Bubble size measurement

http://en.wikipedia.org/wiki/Young-Laplace_Equation

Where I used to work they had a machine for measuring the particle size in nebulised mists. These were very fine.

Can you project their shadows onto a screen and maybe photograph them and then measure?

A long focus microscope with a measuring scale on an reticle should be useful for the task described.

Mailman, finding the right solution for your problem is determined by at least 2 questions:

1. Which is the measurement tolerance you expect ?

2. Do you want to evaluate a momentary situation (like taking a picture and counting / qualifying bubbles by a frame grabber) or do you need a continuous measurement, par example for process control in a loop depending on bubble size and number ?

When you have a lot of bubbles at the same time in a bigger stream they can possibly be analysed by acoustic methods using a signal processor looking at the resonant frequencies determined by bubble diameter as sometimes (with more or less success!) done in bubble tensiometers.

Single bubbles going through a small tube may be detected optically by deflection of parallel light measured by linear optical arrays as used in scanners and fax machines.
They can also be detected by measuring the electrical resistance influenced by (isolating) bubbles which is also used by drawing single bubbles through a small tube.

Regards Uwe

I wonder if there is a way to use the diffraction of laser light. Just an idea.