What distinguishes a laser handheld tachometer from a contact tachometer?

A laser handheld tachometer is distinguished by its use of a laser to measure rotational speed or surface velocity. This method involves directing a laser beam onto a moving surface, which reflects the light back to the device, allowing it to calculate the speed based on the frequency of the reflected light. This non-contact measurement technique is particularly advantageous as it allows for precision even from a distance, thus minimizing wear and tear on both the tachometer and the measured object.

The other options provide context that might seem relevant, but they do not precisely differentiate the laser handheld tachometer from the contact tachometer. While a laser tachometer may be more expensive and indeed requires a power source typically, these characteristics can also apply to other types of tachometers. Accuracy is not inherently inferior in laser tachometers compared to contact ones; in fact, they can often offer high precision without physical interference.