in order to mitigate the negative effects of a change in atmospheric pressure , an improved capacitance diaphragm gauge sensor incorporates an independent ambient atmospheric pressure sensor near the cdg sensor body . the ambient atmospheric sensor is located outside the cdg sensor body to sense the ambient atmospheric pressure surrounding the cdg sensor body . the ambient atmospheric sensor provides an output that represents the ambient atmospheric pressure . a sensor output processing circuit receives the output of the ambient atmospheric sensor as well as the output of the cdg sensor . the processing circuit utilizes the output from the ambient atmospheric pressure sensor to fine tune the cdg measurement of pressure by executing an in situ , real time , automatic calibration adjustment of the cdg .