Stylus force digital scales

You absolutely can use the inexpensive digital scales. Don't let anyone tell you otherwise. I have been using this stylus gauge for the last year, it's $14 shipped.

https://www.amazon.com/gp/product/B00XC2AQN4/

I have a set of calibration weights (I use the 1g and 500mg weights) that I use to check it is accurate, so far it's been perfect each time I have tested it. These kinds of measurements devices have been figured out some time ago, no need to spend a lot of money for a digital scale.

@jbny  unless you have calibration weights that are magnetic and non magnetic you will not see the effect we’ve been discussing

my scales all weigh the same with calibration weights, but once you use a MC cartridge it’s a different matter. And most of the China sourced metal ones read the same, no doubt because they share the same internal electronics. It’s only the custom designed plastic ones that give different results

now most setups will not be sensitive to +/- .05g VTF but unfortunately mine is, needing 1.70-1.75 exactly to perform at its best so I have no choice but to pay the $150 cost of entry for the Rega

I don't think it's an issue though. I had a friend bring over his Ortofon DS-3 and it read exactly the same with my cart. My Delos is supposed to be at exactly 1.72 for it's best, so I'm trying to make sure it's as accurate as possible.

Older Ortofon DS-1 is cheaper than DS-3
My DS-1 works fine and i like it, my ex new DS-3 was deffected and does not read the weight righ from the start. I think there is no need for DS-3 if DS-1 is available for much better price.   

Cleeds,
Imagine that you are the stylus tip.  With the arm wand parallel to the LP surface, someone has set VTF for 1.5gm.  Now imagine that you encounter a record warp that lifts you up in the air by a few mm during each revolution of the LP.  Since you are subject to gravity, you come back down on the other side of the warp, but during the moment when the warp elevates you off the horizontal, the pull of gravity is still perpendicular to the plane of the LP surface.  Yet the tonearm is fixed at its pivot, so your journey back to horizontal must travel in the vertical arc dictated by the tonearm; the stylus tip (you) cannot follow the true vertical.  Therefore, some of the force of gravity in the vertical plane is momentarily bled off by a smaller force due to resistance supplied by the tonearm, a force vector generated because the tonearm does not let the cartridge fall back down vertically.  Hence "net" VTF is momentarily reduced by a small fraction. Got it now?  

If you don't believe me, and if you have an accurate digital gauge, check VTF when you have the cartridge in the plane of a typical LP and then again with the tonearm elevated by a cm or two above the horizontal.  I think the difference might be detectable even in these two static situations.

Another way to think of it:  Imagine that the tonearm has unlimited travel in the vertical plane.  It could then point straight up at the ceiling. What would be the VTF in that case? Zero.