Testo470 tachometer/tachometerDetailed product description：

Testo470 is an optical and mechanical dual-purpose tachometer. After installing the mechanical speed sensor, the speed can be measured through mechanical contact.

One-handed operation
Measure rotational speed, velocity, and length
Low battery warning

Technical data
Probe type	Measurement of rotational speed using optical reflection principle
range	+1... +99999 rpm
Precision	±0.02% of mv (+1 ... +99999 rpm)
resolution	0.01 rpm (+1... +99.99 rpm) 0.1 rpm (+100... +999.9 rpm) 1 rpm (+1000... +99999 rpm)
Operating temperature	0... +50 °C
Storage temperature	-20... +70 °C
Battery types	2 AA batteries
weight	190 grams
size	175x60x28mm
warranty	1 year

Note: mv represents "measured value"