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Inductance/capacitance sensor 'confusion'

Posted by Cougar281 
Inductance/capacitance sensor 'confusion'
February 17, 2020 06:05PM
Everything I've read about the induction sensors we use with 3d printers says that they're 'generally' meant to read thick steel, and that they can be a bit 'less sensitive' to the relatively thin aluminum used for build surfaces. The SN04-N sensor that came with my printer always sensed real close to the build surface - probably 1-2mm off of it. I was doing some searching, looking into sensors out there, I picked up a Taiss 'LJC18A3-H-Z/BX' that's supposed to be good for sensing from 1mm to 10mm. I thought 'great, with an adjustable sensing distance up to 10mm, this sensor should be able to be used with a piece of glass between it and the build plate. Well, it seems to work, but not quite how I expected.

Apparently this sensor is a CAPACITANCE sensor, not an INDUCTANCE sensor, and as a result, it can sense things other then metal. After I put it in place and set the 'home' position high enough off the aluminum build plate to allow a sheet of glass to slide under the nozzle so it wouldn't crash into the glass on homing, I was a 'bit' surprised to find that when I re-homed it, it homed higher, as in it was homing off the glass, not the aluminum.

This seems to be a bit of a win for bed leveling when using glass as a build surface... Is there any reason not to use this kind of sensor over an inductance sensor?
Re: Inductance/capacitance sensor 'confusion'
February 17, 2020 07:01PM
"However, all types of capacitance sensors are affected by capacitance changes in the surrounding environment. Changes in humidity or temperature can interfere with the operation of the sensors, in some cases stopping the sensor from working altogether."
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