ST8030 Mini Digital Photo Laser Digital Tachometer Non Contact High Accuracy MPU LCD Display(Purple) Features 1. Can preset up to 9 impeller quantities, measure more accurately. 2. Hold maximum value, minimum value. 3. Selectable unit of the rotate speed between RPM and RPS. 4. With low battery indication and LCD display. 5. Auto off: switch off Automatically. 6. Combine the microprocessor technology and laser technology, more intelligent and reliable. 7. Mini size, handheld and portable. Specifications 1. Display: 5 Digits LCD display 2. Units: RPM, RPS 3. Measuring range: 100 ~ 30000RPM, 1.7 ~ 500RPS 4. Resolution: - 0.1RPM (100 ~ 999.9RPM), 0.1RPS (1.7 ~ 100RPS) - 1RPM(1000 ~ 30000RPM), 1RPS(100 ~ 500RPS) 5. Accuracy: - +- (0.1%n + 5d) RPM; (100 ~ 9999.9RPM) - +- (0.02%n + 2d) RPM; (10000 ~ 30000RPM) 6. Sampling rates: 1Sec 7. Number of impeller setting: 1 ~ 9 8. Time base: Quartz crystal 9. Circuit: Exclusive one-chip of microcomputer LSI circuit 10. Detecting distance: 10 ~ 40cm 3.9 ~ 15.7in 11. Auto power off: 10 Minutes idle 12. Operational condition: -10 ~ +50 Degree Celsius; 14 ~ +122 Fahrenheit degree; 10% ~ 90% RH 13. Storage condition: -20 ~ +60 Degree Celsius; -4 ~ +140 Fahrenheit degree; 10% ~ 75% RH 14. Power supply: 3 * 1.5V AAA (LR03) (Not included) 15. Product size: 14.3x5.5x2.2cm 16. Product weight: 72g (Without batteries)