1. Requires a dry environment.
2. Files cannot contact the metal restorations.
3. There should be no caries or defective restorations.
4. Requires calibration.
5. Requires a lip clip with good contact.
6. Patient sensitivity.
7. Should use a file that fits the canal snugly.
8. Perforations can give false reading.
9. Contraindicated in patients w/ pacemakers.