A pressure sensor for use with high-pressure extruders utilizing a mechanical force-rebalance system wherein a pressure sensed at a first diaphragm causes a flow of fluid from a source of fluid under pressure to enter a chamber. The fluid pressure acts on a second diaphragm or piston member to balance the force on the first diaphragm through a mechanical system. The amount of fluid pressure at the second diaphragm necessary to rebalance the first diaphragm is indicative of the pressure sensed by the first diaphragm.