OTC Phototach Contact/Non-Contact Tachometer No. 3665 Phototach can be used as a contact as well as a non-contact tachometer. Four styles of contact adapter tips clip easily to the top of the Phototach. The infrared technology makes the Phototach accurate, convenient, and easy to use. The infrared beam is not affected by ambient light and the non-contact design results in zero)torque loss for true precision. It is equipped with a laser pointer for accurate targeting and reflective tape placed on a revolving object can be measured at distances from 2 inch to 20 inch. Wide measuring range and high resolution, 2.5 to 99,999 rpm with a large 5-digit display, auto ranging, min/max memory storage, and low-battery indicator.