Visit http://www.wnet.
Determining Load Cell Range
Rev. C
The specification of load range seems like a simple thing to do, but that is not always the case. The load selection process should include the following considerations:
1) The load range where the required accuracy is needed.
Most loadcells are most accurate at the high end of their range. That is reflected in the fact that most loadcell manufacturers specify the accuracy in % of full scale rather than % of value/reading. Where possible, the loadcell should be selected so that the signal is near the full range of the device when the load of interest is being applied. Most load cells not only are specified in accuracy in % of full range but are only that good down to about 20% of full range. With TAT technology, the accuracy is specified in % of value and the specified accuracy and is good down over the specified range which may be less than or more than 20% of the full range.
With TAT loadcells, it is possible to obtain a very high accuracy and the smaller the specified load range buy the user generally the higher the accuracy is that can be warrantied by TAT. For example, a specification for total digital system accuracy for from 200 grams to 1k gram might be 0.2% whereas a specification for accuracy from 400 to 600 grams might allow a warrantied accuracy of 0.05%.
TAT can also optionally provide software which would allow the load to operate to a higher accuracy over a portion of its range capability on one run and a different portion of it range on another run also to a higher accuracy with the user only having to specify load range to be used during that particular run.
2) In addition to the accurate signal range, the loadcell must also be capable of surviving some level of overload while still retaining full accuracy and sometimes must be able to carrying some even higher overload without physically failing. TAT have as a minimum a 25% overload capability with not degradation in signal accuracy. Much higher overload capability units are available as semi-custom configurations at close to the standard unit price. Overloads as high as 1000% or more are possible in the lower load ranges but usually require an increase in the height of the loadcell and in some cases such high overloads are not available along with highest accuracy specifications.
3) At times there is also a need to consider dynamic loads. Dynamic loading considerations can be very complex and the loadcell manufacturer usually should be consulted if the loadcell must take loads which are highly dynamic.
Copyright © 1997-2000 Total Accuracy Transducers Incorporated. All Rights Reserved.
Home
Tech Notes
Company Profile
Technology
Products
Contact Us