Patent ID: 7456638

Claim:
An apparatus for measuring conductivity, temperature and depth of a liquid, the apparatus comprising: a parallel plate capacitive based conductivity microsensor for measuring the conductivity of the liquid, the parallel plate capacitive based conductivity microsensor comprises an upper chargeable plate fabricated on an upper substrate and a lower chargeable plate fabricated on a lower substrate and positioned in parallel relation to each other and separated by a plate gap such that the liquid to be measured flows within the plate gap, wherein the plate gap is provided by strips of silicon wafer bonded between the upper substrate of the upper parallel plate and the lower substrate of the lower parallel plate; a doped silicon resistive temperature microsensor for measuring the temperature of the liquid, the doped silicon resistive temperature microsensor further comprising a bulk silicon substrate doped with a deep impurity element; and a multiple diaphragm piezoresistive microsensor for measuring the pressure of the liquid, the multiple diaphragm piezoresistive microsensor further comprising a first deformable diaphragm having a first thickness supported by a second deformable diaphragm having a second thickness, wherein the second thickness is greater than the first thickness.