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Forum Index : Microcontroller and PC projects : Measuring water turbidity
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Nimue Guru  Joined: 06/08/2020 Location: United KingdomPosts: 425 |
Morning all Does anyone have any experience in measuring the clarity of water with a turbidity sensor salvaged from a dishwasher or washing machine. These can be bought new with the necessary ADC/trim pot via https://www.amazon.co.uk/DFRobot-Gravity-Analog-Turbidity-Arduino/dp/B075T3CVH6/ref=sr_1_5?dchild=1&keywords=turbidity+sensor&qid=1612780108&sr=8-5 Was wondering if any fish keepers or brewers had rigged one up and if they offer anything "more" than a white LED / photo resistor? My use case would be a desktop aquarium into which I am wiring temperature and pH. Nim Entropy is not what it used to be |
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CaptainBoing Guru Joined: 07/09/2016 Location: United KingdomPosts: 2171 |
Interesting project, close to my heart. I kept tropical marine fish in a 550L tank for many years. I wouldn't be happy with any discernible cloudiness of the water - it had to be gin-clear on return from the filtration - always. This was something judged by shining a pen torch through the return water to see if any beam could be seen. Once you "get your eye in" it is a surprisingly good method of judging for particle contamination. If such a device did a good job, it would have been a useful addition to the final stage of my sump. My suspicions are that the small amounts of particles in suspension typical of a decent aquarium, are a bit below the threshold of the "industrial" nature of these devices as they are aimed at the white-goods market, but I would be happy to be proved wrong. Also, it does depend what fish are going in the aquarium to some degree. Certain types of fish are more susceptible to water contamination than others. Marines are a case in point where *generally* contamination must be as close to zero as you can get it and any keeper of marines will know the routine of testing several times a week for the Ammonia -> Nitrite -> Nitrate cycle, the weekly water changes and the importance of a functional, circular biome. There are some fish which are the Marine equivalent of goldfish (e.g. Damsels) where as others cannot tolerate anything other than background (Mandarins, Leatherjackets etc.). Goldfish (which are carp) are much more tolerant as carp spend much of their time munging around in the black goo at the bottom of lakes and rivers, looking for invertebrates and other scraps of food and so have evolved to be many times more tolerant of poor water quality. All conventional fish lie somewhere on this spectrum. Must be said though, you should always aim for the cleanest environment possible as the poor little fishies have no option of escape. Edited 2021-02-08 21:42 by CaptainBoing |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1584 |
I used to do a lot of underwater photography for swim schools. 2 Pics and you could see exactly how clean the pool was... or wasn't. I remember this one place I went to was like trying to shoot though a thick Fog. Couldn't work it out at first till the penny dropped and I could see the crap in the pics. The TDS levels in that place had to be off the charts. I made sure I kept my mouth closed and put my head under the water as least as possible which lead to a new technique that resulted in my not getting in that muck at all in the end. Some places were Crystal clear but others.... Things I did for money. |
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lew247 Guru Joined: 23/12/2015 Location: United KingdomPosts: 1702 |
SEN0189  https://iopscience.iop.org/article/10.1088/1742-6596/1280/2/022064/pdf |
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| Nimue Guru Joined: 06/08/2020 Location: United KingdomPosts: 425 |
That's is the very sensor I have my eye on. Nice IOP paper though. Good read. Nim Entropy is not what it used to be |
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| CaptainBoing Guru Joined: 07/09/2016 Location: United KingdomPosts: 2171 |
I don't have a downer on this device, but I am even more convinced this will not provide what is needed in the tank. Looking at Wikipedia regarding NTU, the very first picture tells pretty much all you need to know. NTU of 5 is almost still clear water and 50 is unmistakably obvious to the naked eye. Taking these two values to fig 6 and both would barely register voltage-wise and be quite difficult to separate from fluctuations in ADC readings: 0NTU =3.9994V 5NTU =3.9954V 50NTU =3.9594V Just 36mV between barely noticeable versus quite milky and I figure you'd be well below 50NTU in practice Something else that occurred, things suspended in aquarium water tend to get a bio-film coating of slime - bacteria and algae so the efficacy will drop over time leading to false positives. Even with cleaning I reckon your base-level will drift and the thing will need calibrating reasonably often. Of course all this depends on how serious-an-application... for a bit of fun it will demonstrate the principals. Oh, and there is the 3.3V input to the ADC thing, so you'd need a potential divider on the output of this sensor. My 2p |
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| Nimue Guru Joined: 06/08/2020 Location: United KingdomPosts: 425 |
@CaptainBoing >> great summary and you raise some interesting issues. You're right - I hadn't got round to considering the range of the NTU -- even when the tank is "dirty" it will be around 5NTU -- so the sensor are unlikely to be sensitive enough. And the biofilm will kill off that sensitivity eventually. That said, for 20UKP I think I'll still have a look and see if I can replicate the IOP paper from @lew247 N Entropy is not what it used to be |
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| CaptainBoing Guru Joined: 07/09/2016 Location: United KingdomPosts: 2171 |
last word, that pic on WikiP for a potable water filter shows the following in/out NTU. (big boys toys Turbidimeter 1720E - yours for a cool 300 sovs)  |
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| lew247 Guru Joined: 23/12/2015 Location: United KingdomPosts: 1702 |
https://shop.pimoroni.com/products/sparkfun-spectral-sensor-breakout-as7262-visible https://cdn.shopify.com/s/files/1/0174/1800/files/AS7262.pdf?12520236138602309719 |
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