Precision on proximity sensors

hello,

I just ordered some proximity sensors (hall type) for my Z probe. I ordered with 10 mm sensing range so that they can reach through the glass and sense the heated bed.

The 10 mm is given with a tolerance of +- 15%. I assume that this 15% is the absolute value and not the precision.

Does anybody know what kind of precision I can expect?

Remembering this funky chart:


I don't care so much about accuracy as in the end of the day it does not matter if it is sensing at 9 or 11 mm. But I need it to be the same thing all the time.

I am buying this one (but not from that supplier, the Aliexpress where I found it cheapest only list a chinese spec.)
[www.ibuyla.com]

Edited 1 time(s). Last edit at 05/05/2015 06:12PM by LarsK.

What is your bed made of? You only get 10mm range when the metal it's sensing is iron or steel - if it's aluminium you can only expect around 4mm, maybe less.

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David J
What is your bed made of? You only get 10mm range when the metal it's sensing is iron or steel - if it's aluminium you can only expect around 4mm, maybe less.

The heated bed is the MK2a.

You are right

It has an reduction factor of 0.3 to 0.4 for copper ( see: [www.fargocontrols.com] and [blog.pepperl-fuchs.us] )

I did test sensing the heated bed with some 2 mm range sensors that I have and these did not seem to have a 70% reduction. But since my glass is 6 mm then I am already in problem with less than 0.7...

Hmf... Inconvenient. But according to mentioned sources aluminium is 1 so I will just put a alu sheet below the plate. That will also insulate.

Would still like to know about the precision I can expect

Thank you so far.

I was referring to aluminium foils in the above. With reference to:




Why is alu foils so much better then plain alu sheet? No idea, so much to learn.

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LarsK
Why is alu foils so much better then plain alu sheet? No idea, so much to learn.

Aluminum foils don't dissipate the eddy currents as quickly as aluminum plate, so the sensor can detect the material better.

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cdru

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LarsK
Why is alu foils so much better then plain alu sheet? No idea, so much to learn.

Aluminum foils don't dissipate the eddy currents as quickly as aluminum plate, so the sensor can detect the material better.

Interesting...