And if you click on the purchase button, you will get many pages of possible sensors. See how easy it is to find sensors for projects.
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They do (e.g. nitrate) but many are not at all suitable for sticking into something like an aquarium or fish pond and forgetting. The electrodes require constant care, frequent recalibration and test solutions often need to be modified to eliminate or reduce the effect of interfering anions.
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That constant care seems to be something missing in most student projects based on animals and their environment.
Lots of neeto info here https://www.timberlineinstruments.com/ammonia-analyzer/
Can’t agree more. They like watching the fish grow, but are a little short in maintainance.
A littile pricey for a group of high school potential engineers. Thanks
Thanks to everyone. I have found an ammonia sensor, and yes, very pricey. Way to expensive for this project. I’ll keep looking.
I'll tell you how it's done in analytical labs, I ran one years ago.
One caveat, a lot has changed in how analyses are done now, the vast amount of information gleaned from a few millilitres of blood is testament to that.
I don't know of any cheap probe that can be used for nitrates and nitrites.
Standard methods (EPA etc approved), often do not distinguish between the two and report as total nitrate and nitrite nitrogen,
Ammonia is easier to analyse, so nitrates and nitrites are reduced to ammonia. This gives a total nitrogen figure. Ammonia is analysed separately and subtracted from the total nitrogen.
All these methods are colorimetric and rely on colorimeters. An automated system used in clinical and industrial labs was the Technicon AutoAnalyzer.
In the field, test kits and strips are available.
A second method for ammonia exists that is viable for non-industrial i.e. domestic situations.
A standard pH probe is converted to detect ammonia. When ammonium compounds react with strong alkalies like sodium hydroxide, they produce ammonia gas NH3.
A gas permeable membrane typically PTFE separates the glass membrane of the pH probe from the sample. Ammonia permeates through the PTFE membrane and increases the pH.
The pH value is calibrated against ammonia standards.
This method is widely used in continuous monitors.
As others have said, conductivity can be used if you are dealing with just one electrolyte, say ammonium chloride or sodium nitrate, but it won't distinguish between them in mixtures.
For domestic situations like an aquarium, a better bet would be a test kit or test strips.
It might be possible to maybe automate the kits and use a simple spectral method with an Arduino.
As ever, there's the overhead of maintenance and importantly, calibration.
This is what I was hinting at in post #14.
I have been thinking about that. I would have to find a way to automate the manual testing process. But I have until next fall.
Yes, it would be reasonably easy to dip a test strip and measure the colours.
In practice, continuous monitoring is fraught with problems.
Not least is fouling by slime build up.
I installed many analyzers in waste water, which is a huge challenge.
I had to develop a self cleaning filter.
Nitrate is difficult to analyse at it is relatively stable. Nitrite reacts easily with acids.
By adding a pH universal strip you can determine what form ammonia is present as.
The most toxic form is ammonia present at high pH. At lower pH it's more likely to be ammonium.
That's interesting, since I purchased my Laird LoRaWAN Gateway from a winery that used it to measure pH, moisture, etc. in their vineyard. They moved to 4G since it cost less to operate. 10 Types Of Soil Sensors | CODA Sensors
PH and moisture are no problem. Its ammonia that’s the problem.