Ratio metric position sensor and control system

A method of position sensing comprising:

• emitting, by an acoustic transmitter system, a first emitted acoustic waveform through a fluid having a first acoustic impedance toward a first acoustic interface across a predetermined, fixed distance between the acoustic transmitter system and the first acoustic interface;
• emitting a second emitted acoustic waveform through the fluid toward a second acoustic interface across a variable second distance between the acoustic transmitter system and the second acoustic interface;
• reflecting, by the first acoustic interface, a first reflected acoustic waveform based on the first emitted acoustic waveform;
• reflecting, by the second acoustic interface, a second reflected acoustic waveform based on the second emitted acoustic waveform;
• and
• determining a first position of the second acoustic interface based on the first reflected acoustic waveform and the second reflected acoustic waveform.

A non-transitory computer storage medium encoded with a computer program, the computer program comprising instructions that when executed by data processing apparatus cause the data processing apparatus to perform operations comprising:

• emitting, by an acoustic transmitter system, a first emitted acoustic waveform through a fluid having a first acoustic impedance toward a first acoustic interface across a predetermined, fixed distance between the acoustic transmitter system and the first acoustic interface;
• emitting a second emitted acoustic waveform through the fluid toward a second acoustic interface across a variable second distance between the acoustic transmitter system and the second acoustic interface;
• reflecting, by the first acoustic interface, a first reflected acoustic waveform based on the first emitted acoustic waveform;
• reflecting, by the second acoustic interface, a second reflected acoustic waveform based on the second emitted acoustic waveform;
• and
• determining a first position of the second acoustic interface based on the first reflected acoustic waveform and the second reflected acoustic waveform.

A method of position sensing comprising:

• emitting, by an acoustic transmitter system, a first emitted acoustic waveform through a fluid having a first acoustic impedance toward a first acoustic interface across a predetermined, fixed distance between the acoustic transmitter system and the first acoustic interface;
• emitting a second emitted acoustic waveform through the fluid toward a second acoustic interface across a variable second distance between the acoustic transmitter system and the second acoustic interface;
• reflecting, by the first acoustic interface, a first reflected acoustic waveform based on the first emitted acoustic waveform;
• reflecting, by the second acoustic interface, a second reflected acoustic waveform based on the second emitted acoustic waveform;
• determining a phase difference between a second emitted phase of the second emitted acoustic waveform and a second reflected phase of the second reflected acoustic waveform, wherein determining a first position of the second acoustic interface is further based on the determined phase difference;
• and
• determining a first position of the second acoustic interface based on the first reflected acoustic waveform, the second reflected acoustic waveform, and the determined phase difference.