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Flowmeter as an alternative to bubble counter

DaveWatkin

Member
Joined
26 Oct 2020
Messages
223
Location
Aberdeen, UK
Morning, just wondering if anyone has tried using one of the small acrylic flowmeters on their CO2 system? example

My bps isn't really something that can be quantified so is worthless as a measurement to me and I always end up having to tweak things as bottles start to deplete and then when I install a new bottle but I thought a nice easy flowrate would be easily reset and monitored for changes.

I have used these in the past on gas bottles when calibrating gas detection systems but never seen them using on aquatic CO2. What do you think?
 
It would work, but you need a flow meter able to handle a much lower flow rate. For example, the one you linked goes up to 10 litre/minute and starts on 1 litre/minute. The CO2 injection rate in a tank is orders of magnitude below these values (1 liter CO2 = ~1.97 gram). You would need a flow meter with a scale of microlitres or maybe mililitres per minute not litres per minute...
 
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Yeah figured that, just the first one I found, haven't looked into what is available yet, wanted to check there was no major flaw in the concept first or if it had been done before.
 
Yeah figured that, just the first one I found, haven't looked into what is available yet, wanted to check there was no major flaw in the concept first or if it had been done before.
If low flow meters are available they could be a great alternative. But we will probably need to look into lab grade equipment for such high precision meters (e.g. for gas chromatography) , which means a very high cost.
 
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So far I have found that Omega do some at varying ranges but they are roughly £60 so a lot for such a small thing but I suppose it depends how much a person values there time. Will keep on looking and see what else I can find (beats working haha). Connections may be an issue.

Accuracy shouldn't be an issue as I don't actually care what the flow rate is, just looking for something that gives a setpoint I can continuously replicate so I guess any flow meter would do, doesn't need to be CO2 specific, just that the ball is moved to a level.
 
Hi @DaveWatkin

My thoughts turn to the use of a small paddle wheel rotor in the CO2 line. Then use a stroboscope to 'freeze' the motion of the paddle wheel. From this, it should be a simple matter to determine flow rate. Obviously, the paddle wheel would need to have very low friction so as not to restrict the flow. Just a thought.

Good luck!

JPC
 
The smallest analogue/mechanical one I could find is the Cnbtr 100-1000 Ml/min... But sold out at the time...

Other principles of flow meter equipment I could find are the differential pressure meters which could be an interesting DIY concept.
orifice-plate.png


The fluid in the U tube will have a lower level at the high-pressure side of the venturi and a higher level at the pressure drop side of the venturi.

Food for thought on how to make such a thing as small as possible...

fvm1.gif


Halfway there with these..
seachem-u-tube-10mm-co2-glassware.jpg
38104__44688.1581212628.jpg

Maybe?... Then you would need to go from a larger diameter tube to a smaller diameter tube where the T functions as the venturi/bottleneck you need for the pressure difference. Could be a nice and cheap experiment to see if it works... Theoretically it should.

Naamloos.jpg

Maybe a very low viscosity oil, since it's lighter than water and thus will react sooner to lower pressures. But this principle has its limitations at low pressures, to get significant readings. But I have no idea how low that limit would be... Trial and error. I know this kind of measuring device with such a fluid-filled pilot tube is used to set Gas pressure in household central heating units at 25 millibars.
 
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Morning, just wondering if anyone has tried using one of the small acrylic flowmeters on their CO2 system? example

My bps isn't really something that can be quantified so is worthless as a measurement to me and I always end up having to tweak things as bottles start to deplete and then when I install a new bottle but I thought a nice easy flowrate would be easily reset and monitored for changes.

I have used these in the past on gas bottles when calibrating gas detection systems but never seen them using on aquatic CO2. What do you think?

Any particular reason you're not happy to rely on a drop checker to monitor CO2 levels? I finding counting bubbles is largely futile, and it can be largely irrelevant to the CO2 dissolved in the water column. For example, your dissolved CO2 levels will change as your plant mass increases, or if your surface plants cover more of the surface, or your filter outlet moves slightly and generates less or more surface agitation etc. Your dissolved CO2 levels will change, and your drop checker will tell you that, but your bubble counter or flow meter will register no change.

