Biocompatible, bioresorbable polymers comprising a plurality of monomeric repeating units containing an amide group, wherein said amide groups are N-substituted and the N-substituent and degree of N-substitution are effective to lower the melt viscosity, the solution viscosity, or both, compared to the same polymer without N-substitution. The coating layer includes a binder and a inorganic additive. The piston is disposed between an inner mandrel and an outer tubular member that form an annular space therebetween. With this arrangement, it is possible to mount the electric circuit board in a curved state in a limited space on a peripheral wall of the sensor housing, and thus to shorten the axial length of the sensor housing.