I listened to YULitle about calibration and...

[mikeler]

The last month, my shots have been a little more inconsistent than usual. So I decided to purchase a Gamma calibration device from TW which arrived last night. I checked my Gamma X-ST crank machine which I probably have done about 50 rackets on since I bought it. Lo and behold, the machine was pulling about 5 lbs too low. So the moral of the story is that I'm glad I listened to an expert. Now let's see if my game gets back up to par...

 

[jmk2888]

Try a Digital Fish Scale, they are more accurate.

 

[1st Seed]

Will do

Try a Digital Fish Scale, they are more accurate.

Soon as my sp hip hop arrives ,that's the first on my list.

 

[mikeler]

I've read about using the fish scales. The cheap scales I saw only went up to 50 lbs. Since I string at 60, I thought I'd just go ahead with the Gamma unit.

 

[william7gr]

Soon as my sp hip hop arrives ,that's the first on my list.

Tell me how it is because I never calibrated mine.

 

[flash9]

Digital Fish Scale for Calibrating your Stringer

On @Bay there are plenty of Digital Fish Scales that measure up to 40KG (88lbs) and 50KG (110lbs). I personally have the 50KG model, and it works great. You can also purchase this same model from Tim at GSS.

Note: If you are not calibrating your machine after ever 25 frame or so, you really have no idea what tension you are stringing at!

 

[mikeler]

On @Bay there are plenty of Digital Fish Scales that measure up to 40KG (88lbs) and 50KG (110lbs). I personally have the 50KG model, and it works great. You can also purchase this same model from Tim at GSS.

Note: If you are not calibrating your machine after ever 25 frame or so, you really have no idea what tension you are stringing at!

It's so easy to do, I'll probably check it about every 10 string jobs from now on.

 

[kmartin]

TW sells this one: http://www.tennis-warehouse.com/descpage-TENCAL.html

It says Gamma on the description, but shows a picture of an Alpha calibrator. If it is in fact the Alpha they sell, I highly recommend it.

I have the Alpha calibrator pictured, and it has proven to be very accurate. I occasionally confirm it's accuracy with free weights. I check in 2.5 lb increments from 45 to 65 pounds. And it is always right on the mark.

 

[djwurm]

We have a babolat Star 3 machine and I use the calibration tool about every 100 racquets. It usually doesnt need adjustment till about the 1000 racquet and even then its only off a pound or two.

 

[mikeler]

I bought the one from TW. It shows an Alpha, but the one they send is from Gamma. I don't have free weights, but I would like to test it out one of these days.

 

[mellofelow]

50lb digital scale will go up to 60+... they're just rated accurate to within minute tolerance to 50. Even at 60, it may be off by an oz or so, not even measurable in tennis tension terms.

Sorry TW, this thing is so outdated. Welcome to the digital age... and almost 1/2 the cost.
http://www.walmart.com/catalog/product.do?product_id=4328456

 

[Nanshiki]

You're sorely mistaken if you think an 18-dollar gauge of ANY sort with a 50-pound capacity is going to be accurate to within a pound.

Don't forget that you MUST calibrate the calibrator occasionally

(usually this involves sending it to the manufacturer)

 

[mellofelow]

You're sorely mistaken if you think an 18-dollar gauge of ANY sort with a 50-pound capacity is going to be accurate to within a pound.

Don't forget that you MUST calibrate the calibrator occasionally

(usually this involves sending it to the manufacturer)

What??!!! Have you even used a 'modern' digital scale? There are no moving parts. The principle is called stress, or 'Strain' gauge.

When external forces are applied to a stationary object, stress and strain are the result. Stress is defined as the object's internal resisting forces, and strain is defined as the displacement and deformation that occur. For a uniform distribution of internal resisting forces, stress can be calculated by dividing the force (F) applied by the unit area (A).

Since metallic conductors subjected to mechanical strain exhibit a change in their electrical resistance, compact yet complicated circuitry and sensor is incorporate to measure the amount of resistance. Mathematical conversion of this number equals the weight of the property.

