This is a Pulse Sensor case intended for use with a cheap piezo buzzer and 3/8" ID hose. 

Using an oscilloscope you use it to sense changes in pressure. 

There are tiny ½" deep screw holes to mount the buzzer, but it also press fits fine. The top part uses ¾" 4-40 machine screws through ground tabs (soldered to buzzer wires) tightened on the top with keps nuts. Use alligator clips to get the +/- signal from the screws. Make sure to route the wires so they don't get pinched when putting it together. It works great with no modification, but you may want to glue any seams if you want perfection. I also made this to be free standing when not in use for convenience. I may add a version without the “stand” so you can clamp the hose if needed. 

Base diameter is 1.5" if anyone wants to modify either portion.

I would recommend printing with ABS, ASA, or better if used for automotive purposes.

Prints with no supports.

Piezo buzzer part # CEP-1110

Inspiration from the SIU Automotive “Automotive Diagnostic Pulse Sensor for 6 dollars?” YouTube video. 

Let me know if you find it useful.

Edit: Added a top for use with female banana plugs. (part # 108-0903-001)

Edit: Added BNC version