Ordering Weights and Weight Sets

Weights are a tricky subject. To be certain you have the right equipment for the job, consider the following during your next weight or weight-set purchase.

1. How will you be using your weights?
Maybe you simply need a quick reference standard or perhaps you have a Legal-for-Trade application. Use is a big factor in the type of weight(s) and certification you’ll require.

2. What is the minimum/maximum amount of weight you will need at any one time?
Calibration is properly performed using a certain percentage of the scale’s capacity. You’ll need to know the capacity range for your equipment. Also important is the typical range of use. If, on average, you use about half of your scale’s capacity, a weight of a similar value would verify that your accuracy is being maintained.

3. What tolerance are you looking for?
How small is the resolution of your balance or scale? Weights will need to be three to four times more precise to ensure valid calibration and performance. After determining the correct value, refer to the weight tolerance chart in the Rice Lake’s Precision Catalog or reference section of our website to find the correct class of weight.

4. Are there other factors that would impact your resolution needs?
Some industries and agencies are more tightly regulated by the government. This may affect what class of weights you purchase.

5. Do you have requirements such as NIST, ASTM or OIML?
Depending on what country you do business, requirements for traceability and certification may vary.

6. Will you need ISO/IEC 17025 or ISO 9000 laboratory documentation?
Just as weights vary in size, shape and material, certification comes in many forms as well. Understanding your organization’s documentation and traceability needs will help in selecting weights with the proper class of calibration and documentation.

7. What style of weight will work best?
Obviously weights vary in size and mass but they also come in many shapes and materials. Depending on space limitations and application you may be looking for hanging, grip handle, stacking, leaf, or other styles.

8. What is your environment like?

• Indoor/outdoor?
• Wet/dry?
• Breezy/still?
• Corrosive, hazardous, or explosive?
• A clean room?
• Are there biohazard, electrostatic, or magnetic conditions to consider?
• What else is noteworthy?

Environmental factors play a big part in the limitations of your equipment’s accuracy. Weights must be carefully selected to balance both precision and durability needs.

Your existing weights and weight sets should be recertified on a managed periodic basis. The recertification period is determined by a number of factors, including but not necessarily limited to, the environment, frequency of use, demands of the process, quality of the weighing devices in question, age of the weights in question, and handling during use.

For more information on this topic, refer to Rice Lake’s webinars titled ABC’s of Weights or Tolerances and Certificates, featuring industry expert Ann Crowley. Both presentations can be viewed through the Rice Lake website at www.ricelake.com/webinars.

Source: Rice Lake Weighing Systems