Pressure measurement

The Bronkhorst High-Tech EL-PRESS pressure sensor is a
piezo resistive bridge on the surface of a silicon chip.
This chip is drilled out on its reverse side, giving the
inside of the chip the form of a pressure diaphragm
whose thickness determines the pressure range. When a
pressure acts on this chip, the diaphragm flexes, and the
resistor values of the bridge alter in proportion to the
pressure. The measuring cell is separated from the
external pressure by a thin, sensitive stainless steel
diaphragm, and the sealed off cavity between diaphragm
and cell is filled with oil.