Method and device for measuring a vacuum pressure using a measuring cell arrangement

A method for vacuum pressure measurement using a measuring cell arrangement (100) comprising:

• providing a measuring cell arrangement (100), the measuring cell arrangement (100) comprising:
• a capacitive diaphragm pressure-measuring cell (20) for measuring a vacuum medium and comprising a diaphragm (2) as a pressure transducer,
• a first housing body (1) is arranged at a first side of the diaphragm (2) spaced apart from the diaphragm and sealed at an edge region thereof using a joining means (3′) such that a reference vacuum space (25) is formed in between the first housing body (1) and the diaphragm (2);
• a second side of the diaphragm (2) opposite the first side of the diaphragm (2) spaced apart from a second housing body (4) and sealed at an edge region thereof using a joining means (3) such that a measuring vacuum space (26) is formed in between the second housing body (4) and the diaphragm (2),
• the second housing body (4) comprising an opening (27) at which connecting means (5) are arranged for a communicating connection of the measuring vacuum space (26) with the vacuum medium to be measured,
• wherein inside the reference vacuum space (25) at least part of the surface of the diaphragm (2) and at least part of a surface of the first housing body (1) are electrically conductive and form respective capacitor electrodes (7, 7′) for the formation of an electric capacitance (Cx);
• a printed circuit board (10) which is equipped with electronic components (12, 14, Rref, Cref) wherein at least one of said electronic components acts as a temperature sensor,
• wherein the printed circuit board (10) is electrically connected with the capacitor electrodes (7, 7′) of the diaphragm pressure-measuring cell (20),
• wherein the printed circuit board (10) is positioned relative to the diaphragm pressure-measuring cell (20) such that the component that acts as a temperature sensor thermally contacts the first housing body,
• a microchip (12) containing a digital signal processor (DSP) with a temperature-to-digital converter (TDC) and a capacitance-to-digital converter (CDC) which operates using a time measuring method, said temperature-to-digital converter (TDC) and said capacitance-to-digital converter (CDC) being configured to determine a temperature (Tx) and the capacitance (Cx) of the diaphragm pressure-measuring cell (20) in comparison to a reference resistor (Rref) for the temperature being arranged at the printed circuit board and in comparison to a reference capacitor (Cref) for the capacitance (Cx) forming the measure for the pressure to be measured dependent on the deformation of the diaphragm (2),
• correlation means comprising stored relationships determined and saved in advance through a calibration process, and configured to derive a temperature-corrected pressure signal as a pressure signal p=f(Cx, Teff) at the signal output (16);
• the method further comprising:
• connecting the vacuum medium to be measured to the connecting means (5), the vacuum medium then being fluidically linked to the measuring vacuum space (26) and contacting the diaphragm;
• measuring the electric capacitance (Cx) of the capacitor electrodes (7, 7′);
• measuring a temperature using the temperature sensor;
• and
• deriving a temperature-corrected pressure signal p=f(Cx, Teff).