The invention is based on the recognition that an extremely rigid construction of the measuring cell is not necessary, provided that {HEAD ~ the compensation} of the exterior pressure variations is carried out with {TAIL ~ sufficient accuracy} 
is carried out with
The invention is based on the recognition that an extremely rigid construction of the measuring cell is not necessary , provided that { HEAD ~ the compensation } of the exterior pressure variations is carried out with { TAIL ~ sufficient accuracy }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL