Michael Fremer's latest Analog Planet post:

" ...as the cartridge got close to the platform the scale began reacting! There's a magnetic reaction between the cartridge and the scale! "

(I don't see the video that Mikey refers to in this post.)

I haven't checked my Chinese electronic VTF scale yet, but I hadn't noticed anything to date.

Although I have noted here before, that some tonearms, because of their counterweight design geometry (eg. 'underslung' c'weights') have varying VTF with arm/stylus height.

It may depend also on the type of cartridge, ie. magnet strength, construction, shielding.

DarkLantern blog - darklanternforowen.wordpress.com

can't see the vid either.

got out my little bar magnet and checked my $20 "arm load meter" and rega gauge.

both are safely non-magnetic.

ps.  my old shure mechanical balance is non-magnetic too, iirc some very early examples weren't ?

Marc Gomez (designer of the Swedish Analog Technologies tonearm) explains to Analog Planet (Michael Fremer), that this is not affecting his VTF readings, because the 'magnetism' only occurs when the cartridge is being lowered & raised - not when it is stationary on the scale platform.

This is due to Lenz's Law of electrognetism, current being induced in the conductive aluminium platform by the strong magnet of this MC cartridge - only when it is being lowered & raised.

BTW you'll see that the SAT tonearm is one of those arms with (i) very wide & shallow c'wt & (ii) designed for the c't to sit very close to the pivot.
This amplifies the effect of VTF varying as the stylus moves up or down.

DarkLantern blog - darklanternforowen.wordpress.com

SAT tonearms:
You could argue that this is not the best engineering design, but I guess that when/if the stylus is level & always playing perfectly flat records - then no problem

ie. the c'wt centre-to-arm pivot distance varies slightly as the tonearm swings/arcs up or down.
(Worse with short/wide c'wts like this, or 'underslung' c'wts.)

Additionally, when measuring VTF with such arms, the scale platform must be exactly at record height - with my similar VTF scale on my TT, I remove the platter mat when checking VTF, in order to get the platform at record height..

DarkLantern blog - darklanternforowen.wordpress.com