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PostPosted: Wed Jun 05, 2013 8:45 am 
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wow, nice. I'll have to study that for a while.
From experience though, the fishes were on the verge of death through an accident at sensor reading of 24,000+ppmv or with my calculations ~90ppmw.
They were upside down and one jumped out of the tank to get away. I noticed distress at 60ppmw or 16,000ppmv when I was systematically pushing the limits.

So with your calculation of 30,000ppmv @ 45ppmw, is sure death while we know that fish as a whole can survive 45ppmw with no problem. So I would question the algorithm you used.


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PostPosted: Wed Jun 05, 2013 2:54 pm 
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mistergreen wrote:
wow, nice. I'll have to study that for a while.
From experience though, the fishes were on the verge of death through an accident at sensor reading of 24,000+ppmv or with my calculations ~90ppmw.
They were upside down and one jumped out of the tank to get away. I noticed distress at 60ppmw or 16,000ppmv when I was systematically pushing the limits.

So with your calculation of 30,000ppmv @ 45ppmw, is sure death while we know that fish as a whole can survive 45ppmw with no problem. So I would question the algorithm you used.


Yes that is interesting. I am wondering if humidity some how affected your readings in some way. Nevertheless, I will be ordering a sensor soon and experimenting with it to see if my maths is correct.

Did you use a drop checker to verify your readings? The kH reference solution can be tweaked so it turns yellow at whatever concentration of CO2 you want which you could take advantage of to measure different ranges and see what the sensor reads


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PostPosted: Wed Jun 05, 2013 3:48 pm 
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kkara4 wrote:
Did you use a drop checker to verify your readings? The kH reference solution can be tweaked so it turns yellow at whatever concentration of CO2 you want which you could take advantage of to measure different ranges and see what the sensor reads


Yes, I did use a drop checker to verify, 4dKH solution only.


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PostPosted: Wed Jun 05, 2013 3:58 pm 
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kkara4 wrote:
Yes that is interesting. I am wondering if humidity some how affected your readings in some way.

My sensor is sealed in a permeable silicone membrane. CO2 does go in and out. There is no water condensation that I've noticed unless there's a leak.


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PostPosted: Wed Jun 05, 2013 4:37 pm 
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mistergreen wrote:
kkara4 wrote:
Yes that is interesting. I am wondering if humidity some how affected your readings in some way.

My sensor is sealed in a permeable silicone membrane. CO2 does go in and out. There is no water condensation that I've noticed unless there's a leak.


Ah I see sorry, cant seem to see pictures on your thread on my work computer :P.


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PostPosted: Thu Jun 06, 2013 3:05 am 
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ok i see the pictures of your design now. Do you see much difference between the measurements obtained with your floating sensor vs the version 1 submersed sensor?


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PostPosted: Thu Jun 06, 2013 8:03 am 
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kkara4 wrote:
ok i see the pictures of your design now. Do you see much difference between the measurements obtained with your floating sensor vs the version 1 submersed sensor?


The submersed version is a bit more responsive I think. It might be due to the water pressure where gas exchange is forced rather passive like the floating version. Or the pressure stretches the membrane making it more permeable.

The advantages to floating version are: less risk of leaks and its out of the way of the aqua scape.
Make sure to put the sensor by water movement that's not the source of CO2. Water movement is important for gas exchange but if you put it next to the CO2 source, you'll get a skewed reading since it's super saturated with CO2.



Sent from my iPad using Tapatalk HD


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PostPosted: Thu Jun 06, 2013 2:29 pm 
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mistergreen wrote:
kkara4 wrote:
ok i see the pictures of your design now. Do you see much difference between the measurements obtained with your floating sensor vs the version 1 submersed sensor?


The submersed version is a bit more responsive I think. It might be due to the water pressure where gas exchange is forced rather passive like the floating version. Or the pressure stretches the membrane making it more permeable.

The advantages to floating version are: less risk of leaks and its out of the way of the aqua scape.
Make sure to put the sensor by water movement that's not the source of CO2. Water movement is important for gas exchange but if you put it next to the CO2 source, you'll get a skewed reading since it's super saturated with CO2.



Sent from my iPad using Tapatalk HD


On the floating version, how did you seal the edges of the sensor PCB against the polystyrene? Did you use a silicone gel or did you just fit it in the hole you cut out such that it was nice and tight?


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PostPosted: Thu Jun 06, 2013 4:18 pm 
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I use superglue to glue the pieces together around the circuit board for a snug fit. I then silicone the edges to make it air tight.
I'll post a picture of the current iteration tomorrow.


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PostPosted: Fri Jun 07, 2013 8:00 pm 
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The wires are flexible so it can adjust to the water level and glued on floatation works fine.

Image


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