Andrew,
Thank you for reaching out. There are a few tools that are free online that will be useful here.
For a quick check, we can first refer to the DRV5012 Product page. There is a field calculator tool that will give you an estimated distance based on the Maximum BOP specification for the device. This provides the estimated distance where all devices should trigger by. Entering your magnet parameters I see that we expect to trip the sensor very close to the resting position d2.
In addition to this tool, there are a few more advanced options:
K&J magnetics has a very useful 2D calculator tool that will estimate the field at a specific location when you provide it the coordinates.If you can estimate the relative separation of the sensor and magnet during transit, you should be able to find an approximate trip point.
https://www.kjmagnetics.com/fieldcalculator.asp
Also, for a more detailed simulation, you might consider using FEMM. It is an open source tool available online. You can construct a more detailed simulation with this tool.
