Rare earth N42 magnets and temperature

Small changes in the gap due to thermal expansion/contraction might be playing a role as well.

Try making a test using a ceramic spacer and running it over the range.

Also, you mention that the magnet strength is of concern - what about changes in the hall effect sensor?

edit:

per they lose 0.1% per degree C and there are special classes of material with higher temp resistance.

Are you using them with a ferrous magnetic field concentrator?

edit 2:

More detailed info

Neo has a huge tempCo.
And it depends greatly on the operating slope.
Br only changes (alpha ~ 0.12%/C) about 5% over your range, but the Hc changes (beta ~ 0.7%/C) more like 30%.
If this is operating a low slope (as is common with RE materials) you could even be dropping below a knee at you high temp.
Check to assure that you are at a high slope.
This is one reason that Alnico is still used for high temp application, higher service temp and lower tempCo.
There are doped RE grades that give up Energy Product in exchange for better stability, but they get expensive.


= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

Thanks 3DDave and EdStainless. Some pretty interesting reading.

That should be enough to run some tests.