Fangrui Product Details 1. Wintact Wt1357 Digital Sound Level Meter, Range: 30db~130db 2. Features 3. Automatic Calibration To Ensure Accuracy. 4. Automatic Linear Compensation: This Advanced Software Program Improves The Accuracy By Correcting The Nonlinear Accuracy Of The Sensor. 5. Quickly Adjust The Sound Speed Thickness And Quickly Call Out The Stored Data 6. Coupling Status Indication: Observe The Coupling Icon To See Whether The Coupling Is Completed. 7. It Has 12 Thickness Measurement Storage And Calling Functions To Facilitate High-altitude Operation Or Field Operation. 8. Sound Velocity Measurement. 9. The Sound Speed Of 12 Gears Of Different Materials Is Adjustable. 10. Thickness Alarm Setting. 11. Lcd Backlight Display. 12. Low Battery Indication And Automatic Shutdown. 13. Metric Imperial Selection. 14. Specification 15. Accuracy: 1.5db (under Reference Conditions) 16. Measuring Level: 30-130db (a)35-130db (c) 17. Frequency Range: 31.5hz To 8.5khz 18. Linearity Range: 50db100db 19. Digital Display: 5 Digits 20. Resolution: 0.1db 21. Bar Graph: 50 Db (scale At 1 Db Step For Monitoring Current Sound Pressure Level Display) 22. Overload Indication: Overunder 23. Frequency Weighting: A And C 24. Level Ranges: 30-80db, 50-100db, 60-110db, 80-130db 25. Self Calibration Time: 3sec 26. Sampling Rate: 20 Timesseconds 27. Ac Signal Output: 0.707vrms Full Bar Graph, Output Impedance Is About 600ohm 28. Dc Signal Output: 10mvdb,output Impedance Is About 100ohm 29. Dynamic Characteristic: Fast (high Speed)slow (low Speed) 30. Power Supply: 4x Aa 1.5v Battery Or Dc 6v 100ma (not Include)