The process of measurement and calibration has evolved light years since its beginnings, yet the basic fact remains that gage and equipment calibration is critical to the survival of manufacturing, regardless of the industry it is applied to.

The basic purpose for calibrating gages and instruments used to verify and accept manufactured product is to ensure that the gages and instruments are accurate for their intended use.

As a way to institute worldwide manufacturing consistency, the standards of the International Organization for Standardization (ISO) were first introduced in the mid to late 1980s and formally adopted by the United States in the early 1990s. Since their inception, ISO standards have undergone numerous transitions and revisions to improve the standard.

These revisions finally evolved into a completely new standard called ISO 9001: 2000. The new standard replaces the former ISO 9001 (Design, Develop & Manufacture), ISO 9002 (Manufacture Only) and ISO 9003 (Inspect and Test).

ISO 9001: 2000 combines all aspects of the former three standards while adding a new section, "Monitoring and Measurement of Process." This section mandates a strong emphasis on overall customer satisfaction through documented follow up and surveys. An ISO 9001: 2000 registered company must now monitor customer satisfaction ratings through a formal evaluation process of the company's preset goals and objectives designed to measure actual customer satisfaction. If a company is considering ISO registration to open new market opportunities, there is no choice but to adhere to the guidelines.

The standard states that an ISO registered company must have a detailed quality program containing specific quality policies, procedures and a formal calibration program. A calibration program can be performed in-house or by an outside commercial metrology lab.

Typically, there are three options for companies to consider when deciding on a formal calibration program.

• Perform all calibration in-house.
• Send all calibration to an outside metrology lab.
• Send designated master reference standards, such as fixed gages which have at least a 4:1 higher accuracy ratio over secondary and adjustable type gages, to a NIST-traceable metrology lab. Then use the master standards to calibrate and establish NIST traceability to secondary gages.

Most companies that perform in-house calibration use the last option. Costs of establishing a calibration program depend on which option is selected and whether a quality consultant is hired to set up the program. Typically, most manufacturing companies have found that option three is the most economical overall. Justification of cost should be the easiest to establish.

Now, how does one find a reliable commercial metrology lab?

There are many factors to consider when selecting a metrology lab. Do homework prior to arbitrarily sending expensive gages out to a lab just because they make a statement that they offer calibration traceable to the National Institute of Standards and Technology (NIST). Here are some tips:

• Select a lab that is not only traceable to NIST, but also accredited to ISO 17025 by a reputable accreditation organization.
• Request a copy of the lab's quality procedure manual along with a copy of the lab's scope of accreditation to ensure that the lab is capable of performing the requested calibration requirements, and large enough to minimize having to send out calibration to several places.
• Ask who performed the metrology lab's accreditation to ISO 17025. How long has the accrediting body been performing accreditations? Is the accrediting body both nationally and internationally recognized and to what criteria?
• Review the lab's measurement uncertainty statements. Are the stated uncertainties within an acceptable ratio to the accuracy of the equipment? The lower the lab's stated uncertainty, the more accurate the measurements.
• Ask what environmental controls the laboratory maintains. The tighter the temperature control, the less measurement variability and lower uncertainties.
• Ask how long the lab has been in business, and schedule a visit if practical.
• Determine if lab personnel can provide proper technical support and are knowledgeable should there be any questions regarding technical specifications and standards.
• Review the certifications and documentation the lab will provide to ensure correct calibration format is followed: for example, gage IDs, nominal sizes, tolerances, actual sizes before and after readings, listing of all standards used.
• Is the lab capable of providing its customers with Web access, paperless electronic data transfers and downloading of certifications from the Web?
• Is the lab staffed adequately to meet their stated turnaround times?
• How are gages packaged and are they insured during return shipment?
• Are calibration services competitively priced?

The manufacturing process is constantly changing and improving as technology and automation continue to advance. The same can be said for the field of metrology and calibration. Once a company decides on a formal calibration program, begin by asking all the right questions.