by Henry Zumbrun, Morehouse Instrument Company
Load cells are subject to numerous factors that can affect their performance. Some factors include the design of the load cell, the readout used with the load cell, environmental conditions, cable length (if only a four-wire cable is used), overloading, adapters, stability, alignment, and the test method. There are enough load cell intricacies that impact measurement uncertainties to write a book strictly on that subject, which we have already done.
Management often wants to spend the least on equipment and push equipment such as load cells to their lowest operational level. Who can blame them as who would not want less equipment with better performance? Using equipment such as load cells below 5 – 10 % of their capacity or lower, such as 2 %, is a frequent practice that demands attention as it can significantly impact measurement uncertainty as a percentage of applied force. This article examines the impact on measurement uncertainty of using a load cell as low as 2 % of its rated capacity, compliance with ISO 376 and ASTM E74 lowest force point criteria, and how to uphold the reliability necessary to maintain a specific calibration interval. What holds for these standards can apply to any load cell.
