Cartridge for Graham 1.5

Hopefully the scale you bought uses a measuring platform that places the stylus at true record level (like the Wally Malewicz version).
If not, you won't get a true reading with the Graham.

I recently bought one of those small electronic VTF scales that Acoustic Sounds is selling (chinese design, labeled cartridge arm load meter) - except I only paid A$70 locally.

I thought a neat little scale, purpose designed for VTF measurements, would be easier to use than my pocket scale with it's Wally platform copy.
Unfortunately the new scale places the measurement point a couple of mm above the actual playing height. This results in an error of about 0.2g in my setup!!

I thought this was crazy and tested both scales with a One Yen coin (nominally 1g) - both scales measured the same (to the nearest 100th gram). If I raised the weighing platform height of my pocket scale when measuring VTF, I could duplicate the readings on the got with the new VTF scale.

Further testing with my pocket scale/weighing platform (which weighs at actual record height) shows there is even a variation of 0.1g when going from 120g vinyl to 200g vinyl.
I'm going to do some followup testing, but it appears I should be adjusting VTF for different record thicknesses!!??

I have a better scale then what I was using, looks like the AcousTech Electronics Stylus Force Gauge. It is close to record thickness but probably higher but better than the old Shure beam scale. I set the VTF to 2.1 from 2.3 and believe its improved overall. I may still back off the VTF a bit just to listen. I will play with the VTA more before I lock it. I am not inclined to adjust things for each record, I would rather spend the time listening. Hopefully I'm not beyond Keep It Simple Stupid.

Carl, does the scale look like this one - new VTF scale
If so, that scale reads about 0.2g higher than my scale that measures exactly at record level. The scale is shown measuring a 1 yen coin (nominally 1g).
With 1g test weights placed directly on the measuring platforms, both of my scales read the same.

Here are a couple of old pics I took of the pocket scale/wally adapter.
Pocket scale weighing 1 yen coin
Wallyscale clone

Tobes,

Yes, we theoretically should adjust VTF for different record thicknesses. And, we have a more difficult issue with warped records.

Please forgive me if this is ground you have already covered, but there is a real reason for what you have observed. For the Graham 1.5 and for many unipivot arms, the center of gravity is designed to be below the pivot point. This results in a small but real force that acts to restore the arm to the correct positioning with the stylus at the record surface -- any deflection of the arm (such as the stylus lifting above the record surface) causes the VTF to vary. It is analogous to a pendulum wanting to be perfectly vertical, experiencing a force pushing it toward the perfectly vertical position when it is deflected. At one stage of the evolution of unipivot arms, this may have been considered a desirable characteristic because it contributed to the arm's dynamic stability.

Bob Graham has eliminated this effect in his new Phantom arm by designing the center of gravity to be at the pivot point. He instead achieves arm stability with the help of a magnet.

When I set up my 1.5, now upgraded to a 2.2, I needed to be careful how high my weigh scale was when setting my VTF. It needed to be as close as possible to the height of the actual record surface, or else I would have suffered a different VTF than what I wanted. You and Carl have both observed this effect. It sounds to me like your scales are close to accurate, but their heights were different.

Thanks for the photos Tobes. I have the first one accurate to 0.002 +-?. I looked at my Orbe and made a block about 1/8 lower than the platter height. My gauge on platter says 2.152. Gauge on my block says 2.105. It seems as though Jameswei is correct in that the Graham is pushing down somewhat. In my poor mind I don't see it but then again its late and the difference here is below my tolerance level. Learned something new again!
Carl