Electronic stylus force gauge question

I am sure that the minus .01g - .03g reading is caused by the magnet in your cart. pulling up on the scale. This could be confirmed by passing a magnet close to the scale to see if the same thing happens. As far as setting your cart. VTF to as close to 1.75g as possible, consider this: the absolute accuracy of your scale is probably more the +/- .05g! Maybe more if there is no provision to calibrate it with a known weight. My advise is to not sweat it.

Hey John,
You're absolutely right. In retrospect, I wish I had not written the passage about tracking as closely to 1.75 g as possible. The main impetus behind my original post was the concern about the accuracy and reliability of the scale and measurements, not the obsession with the magic number of 1.75. Little did I know I was about to open a big can of worms...

I will give it a shot, even if it's very early and my first cup has not kicked in yet.

Any scale, digital or not, reacts to downward force which causes a downward mechanical action. The cartridge sits on a platform and the amount of downward force is interpreted and displayed as a number. If the platform or any part connected to it has any ferrous parts, as the cartridge's magnets approach the scale from above (as one lowers the arm) they attract these ferrous components upward causing the negative reading. Maybe?

Marek (Actusreus), as an electrical person I'll offer an electrical hypothesis :-)

If, as you suspect, magnetic effects are not the cause, one guess is that the electronic circuitry in the gauge is being affected by either stray capacitance between its various circuit points and the tonearm/headshell/cartridge assembly or the wiring it contains, or by low-level EMI/RFI being emitted from that assembly.

Sensitivity to those kinds of effects could very conceivably vary as a function of battery strength (consistent with Phil's observation). It could also be expected to vary unpredictably during the tonearm's descent, as the angular alignment and the distance between the gauge's circuitry and the tonearm/headshell/cartridge changes.

Alternatively, it could be that digital noise generated by the gauge's circuitry is radiating through its display window (the one part of the gauge that appears to be electrically unshielded across a significant area) into the tonearm/headshell/cartridge assembly, and radiating or capacitively coupling from there through the air into the metallic structure that the stylus is being lowered onto. From there the noise would re-enter the gauge's circuitry, coupling into different circuit points than those from which it originated, again with unpredictable effects.

These kinds of effects could perhaps be viewed as electrical counterparts to the kinds of mechanical effects Doug was referring to in his comment that "ANY scale that resolves to .01g or better will respond to the slightest changes in air currents. I can alter the reading on my scale (different brand, same resolution) by waving my hand over it." :-)

Best regards,
-- Al

Al,

Thank you for your plausible hypotheses. Something tells me you're probably right, as usual, if not about both, at least one of them :)

Now the question I have to ask: can any of this be harmful to the cartridge?