Or if you need a cheaper but effective method, you can purchase Dyne pens.
A set of Dyne pens can be used to measure the approximate surface energy to determine appropriateness for direct dispensing of conformal coatings, adhesives, paint, epoxies, etc.
If the surface energy as measured by the Dyne pens is too low, you may then have to treat the surface prior to coating to provide a suitable surface to bond to.
Dyne pens are relatively inexpensive, ranging from around $65-$125 for a set. Here is one I use http://www.accudynetest.com/adtpen.html
I have not tried any others, so I cannot say this is the best or the worst. 
Others may recommend other Dyne Pen sets. 
My esteemed colleague and friend Dr. Pauls is someone whom I would heed a suggestion from, as to a reputable source. I have copied him directly. He may be quite busy at the moment writing something about half-rational elements from the planet Boron or something like that, however.
dean

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bhanu Sood
Sent: Friday, November 13, 2015 7:09 AM
To: [log in to unmask]
Subject: Re: [TN] Surface Roughness Sample Length

One can measure surface roughness either by using a contact or non-contact method. Some other optical microscope-based methods may be more qualitative.

Contact methods include using atomic force microscopy or surface profilometry. Essentially, run a stylus on the surface and track the rise and fall that corresponds with changes in the surface roughness. The measurement would give you the heights of the valleys and the depths of troughs. You can also calculate a root mean square roughness or RMS roughness. 

Examples of non-contact methods include interferometry that uses white light or discrete wavelengths. 

 The length of the scan essentially depends on the planarity of the sample surface. At some point the global curvature of the sample is going to start influencing the measurements.

I hope this helps.
Bhanu

> On Nov 13, 2015, at 7:52 AM, Eddie Hofer <[log in to unmask]> wrote:
> 
> Wondering if anyone has more experience in the measurement of surface 
> roughness.  I am hoping to better understand the specifications 
> relating to surface roughness and specifically the nuances behind 
> determining sample length.
> 
> Appreciate any input you can provide.
> Thanks!
> Eddie Hofer
> 
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