Embodiments disclosed herein include a method of calibrating a processing chamber. In an embodiment, the method comprises placing a sensor wafer onto a support surface in the processing chamber, wherein a process kit displaceable in the Z-direction is positioned around the support surface. In an embodiment, the method further comprises measuring a first gap distance between the sensor wafer and the process kit with a sensor on an edge surface of the sensor wafer. In an embodiment, the method further comprises displacing the process kit in the Z-direction. In an embodiment, the method further comprises measuring an additional gap distance between the sensor wafer and the process kit.