Moisture can be detrimental to speed sensor operation, ingressing into the sensor body and creating destructive impact to sensor components and solder connections. A leading manufacturer of turbine flowmeters was experiencing speed sensor failures due to moisture ingress from atmospheric conditions on an offshore oil rig. Moisture was ingressing through the sensor tip and causing corrosion of the sensor internals.
In order to prevent moisture ingress into the area around the sensor tip, the sensor body was modified to have a completely sealed front. While this did increase the distance between the sensing tip (pole piece) and the target, an extremely thin wall and special winding/pole piece design was used to ensure that signal loss was minimal. The flush front had the added benefit of preventing damage to the sensor tip from over-tightening during installation.