Tuesday, 21 August 2018

sensor - Does this loadcell's creep mean that I can not let a constant load on the loadcell?


I want to build a connected scale that I can set coffee powder (for example) on it and check over the internet how much of coffee I still have without going to see it.


Usually all loadcells have a creep factor, like this one, which has a creep factor of 0.1%FS/10MIN Does this mean that the output will decrease by 0.1% each 10 minutes at full scale? If this is true, then the connected scale is not a viable product?



Answer



Typical creep (parameter "1") of a Vishay load cell over the stated 30 minute interval.


enter image description here



The Vishay document states:



OIML recommendation R76 requires a 30 minute test and specifies an error limit for this time period, as well as the last 10 minutes (20 to 30 minutes). NTEP requires a one hour test and specifies an error limit for this period.



OIML is "Organization Internationale de Metrologie Legale" (International Organization of Legal Metrology) European standard.


NTEP is "National Type Evaluation Program" of NIST (National Institute of Standards and Technology) US standard.


You might expect inexpensive load cells would not have full accuracy specifications for "Trade" use, but most should behave reasonably and not creep much after the first 10-20 minutes.


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