The sensor protection must not impair the sensor's ability to take measurements but must preserve the service life of the sensor.
Ceramic materials are resistant to abrasive wear, impact-resistant yet extremely hard and inductively neutral. This means that the sensor protection can be extremely thin but still offer lasting protection against wear.
The material used is typically made from impact-resistant zirconium oxide, such as Doceram Cerazur.
Examples of sensors that require protection are the sensors used to check the inner walls of oil and natural gas pipelines.