DT 2234BL Non Contact Laser Tachometer.
Measurement and Range of 10 to 99,999 RPM>
Resolution of 0.1 RPM (<1,000 RPM) 1RPM (≥ 1,000 RPM)
Accuracy of ± (0.05% + 1 digit)

• 5 Digit Display, 10 mm (0.4") LCD, with 
  function annunciation

• Detecting distance of 50 - 2,000 mm typically

• Laser light source of less than 1 mW, 
  Class 2 laser diode. Red. 

• Time base is Quartz Crystal, 4.194 MHz

• Circuit is Exclusive Chip of Microcomputer LSI Circuit

• 0 to 50°C Temperature (32°F to 122°F)

• Less than 80% RH Operating Humidity

• Memory with recall function, last value, 
  maximum and minimum values will be stored 
  into the memory automatically