MEASURE FOR MEASURE
Calibration: Why It’s Important
by Graeme C. Payne
In my July 2005 installment in this series of articles on calibration, I talked about the trilogy of fast service, high quality and low price. Though some may think calibration laboratories skimp on quality because customers often demand low price and fast service, most calibration laboratories strive to deliver the best work they can while meeting other demands of the marketplace. Why? Because the people doing and managing the work know how important it is. Disagreements in a lab are more likely to center around one question: Yes, it’s good, but why can’t we do it better? It is a culture in which “close enough” isn’t part of the vocabulary; we can always do better.
Metrology and calibration are important to all areas, from global commerce to our personal lives. There have been legal requirements for the accuracy and standardization of weights and measures for at least 5,000 years. The current system of international agreements on weights and measures has existed since 1875, when the Metre Convention treaty was signed by the United States and 16 other nations. There are now almost 70 member and associate nations.1 The International System of Units, also called the modern metric system, is the legal basis for measurements in almost every country and is in common daily use in every major country except the United States.2
An Impact on Multiple Levels
At the international level, measurement incompatibility is recognized as a serious trade barrier. In the foreword to S.K. Kimothi’s book, The Uncertainty of Measurements, S.K. Joshi discusses the issue of products manufactured in one country that aren’t accepted for use in another.3 The World Trade Organization also addresses it in the Technical Barriers to Trade (TBT) Agreement.4 Article 5 of the agreement recognizes the right of each country to establish appropriate, fair and equitable standards for protection of its environment, public safety and health interests without giving domestic products an unfair advantage. It also expects member countries to minimize barriers by having conformity assessment arrangements.
Joshi says these conformity assessment arrangements address the operation of calibration and testing laboratories in conformance to ISO/IEC 17025 and the operation of manufacturing and service organizations in conformance to the ISO 9000 series of standards. Article 6 of the TBT Agreement established the system of international mutual recognition arrangements among conformity assessment bodies.
On the national and state levels, historical records show virtually all nations regulate weights and measures. For example, one of the promises acceded to by King John in the Magna Carta was the establishment of a single system of weights and measures throughout England.5 In the United States, establishment of uniform national weights and measures can be traced back to Article IX of the Articles of Confederation in 1777.6 Ten years later, the same governmental authority was added to Article I, section 8 of the U.S. Constitution.
Today, the federal government regulates many measurements and has several calibration requirements. Federal regulations cover areas such as accuracy requirements for radio station transmitter frequencies, aircraft altimeters and automobile speedometers, conditions such as ozone and other pollutant levels in the air or water, and occupational health and safety. In most cases, any measurement taken to assess compliance with a regulatory requirement must be made with a calibrated instrument.
In the United States, each of the 50 states, plus American Samoa, the District of Columbia, Guam, Puerto Rico and the Virgin Islands, has an office of weights and measures. These offices regulate weighing and measuring instruments used for commerce in the state. Some examples of measuring devices regulated by the states include electricity meters, gasoline pumps, supermarket scales, parking meters, and rulers and steel measuring tapes. All these devices measure products or services you buy because the state wants to ensure you get what you pay for.
In most industries, using calibrated instruments is important for financial reasons. Good measurement quality is essential to minimize the costs of production processes. Measurements are useful only when they are made at the correct time and place, have sufficient accuracy and precision for the task, and are repeatable and reproducible. If these conditions are met and the data are recorded and used appropriately, the measurement data can aid management in making important business decisions. Accurate data can help reduce process variation, scrap, rework and other costs of poor quality. However, good quality measurements can only be achieved if calibrated instruments are used.
Calibration, as part of an overall measurement management process, reduces the risks associated with measurements (such as form, fit and function), regulatory requirements and international acceptability. Measurements made with uncalibrated instruments could conceivably result in various legal liability issues. It is not economically possible to eliminate the risks, but a good measurement management process can quantify the level of risk and make it visible to top management. ISO 9001 refers to ISO 10012 as the relevant guidance for a measurement management system.7,8
What, exactly, can a calibrated weighing device do? Here are some examples:
- A scale can
be used to make mass measurements that are part of
an interlaboratory comparison among several national metrology institutes (NMIs). The results can provide assurance of measurement comparability at the international level.
- An NMI can calibrate mass standards using the same scale for state, corporate and independent commercial calibration standards labs that use them as transfer standards.
- Manufacturers of package weighing instruments can use their own standards, which are calibrated using the transfer standards, to check and adjust their products. If their standards are not calibrated properly, then the scales produced may be inaccurate.
- Weight can affect an international shipping company that recently purchased a package weighing scale in several ways. First, packages are transported in the company’s aircraft. All airplanes have limits on the amount of weight they can carry, and the weight has to be properly distributed so the plane will fly correctly. Weight and balance calculations are a critical part of preflight checks on every airplane.
Second, all packages are, at some point, transported in trucks. Both the truck and the road have weight limits, and states tax or fine truck drivers based on the weight they are carrying.
Third, the shipper charges the customer by weight. If too little was paid for shipping, the customer has to pay an additional fee. These and other reasons require the package shipping company to regularly calibrate its scales to reduce loss from insufficient revenue or increased costs.
- A producer of bulk materials can use a scale to fill packages. The price charged is based on a count, but rather than count a large number of small items, the company uses the average mass and fills packages by weight. If the scale is not properly calibrated, the company could either ship fewer or more items than intended. To minimize both types of loss, the company should calibrate its scale.
- A small business uses a scale to weigh packages to determine the shipping cost. If it doesn’t pay enough, the package will be returned, causing rework. If the company pays too much, it is simply wasting money. (I have never seen a package or letter come back because I paid too much to send it.) Top management has to balance the cost of regular calibration of the scale against the rework cost or the unknown cost of paying too much for shipping.
Calibration can make an impact at several levels: international, national, state, business and individual. Therefore, it is important to remember the dedicated men and women at the heart of the system who strive to provide their customers with the best possible calibration service in a timely manner and at a fair price.
REFERENCES AND NOTES
- International Bureau of Weights and Measures, www.bipm.fr/en/convention.
- United States Metric Association, www.metric.org.
- S.K. Kimothi, The Uncertainty of Measurements, ASQ Quality Press, 2002.
- World Trade Organization, “Agreement on Technical Barriers to Trade,” www.wto.org/english/docs_e/legal_e/legal_e.htm.
- National Archives and Records Administration, Magna Carta exhibit, www.archives.gov/exhibit_hall/featured_documents/ magna_carta/index.html. See clause 25 in the translation of the Magna Carta as reconfirmed by King Edward I in 1297.
- Erik Bruun and Jay Crosby, Our Nation's Archives, Black Dog & Leventhal Publishers, 1999, pp. 138-142.
- ANSI/ISO/ASQ Q9001-2000: Quality Management Systems: Requirements, note to clause 7.6, ANSI/ASQ, 2001.
- ISO 10012:2003: Measurement Management Systems—Requirements for Measurement Processes and Measuring Equipment, International Organization for Standardization, 2003.
GRAEME C. PAYNE is the president of G.K. Systems Inc., a technical consulting company near Atlanta. A Senior Member of ASQ, Payne has been working in electronic calibration and product testing since 1981. He is a certified quality engineer, calibration technician and quality technician. He is also chair of the Measurement Quality Division and a member of NCSL International.