NE555-based fluid analyzer

Here comes my newest experiment:
A NE555 based analyzer for fluids.
It's basic task is to differ between different types of fluids like water, cream soap and so on based on their viscosity.
The basic idea is the following:
I encapsulate some liquid in a box with some kind of slider like this:
If I move the Slider like this

the fluid would move like that:

So if I use a constant velocity to move the slider,
I'll have to use a differing force based on the friction, which is defined by the viscosity.

Now my idea was to use a piezo stripe and a constant frequency.
The piezo would be the slider and the constant frequency would have the effect of a constant velocity.

Gone through all this, I built a small circuit with the NE555, a piezo stripe which I cut from a piezo speaker and a plastic box.
Here is the schematic:

I used one multimeter to measure the current through the piezo and another one to measure the system voltage.
The voltage defines the strength that the slider moves with.
Here is some data:

Tested object	Current(5V)	Current(10V)
Water	9mA	22mA
Ethanol	7mA	18mA
Cream Soap	10mA	30mA

All aquired at 19°C room temperature. with a 1.8 x 4 cm piezo stripe.

You can see easily the differences in viscosity between the fluid.
Ethanol has a rather high viscosity, so it takes little strength to move the slider.
Cream Soap is - like the name says - a cream and has a rather low viscosity.

How could I use this thing?
Well, in this configuration, it can differ between cream soap and water.
It's not everything, but hey, a proof of concept.
If you calibrate it and build a mechanical more stable version, you could use it to make automatic quality controls on your cream soap or such.
You could build one in SMT into a glass to measure if it contains beer or cola (or cream soap ;-).
Let's see what future will give us...

/apexys/01022011/1940