The Optical Tachometer is a hand-held device that can be used to measure the rotor head RPM remotely. It has a range of 1000 - 2400rpm. Uses standard  9v 6LR61 battery (not supplied)

• RPM RANGE 1000-2400
• ACCURACY 1%
• OPERATING BATTERY DRAIN 29ma @9V
• SPEEP BATTERY DRAIN 70ua @9V
• SLEEP TIME 30 SECONDS
• BATTERY TYPE 9V ALKALINE (PP3) 6LR61