The full increment weights should be readable ever time they are added. The half weights MAY or MAY NOT trip the beam and this is within the margin of error. This can be continued for as long as there are test weights up to full capacity.Īt each calibration test point add a test weight equal to one half the smallest beam increment and then a test weight equal to the beam increment. Then add a beam increment counter poise and check at zero with the same test weights. This double check is not an official test but will tell you if the scale and added poise are acurate in a limited range.Īfter zeroing the scale add test weights equal to the full beam marking and check with the sliding poise. The first tests I ran on my 1000 pound Fairbanks was to zero, then weighed the additional counter poise (5, 2 and two 1 pound weights) which are more accurate than the scale could measure.Įven after purchasing hundreds of pounds of test weights I am far short of enough to run a full test on any of my larger fairbanks scales. Some writers recomend a mid range test OR testing at the most commonly used range with any object of known weight. If testing for yourself (non-commercial) and you do not have suitable weights to run the full range test then do what youy can. This should be signed and dated by the test operator. The worksheet with these values becomes the calibration test record or certification. Error is calculated in percent and recorded. The test weight is recorded and the measured value. Standard testing is done at 25%, 50%, 75% and 100% of full capacity. If after zeroing, the scale is off at the full beam scale with an equal calibration weight in place then the poise hanger may be at fault and require adjustment. Often these hangers are a specific weight to counter balance the weight of the platform. On scales with a poise hanger it should be in place and the correct hanger. ~70☏ (20☌) is the standard temperature for the use of virtually all precision devices. While not stated in the standard methods the test weights should also be normalized in place. I also purchased an antique set of brass balance weights in the sizes 4, 2, 1, 1/2 and 1/4 pounds and a NEW 2 oz (1/8th pound) weight.įor accurate testing the scale should be tested in the place and environment it will be used in.Ī 24 hour normalizing period is recommended after moving and setting up a scale including any leveling. This gives the capability to test up to 205 pounds in 5 lb increments. This set of weights includes rectangular cast iron weights with integral handles in the sizesġ00, 50, 20-a, 20-b, 10, and 5 pounds. I also planned on testing these against each other and to the scales on hand. However, many of these had testing and certification marks and could be assumed to be fairly accurate (or had been) if not obviously worn or broken. Weights should be checked for condensation and dried if necessary.įor my purposes I purchased used undocumented weights on-line. The red is my added comments and suggestions.Īll official and critical testing should be done with weights traceable to your country's Bureau of Standards and traceable to International standards.ĭocumentation should be on file and up to date. National Institute of Standards) and other documents. Since I have numerous odd scales not used in commerce and one I am repairing I want to do my own testing. If you don't use your scale in commerce and just want to know if it is accurate then you can do your own testing. However, testing is usually done on an annual basis.
In general the springless platform scales built by Fairbanks (the oldest scale company in North America) and others are durable and rarely do not perform acurately. The scale is then labeled "Certified for Trade". If you sell anything by the pound, ounce or kilogram then your scales must be certified by your local bureau of weights and measures. Turn a screw or rotate a weight on a screw until the scale zeros and then you are done.īut commercial law requires that the scale be tested within its range and certified for use in commerce.
Scale calibration adjustment is relatively simple.