1Speed sensor with groove measures speed and length of wire, cable and rope conveniently. 2Wide measurement range and high resolution. 3Automatically store max value, min value and the last measurement value. 4Contact part and photo part can be interchangeable at any time to achieve multi-purpose use. 5Automatically prompt when the voltage of power supply is lower than the specified value.This item adopts the microcomputer (CPU) technique and junctionlaser technique for one instrument which combines Photo Tach (RPM) and ContactTach (RPM, m/min). Features:1. Speed sensor with groove measures speed and length of wire, cable and rope conveniently.2. Wide measurement range and high resolution.3. Automatically store max value, min value and the last measurementvalue.4. Contact part and photo part can be interchangeable at any time toachieve multi-purpose use.5. Automatically prompt when the voltage of power supply is lower thanthe specified value.6. Ultra-large LCD screen for clear reading.Specification:Model: DT6236BMeasuring Range:Photo Tach: 2.5~99,999RPM,Contact Tach: 0.5~19,999RPM,Surface Speed: 0.05~1,999.9(m/min)Resolution:Photo Tach: 0.01RPM(2.5~999.99RPM) 0.1RPM(1,000~9,999.9RPM) 1RPM(over 10,000RPM)Contact Tach: 0.01RPM(0.5~999.99RPM) 0.1RPM(1,000~9,999.9RPM) 1RPM(over 10,000RPM)Surface Speed: 0.01m/min(0.05~99.99m/min)0.1m/min(over 100m/min)Accuracy: (0.05%+1 digit)Sampling Time: 0.5sec(over 120RPM)Detecting Distance: 50~500mmScreen: 5 digits 18mm (0.6") LCDRange Select: Auto-RangingTest Base: 6MHz Quartz crystalBattery: 3x1.5V AAA batteries (NOT included)Power Consumption: Approx 45mAColor: BlackSize: 20*7.5*3.5cm /7.87*2.95*1.38inWeigh