KKmoon GM100 LCD Digital Ultrasonic Thickness Gauge Tester Depth Gauge + Sound Velocity Meter Range 1.2~225mm Auto calibration to assure the accuracy. Auto linear compensation: this advanced software program enhances the precision by correcting the non-linear accuracy of transducer. Coupling status indication: Observing the coupling icon to learn if the coupling is accomplished or not. 10 thickness measurement storage and recall function available, which facilitates the height work or working in wild area. Sound velocity measurement.