Advantages : 1. No direct physical contact of the meter with rotating shaft whose speed to be measured. Hence no additional load on the shaft. 2. Output is in digital format. 3. No A/D converted is required. 4. Electronic circuitry is simple because the pulse amplitudes are constant. 5. Continuous measurement is possible.
Disadvantages: 1. Life span of light source is limited (typically 50,000 hours.) 2. The accuracy of meter depends on the error represented by one pulse.