Digital Scale for tracking weight?

[elcoholic]

From 3 years ago

Test Equipment:

Toshiba SR-F770 DD Turntable w/ Signet TK7EA Cartridge
100 gram x .01 g Mini-CD Stealth Scale
Levolution 12" Spirit Level
Starrett 6" Combination Square (height gauge)
George Shearing, The Shearing Touch LP (Capitol ST-1472)
36 RIAA Equalized Ceramic Poker Chips (blue and white randomized to discourage standing waves and/or 3rd order harmonics)
1 Andrew Jackson Family Portrait for Control

Test Setup:

Cowboy Junkies on the stereo. TT leveled. Arm leveled. Platter removed after 'normal' play height measurement taken using The Shearing Touch LP which seemed a nice smooth, calm choice.

Test Procedure:

In all 50 measurements were taken. 10 for control and 10 at each of 4 heights as per the table below. The arm would not go any lower or another set of measurements would have been captured. The scale was shut off and then powered up to self zero for each measurement. The stylus contact location on the scale remained very close for all measurements. The tracking force was set to 1.25 g for measurement 1 at +0.63 inches. The 0.26 inch above normal measurement corresponds to this scale on this turntable with the rubber matt removed.

In Conclusion:

As the arm was lowered the measured tracking force followed.
The rate of change in measured tracking force seems to be fairly linear.
The deviation of the control measurements exceeded the tracking force measurements.
The maximum deviation for all 40 measurements was 0.11 g. The control deviation was 0.04 g. Therefore the maximum deviation of measured tracking force can reasonably be said to be .5(0.11 - 0.04) = 0.04 g

Opinion:

Until I get an expensive SoundSmith strain gauge or Ortofon SPU cartridge my $15 digital scale should do just fine.
I still don't understand why the measurements follow the arm. Intuition tells me this is backwards. As the angle is increased the pivot would seem to bear more of the force, so the force at the stylus should decrease?

Just For Sh!ts and Giggles:

I took a few measurements at the +0.63 inch elevation with the same 9 chips on the scale. The weight of chips is 76 grams which puts the measurement much closer to midrange for the scale. The control bill still weighed in a 0.98 grams, but the TF consistently measured 1.32 grams or 0.06 g higher than the average at that height.

Still probably negligible.

http://www.audiokarma.org/forums/attachment.php?attachmentid=260423&d=1299275930

 

[mrkmpn]

That's weird... like the person posting that, I too would have assumed the lower the stylus the heavier the reading would be.

So I take from that you want as close as possible to the level at which the stylus would be sitting on the record, for most accuracy.

 

[elcoholic]

Yes, that's what I do. The little mini CD case scale gets fairly close with the platter mat removed.

 

[mrkmpn]

Good to know, if I remember right the guy I saw using a digi scale on youtube just set the scale on top of the platter, mat and all... and it was a somewhat thick scale.

I had a feeling that might throw off the accuracy of the measurement as compared to a real TF scale, but still surprised the throws it in the opposite direction I'd expected.

 

[cgutz]

I'm thinking to hard here. The suspension on the stylus will allow it to flex and actually need more weight to measure correctly versus a fixed guard ?

I think the only reason to consider using a stylus guard when measuring is to protect the stylus from damage.

I don't think cantilever "springiness" will affect the reading on the scale significantly.

Elcoholic, nice work on trying to quantify the effect of height on VTF measurements. One factor to consider is that I've read most of these cheap digital scales are more accurate the closer you get to the midpoint of their ranges. By adding chips, you would move the scale closer to its most accurate "sweet spot," and hence maybe introducing some error due to scale accuracy variance. I wonder what the measured effect would be if you stacked things under the scale, so that the scale was always operating in the same portion of its useful range, hence giving more consistent results of the actual force from the arm.

While I have not done systematic measurements like yours, my few experiments show that within the limited vertical range of motion of the arm (+ or - .5 inch or so), the effect on measured tracking force is negligible, perhaps .1g or less. It is however, best to measure at about record height to achieve maximum comfort about the accuracy!

 

[elcoholic]

I think the only reason to consider using a stylus guard when measuring is to protect the stylus from damage.

I don't think cantilever "springiness" will affect the reading on the scale significantly.

Elcoholic, nice work on trying to quantify the effect of height on VTF measurements. One factor to consider is that I've read most of these cheap digital scales are more accurate the closer you get to the midpoint of their ranges. By adding chips, you would move the scale closer to its most accurate "sweet spot," and hence maybe introducing some error due to scale accuracy variance. I wonder what the measured effect would be if you stacked things under the scale, so that the scale was always operating in the same portion of its useful range, hence giving more consistent results of the actual force from the arm.

