In effort to increase response time for the pH probe method using a KH reference solution, I realized that I needed to forgo the air gap common in drop checkers. Ininitally I adapted the air gap similar to that of a drop checker CO2 test.
The velocity at which the flux of gas transfers across the water to air and then from air to water is compounded and rather slow. Perhaps 2 hours to equilibrate or so based on several folks measurements(use 2 of them, one in the tank as reference for the tank's CO2 ppm, then add another and time the color change till both the units are equally resolved). Test Ref tank (t) to equilibrate equally to tank ref = response time. You place the ref test inside the tank 1 day prior and assume the tank's CO2 ppm is stable(caveat: it's not stable at longer response times, but this is close enough. But.....this is suitable and avoids such assumptions if you use the pH probe method and where the response times are reduced with the membrane visual checker).
So with the membrane method, there's a better way to measure the response time's accuracy as well.
Note, this same test method works well for the below version I recently tried out and also for testing pH probe set ups(but you need two pH probes/meters).
I have been suggesting a membrane approach to transfer, this involved no phase intereface changes which slow things down a good deal and prevents large gas bubbles from causing some potential issues.
Seconds versus hours.
Now apply this same idea conceptually to the drop checker method suggested by Vaughn.
A thin sealed box with the membrane snapped in with a notch and a lip with an O ring. You need enough KH ref solution inside to get a decent color resolve and placing a white backing on the container would certainly help.
Now you have only to the membrane itself to cross, and no phase shift changes.
This idea is a lot like the SeaChem (Greg Morin, are you listening??) Ammonia Alert visual test "hang in the tank" idea and could certainly be commercialized and adapted.
I think such a unit would only cost perhaps 5-10$ from a vendor.
Response time estimations should be about 5 mintues or so.
A bit better than the 2 hours.
If you want to do DIY,a simple small thin container you can wrap the DO membrane around and keep the KH ref solution seperated from the tank water and place in a semi high current region. Change and clean as needed.
Regards,
Tom Barr
www.BarrReport.com
The velocity at which the flux of gas transfers across the water to air and then from air to water is compounded and rather slow. Perhaps 2 hours to equilibrate or so based on several folks measurements(use 2 of them, one in the tank as reference for the tank's CO2 ppm, then add another and time the color change till both the units are equally resolved). Test Ref tank (t) to equilibrate equally to tank ref = response time. You place the ref test inside the tank 1 day prior and assume the tank's CO2 ppm is stable(caveat: it's not stable at longer response times, but this is close enough. But.....this is suitable and avoids such assumptions if you use the pH probe method and where the response times are reduced with the membrane visual checker).
So with the membrane method, there's a better way to measure the response time's accuracy as well.
Note, this same test method works well for the below version I recently tried out and also for testing pH probe set ups(but you need two pH probes/meters).
I have been suggesting a membrane approach to transfer, this involved no phase intereface changes which slow things down a good deal and prevents large gas bubbles from causing some potential issues.
Seconds versus hours.
Now apply this same idea conceptually to the drop checker method suggested by Vaughn.
A thin sealed box with the membrane snapped in with a notch and a lip with an O ring. You need enough KH ref solution inside to get a decent color resolve and placing a white backing on the container would certainly help.
Now you have only to the membrane itself to cross, and no phase shift changes.
This idea is a lot like the SeaChem (Greg Morin, are you listening??) Ammonia Alert visual test "hang in the tank" idea and could certainly be commercialized and adapted.
I think such a unit would only cost perhaps 5-10$ from a vendor.
Response time estimations should be about 5 mintues or so.
A bit better than the 2 hours.
If you want to do DIY,a simple small thin container you can wrap the DO membrane around and keep the KH ref solution seperated from the tank water and place in a semi high current region. Change and clean as needed.
Regards,
Tom Barr
www.BarrReport.com
