Measuring blood pressure in a non-electric way

[rainydays233]

Homework Statement

I have to conceptually design a device that works with a sphygmomanometer but does not need the stethoscope. So it needs to function with the oscillatory method (analyzing the signal of pressure changes as heart pumps blood as opposed to listening to the Kirchoff's sounds). This device needs to be low cost and fully non-electrical.

Homework Equations

I know that P_systolic = 0.55 * A_max (A=amplitude of oscillatory signal)and P diastolic = 0.85 * A_max

The Attempt at a Solution

I have divided the task into 4 functions:
Part 1 - Sense the pressure change
Part 2 - Change the pressure into an oscillatory signal (possibly need to amplify)
Part 3 - Analyze the amplitude
Part 4 - Display an output (systolic and diastolic pressure values)

I believe Part 1 can be accomplished with a diaphragm.
I am currently stuck on Part 2. The problem is in my research I cannot seem to find a way to detect pressure changes and then change them into an oscillatory signal which will then be displayed all without a circuit (i.e without an ADC etc.) The device has to be fully mechanical (cannot have an electrical part) and accurate to 3 mmHg. So can anyone suggest anything to steer me in the right direction, given my minimal experience in mechanical design?

 

[nilesh_pat]

I am thinking of a pressure-sensing diaphragm connected to a bellows-like structure and then to a series of levers, in order to create a mechanical link to a pointer or a needle or something that will be able to display the oscillatory signal. Any help would be greatly appreciated. Thanks!