Pressure sensor development using hard anodized aluminum diaphragm and sputtered Pt-W thin film strain sensors

Pressure sensors with a metallic diaphragm and bonded strain gauge are by far the most widely used sensors in pressure measurement. In this work, we describe a method to fabricate a low power, light weight and low cost pressure sensor using aluminum diaphragm. The diaphragm is hard anodized to get insulating base over which Pt-W (Pt: 92%, W: 8%) thin film strain sensors are sputter deposited for sensing the pressure. Hence, this technique eliminates the application of adhesive to bond the strain gauges to the metallic diaphragm. The required level of insulation resistance (in the range of giga-ohms) between the metal diaphragm and the sputtered stain gauge is provided by the hard anodic film. The hard anodic coating is obtained by the wet electrochemical method with pulsed power supply arrangement. The details of diaphragm fabrication, hard anodization of aluminum, testing, calibration of sensor and its applications are discussed and compared with sensors fabricated from different aluminum alloys (AA2024, AA6061 and AA7075).