.


1. Jay Bucher, The Quality Calibration Handbook, ASQ Quality Press, 2007

JAY L. BUCHER is president of Bucherview Metrology Services, a consulting company specializing in quality calibration systems. He is co-author and editor of The Metrology Hand-book (ASQ Quality Press, 2004), and author of The Quality Calibration Handbook (ASQ Quality Press, 2007) and Paperless Records—Designing and Creating Your Own Electronic Forms (Bucherview Metrology Services, 2007). He is the treasurer of the ASQ Measurement Quality Division. Bucher is a senior member of ASQ and a certified calibration technician.

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