Patent EA-004582-B1 (EA)
Title: Pressure measuring cell and method for the manufacture thereof
Inventor: BANHOLZER KARL-HEINZ
IPC: G01L9/00
Filed: 2001-09-15
Abstract: 1. A pressure measuring cell comprising a base body (1, 23, 25), a membrane (5, 27) that is connected to the base body (1, 23, 25), thus forming a measuring chamber (3, 29, 31), during operation, the membrane is subjected to a deflection which is dependent on a pressure (p, p1-p2) that is to be measured, the cell also comprises a membrane bed, formed by a surface of the base body (1, 23, 25) that faces the membrane, at least one electrode (7, 33, 67) being mounted on said bed, said electrode, together with a counter-electrode (9, 35, 69) that is mounted on the membrane (5, 27), forms a capacitor, whose capacitance represents a measurement for the deflection of the membrane (5, 27), and a contact pin (13, 59, 73) that is guided in a bore (11, 57, 71) through the base body (1, 23, 25), the electrode (7, 33, 67) is electrically connected by means of said pin for measuring the capacitance and the pin is soldered into the bore (11, 57, 71) on the membrane side, using a solder (19, 57, 75), wherein the contact pin (13, 59, 73), the solder (19, 57, 75) and the membrane bed form a smooth surface. 2. The cell of claim 1, characterized in that the base body (1, 23, 25) and/or the membrane (5,27) are made of ceramics or a monocrystal. 3. The cell of claim 1, characterized in that the contact pin (13, 59, 73) is made of tantalum, and the solder is an active refractory solder, in particular, silver-copper solder. 4. The cell of claim 1, characterized in that during operation the membrane (5, 27) is subjected to pressure (p) being measured while very low pressure, close to 0 mbar, dominates in the measuring chamber (3) of the cell or a reference pressure (pR) supplied through the base (1). 5 the membrane (27) is arranged between the base (23) and an additional base (25), the membrane (27) and the additional base (25) form an additional measuring chamber (31), wherein during operation the first pressure (p1) dominates in the measuring chamber (29), while the second pressure (p2) dominates in the additional measuring chamber and the deflection of the membrane (27) depends on the pressure being measured which corresponds the difference between the first and the second pressures (p1-p2). 6. The cell of claim 5, characterized in that the base (23) comprises a through bore (37) extending into the measuring chamber (29) in which a pressure pipe (39) is provided for supplying the first pressure (p1) to the measuring chamber (29) and the additional base (25) comprises a through bore (41) extending into the measuring chamber (31) in which a pressure pipe (43) is provided for supplying the first pressure (p2) to the measuring chamber (31). 7. A method for manufacturing a pressure measuring cell according to one of preceding claims in which a contact pin (13, 59, 73) is guided in a bore (11, 57, 71), and between base body (1, 23, 25) and the contact pin (13, 59, 73), on the membrane side a solder (14, 61, 75) is placed, soldering in the contact pin (13, 59, 73), polishing the membrane bed, the electrode (7, 33, 67), the base body (1, 23, 25) and the membrane (5,27) are provided on the smooth surface and rigidly connected therebetween. 8. The method for manufacturing a pressure measuring cell according to claim 6, characterized in that the membrane (27) is connected to the base (23) and the additional base (25) by assembly means (34) and the first pressure pipe (39) is soldered in to the base (23), and the second pressure pipe (43) is soldered in to the additional base (25).