ERT 300 vs Stringlab

[Ash_Smith]

quick question - anybody direct experience of these devices to compare, the ERT i've used before but not the Stringlab - do they essentially do the same job on the strings?

Cheers

Ash

[Technatic]

Yes they do the same job, and use the same principle. They generate the natural frequency of the vibration with the tool as the mass and the stiffness of the stringbed as the spring.
The value of the result is the same, but ERT calls it DT value and SW calls it kg/cm for stiffness.

The thing that is difficult to understand is that ERT calls it the "dynamic stiffness". I do not think that there is anything dynamic about the result (apart from the vibration).

The differences are:
- The way of analysing the measurement.
- The Stringlab is part of a total system with the Tension Advisor and the routemaps.

[Ash_Smith]

Cheers Tech!

The ERT has a rough system similar to the SW Tension Advisor but it doesn't take into account the racquet length and width as far as I'm aware. I think the SW system is much more detailed in that respect.

It was more the devices themselves I was curious about as I've never used the stringlab. As for Dynamic Tension, I guess they use that term as it's a measure of the force required to deflect the stringbed as opposed to the 'static' tension which the tension the strings hold. Only a thought!

Ash

[Technatic]

Concerning the dynamic tension:
As you might have noticed I am a big believer in using the elongation figures of strings to classify strings so that stringers know what string to pick for whom.

I had a discussion with Tenneseawilliams in this thread about that.

http://tt.tennis-warehouse.com/showthread.php?t=335316

And he came up with this very interesting site
http://tt.tennis-warehouse.com/showthread.php?t=335316

They say about static stretch:
Static elongation is of interest to stringers for determining string lengths but does not have much relevance to hitting a ball. That is dynamic stiffness and is listed below ('stiffness')

This statements confuses me:
You can calculate the elastic and remaining elongation out of a static stretch tests of strings very well. And these figures tell everything about the power, control and loss of tension of a certain string.
So the static elongation is not only useful for stringers to determine the length of string that as stringer uses.

They say about stiffness:
Stiffness is measured dynamically during the impact. The measurement indicates the force necessary to stretch the string 1 inch during impact.

They do a dynamic test with a swinging hammer, this really the dynamic stiffness during a movement.
I think that Beer wanted to let people believe that the ERT really shows the behaviour during impact of the ball.

Because of the minimum deflection during the vibration you only measure the stiffness caused by the stringing tension and the behaviour of the string does not influence the ERT measurement.
That is why there is a good relation between the measurement and the stringing tension.
The only influence of the string is the difference of loss of tension.