Methods and apparatus for calibrating pressure gauges in a substrate processing system

A method for calibrating a pressure gauge in one or more process chambers coupled to a transfer chamber having a transfer volume, comprising:

• providing a first pressure in the transfer volume and in a first inner volume of a first process chamber coupled to the transfer chamber, wherein the transfer volume and the first inner volume are fluidly coupled;
• measuring a first plurality of outputs from a first pressure gauge coupled to the first process chamber at the first pressure;
• determining a standard deviation from an average value of the first plurality of outputs;
• resetting a zero offset of the first pressure gauge to the standard deviation if the standard deviation range is greater than a predetermined percentage of the average value;
• injecting a calibration gas into the transfer volume to raise the first pressure in the transfer volume and in the first inner volume to a second pressure;
• measuring the second pressure using each of a reference pressure gauge coupled to the transfer chamber and the first pressure gauge coupled to the first process chamber while the transfer volume and the first inner volume are fluidly coupled;
• and
• comparing the second pressure measured by the reference pressure gauge to the second pressure measured by the first pressure gauge.