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What is Test Weight for Scales and Balances?

Scales and balances need to be calibrated regularly to ensure they are accurate. To calibrate a scale or balance, you will need reference weights with an accuracy class greater than the scale’s resolution or readability.

What is a Test Weight?

A test weight is a standard mass used for calibration of scales and balances. It is designed for safe handling and is typically provided with a certificate of traceability from a national laboratory or similar authority.

The type of test weight required depends on the accuracy class of the scale or weighing instrument. To determine the correct weight class, it is necessary to know what the instrument is intended to weigh and its maximum capacity.

Calibration weights are usually labeled in units of measurement such as kilograms or grams, although they may also use avoirdupois or metric measurements. The precise mass of a test weight makes it suitable for calibrating a scale and ensuring subsequent measurements are accurate.

Changzhou Fuyue Weight Co., Ltd offers an extensive portfolio of calibration weights from 1 milligram to 5 tons in both OIML and ASTM standards. Large stainless-steel weights are available as individual weights or sets. Smaller precision weights are designed to be held in a hanger and can accommodate slotted weights or cylindrical weights that fit into them.

How do Test Weights Work?

Test weights allow you to perform routine testing on your scales and balances between scheduled calibrations. These tests can help identify non-conformance with your weighing process requirements early, avoiding expensive problems later.

While test weights are not as precise as a calibration weight, they should be treated with care to ensure their longevity and accuracy. Ideally, they should be stored in their protective case and kept away from moisture and other environmental contaminants that could affect their readings. Avoid touching test weights with bare hands as this can produce scratches on the base that decrease their mass, which could result in unreliable measurements. Use clean forceps or tweezers to handle the weights when performing daily weighing checks and store them in a secure, protected case when they are not in use.

What is the Difference Between a Test Weight and a Calibration Weight?

Buying test weights can be confusing, particularly if you’re not familiar with terminology such as “class”, tolerance and certification. It’s important to understand the differences between these different types of test weights before you start shopping.

Class test weights are made from stainless steel and can be used for most industrial scales. They’re ideal for washdown and hygienic environments. These high-precision test weights should only be handled with gloves or tweezers.

OIML and ASTM calibration weights are often cast iron or stainless steel and come in different sizes and accuracy classes. They’re best suited for use in industrial applications or specialized scales like cranes. These weights must be handled with care and kept in a lined case or box in a non-condensing clean environment to avoid damage. They are often accompanied by documents to confirm their traceability and accuracy.

How do I Buy Test Weights?

There are different classes of test weights available to meet the accuracy requirements of the weighing device being tested. The class required will be determined by the weighing devices maximum capacity, weighing tolerance, and safety factors.

Many users don't have the cost-effectiveness to maintain their own test weights and require routine testing of their scale or balance by a professional service technician. This allows companies to identify any issues that could affect the integrity of their weighing process and address them quickly.