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I'm trying to accurately measure height data during the bench press exercise. I'm using a barometer and a thermometer sensor attached to the bar to capture the data. To calculate altitude, I've been using the hypsometric formula.

The sensors I'm using start and stop recording data at the same position - However, the calculated starting and ending altitudes are completely different (more than 0.3 m off).

Here is a sample of the data that I've captured. The graph library messed up the y axis, but it should be 949.xx hPA:

enter image description here

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The resulting altitude calculations of the pressure and temperature data. enter image description here

Am I using the hypsometric formula correctly here? Or is this just a case of bad sensor data? I've seen this similar pattern happen in other readings I've taken.

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2 Answers 2

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The formula seems to be of a meteorological context, it is an approximation, that should work on length scales larger than 0.3 meters.

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    – Community Bot
    Commented Jun 20, 2022 at 22:31
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I think the formula you are using is not especially accurate for the small ranges you are moving.

The temperature will impact the pressure measurement but you have a pretty small temperature change, and it looks like it may be over correcting.

One suggestion is that the height at the bottom of your motion when the bar is on your chest is a known reference point. So since that height is known you can adjust your correction so those points are at the same height. I assume your arm at full extension might also give you a set of points that are the same height.

Another thing you can do if you have another sensor is to have the second sensor not move and the use that data to understand how to correct for the changes in pressure due to the temperature change.

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