Abstract: The invention is a method to determine stress within a formation, the method comprising the steps of: providing a closed reference pressure volume within the formation; providing a flexible diaphragm which can be exposed on one side to formation, and on the other side to the closed reference pressure volume; providing a switch wherein the switch generates a signal based on the diaphragm being in a position indicative of the diaphragm being flexed by pressure on one side of the diaphragm being greater than pressure on the other side of the diaphragm; cycling a pressure within the reference pressure volume to between a pressure at which a signal is generated and a pressure at which a signal is not generated; and determining the formation stress as the pressure at which the signal changes. Another aspect of the invention is the apparatus useful in this method. The switch is preferably an electrical contact that is activated by movement of the diaphragm.