Unless the computer circuitry fails, the tension applied should always = electrical resistance. That's why it resets itself to zero resistance after every use. Please explain how do you calibrate scientific electrical property?

Like it or not, it's the same method of lots of new measuring devices. For my tires... I trust my life on these rather than floating PSI stick.

 

[Nanshiki]

I'm only saying that low-grade fish scales, etc were never intended to give you more than a couple pounds of accuracy (besides not being able to calibrate them, which is vital in maintaining gauge accuracy).

FYI, the picture of the tire gauge you're showing is of a high-quality digital gauge (IIRC it's about 25 bucks, which is a lot for a tire gauge that isn't racing-grade) intended to be reasonably accurate when measuring PSI.

You might as well try to customize a racquets weight my five-dollar food scale that's easily 3-4 ounces off every time you try to weigh something because it's a POS and has a 5-pound capacity. This is why the more accurate a gauge is, versus it's capacity, the more it costs. It's why a gauge that measures 100 pounds, but by the gram, will cost many, many times that of a bathroom scale that will weigh 300 pounds but only to within a pound or so. And don't forgot that even a scale that is able to measure to within a gram doesn't mean much if it wasn't calibrated to display correctly in the first place. If the calibration was off by say 1%, and the you can measure precisely to the gram, at 100 kilograms (220 pounds), you're off by 1000 grams even though the scale could actually measure it precisely. (precision versus accuracy)

For the record, I use a 30-dollar mechanical racing-grade gauge on my car and wouldn't touch one of those 'sticks' with a 10-foot pole.

Also, the more precise a measuring devise needs to be (INCLUDING electrical devices used to calibrate other devices!), the more often they have to be calibrated. For the purpose of a stringing machine, you'd be fine with an accuracy of a pound or so, as long as it's consistent, because stringing tension is purely a reference tension anyway, and every machine is a little different.

 

[mellofelow]

I'm only saying that low-grade fish scales, etc were never intended to give you more than a couple pounds of accuracy (besides not being able to calibrate them, which is vital in maintaining gauge accuracy).

Oh yeah? I challenge your statement by providing a proof of how this digital technology can be off by couple of pounds... if control environment and method of measuring are identical.

On Berkley's website they state the accuracy of this scale is +/- 1/4 oz.

http://www.berkley-fishing.com/prod.php?k=79557&u=CFS50MT

The reason your $5 food scale is a POS obviously 1) it has very inferior components and 2) it uses gravitation force and 3) probably incorporates poor mechanical parts that can influence resistance measurements. Let me elaborate.

1) Cheap digital circuit plus poor electronic gauge basically makes measuring defective.

2) Gravitation measuring requires solid platform and perfect perpendicular stance. For example, measuring your weight (on bathroom scale) can result in different reading between solid concrete and carpet. Go ahead... try this yourself... instant weight loss. Secondly, if the scale is sitting at an angle of 1/2 a degree or more, this can also affect true weight reading.

3) Whatever the device, it still needs mechanical parts to make it work. Ie, flat dish, connection to resistance gauge... etc.

Having said that, a digital hanging scale is not like a food scale sort of. Hanging scale measures resistance from opposite directions, regardless of gravitation force. Therefore, it eliminates #2 variable described above. The main reason the fishing scale is rated to 50lb is because the combination of the handle and metal link hook are made to tolerant or withstand the weight up to 50-ish pounds. More than that it will snap the mechanical parts. Ergo, the 75lb scale uses heavier duty hook and handle.

Up to this point, I still haven't heard your theory how an old fashion sliding spring can be more accurate than a digital strain gauge. Furthermore, it requires one's eyeballing (guessing) it's on mark. Oh, and the only advantage your mechanical tire gauge has over mine is the fact it does not need a battery.

Embrace technology everyone. It's the same principle that brought you Wii FIT.

 

[Zhou]

Lets put it this way. No point to use a digital scale that goes only to 50 if you are stringing tennis racquets.

If you stringing badminton racquets, it should be fine.

You know, majority of the people string above 50 lbs...

