Patent ID: 7568394

Claim:
For sealing an aperture, an external diaphragm, the aperture otherwise in fluid communication with a chamber containing an intermediary fluid except for sealing of the aperture by the external diaphragm, the intermediary fluid having a pressure level, the chamber being defined by housing portions and the external diaphragm, the housing portions having an overall coefficient of thermal expansion and being included in an implantable pressure measuring system to measure pressure of a sampled fluid within a biological structure, the pressure measuring system further including a pressure sensor in fluid communication with the intermediary fluid, the intermediary fluid having a coefficient of thermal expansion larger by a difference than the overall coefficient of thermal expansion of the housing portions, the external diaphragm comprising: a first diaphragm portion having a first coefficient of thermal expansion, the first diaphragm portion positioned in the external diaphragm to contact the intermediary fluid when the external diaphragm is sealing the aperture with the pressure measuring system implanted in the biological structure; and a second diaphragm portion having a second coefficient of thermal expansion, the second diaphragm portion in juxtaposition with the first diaphragm portion, the first diaphragm portion and the second diaphragm portion, shaped, sized, and positioned in the external diaphragm to cause the external diaphragm to expand away from the chamber to increase volume of the chamber when temperature of the intermediary fluid and the housing portions increases to substantially compensate for the difference between the coefficient of thermal expansion of the intermediary fluid and the overall coefficient of thermal expansion of the housing portions and geometrical configuration of the housing portions to allow the pressure level of the intermediary fluid to be substantially unaffected by changes in temperature of the intermediary fluid for conditions including over an operational range of the pressure measuring system.