We collaborated with Erwin's Piano Restoration to provide this new version of the Erwin Action Ratio Gauge. This gauge provides fast, precise measurements of grand piano action ratios.
The sand-weighted gauge depresses one key exactly 6mm. Measure the amount of resulting hammer rise, and refer to the chart on the top of the gauge to determine the action ratio. Download the PDF below for more detailed instructions and helpful information on using the gauge for optimal results.
Detailed instructions and tips on working with action ratios (PDF).