 

[mellofelow]

Lets put it this way. No point to use a digital scale that goes only to 50 if you are stringing tennis racquets.

Agree... but did you read my first post? Are you absolutely positive a 50lb scale will not register beyond 50? Maybe mine is an old copy but it goes 60+. The problem is the hook and handle may break. Take this as a warning. But if you're gonna calibrate 4 times a year like I do, it's perfectly fine.

The reason I tried it because I bought an Eagnas 3yrs ago and wanted to make sure the tensioner was accurate. Rather than wait, in a pinch I figured the Walmart unit can calibrate to 50lb... then 60lb cannot be to far off. Much to my surprise, it goes beyond 50.

I now have a 75lb unit off e-b-a-y though.

 

[Nanshiki]

Oh yeah? I challenge your statement by providing a proof of how this digital technology can be off by couple of pounds... if control environment and method of measuring are identical.

On Berkley's website they state the accuracy of this scale is +/- 1/4 oz.

http://www.berkley-fishing.com/prod.php?k=79557&u=CFS50MT

The reason your $5 food scale is a POS obviously 1) it has very inferior components and 2) it uses gravitation force and 3) probably incorporates poor mechanical parts that can influence resistance measurements. Let me elaborate.

1) Cheap digital circuit plus poor electronic gauge basically makes measuring defective.

2) Gravitation measuring requires solid platform and perfect perpendicular stance. For example, measuring your weight (on bathroom scale) can result in different reading between solid concrete and carpet. Go ahead... try this yourself... instant weight loss. Secondly, if the scale is sitting at an angle of 1/2 a degree or more, this can also affect true weight reading.

3) Whatever the device, it still needs mechanical parts to make it work. Ie, flat dish, connection to resistance gauge... etc.

Having said that, a digital hanging scale is not like a food scale sort of. Hanging scale measures resistance from opposite directions, regardless of gravitation force. Therefore, it eliminates #2 variable described above. The main reason the fishing scale is rated to 50lb is because the combination of the handle and metal link hook are made to tolerant or withstand the weight up to 50-ish pounds. More than that it will snap the mechanical parts. Ergo, the 75lb scale uses heavier duty hook and handle.

Up to this point, I still haven't heard your theory how an old fashion sliding spring can be more accurate than a digital strain gauge. Furthermore, it requires one's eyeballing (guessing) it's on mark. Oh, and the only advantage your mechanical tire gauge has over mine is the fact it does not need a battery.

Embrace technology everyone. It's the same principle that brought you Wii FIT.

I wasn't even arguing that mechanical gauges are better than electronic ones, simply that gauges that aren't used for the purposes they were intended for usually give you substandard results.

My food scale isn't even digital BTW

 

[mellofelow]

My food scale isn't even digital BTW

You might as well try to customize a racquets weight my five-dollar food scale that's easily 3-4 ounces off every time you try to weigh something because it's a POS and has a 5-pound capacity.

Then WTF are you talking about? You first discredit the accuracy of my $18 digital scale and then comparing it to your $5 POS... which isn't even digital?

Sorry but... it's absolutely annoying when people make authoritative comments or statements when they have absolutely no experience of actually using the product.

I still have my good ol' Ektelon spring load gauge for 25+ yrs now. Too bad it hasn't seen the light of day since the Berkeley.

 

[mikeler]

I'd rather pay the extra money and know that I'm using a device that is geared for checking string tension. Now that my rackets are back to the tension I was used to, I'm playing much better.

 

[mellofelow]

Then you should use what the stringing professionals use.

http://www.racquetmaxx.com/equipment.shtml

 

[mikeler]

Too late for me. I only string my own sticks, so I'm not that worried about it.

 

[MAX PLY]

For what it is worth, I have both a Prince Digital (which alas they do not make anymore) and an older Gamma analog (must have had for years--just like the current one) and have had no trouble. They always agree with each other so I think you can feel pretty comfortable with what is generally commerically available. I have no comment on the fish scale as I have never used for fish or for stringing machine calibration.

