Stylus force digital scales

John_tracy is absolutely correct, once the weight of the cartridge is supported by the measuring platform the magnetic force is neutralised, as he says "think about it".
For me the most crucial issue is that the height of the measuring platform is exactly the same as the height that the surface of the record would be. Even small differences less than 1 mm can influence the force by >0.1 gram. This obviously depends on where the the centre of gravity of the tonearm is, these numbers refer to the Kuzma 4 point. I suspect that people who change the tonearm height for different thickness records, are actually hearing the change in tracking force, rather than VTA/SRA, since such small adjustments make hardly any difference to VTA/SRA but make a huge difference to tracking force.
I have found the Ortofon DS-3 (only available in Japan) to have a measuring platform, close to the thickness of an lp. The Clearaudio is much too high as are most of the others, including the el cheepose.

Whether or not the tracking force is affected by magnetic attraction depends on what the LOMC cartridge is attracted to. If it's the platform alone then yes, the scale will read true. But if the cartridge is attracted to internal components or the chassis of the scale then no, the cartridge will be trying to pull itself past the platform and the force will not read true.

And even if the cartridge is only being attracted to the platform, a strong attraction will collapse the cantilever suspension when the magnets within the cartridge body pull the cartridge onto the platform. It may weigh correctly, but the stylus and cantilever will be shoved up against the cartridge body. Trust me, I've seen it happen. :-)

My recommendation is to buy a good durable scale and make a platform adapter out of an old pre-paid "credit" card. I tried one of the low profile "audiophile" scales but it was fragile, not very consistent, and it failed after about 18 months. The scale I ended up with is a My Weigh Palmscale 7.0. It's built like a proverbial tank and is extremely consistent in VTF measurements. Unfortunately My Weigh doesn't carry it anymore but it's still available from many retailers. Their are other scales from My Weigh that would work as well. The prices are reasonable and they have a great warranty policy.

Here's a picture of the credit card platform adapter:
John Elison's example posted at VinylAsylum

You don't need to cut the card down if you don't want to. You can make the adapter so it sits a little too low and then adjust the height above the platter by adding shims.

Regards,
Tom

great tips - thanks guys.

I made something similar out of two pieces of acrylic and a long bolt to use with a lab style full size top loader. Works great.

Although a bit pricey, you might consider checking out this
Ortofon gauge. It puts the stylus at lp height and its flat measuring surface works well with cartridges with very short cantelevers like my Transfiguration. Good luck.