Calibration weights ensure scales and other devices offer accurate results in the lab. However, they calibrate different instruments and are made of different materials.
They are given a class based on their accuracy. This article looks at various classes and considerations when choosing one. What are Calibration Weights? Calibration weights check a scale’s accuracy. They are commonly certified by industrial laboratories or bodies such as ISO, ANSI, NIST, and ASTM. Each weight often has a precise mass, ensuring the scale at hand is working precisely. And to ensure they meet international or national standards; they will come with supporting documents. The documents contain information such as cavities, surface finishing, design, tolerance, and material. Calibration weights can also check the accuracy of balances and weight cells. As you’d expect, the weights are used for different reasons, with those used in scientific labs having a higher benchmark. Classes of Calibration Weights Generally, there are three main calibration weight classes. They include NIST, ASTM, and OIML. NIST The National Institute of Standards and Technology (NIST) class F weights are standard in industrial settings. They verify Class III, Class IIII, and non-designated scales. They are common in manufacturing and warehouse settings where large products are produced or shipped. Since they are not accurate enough, scientific laboratories don’t use them. ASTM ASTM International is a non-profit organization dealing with the production of voluntary consensus standards. The organization has developed ten weight classes: Class 000 to Class 7. The Class with the lowest number has less tolerance. Laboratories will often use Class 000 to Class 4. ASTM classes are most common in USA laboratories.
OIML The International Organization of Legal Metrology (OIML) is an international organization dealing with the provision of standards and systems in the metrology industry. They ensure adherence to harmonic and legal procedures, with the lowest Class being the most accurate. OIML classes are E1, E2, F1, F2, M1, M2, and M3. They are popular outside the US.
While these are the most common calibration weights, some manufacturers like Troemner have unique Class weights. They are UltraClass Platinum, UltraClass Gold, and UltraClass. Obsolete classes The following classes are no longer in use.
Factors to consider when choosing calibration weights Material Cast iron and stainless steel are often used for OIML Class M1 and M2, as well as NIST Class F and ASTM Class 6 and 7. Cast iron is recommended for weights that are 10 kg or heavier. If the weight is in metric units, it will have gold paint, while avoirdupois units will have silver paint. Weights between 5 kg and 10 kg can be stainless steel, steel, or iron. For weights between 5g and 5kg, they should be of a material with a hardness of Rockwell B80 and above. All calibration weights should be of wear and corrosion-resistant material. OIML E1, E2, and F1, as well as ASTM 000 – 4, are of a highly polished material such as stainless steel. As such, one should handle them with care. We recommend using tweezers or gloves. Shape Weight scale calibration uses classes of different styles, the most common being a leaf, cylindrical, slotted, and grip handle.
Measurement units For best results, you should use calibration weights with similar units as those of the scale. For example, consider buying a metric weight if the subject is in metric units. Magnetism Avoid buying weights with magnetic material to avoid scale damage and incorrect calibration. Test load configuration To avoid errors, use a few calibration weights. For example, if the test point is 20 kg, use one 20kg instead of two 10kg weights. Weights certification The application will require calibration weights to come with a certificate. It confirms they are accredited, hence will offer accurate results. Some typical accreditations are:
Construction Typical calibration weights are made of one cast metal piece. However, weights such as Troemner’s 1g and above UltraClass consist of two parts. The calibration weights consist of a knob and a body. If you would like to learn more about calibration weights or weight scale calibration Biotechnical Services Inc. has the know-how to help you out. Get in touch with us today. Original Source: https://www.biotechserv.com/a-brief-guide-for-standard-calibration-weights/
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