A magnetic rubber encoder employing a rubber magnet, of a kind which, within a
predetermined range of polarization pitches, the maximum magnetization intensity
for the selected polarization pitch can be obtained, is provided. The magnetic
rubber encoder 1 includes an annular magnetic member 2 made of a
rubber material containing a magnet material and having a plurality of opposite
magnetic poles N and S alternating with each other in a direction circumferentially
thereof. The relationship between the polarization pitch p of each magnetic pole
and the thickness w of the magnetic member 2 is expressed by 0.4 pw1.0
p. The polarization pitch p is chosen to be within the range of, for example, 0.5
to 1.5 mm.
