ERT 300 Tennis String Tester

The ERT 300 Tennis String Tester is a professional diagnostic tool designed to accurately measure the Dynamic Tension (DT) of a strung tennis racquet in just seconds. Rather than relying on feel or guesswork, the ERT 300 provides an objective measurement of the string bed, helping players and professional stringers understand how a racquet is performing.

Often described as measuring the “engine of the racquet”, the ERT 300 is particularly valuable for monitoring string-bed consistency, comparing freshly strung racquets and identifying tension loss as strings are played.

Key Features

• Measures Dynamic Tension (DT) – Provides a numerical measurement of the overall stiffness and playing characteristics of the string bed.
• Fast Measurement – Check a racquet's Dynamic Tension in just a few seconds.
• Monitor Tension Loss – Regular testing makes it easier to track how the string bed changes as strings lose tension through play and over time.
• Improve Stringing Consistency – An excellent quality-control tool for professional stringers wanting to compare racquets after stringing.
• Match Multiple Racquets – Helps competitive players maintain greater consistency between racquets in their bag.
• Objective Performance Data – Provides measurable information rather than relying solely on how tight or loose the strings feel.
• Useful for String & Tension Testing – Compare different strings, tensions and setups to help determine which configuration works best for an individual player.
• Professional Stringing Tool – Particularly valuable for racquet technicians, tennis stores, coaches and serious competitive players.

What is Dynamic Tension?

Dynamic Tension (DT) is a measurement of the stiffness of the complete string bed rather than simply the tension originally selected on the stringing machine.

Two racquets strung at the same reference tension can produce different string-bed characteristics depending on factors such as the string type, gauge, racquet head size, string pattern and stringing process. Measuring DT gives the stringer or player another useful way of assessing the finished string bed and monitoring how it changes over time.

Ideal For

Professional racquet stringers, tennis stores, coaches and serious players who want a more accurate way to monitor string-bed performance. The ERT 300 is particularly useful for quality control, matching multiple racquets, tracking tension loss and refining individual string and tension setups.