The first thing that alerts me to my CO2 tank running out is I notice my drop checker is suddenly a darker green than usual as I don't open the cupboard and inspect the bubble counter every day.
 
Any particular reason you're not happy to rely on a drop checker to monitor CO2 levels? I finding counting bubbles is largely futile, and it can be largely irrelevant to the CO2 dissolved in the water column. For example, your dissolved CO2 levels will change as your plant mass increases, or if your surface plants cover more of the surface, or your filter outlet moves slightly and generates less or more surface agitation etc. Your dissolved CO2 levels will change, and your drop checker will tell you that, but your bubble counter or flow meter will register no change.

The first thing that alerts me to my CO2 tank running out is I notice my drop checker is suddenly a darker green than usual as I don't open the cupboard and inspect the bubble counter every day.
I use drop checkers and have nice stable system, this is purely for when setting the needle valve after a bottle change. There always seems t be a little discrepancy that creeps in on the flow rate which means I have to spend a few days fine tuning it in based on my drop checkers and my own observations of bubble spread through the water. However the flowrate will be the same always and that is what I'm adjusting when I fine tune after a bottle change. If there was a flow meter attached to the line then all that would need to be done at any time (bottle change, regulator service, new diffuser ceramic) would be to adjust the needle to match the previous flow.

I don't check my bubble counter either, I just check my bottle pressures every now and then and watch my tank. This is just for a quick and easy set up after any change.
 
The smallest analogue/mechanical one I could find is the Cnbtr 100-1000 Ml/min... But sold out at the time...

Other principles of flow meter equipment I could find are the differential pressure meters which could be an interesting DIY concept.
orifice-plate.png


The fluid in the U tube will have a lower level at the high-pressure side of the venturi and a higher level at the pressure drop side of the venturi.

Food for thought on how to make such a thing as small as possible...

fvm1.gif


Halfway there with these..
seachem-u-tube-10mm-co2-glassware.jpg
38104__44688.1581212628.jpg

Maybe?... Then you would need to go from a larger diameter tube to a smaller diameter tube where the T functions as the venturi/bottleneck you need for the pressure difference. Could be a nice and cheap experiment to see if it works... Theoretically it should.

View attachment 179909
Maybe a very low viscosity oil, since it's lighter than water and thus will react sooner to lower pressures. But this principle has its limitations at low pressures, to get significant readings. But I have no idea how low that limit would be... Trial and error. I know this kind of measuring device with such a fluid-filled pilot tube is used to set Gas pressure in household central heating units at 25 millibars.
I suppose this could be rigged up over the needle valve which is essentially an OR but off the shelf would be easier. Nice idea though, could be a product in it.
 
Any particular reason you're not happy to rely on a drop checker to monitor CO2 levels? I finding counting bubbles is largely futile, and it can be largely irrelevant to the CO2 dissolved in the water column. For example, your dissolved CO2 levels will change as your plant mass increases, or if your surface plants cover more of the surface, or your filter outlet moves slightly and generates less or more surface agitation etc. Your dissolved CO2 levels will change, and your drop checker will tell you that, but your bubble counter or flow meter will register no change.

The first thing that alerts me to my CO2 tank running out is I notice my drop checker is suddenly a darker green than usual as I don't open the cupboard and inspect the bubble counter every day.
You are entirely correct. <I share your opinion>. A bubble counter or a flow meter will say nothing about the actual CO2 concentration in the tank, which is what matters.

However, the flow meter could help recalibrating the CO2 flow, especially after swapping the CO2 cylinder or accidentally changing the needle valve. With the bubble counter we need to start the process almost from scratch . But with a flow meter it should be easier to reset the valve to its previous position.
 
Good catch! These are cheap! I will to do some calculations to check if this range works for CO2 injection...

Could also be a good starting point, if you could open them up and exchange the ball in it with a lighter material ball you could calibrate them I tad yourself.
I notice the projectile in this flow meter has a flat top, and since it was put in, there might be an easy way to get it out. It looks like it has a screw cap on top. Then make this projectile lighter by sanding the flat top. :)
 
I suppose this could be rigged up over the needle valve which is essentially an OR but off the shelf would be easier. Nice idea though, could be a product in it.

