The Gefran RK series offers super compact electronics integral to the probe, or for more optional features, remote electronics connected by cable. Using magnetostrictive measuring principles, the RK measures the position of a magnetic field along the length of a 10mm SS rod.
Typically the magnet is a ring, but it can be other shapes, or built into a float for level measurement. The attraction is extreme accuracy and resolution with 0.02% accuracy being typical and readings every few milliseconds.
Different models can measure two positions simultaneously, [with two magnets] or offer Canbus, or start/stop digital outputs. The RKA has voltage or 4-20mA output and integral electronics .
Two form factors are available. Thread mounted, with electrical connector M12. This version suits general purpose industrial and level applications. Clamp mount - the most compact version, is for mounting [wholly] inside hydraulic [to 700bar] or pneumatic cylinders.
The electronics package is only 36mm long and 30mm diameter and may be installed in a way to allow a yoke to be fitted on the cylinder end. There are "no measure" zones as a result of the measuring technique - but these are very small in this series at 63mm at the rod end and only 35mm at the head end.
Gefran has three series of magnetostrictive displacement sensors, MK, IK and RK and these are differentiated by their overall construction and mounting, so if RK appears unsuited, the others may provide an answer. These are industrial devices with IP67 sealing, high vibration resistance and industrial signal outputs. Because they are non contact, they are non wearing and not damaged by contamination of their installed environment.