 

[Nanshiki]

Then WTF are you talking about? You first discredit the accuracy of my $18 digital scale and then comparing it to your $5 POS... which isn't even digital?

Sorry but... it's absolutely annoying when people make authoritative comments or statements when they have absolutely no experience of actually using the product.

I still have my good ol' Ektelon spring load gauge for 25+ yrs now. Too bad it hasn't seen the light of day since the Berkeley.

Come back when you've shown it actually has 1/4 ounce accuracy.

 

[MAX PLY]

I also recently noticed that SP apparently offers a digital calibrator if anyone is interested.

 

[miniRafa386]

im going to purchase a stringing calibrator- which one do you recommend between the eagnas, gamma, and alpha calibrators?

thanks alot everyone

 

[Rorsach]

Got a cheap digital fishscale (upto 40 Kilograms) from the local Craigslist. 17 bucks including shipping, where as an official tension calibrator would have set me back about 60 bucks.

I tested the fish scale with several weights from my dumbells and it's as reliable as anything.

Turned out my stringer was out of whack by 6 kilos.

Stupid question number one: Do i calibrate the stringer to the maximum weight it displays, or should i wait for the tension to stabilize?

 

[origmarm]

Soon as my sp hip hop arrives ,that's the first on my list.

Isn't the HipHop a drop weight?

 

[origmarm]

Stupid question number one: Do i calibrate the stringer to the maximum weight it displays, or should i wait for the tension to stabilize?

I very good question. I have always gone with the max but I'd like to know the "official" line on this one.

 

[mikeler]

That is a good question. Higher tensions would show bigger percentage deviations. Say your tension is off by 10%:

65 lbs x 0.1 = 6.5 lbs adjustment
45 lbs x 0.1 = 4.5 lbs adjustment

I always just check it at the tension I'm going to be stringing at which is 60 lbs.

 

[SW Stringer]

Lets put it this way. No point to use a digital scale that goes only to 50 if you are stringing tennis racquets.

If you stringing badminton racquets, it should be fine.

You know, majority of the people string above 50 lbs...

Wrong!! Why? One word: extrapolation. The response curve of your stringing machines tension head is linear. Once you've measured several points below the fifty pound (mechanical) limit of the digital fish scale, plug the numbers into the Excel linear regression function and extrapolate to 75 pounds and know it's accurate. You can then print out a chart of actual tension versus reference tension that goes from 1 to 100 pounds in 1 pound increments and use it as you string. Recalibrate every n string jobs or once a month and reprint the chart. Fairly simple if you have a few computer skills.

 

[mikeler]

Wrong!! Why? One word: extrapolation. The response curve of your stringing machines tension head is linear. Once you've measured several points below the fifty pound (mechanical) limit of the digital fish scale, plug the numbers into the Excel linear regression function and extrapolate to 75 pounds and know it's accurate. You can then print out a chart of actual tension versus reference tension that goes from 1 to 100 pounds in 1 pound increments and use it as you string. Recalibrate every n string jobs or once a month and reprint the chart. Fairly simple if you have a few computer skills.

That sounds like fun. I may have to buy a fish scale just to create some cool regression charts.

 

[TenniseaWilliams]

...
Stupid question number one: Do i calibrate the stringer to the maximum weight it displays, or should i wait for the tension to stabilize?

Not so stupid a question, I was always told to let it stabilize, and to use kevlar for the test string. On a drop-weight I would re-level the bar after it stabilized, and let it re-stabilize if the string elongated much.

Wrong!! Why? One word: extrapolation. The response curve of your stringing machines tension head is linear. Once you've measured several points below the fifty pound (mechanical) limit of the digital fish scale, plug the numbers into the Excel linear regression function and extrapolate to 75 pounds and know it's accurate. You can then print out a chart of actual tension versus reference tension that goes from 1 to 100 pounds in 1 pound increments and use it as you string. Recalibrate every n string jobs or once a month and reprint the chart. Fairly simple if you have a few computer skills.

Wouldn't this only be true for drop-weights? Why redo it?