Abstract: A system is provided for tuning at least one control parameter of a controller in a control loop wherein the system includes an oscillation function not in series with the controller for selectively causing the control loop to oscillate at a tuning frequency, while the controller is in control of the process. While oscillating at the tuning frequency, a tuner is responsive to the tuning gain of the control loop and its tuning frequency for determining control parameters for tuning the controller.

Abstract: An apparatus for sensing differential pressures is provided. The apparatus includes a housing having an inner chamber filled with an incompressible working fluid. First and second diaphragms are provided in said housing for interacting with the fluids being measured. A flex-tube is provided in the housing and is coupled to one of the diaphragms for sensing the differential pressure. One end of the flex-tube is securely mounted to the housing and the other end is coupled to the diaphragm. A quartz sensor is positioned on the core for sensing strain applied to the flex-tube by the differential pressure exerted on the diaphragm.