Calibration Weights

Calibrated weights and test weights are two expressions for the same thing. Calibration weights and test weights comply with OIML and ASTM guidelines and can be purchased with or without a calibration certificate.

While there are different types of weight construction, the main difference between balance calibration weights and scale calibration weights is the nominal weight value. In the laboratory, weighing instruments are often referred to as balances. For such applications, METTLER TOLEDO’s weight portfolio includes balance calibration weights from 0.05 mg (50 µg) up to 50 kg. In industry, weighing instruments are often referred to as scales. For these applications, we offer weights for scale calibration from 1 kg up to 5 tons.

If you are unsure which calibration weights you need, our free GWP^® Recommendation service helps you select the right weights for your application and process accuracy requirements. For a more comprehensive assessment of your needs, our GWP^® Verification service provides you with a full routine testing and calibration schedule, including the test type, test frequency, calibration weights, and weight class according to your precise needs.
Contact your local METTLER TOLEDO representative for a free GWP^® Recommendation.

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Read more about our GWP^® Verification service here:

Weighing Devices - Verifying and Maintaining Accuracy Over Time

OIML single calibrated weights have classes E1, E2, F1, F2, and M1.

ASTM single calibrated weights have classes 1 to 4.

Yes, single calibration weights can be purchased with or without a calibration certificate. However, if it is necessary for you to be able to prove traceability, you should always purchase balance calibration weights and scale calibration weights with a calibration certificate.

To test your balance or scale, only two calibrated weights are required. We recommend using one calibrated weight equivalent to the capacity of your weighing instrument and a second calibrated weight equivalent to around 5% of the capacity. You may wish to use a third weight to test your balance around a specific weight value. You can purchase our calibrated weights separately, or our CarePacs offer a cost-effective solution. Each CarePac contains two selected weights and weight handling tools appropriate to the weight value together in one convenient easy-clean plastic box. However, if you have many balances or scales with different capacities, a full set of calibrated weights may be the more cost-effective option.

Spheres are used because the volume can be determined according to the definition of volume by a length measurement. Silicon (Si) spheres have the same homogenous atomic structure as a perfect diamond without voids or dislocations, so the density is more accurate than other materials. This is why a silicon sphere with a homogenous atomic structure serves as a reference for specialized volume measurement.

There are some golden rules for handling calibration weights for scales and balances that also apply to all knob, sheet and wire weights:

1. Store in the container provided
2. Keep clean
3. Acclimatize before use
4. Used dedicated tools for handling
5. Never touch with bare hands
   
   

For further information and more valuable tips:

Watch our video:

Download our weight handling guide:
Correct Test Weight Handling Guide: 12 Practical Tips

As a handy reminder, download our weight handling poster to hang on the wall close to your balance or scale:
Laboratory Poster: 10 Practical Tips for Correct Test Weight Handling

Yes, you should never touch a calibration weight with your bare hands. This prevents oils and dirt being transferred to the surface of the calibration weight and protects its integrity over time. Appropriate weight handling tools are provided with our weight sets and CarePacs or the tools can be purchased separately.

View our tools and weight handling accessories

Monobloc calibration weights are made in one solid piece whereas a calibration weight with an adjusting cavity has a top that can be removed to reveal the cavity within the body of the weight. During the weight calibration process, minor adjustments can be made to the overall weight value by adding or removing special material. This should only be carried out by accredited calibration laboratories.

METTLER TOLEDO offer monobloc calibration weights as well as calibration weights with an adjusting cavity. However, the construction depends on the weight class as can be seen in the table below.

METTLER TOLEDO offers both sheet and wire milligram calibrated weights. However, the shape depends on the weight class as can be seen in the table below. In the higher weight classes, E1 and E2, only wire weights are available. This is because their smaller surface area, in comparison to sheet weights, makes them less susceptible to the effects of air buoyancy and the influences of air drafts. Hence, their higher level of accuracy.

Calibration of weights on a regular basis is essential if accuracy, repeatability, and traceability are important to you. Scale calibration weights and balance calibration weights will need to be sent to a special service provider to be calibrated against weights of a higher weight class. You may find it useful to have a second set of calibration weights so that you can continue to test the performance of your balances and scales while the other set is being calibrated.

Yes, METTLER TOLEDO offers the calibration of weights in several countries around the world. Please contact your local representative for further information.

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METTLER TOLEDO scale calibration weights and balance calibration weights are made from premium stainless steel to provide extremely high resistance to corrosion. Monobloc calibration weights are designed for long-term stability, which is further enhanced by electrolytic polishing processes. Calibration weights with an adjusting cavity simplify weight adjustment for calibration laboratories who can access the cavity without the need for highly specialized equipment.

Yes, our calibrated weights are intended for routine testing of balances and scales.

There is no difference. METTLER TOLEDO calibrated weights can be used for both routine testing and the calibration of balances and scales.