CO2 probe meter

oliverpool

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Is the probe available for sale? Have not seen any updates on this for a while.
 

ShadowMac

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I remember you mentioning an approximation of a probe would be using a pH probe with a gas permeable membrane around the electrode filled with a known reference solution (4 dkh). Would the type of material Kordon breather bags are made of work for this?
 
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edwardsmith

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This is a great topic. I have an Apex and planned on monitoring pH (will be keeping discus). I know constant pH monitoring isn't necessary....but I already have the equipment. Would love to know how to use the same setup for CO2 monitoring.
 

shoggoth43

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When these wear out, what symptoms should we expect to see?


Is it the probe itself that is no good, or is it just that the membrane and solution would need to be replaced?


How often should we be calibrating/checking these?


Do the membranes have a shelf life, as in don't buy more than two or three because by the time you use them they'll be useless for this?
 

Tom Barr

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DO membrane gets fouled up, the KH solution leaks out, the readings seem off even if the plants look good etc.


You can always check it against a known system and a pH probe also.


This cost more, but it a good method to check and calibrate.
 

edwardsmith

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Thanks Tom, this is great. Can this be used to avoid molding the probe?: 3/8 inch Inline Probe Mounting Gland with Compression Fitting


Thanks
 

Tom Barr

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Marcel G

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shoggoth43 said:
When these wear out, what symptoms should we expect to see? ...
I do own Extech SDL150 DO meter, and according to my experiences and the information in the datasheet the DO membranes need to be replaced each 2-4 weeks !!!


Once I was using the membrane cap for more than 4 weeks, and the data it showed were distorted (the results were definitely wrong). But I should say that the DO probe is from different material than pH probe, so with pH probe it can have maybe longer lifetime before it shows up somehow distorted data, but if you have the pH probe with DO membrane in your tank, it will not remain clean for a long time (and according to the information from Extech, the membrate itself can't be cleaned). So if you want somehow reasonable results I would recommend to change the DO membrane once a month.


PS: Maybe Tom tested it for a longer period so he may tell us how long the measurements are stable and correct.
 

pepetj

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Now this is an interesting project! Looking forward to spend some time building one like... this Saturday evening! I know I have at least one DO membrane (think it's Oakton) and a few ph probes and meters around...


Thanks


Pepetj


Santo Domingo
 
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stfn

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Sep 16, 2016
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Tom Barr said:
I'll do a video how to.

Hi Tom,


Did you ever made the video? If yes, where can I find it?


If no, could you please re-upload the pictures from your first post, so a non-english reader could better understand the involved steps?


Thanks!
 

keval

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I also arrived at my own design for such a piece of kit as described by Tom Barr in this thread. I hit on the idea a good few years ago. The principle behind this design was first implemented just over sixty years ago by a Dr John Severinghaus and it was used for oxygen and carbon dioxide determination in blood. More to follow tomorrow...

keval