An energy harvesting module, PEH, comprising: - an elongated envelope tube; - contained inside the tube, a pendular unit comprising:. a piezoelectric transducer, PZT, beam, the beam extending in axial direction between a clamped proximal end and a free distal end and being elastically deformable in bending;. an inertial mass, coupled to the free distal end of the beam and mobile in transverse direction inside the tube; and. a beam mount, adapted to be secured to the tube and fastened to a clamping part for the beam at the proximal end of the beam, wherein the pendular unit is adapted to convert a mechanical energy produced by oscillations of the pendular unit under the effect of external stresses undergone by the module into an oscillating electrical signal collected by surface electrodes of the beam, characterized by further comprising: - a symmetrization insert, for calibrating and symmetrizing in transverse and lateral directions the pendular unit oscillations, the symmetrization insert being arranged inside the tube in a region of free travel of the beam near the inertial mass, wherein the symmetrization insert is distinct from the beam mount and comprises:. a peripheral portion adapted to be secured to the tube independently of the beam mount, the tube having an inner shape mating with the outer shape of the peripheral portion at the place where the peripheral portion has to be secured; and. a central portion with an axial through-cavity inside which the beam extends in said region of free travel, the axial cavity extending between opposite travel limitation surfaces (76, 76), the travel limitation surfaces (76, 76) being symmetrical and being capable of coming into contact with the beam in a bending configuration of the latter. - an elongated envelope tube; - contained inside the tube, a pendular unit comprising:. a piezoelectric transducer, PZT, beam, the beam extending in axial direction between a clamped proximal end and a free distal end and being elastically deformable in bending;. an inertial mass, coupled to the free distal end of the beam and mobile in transverse direction inside the tube; and. a beam mount, adapted to be secured to the tube and fastened to a clamping part for the beam at the proximal end of the beam, wherein the pendular unit is adapted to convert a mechanical energy produced by oscillations of the pendular unit under the effect of external stresses undergone by the module into an oscillating electrical signal collected by surface electrodes of the beam,. a piezoelectric transducer, PZT, beam, the beam extending in axial direction between a clamped proximal end and a free distal end and being elastically deformable in bending;. an inertial mass, coupled to the free distal end of the beam and mobile in transverse direction inside the tube; and. a beam mount, adapted to be secured to the tube and fastened to a clamping part for the beam at the proximal end of the beam, - a symmetrization insert, for calibrating and symmetrizing in transverse and lateral directions the pendular unit oscillations, the symmetrization insert being arranged inside the tube in a region of free travel of the beam near the inertial mass, wherein the symmetrization insert is distinct from the beam mount and comprises:. a peripheral portion adapted to be secured to the tube independently of the beam mount, the tube having an inner shape mating with the outer shape of the peripheral portion at the place where the peripheral portion has to be secured; and. a central portion with an axial through-cavity inside which the beam extends in said region of free travel, the axial cavity extending between opposite travel limitation surfaces (76, 76), the travel limitation surfaces (76, 76) being symmetrical and being capable of coming into contact with the beam in a bending configuration of the latter.. a peripheral portion adapted to be secured to the tube independently of the beam mount, the tube having an inner shape mating with the outer shape of the peripheral portion at the place where the peripheral portion has to be secured; and. a central portion with an axial through-cavity inside which the beam extends in said region of free travel, the axial cavity extending between opposite travel limitation surfaces (76, 76), the travel limitation surfaces (76, 76) being symmetrical and being capable of coming into contact with the beam in a bending configuration of the latter.