Turbidity measurement

[Markos]

Hi,

Very interesting project.

I'm curious to understand in more detail the system for measuring turbidity.

What is the source of light and the detector used for turbidity
measurements.

And what is the electronic circuit to the turbidity readings?

I'm thinking about doing something similar for a respirometer project
that I have worked: http://www.c2o.pro.br/en/automation/x73.html

Congratulations for the amazing work.

Markos

[Chris Takahashi]

Hi Markos,

It's actually a pretty simple mechanism.  I use a 650nm laser as a light source and two light-to-frequency photosensors.  Figure 2 of the paper (http://pubs.acs.org/doi/abs/10.1021/sb500165g) explains the theory of operation.  I choose the 650nm laser (digikey PN: VLM-650-03-LPA-ND ) because it was a cheap commodity part and to prevent multi-path issues I was having with LEDs.  Really, any laser from a cheap laser pointer will do.  One thing to keep in mind about all LEDs (including laser diodes) is that they are VERY sensitive to temperature so you need to be careful to cancel any noise induced by temperature changes.  It's also a good idea to let the laser run for a bit before using it so it can reach temperature equilibrium.  The photosensors (digikey PN:TSL235-R-LF-ND) were chosen because of their extremely large dynamic range (important when log-transforming signals).

Hope that helps and good luck with your project!

Chris

[Markos]

Hi Chris,

Thanks for the tip on the sensitivity of LEDs to temperature changes.

I do not have access to download this paper.

You could send by email a pdf file?

Thank you,
Markos

[Chris Takahashi]

I can't send PDFs but I have a limited number of "e-prints" that I can send.  check your email for a link.