Apparatus for measuring mechanical stresses and hydraulic pressures

Claim 1

A PRESSURE CELL FOR MEASURING MECHANICAL STRESSES AND HYDRAULIC PRESSURES COMPRISING A HOUSING, A THIN DIAPHRAGM OF A MAGNETICALLY CONDUCTIVE MATERIAL SECURED ADJACENT TO ITS PERIPHERAL EDGE WITHIN SAID HOUSING HAVING OUTER AND INNER SIDES, SAID OUTER SIDE BEING ADAPTED TO BE ACTED UPON BY AN EXTERNAL PRESSURE TO BE MEASURED, AN ELECTROMAGNET ADAPTED TO BE CONNECTED TO AN ELECTRIC CIRCUIT AND HAVING A LARGE PLURALITY OF POLE PIECES OF ALTERNATING POLARITY CLOSELY ADJACENT TO EACH OTHER AND FACING THE INNER SIDE OF SAID DIAPHRAGM, MEANS FOR CONNECTING SAID HOUSING TO A PRESSURE LINE FOR SUPPLYING A PRESSURE MEDIUM INTO SAID HOUSING SO AS TO BUILD UP AN INTERNAL PRESSURE ON THE INNER SIDE OF SAID DIAPHRAGM, SAID POLE PIECES ENGAGING WITH AND SUPPORTING SAID DIAPHRAGM UNTIL SAID INTERNAL PRESSURE HAS BEEN BUILT UP TO A STRENGTH EQUAL TO THE STRENGTH OF SAID EXTERNAL PRESSURE, SAID DIAPHRAGM BEING ADAPTED TO SEPARATE FROM SAID POLE PIECES AS SOON AS SAID INTERNAL PRESSURE SLIGHTLY EXCEEDS SAID EXTERNAL PRESSURE, WHEREBY THE RELUCTANCE OF SAID CIRCUIT IS CHANGED.