Pressure sensor with a radially tensioned metal diaphragm
A pressure sensor having a radially tensioned diaphragm for measuring fluid pressure. The pressure sensor includes a first generally concave metal body member and a second generally concave metal body member, and a radially tensioned flexible metal diaphragm disposed therebetween that is tensioned by heating the sensor. The first and second body members are formed from a material having a coefficient of thermal expansion in the range of approximately 0.0000056 inch/inch/° F. to 0.0000064 inch/inch/° F. The diaphragm is formed from a precipitation hardening metal material having a coefficient of thermal expansion of approximately 0.0000060 inch/inch/° F. The first body member and the second body member are formed from a ferromagnetic metal material such that the first and second body members shield the diaphragm from magnetic fields which may otherwise cause movement of the diaphragm.
1. A method of forming a pressure sensor comprising the steps of:
providing a first body member and a second body member;
preheat-treating said first body member and said second body member;
disposing a flexible diaphragm formed from an annealed precipitation hardening material between said first and second body members after said first and second body members have undergone said preheat-treating;
attaching said body members to said diaphragm such that a first fluid chamber is formed between said first body member and said diaphragm and a second fluid chamber is formed between said second body member and said diaphragm; and
heat treating said first and second body members and said diaphragm to tension said diaphragm.
2. The method of claim 1 wherein said first and second body members are heated to approximately 900° F. or higher during said preheat-treating step.
3. The method of claim 1 wherein said first and second body members are heat treated to approximately 1000° F. during said preheat-treating step.
4. The method of claim 1 wherein said first and second body members and said diaphragm are heated to approximately 900° F. during said heat treating step.
5. The method of claim 1 wherein said first and second body members are formed from a precipitation hardening material.
6. The method of claim 5 wherein said precipitation hardening material that forms said first and second body members comprises: C, up to about 0.07 wt %; Mn, up to about 1.00 wt %; P, up to about 0.040 wt %; S, up to about 0.030 wt %; Si, up to about 1.00 wt %; Cr, 15.00–17.50 wt %; Ni, 3.00–5.00 wt %; Cu, 3.00–5.00 wt %; Nb plus Ta, 0.15–0.45 wt %; and the remainder Fe.
7. The method of claim 5 wherein said precipitation hardening material that forms said first and second body members comprises: C, up to about 0.09 wt %; Mn, up to about 1.00 wt %; P, up to about 0.040 wt %; S, up to about 0.030 wt %; Si, up to about 1.00 wt %; Cr, 16.00–18.00 wt %; Ni, 6.50–7.75 wt %; Al, 0.75–1.50 wt %; and the remainder Fe.
8. The method of claim 1 wherein said precipitation hardening material of said diaphragm comprises: C, up to about 0.07 wt %; Mn, up to about 1.00 wt %; P, up to about 0.040 wt %; S, up to about 0.030 wt %; Si, up to about 1.00 wt %; Cr, 15.00–17.50 wt %; Ni, 3.00–5.00 wt %; Cu, 3.00–5.00 wt %; Nb plus Ta, 0.15–0.45 wt %; and the remainder Fe.
9. A pressure sensor made according to the method of claim 1 , said pressure sensor adapted to compensate for Span thermal error.