Patent ID: 7021119

Claim:
A liquid flow proximity sensor, comprising: a junction that divides liquid input into the liquid flow proximity sensor into a reference channel and a measurement channel; a first switching device coupled to the measurement channel and to a plurality of measurement branches, wherein said first switching device permits liquid to flow in one measurement branch at a time and can be used to switch the flow of liquid from one measurement branch to another measurement branch; a first porous flow restrictor placed along the reference channel, wherein said first porous flow restrictor evenly restricts liquid flow through the reference channel; a plurality of measurement branch porous flow restrictors, placed along said plurality of measurement branches, wherein each measurement branch porous flow restrictor evenly restricts liquid flow through a respective measurement branch; a reference probe at an end of the reference channel, whereby liquid exits the reference channel through the reference probe and travels across a reference standoff to impinge upon a reference surface; a plurality of measurement probes, wherein a measurement probe is placed at an end of each of the measurement branches, whereby liquid exits a measurement branch through a measurement probe and travels across a measurement standoff to impinge upon a measurement surface; a second switching device coupled to a bridge channel and to said plurality of measurement branches, wherein said second switching device permits liquid to flow in one measurement branch at a time and can be used to switch the flow of liquid from one measurement branch to another measurement branch; and a liquid mass flow sensor coupled between the reference channel and said second switching device for sensing the liquid flow therebetween, whereby, the difference in standoffs between the reference surface and a measurement surface can be sensed.