Good info
@Tecnico. Leave it to you to find and point this out.
I have corresponded with Yuriy about the Samsung tablet issue and have found him to be a very knowledgeable and competent individual.
I confess that I have wondered about how magnetic can achieve its stated accuracy. Quadrature encoding only gets you so far. And the linearity of magnetic fields is never going to be perfect.
I've also come to believe that glass can only be as good as its base etching.
Scale can be a confusing thing. We humans can do a fairly good job of judging scale within our normal sphere of experience, but that tends to fall apart as things get very big or very small.
I did some basic qualification type testing on my Ditron 1 micron magnetic scales when I first installed them. I confess I was shocked at how good they were. Each and every measurement repeated EXACTLY. Within the limits of my testing equipment, they were also bang on for accuracy.
But I do not have the metrology equipment required to test the Ditron scales over long distances. And I certainly don't trust my leadscrew and handwheels. So I had to accept them as is. I rationalized that it was inevitably "good enough" whatever it is. Longer lengths are inherently fraught with accumulated errors. But does it really matter if a part is exactly 30.000mm long or just measured 30.000 but is actually 30.002?
I suppose it does in some situations, but not in anything that I do. It is important to remember that the longer something is, the more it stretches or shrinks with temperature and load. A tenth "might" matter over a short distance but gets lost in the fog at long distances.
For me at least, I am happy with magnetic. They are much more compact than glass and easier to install. That's worth a lot to me but might not be so important to someone else. The ability to stick a piece of magnetic tape onto a surface without a frame is also extremely valuable.
Iron dust happens all the time in my shop because I mostly work with steel (and..... I have a surface grinder...... LOL!) BUT, I have found that it is a zero problem because it wipes off easily and does not collect on the sensor - only on the tape and even there to a very very minor degree. I even ended up abandoning the need for Shields. With very minor maintenance, I have found that they are just not necessary. YMMV.
Life is full of compromises and glass vs magnetic is just another set of compromises that have to be sorted out by each of us to suit our situation.
I also found it interesting that he said magnetic scales are less costly to produce. They are definitely higher priced when it comes time to buy them. Marketing vs. reality.
I believe I said the same thing way back when. I used it in the context of negotiating a better price. Of course, they will never share that with the world but its a no brainer that a magnetic strip is less costly. They know it too but they wouldn't admit it. However, having an idea of cost is always important when you are trying to negotiate a fair price.
Thanks for sharing this info. I am wiser now.
Edit - I sent Yuriy a private note asking him how he did the testing. I'm interested in duplicating it or at least reviewing it from a scientific perspective.
