Fluid gauge proximity sensor and method of operating same using a modulated fluid flow

Abstract

A system and method that use a fluid gauge proximity sensor. A source of modulated unidirectional or alternating fluid flow travels along at least one path having a nozzle and a flow or pressure sensor. The fluid exists at a gap between the nozzle and a target. The sensor outputs an amplitude modulated signal that varies according to a size of the gap. The amplitude modulated signal is processed either digitally or in analog devices, which can include being filtered (e.g., band pass, band limited, high pass, etc. filter) to include the modulated frequency and sufficient bandwidth on either side of that frequency and/or being demodulated using a demodulator operating at the acoustical driver modulation frequency. Using this system and method can result in only ambient acoustical energy in a desired frequency range of the device actually having the opportunity to interfere with the device operation. This can lower the devices overall sensitivity to external acoustical noise and sensor offset.

1. 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. 
 
     
     
       2. The fluid flow proximity gauge of  claim 1 , wherein:
 the signal processor processes the amplitude modulated signal to remove low frequency errors, a carrier frequency, or noise. 
 
     
     
       3. The fluid flow proximity gauge of  claim 1 , wherein the signal processor comprises analog or digital hardware or software. 
     
     
       4. The fluid flow proximity gauge of  claim 1 , wherein the measuring and reference channels respectively have first and second ones of the flow or pressure sensor. 
     
     
       5. The fluid flow proximity gauge of  claim 1 , wherein the flow or pressure sensor comprises a flow sensor, a differential pressure sensor, or an absolute pressure sensor. 
     
     
       6. The fluid flow proximity gauge of  claim 1 , wherein the modulated fluid flow device comprises:
 an external supply of conditioned fluid that is fed through a high speed variable flow controller, the flow controller both regulating and modulating the flow to the fluid gauge. 
 
     
     
       7. The fluid flow proximity gauge of  claim 1 , wherein the modulated fluid flow device comprises:
 an external supply of conditioned fluid; 
 a constant flow controller that regulates flow; and 
 a control valve that modulates the flow, 
 wherein the external supply of conditioned fluid is sequentially fed though both the constant flow controller and the separate control valve. 
 
     
     
       8. The fluid flow proximity gauge of  claim 1 , wherein the modulated fluid flow device comprises:
 an external supply of conditioned fluid; 
 a constant flow controller that regulates flow; and 
 an acoustic driver that produces alternating flow, 
 wherein the external supply of conditioned fluid is first fed through the constant flow controller, then the regulated flow is summed with the alternating flow, which results in a modulated flow. 
 
     
     
       9. The fluid flow proximity gauge of  claim 1 , wherein the modulated fluid flow device comprises:
 an acoustic driver that produces an alternating fluid flow using ambient fluid. 
 
     
     
       10. The fluid flow proximity gauge of  claim 1 , wherein at least one of the reference channel or the measuring channel has a restrictor. 
     
     
       11. The fluid flow proximity gauge of  claim 1 , wherein:
 the signal processor is configured to process the amplitude modulated signal to remove low frequency errors, a carrier frequency, and noise, wherein the signal processor comprises,
 a first band pass filter and a second band pass filter; and 
 first and second corresponding demodulators. 
 
 
     
     
       12. The fluidly proximity gauge of  claim 1 , wherein the fluid comprises one of a gas or a liquid. 
     
     
       13. The fluid flow proximity gauge of  claim 1 , wherein the reference channel has a first one of the flow or pressure sensor that produces a first signal; and
 the measurement channel has a second one of the flow or pressure sensor that produces a second signal, 
 wherein the first and second signals are subtracted to produce the amplitude modulated signal. 
 
     
     
       14. The fluid flow proximity gauge of  claim 13 , wherein the first and second ones of the flow or pressure sensor comprise flow sensors, differential pressure sensors, or absolute pressure sensors.