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Joe Albright's avatar

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Top*: https://albrightj.substack.com/p/e467-validation/

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Start Notes: https://albrightj.substack.com/p/e467-validation/comment/167452017

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Charles Hoppe's avatar

I have a question, maybe more of a comment, that could apply to both the second harmonic and the Slow Rate Ramping topics. The assumption appears to be that the dynamometer and the UUT cell are both linear from zero through the lower load point and to the upper load point. I have never seen this to be the case. We setup the static calibration specific to the two end points because of this. If the load cell has a slight concavity to its curve and the dynamometer a slight convexity (for lack of a better term but it should give the visual. The error seen between them in the middle of the curve would be present and in the same direction every cycle. This would look the same as the second harmonic. If from the low load point to zero the two have different curves this could also explain the error during the slow rate ramp. To analyze this and ensure our model does in fact have an unexplained issue, a static calibration would need to be done with data points from zero to the first data point, I would suggest at least 5 total points including zero and the lowest data point. Also to see errors between the endpoints a static calibration with data taken ever 5% of the span from lower endpoint - 5% of span throughout the span to +5% of the upper endpoint.

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