MEASURE FOR MEASURE
Verifying the Art
Mastery of metrology involves judgment, experience
by Craig Niemann
"Measurement may be considered both a science and an art. It is a science in that it is based upon the laws of physics and mathematics. It may be considered an art because elements of human judgment and skills, gained through experience, are necessary to translate a measurement from an abstract concept to real application."
The quote comes from an old Navy manual, NAV AIR 17-35 QAL-2, Revision 3.1 The entire manual—and this quote in particular—was assigned reading for me more than 20 years ago when I first started in metrology. Despite advances with test and measurement equipment, making a precise measurement is still considered an art. Even with automation in today’s calibration laboratories, the art is prevalent and demonstrated by calibration technicians across the world. We still need their judgment and skills to translate measurement concepts into application.
The question then comes up, "How do you verify the capability or art of a metrology technician?"
To verify capability, the one tried-and-true method is to observe the process with an over-the-shoulder evaluation, or process review. Having a technician perform an entire calibration under the observation of a trained quality evaluator (QE) is one of the best ways to gain confidence in the metrology technician’s art form.
Additionally, the process review gives management insight into the effectiveness of the technician’s management system (MS). The goal of every MS is to provide a quality product that meets customer expectations. While an internal audit provides a point-in-time measurement of this goal, ongoing and robust process reviews provide daily data on the effectiveness at the point of execution. But the best policies and procedures aren’t worth the paper they’re printed on if the organization doesn’t embrace and follow them.
On the surface, the process review appears to be solely technician-focused. If done correctly, however, it also provides documented evidence on how the laboratory is managed and whether management is living up to its responsibilities. To produce a properly calibrated piece of test equipment in a timely manner, management need to give technicians the right training, technical data, tools and equipment. A thorough process review highlights deficiencies and improvement opportunities in these areas, too.
Ideally, every calibration laboratory would hire fully trained calibration technicians. However, even if the employer does manage to hire someone fully trained from a diminishing pool of candidates, advances in technology and equipment will require ongoing training and familiarization.
An opportune time to target a process review is immediately after a technician receives training on a new measurement technique or a new piece of equipment. Any deficiencies noted during this type of review could identify an improvement opportunity in the training program. The timing of this review is especially important because it identifies training issues at the outset, and before the technician calibrates several items that will require recall analysis due to the faulty process.
Tools and data
Management also owes its metrology professionals to provide the right tools to do the job. Due to the complexity of some measurements, simple tools, such as a high-frequency adapter or pressure fitting, might make a difference in the endresult of a measurement. To achieve the smallest amount of measurement uncertainty, standards have increased in complexity, so these small details can influence the measurement just as much as the equipment itself.
Laboratory management also has a responsibility to provide its technicians with the right technical data to perform a calibration. But this data are never flawless, and despite an author’s best effort, there will always be instructions that can be interpreted differently. A process review identifies these errors because the QE is separate from the normal process, and the QE provides another point of view. Additionally, the evaluator should ask questions not only to verify the technician is following the data, but also to ascertain the technician’s level of understanding.
Equipment had the most obvious impact on a calibration. Management cannot expect technicians to produce a quality item if it gives them improper or substandard equipment. By having a QE perform a process review, the evaluator not only identifies these deficiencies, but he or she also can identify improvement opportunities to do the job faster, safer or cheaper.
But the requirement is not only that the laboratory possesses the right equipment, but also the technician knows how to use it. With the exception of some very low-level measurements, the days of merely hooking up to a voltmeter to make a measurement are long gone. Equipment fielded today is more complex and requires deeper knowledge of understanding for proper use. Once again, a thorough review of the process can reveal and highlight training deficiencies and knowledge gaps, if they exist.
After being involved with calibration and metrology for 22 years, including seven years assessing U.S. Air Force Precision Measurement Equipment Laboratories, I am convinced we still need technicians schooled in the art of measurement. Evaluation of this art form is not only beneficial to all involved, but also essential to maintaining the unbroken chain of traceability.
- U.S. Navy, Training Manual—Physical Measurement, NAV AIR 17-35 QAL-2, Revision 3, January 1977.
Craig Niemann is a Chief Master Sergeant with the U.S. Air Force stationed in Germany. He is currently the Flight Chief of the Ramstein Air Base Precision Measurement Equipment Laboratory and has served as the Chief of the U.S. Air Force Laboratory Certification Team. He received his associate’s degree from the Community College of the Air Force in 1997. Niemann is a senior member of ASQ and a certified calibration technician.