Well started a new project destined to not be completed (it's a gift)...
Was researching methods to do a more accurate Nitrate reading.
found this article:
And the "key" was this:
We selected LaMotte Company reagents for the Nitrate colorimetric test because: (a) The
recommended wavelength, 540 nm, is very close to the 565-nm wavelength setting on the
That's green btw.
initial photoshop checks of the Salifert Nitrate test revealed indeed green was selectively removed from the spectrum.
Couple that w/ cheap Lux meters that are heavily weighted (or should be) to measure green.. well it all sort of came together..
Couple of catches: Obviously the Nitrate test needs to produce a magenta sample (Cadmium reduction types which also work by turning nitrate to nitrite and actually sampling that.. so really all these "nitrate" tests are really Nitrate+Nitrite (which should be zero (Nitrite). Note: when cycling this actually could be an issue but just think about it for now ))
Well tried to buy an already built unit (like the Vernier, which btw is pretty cheap on the bay, BUT that is only one PART of a chain making a complete "meter" costly.
I'm sure a "box" could be played with but why? All it would be is buying 4 LED diodes and box and switch)
Anyways more to results:
Made a housing to cover the sensor of a LX-200 Lux meter.
drilled a 1/4" hole as an entry point
took a sample jar (about 1" round) for the "cuvette".
Put it on top w/ 1ml water
Shined an LED flashlight though it, resting on the lip and centered
Recorded reading 1000Lux
took out water added a sample of about 50ppm Nitrate Salifert test
measured reading 830Lux
Now this is w/ out using a more selective diode.
Ideally a 540nm green should be used BUT not in my stable (actually don't have any high power greens atm..
Now for fun I cheated:
Had a small minibar bottle of Tanqueray which, is a nice green color.
Sadly bottle was almost empty..
will see how that effects readings along w/ th next step of creating a Nitrate sample and diluting it to plot..
Sooo for the more ambitious.. That is the groundwork.
Seems solid, simple and accurate..
Oh I plotted the G of the rgb components of the salifert sample chart and it was pretty darn linear..May mean something, may not..
Oh using the LUX meter I'm not sure the light needs to be filtered, just consistent..
either way should work..