Predetermined reference voltages v1, v2 are AD-converted to achieve corresponding digital data d0, d1, d2. Also, a composition comprising microspheroidal support particles having at least one catalytically active metal or precursor thereof distributed in a layer below the surface of the particles, the layer being between an inner and an outer region of the support particle each having a lower concentration of metal or precursor. The protective sleeve is shaped and sized such that in the extended position, the protective sleeve envelops the user’s lower arm.