Apparatus comprising: a pressure sensor assembly comprising: a printed circuit board having a front side and a back side; a pressure sensor having a front side and a back side, the pressure sensor mounted to the printed circuit board with the back side of the pressure sensor facing the front side of the printed circuit board; and a force transmitting member having a front side and a back side, wherein the front side of the force transmitting member includes a cured silicone elastomer and the back side of the force transmitting member engages the front side of the pressure sensor, wherein the force transmitting member transmits a force applied to the front side of the force transmitting member to the front side of the pressure sensor; the apparatus further comprising a reservoir including one or more extensions that define an opening, wherein the front side of the force transmitting member is exposed to the interior of the reservoir, and wherein the one or more extensions are configured to engage the front side of the force transmitting member to seal the opening characterised by a clip configured to secure the pressure sensor assembly within the opening of the reservoir, to apply a force on the printed circuit board of the pressure sensor assembly and to push the pressure sensor assembly against the one or more extensions. a pressure sensor assembly comprising: a printed circuit board having a front side and a back side; a pressure sensor having a front side and a back side, the pressure sensor mounted to the printed circuit board with the back side of the pressure sensor facing the front side of the printed circuit board; and a force transmitting member having a front side and a back side, wherein the front side of the force transmitting member includes a cured silicone elastomer and the back side of the force transmitting member engages the front side of the pressure sensor, wherein the force transmitting member transmits a force applied to the front side of the force transmitting member to the front side of the pressure sensor; a printed circuit board having a front side and a back side; a pressure sensor having a front side and a back side, the pressure sensor mounted to the printed circuit board with the back side of the pressure sensor facing the front side of the printed circuit board; and a force transmitting member having a front side and a back side, wherein the front side of the force transmitting member includes a cured silicone elastomer and the back side of the force transmitting member engages the front side of the pressure sensor, wherein the force transmitting member transmits a force applied to the front side of the force transmitting member to the front side of the pressure sensor; the apparatus further comprising a reservoir including one or more extensions that define an opening, wherein the front side of the force transmitting member is exposed to the interior of the reservoir, and wherein the one or more extensions are configured to engage the front side of the force transmitting member to seal the opening characterised by a clip configured to secure the pressure sensor assembly within the opening of the reservoir, to apply a force on the printed circuit board of the pressure sensor assembly and to push the pressure sensor assembly against the one or more extensions.