Calibration of Stylus Profilometers

Have you considered using an Atomic Force Microscope (AFM) for such a calibration? or perhaps you might use some "grid" of those sold for AFM calibration purposes. Typically I think they consist in silicon micromachined elements with trenches of well-determined depth.

No I have not. In fact I have never heard of an AFM. But I will certainly look into it. Any direction that you can provide would be appreciated. Thanks.

I too was unfamiliar with this device until now. A quick Wiki search offers the following......here

http://en.wikipedia.org/wiki/Atomic_force_microscope

Very interesting stuff!

Thanks for your response. They are interesting devices, but I expect that they are a bit pricey for my industrial strength application -- surface roughness of polished ceramic face seals.

If your existing equip has accuracy and range to use a finer standard - then perhaps you can calibrate your equip to a standard used for that equip (AFM).

I think that they are too small and too fine (in terms of pitch), but I am going to take mtcuberes suggestion and try one.

Here is a link describing one company's standards:

http://www.spmtips.com/tgz/.

(btw, I agree with Einstein)

If you use a stylus you should consider that the radius has a cutting effect if the roughness is small with respect to it. In the range of 0.1 to 0.5 µm you should have a radius which should be at the contact end with a radius less 1/5 of the roughness it self. do you have it?

The short answer is no, I do not have a stylus radius anywhere near 1/5 of the roughness range that I am measuring. In fact I have never heard of a stylus for a profilometer having a radius that is so small. I an using what is considered to be a standard stylus of 5 microns radius. What is the basis of your saying that it should be 1/5 of the roughness?

If the radius is not small enough it will not follow the true profile of the roughness. You will get a "smoothing" effect i.e. the roughness you record is less than the true one. In fact it is not the roughness itself which limits but the "wave length". Since the two are usually connected...

The error is made in the valleys not on the peaks. You will record correctly the peaks but you will follow the "valleys" only as deep as the radius will allow it.

Imagine a "V" the smaller the radius the deeper you can go in and come nearer to the apex.

nick name,

I understand what you are saying, and it certainly makes sense. There are 2 problems that I face with what you point out: 1) the profilometer that I use has styli that go down to 1 micron, but not .1; 2) the surfaces that I am measuring are porous molded ceramics, which cause too much scatter even with a 5 micron stylus. Googling has led me to one company that makes a high resolution profiler that has styli down to .1 micron. I will take this all into consideration regarding our surface characterizations. However, I am still left with the issue that started this discussion thread: where can I find calibration standards in the .1-.5 micron range? Thus far, I have learned of atomic force microscope standards, that may work for my application.

Thanks for your input.