Beers ERT 300 Tennis Computer, Black

....and those who desire to play with the best condition equipment. These are not easy to come by, as they seem to sell out before you get a chance to grab one. I got mine and I won't let it go. What does it do? Well strings are like the cardio system of a tennis racquet. If the strings are not fresh, they don't snap back, and therefore they don't create the spin they did when fresh. This happens at differing times depending on the player, the amount of power they hit with, the racquet head size and flexibility, and the string pattern. Most regular players will see about 20-30 hours of play before the racquet becomes less playable, and given the next 10 or so hours the racquet is not playing to spec and the player will find their shots going long (not getting enough spin to create the downward force of the ball) or their kick serve not kicking up as it normally does. They start losing control, and most people will actually assume the problem is their own, and they begin to change their game/strokes, etc to accomodate what is actually happening with the racquet. This device the Beers ERT-300 helps you recognize your tension level, and monitor it as you lose tension. When the racquet gets to that 20%+ lost tension mark - you will find the racquet plays different. When it's at 25-30%, it is what the tennis stringing community calls "Bagged Out" and within a few hours after that (if you hit the ball with any amount of power) the string will have no more elasticity and it will break. So about 10-20 hours after the racquet stopped playing at optimal levels, most players will not make the change to fresh strings as they should, instead they play till the string breaks, all the while frustrated with how poorly they played this entire last week. Love this product, friends, customers, other players ask to have their tension checked. Works like a charm, it's my secret weapon! LOL

It simply doesn't work 9 out of 10 attempts. Either fails to start a measurement or comes back with bogus values. For a tool this pricey it is a complete disappointment.

This item is ok. You have to take the reading the device gives you and then use a little handheld chart with a wheel to figure out the tension, its a pain. Main gripe is that with polys and the low tension they are strung at, after a few hitting sessions, this computer can't read the tension, its below its lowest range - not good after spending this kind of money.

This is the greatest invention since sliced bread! I've had 2 of them for four years -- just to cross reference and make sure that I wasn't getting a faulty reading. Both of them still give me the exact same reading ever time -- amazing! The reviewer that said you get a different reading every time just doesn't know how to use it -- you have to follow the directions but once you do that, it is incredibly consistent. Once you know the ERT 300 value range that you want to play with, you never have to look at the chart. Also, when you tell 2 stringers to string your racket at the same tension, the actual tension that your racket gets strung at could vary by as much as 10 pounds -- and only the ERT 300 will tell you that. A racket strung on a lock out stringing machine will loosen much more than one strung on a constant tension machine -- and then there's the issue of whether the machine has been calibrated recently and the difference in how a stringer ties the knots, etc. The ERT 300 will measure the tension down to well below 40 pounds -- I've strung mine at 44 recently and it could measure that low easily --- so it's only if you want your racket strung at a very low tension that you won't be able to use it.

It doesn't work . It gives you a different reading every time. And on some racquets it doesn't work at all

I've had this tool for over a year. This is a third generation of a device for measuring dynamic tension of strings in tennis racquets. Each generation gets smaller and smaller. The principle of its operation is the measurement of resonance frequency of string bed vibration. This frequency depends on many factors: length of the strings, material of the strings, string tension, among others. Therefore, it is important to know that the ERT-300 should always be placed in the same location (exactly in the center of the racquet), that its readings are in units proportional to string bed resonance vibration frequency (not a string tension in Lbs), and that you will not get the same value for different racquets or different strings, even if the tension is the same. There are no tools available to measure tension of strings after racquet has been strung. This tool is one of the best means to characterize string bed tension on a strung racquet.My son and I string our racquets ourselves, and we always validate the stringing job by measuring DT with ERT-300 after stringing. We also use ERT-300 to check how DT drops over time. We restring after 10 to 15% drop in DT, compared to as-strung value.We do not try to convert DT into string tension in pounds or kg. This is not a value added task because such conversion is very inaccurate. All that matters, is when we string the same frame with the same strings and tension over and over again, we get the same DT. The second thing that matters, is decrease of DT over time.My son also used ERT-300 for his middle school science project. He mapped DT across string bed of several racquets. We also took ERT-300 to a local tennis shop when we were picking demo racquets and measured pretty much all of their demo racquets. A few things which we learned.1) One has to be very careful with placing the ERT-300 right in the center of the string bed, if you want to take just a single measurement. If you move it off center, vibration frequency will change (shorter strings, it is just physics) and you would get a different (usually, higher) value.2) The readings are very reproducible, within +/- 1 unit of DT. We usually take 3 measurements and average the readings, to get accuracy down to 0.5 units.3) In order to get a readings, the string bed should vibrate within the range in which the tool measures, and amplitude of vibrations should be sufficient for the gadget to measure it. When string bed gets "dead" (loses tension big way with storage), the ERT-300 may no longer be able to take measurements. Usually, you restring your racquet every 1 to 2 months, to maintain playability. Pro players play not more than one set with a freshly strung racquet, after which it is restrung again. If you did not resting in half a year or more, or bought a racquet with strings installed in a factory, you have a good chance to end up with a "dead" string bed, which more savvy players would call unplayable, which ERT-300 will not be able to measure. If you consistently get an error message on your racquet, it means your string tension is way too low, way outside of its range, and you should have restrung your racquet long time ago. When we tested about 80 demo racquets at our local tennis shop, only about 10 of them were measurable, and only about 5 had DT in a playable range. The other 5 had extremely low DT, while the majority had strings which were hopelessly dead. Not only you get primarily the cheapest synthetic gut on demo racquets, but you get dead synthetic gut ...4) Battery lasts a very long time, hundreds of measurements.5) As I already wrote, even though the unit includes a mechanical calculator to convert DT readings to string tension, this calculator gives a rough estimate at best. This is because DT depends quite a bit on material of the strings and string pattern, not just on racquet head size which is the only parameter which the spinning wheel calculator takes into account. The calculated tension may be way off. I do not recommend that you even use this calculator. You should not care about the tension per se, you should care about how the racquet feels and how consistent is the DT from one string job to the other. If you change strings to a different type, brand, gauge, or model, you may end up with a different DT for the same tension. Since DT is a better representation of how the string bed feels and plays than the actual tension, you would most likely find, as I did, that you care about DT more than about actual string tension when you compare different strings. You might end up adjusting tension of strings "A" to match DT which you got used to with strings "B".At this point, after a year of use, it became a habit to validate each restringing job with ERT-300 and to confirm with ERT-300 that it is time to restring again. I keep a record of DT values from our previous string jobs and know what DT I should get for a given tension and strings. With properly calibrated stringing machine, you get very reproducible DT readings on a freshly strung racquet. This way, I know I get the same result each time I restring.This tool is a must for a tennis player who cares about his gear (racquet and string), regardless of his/her level. You swing a racquet, but hit the ball with strings. Strings are incredibly important for your game, at any level. Measurement is the only way to determine the condition of your string and to judge how good of a job your stringer does. Just do not expect that it will tell you string tension in pounds. No tool on the market can measure it accurately on a strung racquet. Tension is used while stringing, string bed resonance frequency or deflection is used to characterize strings on a strung racquet.If you do not get your racquet restrung more often than once per year, if at all, or if you think that getting a racquet strung at a factory is a good thing and a good buy - then do not waste your money on this tool as you will not benefit from it at your current level of understanding of tennis gear turning.A properly tuned racquet with quality strings can improve your game by up to a full level - accuracy, power, feel, impact on your elbow and arm. It is a big deal in tennis, valid from beginner level to advanced players.