Not satisfied with inductive sensor? I am now!
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I'll start off with the caviet I am a number chaser, so this may be over the top for many...
I have several of the standard NPN normally closed ljXXa3-4-z/bx sensors from 12 to 18mm. I got them to fairly well being VERY selective with low voltage drop diodes. I was just never satisfied with their performance particularly the response on aluminum plates, the 500 Hz response time, and their spec sheet repeatability (or drift). The response time has irked me for a long time, because of this. Let's say your probe speed is 5 mm/s, that means your result can vary by .01 mm just by virtue of how fast it responds. After doing some thinking over time and just poking around with what's available, I decided I could affordably pick two of my concerns and address them. I picked up an IE5390 sensor off of E-bay for $20 (it's normally a $100+ industrial sensor). Specs for it are PNP normally open 8mm K=1( ie all metal) inductive sensor with 1kHz switching freq and 1.5mm (max) sense distance.
After getting it installed and adjusted (I mount mine on a lockable ball hinge so I can adjust to get uniform triggering in the X and Y against a small metal cylinder, every little bit matter when dealing with Delta printers), I have +/-.0015 mm repeatability when probing now*.
I'm VERY satisfied with the results and my G32 bed leveling is down to .014 (It would be better but I have mag-arm issues that I need to address next according to the ripple in G29). I believe that the response frequency was one of the primary contributors to the increased performance. You can find inductive sensors with up to 5 kHz switching frequency, but I couldn't find any good deals on an all metal one.
So I'd though I'd share my experience since I haven't seen people go into the higher quality inductive sensors out there. I hope some of you find this interesting and possibly helpful.
*Custom Rostock Max Metal, 0.9 deg steppers, Duet Wifi, 20 tooth pulleys, 0.0015625 theoretical microstep resolution.