While I have not done systematic measurements like yours, my few experiments show that within the limited vertical range of motion of the arm (+ or - .5 inch or so), the effect on measured tracking force is negligible, perhaps .1g or less. It is however, best to measure at about record height to achieve maximum comfort about the accuracy!

Ah the stuff you have time for when recovering from back surgery. Your point is well taken. Generally you want to be in the middle of the range. These little strain gauges are so linear that the bill weighed 0.98 g no matter what so it might have taken another decimal place to see the delta

Another nice advantage to the digital scale is you get to skip balancing the arm all together. I set the TF and then set the indicator ring on the counter weight to read the same.

 

[cgutz]

Another nice advantage to the digital scale is you get to skip balancing the arm all together. I set the TF and then set the indicator ring on the counter weight to read the same.

Yup, and you will also find the calibration on the dial will be slightly off based on mass of cart and headshell. Unless the mass of both are indentical to the mass used in the tonearm design calculation, the markings on the dial won't be perfectly calibrated.

On my Kenwood, the dial is about .1g off - likely because I use a much lighter aftermarket headshell.

A scale is the only way to be sure you are spot on VTF....

 

[janikphoto]

Thanks, all! I've been thinking about buying a scale for a while, and this thread with links to suggested models made me bite the bullet. I got one, and I was glad to see that my settings were pretty close... but, now they are exactly where I want them!

 

[skriefal]

Is there anything available similar to the Ortofon DS-1 scale, but at a more realistic price (i.e. less than the $159 price for the Ortofon)? I like this one because the stepped platform keeps the cartridge as close as possible to the platter/mat surface, and it looks like a much higher quality product than the cheap DealExtreme scales (which I own, but the quality of which is highly variable at best).

 

[PureQuill]

No digital for my analog!

Maybe its just me being an analog guy but I don’t trust digital scales.
I have never found them to be accurate & have no faith in some cheap digital plastic piece of crap.
I can get on & off my digital scale in my bathroom & lose or gain weight every time I step on it. Same thing with our digital kitchen scale same steak changes weight every time I put it on the digital scale.

My other 1/2 is an industrial chemist they use a triple beam balance in the lab no digital scales allowed where she works:thumbsdn:

Me I'll stick with a tried & true analog scale. No batteries, last as long as gravity is a constant force $32.45 on the bay shipped to your door.
I’ll stick with a scale with proven track record pun intended!:thmbsp:
http://www.shure.eu/products/accessories/sfg-2

Just my opinion as always YMMV.
PQ

 

[janikphoto]

Maybe its just me being an analog guy but I don’t trust digital scales.
I have never found them to be accurate & have no faith in some cheap digital plastic piece of crap.
I can get on & off my digital scale in my bathroom & lose or gain weight every time I step on it. Same thing with our digital kitchen scale same steak changes weight every time I put it on the digital scale.

My other 1/2 is an industrial chemist they use a triple beam balance in the lab no digital scales allowed where she works:thumbsdn:

Me I'll stick with a tried & true analog scale. No batteries, last as long as gravity is a constant force $32.45 on the bay shipped to your door.
I’ll stick with a scale with proven track record pun intended!:thmbsp:
http://www.shure.eu/products/accessories/sfg-2

Just my opinion as always YMMV.
PQ

I like the cheap digi scale, because it seems more accurate than not having a scale at all. I see a point to having a high quality analog measuring tool, though.

 

[Beatnik]

Is there anything available similar to the Ortofon DS-1 scale, but at a more realistic price (i.e. less than the $159 price for the Ortofon)? I like this one because the stepped platform keeps the cartridge as close as possible to the platter/mat surface, and it looks like a much higher quality product than the cheap DealExtreme scales (which I own, but the quality of which is highly variable at best).

You can make your own using double sided tape and a piece of properly bent plastic or sheet metal.

 

[mrkmpn]

Thanks, all! I've been thinking about buying a scale for a while, and this thread with links to suggested models made me bite the bullet. I got one, and I was glad to see that my settings were pretty close... but, now they are exactly where I want them!

Mine was WAY off... Not because of the inaccuracy of the markings on the tonearm weights though, I think it was because I had adjusted the tracking weight and anti-skate a few times without starting over from scratch or something.

Once I redid it, it was off but not much. When I 1st tested it it was almost a gram over.

 

[12ax7]

Is there anything available similar to the Ortofon DS-1 scale, but at a more realistic price (i.e. less than the $159 price for the Ortofon)? I like this one because the stepped platform keeps the cartridge as close as possible to the platter/mat surface, and it looks like a much higher quality product than the cheap DealExtreme scales (which I own, but the quality of which is highly variable at best).

Beatnik's suggestion is a good one. I picked up this one on eBay for a grand total of $6.97 shipped. Sure does look similar.