Test / Calibration Weights

About Test / Calibration Weights

Accuracy is vital as weights are used to calibrate scales and other weighing equipment, an inaccurate weight, in turn, will have a knock-on effect and will produce erroneous scale calibration. A calibrated set of weights allows the balance scale error to be assessed and corrected to the highest accuracy.

The periodicity of calibration is dependent on weight use and the accuracy class of the weights but annual calibration is generally advised.

The International Organisation of Legal Metrology (OIML) is an intergovernmental organisation that provides standards and systems to harmonise legal metrology procedures. From lowest (most accurate) to highest tolerance, the OIML classes are E1, E2, F1, F2, M1, M2, and M3. Most laboratory applications require OIML weights of Class F2 or below.

FAQs

• What are calibration weights used for?
  Calibration weights test the accuracy of scales and balances. Providing a known mass helps ensure that the measuring device functions correctly and gives accurate readings. They help verify whether a scale is over- or under-measuring.

• What are the different classes of calibration weights?
  Calibration weights have two primary standards: OIML and ASTM. OIML classes range from E1 (the highest precision for ultra-sensitive balances) to M3 (used in less demanding industrial applications). ASTM weights follow a similar system, with Class 0 for ultra-precise measurements in metrology labs, going down to Class 3 for routine industrial use.

• Can I calibrate my scale with any weight?
  Calibration requires specific certified weights that meet the precision requirements for your scale or balance. Using uncalibrated, uncertified weights or weights that do not correspond to the necessary standards can result in incorrect measurements.

• What is the difference between OIML and ASTM calibration weights?
  OIML (International Organization of Legal Metrology) weights adhere to international legal metrology standards. ASTM (American Society for Testing and Materials) weights follow U.S. standards tailored for American industries.

• How does temperature affect calibration weights?
  Maintaining a consistent temperature establishes reliable and accurate calibration of weighing instruments. Fluctuations in temperature can cause the weights to expand or contract, resulting in inaccurate readings. Using calibration weights in a temperature-controlled environment allows them to adjust to the ambient temperature before use.

• What is the difference between calibration and verification?
  In essence, calibration focuses on making adjustments and verifying the accuracy of the equipment against a standard. Verification establishes if the equipment is functioning correctly and meets specifications without necessarily making any adjustments.

• How do you know when a scale needs recalibration?
  When your scale displays inconsistent readings or has endured a strenuous period, it is generally a good time to recalibrate your instrument. Significant environmental changes, physical damage, and the amount of time since the last calibration are also good indicators.

• What materials are calibration weights made from?
  Various materials are involved in constructing calibration weights. Stainless steel is a regular choice because of its corrosion resistance, durability, and stability. Other popular materials include aluminium and brass.

• How do you store and maintain calibration weights?
  Store weights in a clean, dust-free environment with controlled temperature and humidity. Use cushioned containers, avoid direct sunlight, and clean regularly. Handle with gloves, check against standards, and replace compromised weights. Avoid exceeding weight limits to prevent deformation.