a thrombus after catheter 12 has been positioned. In the unblocked aspiration state, fluid pump 18 draws fluid from catheter 12 through fluid switch 14 and fluid flow sensor 16 to fluid pump 18. For example, a clinician may operate fluid pump 18 to generate a negative pressure and may operate fluid switch 14 to be in an “open” position. Fluid flow sensor 16 may be configured pass the aspiration fluid through fluid flow sensor 16 while generating vibrations capable of detection by the clinician operating aspiration system 10. For example, fluid flow sensor 16 may oscillate the flow of the fluid from catheter 12 and through fluid flow sensor 16 to generate the vibrations. 

[0072] FIG. 2C is a conceptual block diagram illustrating aspiration system 10 of FIG. 1 at a blocked aspiration state. For example, aspiration system 10 may operate in a blocked aspiration state after catheter 12 has engaged the thrombus such that the thrombus is partially or fully blocking distal opening 36 of catheter 12. In the blocked aspiration state, fluid pump 18 may draw reduced amounts of fluid from catheter 12 through fluid switch 14 and fluid flow sensor 16 to fluid pump 18. For example, a clinician may operate fluid pump 18 to generate a negative pressure and may operate fluid switch 14 to be in an “open” position. Fluid flow sensor 16 may be configured pass any aspiration fluid through fluid flow sensor 16 at a reduced rate, including no passage of fluid. In this circumstance, fluid flow sensor 16 oscillates or vibrates at a reduced frequency or magnitude, or not at all. 

[0073] As explained above, fluid flow sensors discussed herein may be configured to oscillate flow of fluid, such as a fluid jet or stream, at least within the fluid flow sensors. In some examples, fluid flow sensors discussed herein may generate flow-induced vibrations by diverting fluid within a fluid oscillator. FIG. 3A is a diagram of an example fluid flow sensor 40 that includes a fluid oscillator 42 including a fluid diverting portion 52. Fluid flow sensor 40 is an example of fluid flow sensor 16 of FIG. 1. Fluid flow sensor 40 may include a fluid inlet 44 configured to receive fluid from catheter 12 either directly or indirectly through aspiration tubing and/or other structures such as switch 14. Fluid inlet 44 includes an inlet connector 48 that may be configured to couple to a fluid conduit such as aspiration tubing or a fluid switch. Fluid flow sensor 40 includes a fluid outlet 46 configured to discharge the fluid. Fluid outlet 46 includes an outlet connector 50 that may be configured to couple to a fluid conduit, such as aspiration tubing 30 or a fluid pump 18. 

[0074] Fluid flow sensor 40 includes flow oscillator 42 configured to oscillate flow of the fluid through fluid flow sensor 40 to generate flow-induced vibrations. In the 

