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Calibration Weight Classes will let you know the tolerance of the calibration weight you are using. There are two major governing bodies that assign classes to weights: ASTM International (Formerly the American Society for Testing and Materials), OIML (International Organization of Legal Metrology).
By raw definition, weight tolerance is the difference between the maximum and minimum values of a given nominal value. Click the link to read more about calibration tolerances as determined by ASTM, OIML.
Check for contaminants, scratches, and discolorations. Be sure to look on the bottom of the weight, since occasionally matter attaches itself to the bottom and it may go unnoticed.
The weight error is the measured value correction plus its associated uncertainty. You can use the weight to determine the balance error, but you can never use the balance to determine the weight error. This means that if you want to determine the weight error, you must have a mass standard with a certificate that enumerates the value correction plus its associated uncertainty or you must have another certified weight to make a comparison. If you want to determine the balance error, it is relatively easy if you have a certified mass standard with the aforementioned data. With this information you should know how the weight performs plus or minus its associated uncertainty value. Therefore, the balance error can be deduced by performing multiple measurements to see how well the balance executes a measurement. This, of course, can be recorded and tracked over time, so that a balance uncertainty can be ascertained as well.
It is recommended that if you use your weights infrequently to moderately, you should have them recalibrated once a year. However, if your weights are used very frequently or several times a day, then you should have them calibrated once every six months. Although there are no standards or regulations that specifically address recalibration intervals, this is the industry norm in order to ensure that these standards are still within their specified tolerances. It is not unusual to see significant “as found” failure rates on those weights that are not recalibrated on an annual basis.
LEIHAU is a leading supplier of high precision calibration weights, scale weights, and test weights. Flexibility in production allows us to produce both small and large series at attractive prices.