In theory, it should work but I don't know its limits in pressure difference to make the fluid in the tube show it... The smaller the mass of fluid it contains will lower the pressure limits... Maybe worth a try... It's easy and cheap to DIY to find out with readily available products.
 
I use drop checkers and have nice stable system, this is purely for when setting the needle valve after a bottle change. There always seems t be a little discrepancy that creeps in on the flow rate which means I have to spend a few days fine tuning it in based on my drop checkers and my own observations of bubble spread through the water. However the flowrate will be the same always and that is what I'm adjusting when I fine tune after a bottle change. If there was a flow meter attached to the line then all that would need to be done at any time (bottle change, regulator service, new diffuser ceramic) would be to adjust the needle to match the previous flow.

I don't check my bubble counter either, I just check my bottle pressures every now and then and watch my tank. This is just for a quick and easy set up after any change.
You are entirely correct. <I share your opinion>. A bubble counter or a flow meter will say nothing about the actual CO2 concentration in the tank, which is what matters.

However, the flow meter could help recalibrating the CO2 flow, especially after swapping the CO2 cylinder or accidentally changing the needle valve. With the bubble counter we need to start the process almost from scratch . But with a flow meter it should be easier to reset the valve to its previous position.

Whilst I agree with you both that a flow meter would be a good way to gauge or recalibrate CO2 flow when you change a tank - it’s fixing a symptom, not the problem.

You should be asking why your flow rate is changing when you change a bottle. With a two stage reg, and a decent needle valve, it shouldn’t. I never need to adjust anything when I change bottles.

Upgrading your needle valve might be worth considering.
 
Si bien estoy de acuerdo con ustedes en que un medidor de flujo sería una buena manera de medir o recalibrar el flujo de CO2 cuando cambia un tanque, está solucionando un síntoma, no el problema.

Debería preguntarse por qué su tasa de flujo cambia cuando cambia una botella. Con un regulador de dos etapas y una válvula de aguja decente, no debería. Nunca necesito ajustar nada cuando cambio las botellas.

Puede valer la pena considerar actualizar su valvula de aguja
Esta Your concept is fine, but for those of us who work with numerous BPS, these devices give us a correct measurement, when they ask me how many bubbles do you apply? I can not answer ,Since I can't count them
 
Esta Your concept is fine, but for those of us who work with numerous BPS, these devices give us a correct measurement, when they ask me how many bubbles do you apply? I can not answer ,Since I can't count them

But you don’t need to answer that question and they (whoever they are) shouldn’t really be asking as it’s an irrelevant measure when comparing different tanks. Bubble size can vary significantly between tanks, and is dependent on numerous factors. The bubble rate is only relevant for comparisons on the same tank.

A flow meter would potentially make comparisons between tanks possible, but only from the perspective of CO2 usage, it has little bearing on any comparison of the CO2 dissolution or distribution between tanks.
 
Whilst I agree with you both that a flow meter would be a good way to gauge or recalibrate CO2 flow when you change a tank - it’s fixing a symptom, not the problem.

You should be asking why your flow rate is changing when you change a bottle. With a two stage reg, and a decent needle valve, it shouldn’t. I never need to adjust anything when I change bottles.

Upgrading your needle valve might be worth considering.
I mean, you are right it doesn't change THAT much but like everything in this game it gives us something to do/play with/overanalyse. :) It's just like fert dosing or water treating, it isn't particularly necessary to know every detail of it and measure every parameter but we do. Really tanks just need consistency and, as in nature, the plants/livestock will adapt to what they have (within reason of course).

I do find it funny that the tank I get most positive comments about and always looks the best with pretty much zero algae is the one I do nothing with really and has no CO2 and low lighting. It's just run for so long that it has sorted it's own self out. All I do is change some water when I remember every few weeks and wipe the glass occasionally. But I digress, really this is just a little project to play with that might make life easier. It would really prove it's usefulness after regulator maintenance or worst case replacement.
 
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