Patent ID: RE42650

Claim:
A fluid flow proximity gauge, comprising: a measuring channel having a measuring gap between a nozzle and a measuring surface; a reference channel having a reference gap between a nozzle and a reference surface; a source device of modulated unidirectional or alternating flow of a fluid at the respective gaps between the nozzles and the measuring and reference surfaces; a symmetrical bridge between the reference channel and the measuring channel, wherein the bridge is modulated at one carrier frequency, while the reference channel is modulated at a second carrier frequency; a flow or pressure sensor positioned between the reference channel and the measuring channel in the symmetrical bridge, the sensor outputting an amplitude modulated signal that varies according to a size of the gaps; and a signal processor that processes the amplitude modulated signal, wherein the signal processor filters and demodulates the sensor signal to determine the reference gap and to determine a differential gap between the reference gap and the measuring gap.