Fluid exchange devices and related controls, systems, and methods

1. A device for detecting properties of a piston, the device comprising:

a first sensor and a second sensor positioned proximate a chamber;

a piston comprising one or more detection features arranged about a surface of the piston, wherein the piston is configured to travel within the chamber;

wherein the first sensor and the second sensor is each configured to produce a signal based on a proximity of the one or more detection features; and

a control system operatively configured to:

measure an electrical property in the first sensor;

detect the piston with the second sensor;

measure an electrical property in the second sensor; and

compare the electrical property in the first sensor with the electrical property in the second sensor to determine of the piston has passed by both the first sensor and the second sensor.

2. The device of claim 1 , wherein one of the first sensor and the second sensor comprises at least two coils spaced a first distance apart along an axis of the chamber.

3. The device of claim 2 , further comprising a third coil arranged around the chamber a second distance from one of the at least two coils.

4. The device of claim 1 , wherein the one or more detection features comprise one or more magnets configured to induce a current in first sensor and the second sensor.

5. The device of claim 4 , wherein the one or more magnets comprise multiple magnets that are arranged such that a same pole of each of the multiple magnets faces radially outward.

6. The device of claim 5 , wherein the multiple magnets are imbedded into the surface of the piston.

7. The device of claim 1 , wherein the control system is operatively configured to calculate a velocity of the piston based on the voltage level detected in at least one of the first sensor or the second sensor.

8. A system for exchanging pressure between at least two fluid streams, the system comprising:

a pressure exchange device for exchanging at least one property between fluids, the pressure exchange device comprising:

at least one chamber comprising:

a first end for receiving a clean fluid with a first property; and

a second end for receiving a dirty fluid with a second property; and

at least one piston in the at least one chamber, the at least one piston configured to separate the clean fluid from the dirty fluid;

a valve device configured to enable the first property of the clean fluid to be at least partially transferred to the dirty fluid through the at least one piston; and

at least one sensor arranged about the at least one chamber, wherein the at least one sensor is configured to detect one or more properties of a motion of the at least one piston, wherein a control system of the valve device is configured to stop flow of the dirty fluid while maintaining flow of the clean fluid into the at least one chamber for a dwell period responsive a location of the at least one piston.

9. The system of claim 8 , wherein the at least one sensor is configured to detect a velocity of the at least one piston.

10. The system of claim 8 , wherein the at least one piston in the at least one chamber comprises a first chamber with a first piston configured to travel in the first chamber and a second chamber with a second piston configured to travel in the second chamber, and wherein the valve device is configured to maintain a substantially 180 degree cycle difference between the first piston and the second piston.

11. The system of claim 10 , further comprising another pressure exchanger, wherein the valve device of the pressure exchanging device is configured to maintain a cycle of the first piston and the second piston of the pressure exchanging device at an equal cycle difference from a first piston and a second piston of the another pressure exchanger.

12. The system of claim 8 , wherein the control system of the valve device is configured to redirect the flow of the clean fluid after the dwell period.

13. A method of measuring a velocity of a piston comprising:

passing a piston through at least one of a first sensor or a second sensor;

inducing an electrical property in the at least one of the first sensor or the second sensor with the piston;

measuring a change in the electrical property in the at least one of the first sensor or the second sensor over time;

calculating a velocity of the piston based on the change in the electrical property in the at least one of the first sensor or the second sensor;

detecting the piston with the first sensor;

measuring a voltage level in the first sensor;

detecting the piston with a second sensor;

measuring a voltage level in the second sensor; and

comparing the voltage level in the first sensor with the voltage level in the second sensor to determine of the piston has passed by both the first sensor and the second sensor.

14. The method of claim 13 , wherein measuring the change in the electrical property comprising monitoring at least one of a current or a voltage.

15. The method of claim 13 , wherein calculating the velocity of the piston comprises calculating the velocity of the piston based on a magnitude of the change in the electrical property in at least one of the first sensor or the second sensor.

16. The method of claim 13 , wherein calculating the velocity of the piston comprises calculating the velocity of the piston based on a detected rate of change of the electrical property in at least one of the first sensor or the second sensor.

17. The method of claim 13 , further comprising passing the piston through at least one of the first sensor or the second sensor comprising a first coil and a second coil, wherein the first coil and the second coil are axially aligned and spaced by a first distance.

18. The method of claim 17 , further comprising:

inducing a current in the second coil;

measuring a change in the electrical property in the second coil over time; and

calculating the velocity of the piston based on a difference between the change in the electrical property of the first coil over time and the change in the second coil over time.

19. The method of claim 13 , further comprising passing the piston freely through a chamber only with a force applied to the piston by fluid in the chamber.

20. A method of measuring a velocity of a piston comprising:

passing a piston through at least one sensor;

inducing a voltage in the at least one sensor with the piston;

measuring a change in the voltage in the at least one sensor over time responsive to the passing of the piston;

calculating the velocity utilizing the change in the voltage over time;

if the velocity is over a threshold velocity level, measuring another change in the voltage in the at least one sensor over time responsive to the passing of the piston; and

calculating another velocity utilizing the another change in the voltage over time.