Gabriel Hughes was once asked to calibrate a 2x4 at a previous job. While this may sound strange, the customer sent it in to have the precise dimensions calibrated. The wood was used to keep a door closed at a certain height, which they needed to monitor because of airflow.
“That’s probably the weirdest one that I’ve ever seen,” says Hughes, now a calibration technician at Intertek’s Plano, TX, lab.
Strange examples abound, but calibration is a serious task. The science of measurement would be nothing without calibration. In fact, a reliable measurement device is the foundation of quality. Experts explain the importance of calibration and how to get the best results from the process. As NIST says, “The calibration services of the National Institute of Standards and Technology (NIST) are designed to help the makers and users of precision instruments achieve the highest possible levels of measurement quality and productivity.”
This is a serious mission, and calibration technicians like Hughes take this work seriously. Even if it may seem like your equipment is taking a long time to get back to you, this is because it is a carefully considered process. “We’re not trying to hold anybody up,” Hughes says. “Every piece of equipment I touch has somebody’s life in its hands. For example, a torque wrench. If I don’t take the utmost care of it, somebody could get hurt.”
On the customer side, keeping equipment working well depends on a few factors. Basic maintenance should not be overlooked, Hughes says. “Often, a simple cleaning and observing your unit on the customer end can keep the unit working or prepare the customer for what’s coming out of the line.”
Taking care of the units being tested is perhaps the best advice, he says. And if a unit was dropped, be prepared that it might be out of tolerance soon.
William Hangartner, president of Quality Calibration Service Inc., offers these tips on calibration: “Be sure to set up a well-documented and disciplined program whether performing the work yourself or subcontracting your calibration. Also make sure that proper measuring equipment, procedures, and software are being utilized to assure the most accurate calibration and the lowest measurement uncertainty possible. If subcontracting, be sure to select a reputable and accredited laboratory.”
He continues, “Always assure you are using the right equipment, standards, procedures, software, and properly trained personnel in a proper climate controlled environment when performing calibration. Check and double check any questionable readings. Always assure proper setup before performing any measurements. Do not over calibrate and do not under calibrate. Always maintain a well-documented and audited system.”
He’s also seen some confusion regarding calibration. “Over and under calibration frequencies are applied in industry,” Hangartner says. “Frequencies should be based on gage and instrument use and wear trends. Unnecessary cost can occur when people over calibrate and the risk of accepting bad product can occur if calibration of the gages or instruments used for product acceptance are not calibrated with enough frequency. I have seen insufficient equipment and inadequately trained personnel used for performing calibrations in the manufacturing world.”
Hughes has also seen his share of calibration issues. “The most common misunderstanding: calibration is not adjustment,” Hughes says. “In the best case scenario, we would never have to adjust a unit. The biggest misunderstanding is the purpose of calibration, making sure that the customer understands the way the unit is operating, and a traceable record.”
The difference between calibration and adjustment is a fairly common question, Hughes noted. But if you have high quality equipment, you may not need to worry about adjustment for a long time.
Quality equipment can stay in tolerance for decades. Hughes recalls an item from the mid-80s that still worked and was in tolerance. This particular device had been used in the Navy and was well taken care of. With certain brands, he’s seen devices out of tolerance only one in every 20, or every 100. “You pay for the quality,” Hughes notes.
With cleaning, careful handling, and regular calibration, customers can understand how well it is operating.
And on the lower scale, while it may not cross your mind, items like tape measures still need to be calibrated and checked, Hughes says.
Calibration can be done at a customer facility, or at an outside calibration lab. When the technician goes to a customer facility, Hughes points out that it doesn’t take less time to calibrate, but the difference is that the technician can hand it back to you instantaneously. “Most quality control departments understand you can’t really rush quality,” Hughes says. Nonetheless, the calibration labs do try to get the equipment back quickly.
If any piece of test equipment is out of tolerance, customers should consider how it is out of tolerance and what options are available, such as if it can be adjusted. If an adjustment is not possible, perhaps a special or limited calibration would be an option. In this type of situation, the customer would recognize what was out of tolerance and see if this could be worked around. “Generally speaking, when the unit is significantly out of tolerance, it can’t be adjusted,” Hughes says. In that case, “eventually, preferably soon, replacement is a good option.” In some situations, the items could be repaired by a qualified repair facility.
And speaking of qualified facilities, calibration lab standards have changed.
When applicable, Intertek also lets clients know about changes to calibration standards, such as ISO/IEC 17025: 2017. According to ISO, “ISO/IEC 17025 enables laboratories to demonstrate that they operate competently and generate valid results, thereby promoting confidence in their work both nationally and around the world. It also helps facilitate cooperation between laboratories and other bodies by generating wider acceptance of results between countries.”
For customers considering a calibration lab, Hughes recommends talking to the people involved, viewing the calibration facility and looking at how the lab operates.
One of the priorities for any potential customer should be talking to the people involved. Most labs allow a customer to view the calibration facility. These calibration techs are handling your equipment so it makes sense to see how they operate.
The important thing is to make calibration a priority. And for best results, consider quality rather than cost.
“I have seen some strange things that usually occur when someone is not properly educated in proper means of calibration,” Hangartner says, “or when they are trying to cut corners and let expense dictate the calibration applications.”