How do you measure tape tension

[Dave Cawley]

How do you measure tape tension?  Is there something you can buy, or is it so simple I am missing something?

Thanks

Dave

[ironbut]

Hi Dave,

I use a device called a Tentelometer. You can find them on eBay for pretty cheap but it's kinda hit and miss as far as accuracy goes.
There are many different models and I prefer the ones with the rolling probes (you'll see what I mean when you visit their site).
Also, you need to get one that's made for the right tape width and tension range. When you get it, you should calibrate it to the range you're going to be measuring. There's instructions for this on their site also. I use some cheap weights I got from Edmund Scientific for this.

http://www.tentel.com/Default.htm

I'm pretty sure that this is covered in the " Beginners Guide" located in a sticky above the General forum.

[Dave Cawley]

Hi Steve

I won!

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150412401519

Thanks so much.

Regards

Dave

[ofajen]

Hi Dave,

I use a device called a Tentelometer. You can find them on eBay for pretty cheap but it's kinda hit and miss as far as accuracy goes.
There are many different models and I prefer the ones with the rolling probes (you'll see what I mean when you visit their site).
Also, you need to get one that's made for the right tape width and tension range. When you get it, you should calibrate it to the range you're going to be measuring. There's instructions for this on their site also. I use some cheap weights I got from Edmund Scientific for this.

http://www.tentel.com/Default.htm

I'm pretty sure that this is covered in the " Beginners Guide" located in a sticky above the General forum.

Interesting! I've never used a tentelometer, nor measured tape tension per se.  My tape machines (3M and Otari)don't have specs for tape tension, nor do the manuals include a tape tension measurement as part of the transport alignment process nor do they spec a tentelometer as part of the maintenance kit.  I'm not really sure what I would do with the data.

I do use spring scales in the spec'ed ranges  for reel motor torque and for capstan/pnch roller pressure adjustment on the Otari.  On the 3M machines, the capstan/pinch roller pressures are set by a cailbrated procedure, not by pressure measurement and corresponding adjustment.   

Any idea how long the tentelometer has been around?  It may not have been an option back in the early '60s, when 3M designed the Isoloop transport for their audio recorders.

Cheers,

Otto

[ironbut]

Hey Otto,

If I had to guess, I'd say that the brand Tentelometer was from the 70's. Of course, there have been meters for measuring this sort of tension since early industrial days when they were used to measure thread tension on looming machines (the kind that make fabric, not the ones that are so enormous that they intimidate).
I think the main advantage of these types of devices over measuring motor torque is that it takes tape and the tape path into account. I've seen as much as 5 grams difference from tape to tape and I've always attributed this difference to tape thickness, backing compliance, and the friction that the coating(s) create. Of course, the specified tensions are +/- 5 grams (on the Technics machines) so I don't feel like I have to get the tensions spot on but I am careful to keep the ratio of take up and supply tensions very close (which are 10 grams different).

It seems like the 3M designers were acutely aware of the factors that tape tension and the tape path contribute to. I would imagine that the calibration procedures for those machines are far more comprehensive and exact than just using any tension device would be.

[ofajen]

It seems like the 3M designers were acutely aware of the factors that tape tension and the tape path contribute to. I would imagine that the calibration procedures for those machines are far more comprehensive and exact than just using any tension device would be.

Yes, 3M did pay attention to this.  The Isoloop is a capstan-driven transport, so setting the incoming and outgoing capstan/pinch roller pressures pretty much gets things working as they should.  The reel motor torque is just there to keep the tape from going slack.  The tape tension is applied to the tape within the loop (by the differential radii of the tape passing by the two sides of the capstan) and it is slightly stretched, so it actually moves faster than the tape outside the loop. 

It's been my observation that the 2" diameter capstan seems to handle differences in tape thickness more readily than standard style transports with small capstans.  Certainly, the adjustment is far easier to do on the 3M than adjusting capstan/pinch roller pressure on the Otari, since you just need to pull off the top transport cover and you can easily do everything from the top with a single screwdriver, versus having to pull the bottom cover, swinging out the transport card and reaching way inside to try to adjust the two nuts that set the pressure on the Otari (and then having to right the machine to test the thing after each tweak).

Cheers,

Otto

[squasher]

Can someone please advise / lead us through the exercise of measuring tape tension WITHOUT a tentelometer?

In the section related to tape tension, my Studer A807's manual states:

  "Insert a tape tension meter between the left reel and tape tension sensor. Press the key PLAY. By means of of the trimmer 'Play' adjust to 70p +/- 2p; the distance "X" should be in the range of 56 to 58mm."

I'm pretty sure I can understand the procedure if I had a tentelometer (what are "p" units, however?). Is there another tool that will do the same job? If the answer is a spring tension gauge, how does this work?

One last question: is it possible to perform the procedure above without a tension meter altogether? i.e. Just by turning the trim pot until distance "X" is in the right range?

Thanks in advance,
Chris

[Ki Choi]

Hi Chris:

Since I haven't had to adjust my A807s tension in several years... so I will go by what I do with the A810 left tension adjustment.

You can get pretty close to the 70g (BTW P = g) of tension by adjusting Play trimmer and watching the position of the tension roller.  I believe the factory spec calls for 10 deg down from deck's horizontal line.  I normally adjust the tension so that top edge of the left tension roller cap is at the horizontal position as the recorder plays with equal amount of tapes on both reels.  It is a rough way of setting the tension but often I measure 70 to 80g of actual tension with the tension meter from this method and make the fine adjustment afterwards while watching the tension meter.

Hope it helps.

[ironbut]

Hey Chris,

The big advantage that a tensiometer has over a simple tension gauge is it measures the force while the tape is in motion which is a more real world measurement.
If you're going to do you're own adjustments, you need a tensiometer. The Tentelometers aren't that hard to find on ebay. Getting one that works correctly at the range you need is a different matter. Luckily, they aren't too expensive. Buy yourself a decent set of weights for calibrating it to the range you plan to measure. Also, try and find one with the rollers on the probes. Otherwise, the readings will be skewed depending on which direction the force is coming from.
If you can't find one with the rollers, a work around is flipping the meter over on the same side you've already made a measurement (take up or supply), laying on your back and using that measurement for the other side.

You should always have a reel of tape that's the same as the tape you plan to use (don't use an important tape for doing any measurements/adjustments, they can easily be damaged). Tape backing thickness and stiffness can make a few grams difference in the measurements.

[ironbut]

BTW
The Tentelmeter that's on eBay right now (03/02/2010) is currently selling for about 3X what I've ever paid for one.
There's way too many things that could be wrong with one to pay much more than $50 for one (and if anything is wrong with a measuring device meant for fine calibration, it's garbage!).

[tapepath]

In calibrating my A80 RC  I came across this very helpful thread. A belated "Thanks!" to everyone who contributed to it. As an aside I've found out that the "P" referenced in the Studer manual is for "pond" derived from the latin word for "weight". It is a unit of force measurement and does equate one-to-one to a gram-force. For those who want to learn more:
https://en.wikipedia.org/wiki/Kilogram-force