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 ACCURACY IN PERCENT OF READING VERSUS PERCENT OF FULL SCALE

A device with a specification of accuracy as a percent of reading will provide a more accurate device, if used at lower loads, than if the same percentage is specified as a percent of full scale for the purchased load cell. This is important to keep in mind since most load cells are specified in percent of full scale and may produce much higher than expected errors when used at a load which is a small part of the full range of the device. 

For example, a 1lb load cell with a 0.1% of full-scale accuracy, at half full scale or 0.5 lb. could have an error of 0.001 x 1lb. (full scale) = .001 lb.  That would be 0.2% of the 0.5lb load or twice the percent error to be expected at full scale.

A 1lb load cell with a 0.1% of value accuracy at 0.5 lb. would have a maximum error of 0.005 lb. which is half that of a device which has an error specified as percent of full scale and achieves the expected accuracy at lower loads.

Again, the 0.1% of full scale device, on the other hand would be come less and less accurate in percent of applied load as that measured load becomes a smaller percentage of full scale.

If the load cell is only used at the upper end of its load range, then the difference between a device specifying accuracy as a percentage of full scale as compared to a percentage of reading might be small.

If a load cell must measure load over a wide range, then the user should specify accuracy as percent of reading at the load to be applied to get the accuracy they need.

 

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