Abstract: A miniature transducer having an ultrathin tensioned silicon diaphragm so as to be responsive to extremely small changes in pressure. A silicon wafer is masked to define diaphragm areas, and etched to form a setback or capacitor gap a predefined depth. The mask is removed, and the entire silicon wafer is etched a second time to achieve the desired diaphragm thickness. The first and second etches are carried out independently, and thus the capacitor gap and diaphragm thickness can be independently formed. Mask and metallizing steps are carried out on glass wafers, and sandwiched around the processed semiconductor wafer, whereupon a large number of the miniature transducers are fabricated simultaneously. Unique patterning, etching and metallizing steps carried out on the sandwich structure allow a number of quadrature unit cells to be formed, thereby maximizing the area of the semiconductor and glass structures.

Abstract: A pressure transducer is automatically calibrated electronically by periodically subjecting the transducer to a reference pressure for a brief period of time. During this period of time the transducer electrical output is automatically adjusted to a level that represents the desired value for the reference pressure. The calibration can be accomplished just prior to taking a measurement or it can be accomplished at regular intervals spaced to ensure the accuracy of readings taken between calibrations.

Abstract: A flow meter includes a variable area obstruction mounted in a conduit and a differential pressure transducer having its two ports mounted on opposite sides of the obstruction in fluid communication with the fluid flowing through the conduit. The variable area obstruction is formed of one or more flexible leaves which extend into the flow stream and are deflectable under the influence of fluid pressure, such that an increased flow rate increases the deflection of the leaves and decreases the area of the obstruction.