Cheap CO2 Flow Meter Review

[Yugang]

Does this mean if it's close to a solenoid, that the heat from the solenoid could throw the readings off? I wonder if that is part of the discrepancy I see between my flowmeter and the digital one.

Possibly, but I am not sure. I believe in any case, calibration would be useful if you care about absolute values. If you're interested in relative values, or just keeping flow constant less so.

 

[Sulla]

Let me know if you need any help/code when the time comes. I have played around a lot with the calibration process and think I have it pretty settled now.

@JacksonL I was going DM you, but I figured seeing as there was interest from others, maybe public could be good.

So you saw my jerry rig earlier (its messy as hell, but at the moment I dont care, I just want to prove it works, can invest in neatening setup later) - but long story short, it all works (bus readings are good, home assistant integration works, etc) and now I need to calibrate.

With both caps on I'm getting the 32000 reading, which seems to be the standard 0 reading. So...any advice on how to calibrate now that its setup?

 

[renesis]

@JacksonL I was going DM you, but I figured seeing as there was interest from others, maybe public could be good.

So you saw my jerry rig earlier (its messy as hell, but at the moment I dont care, I just want to prove it works, can invest in neatening setup later) - but long story short, it all works (bus readings are good, home assistant integration works, etc) and now I need to calibrate.

With both caps on I'm getting the 32000 reading, which seems to be the standard 0 reading. So...any advice on how to calibrate now that its setup?

I haven't calibrated yet, but I also saw the 32k reading as baseline.

I was planning to calibrate by putting a syringe on the end after the needle valve, and timing how long it takes to fill, unless there's a better and more accurate way. Hopefully JacksonL has some insight.

 

[Sulla]

I haven't calibrated yet, but I also saw the 32k reading as baseline.

I was planning to calibrate by putting a syringe on the end after the needle valve, and timing how long it takes to fill, unless there's a better and more accurate way. Hopefully JacksonL has some insight.

So using a syringe its pretty easy to calibrate - for air.

The question is what is an appropriate conversion factor from air>>co2 for this sensor. that I cant find anywhere. The closest I got is the AS200 manual from the same manufacturer that states correction tables, but I couldnt find anything stating that the AS200 uses the same sensor etc as the AFS01...I might just write an email to the manufacturer and try my luck there.

Have you had any luck on that? Or found any way to syringe co2 instead of of air maybe?

 

[Bettatail]

conversion factor is 0.74, from air to co2, for most of the thermal mass flow meters with co2 flow range below 5L/m.

for calibration, use another proven Mass flow meter with four times higher precision(four times lower error margin, or 4+ other flowmeters with the same error margin). Or use a weather balloon(perfectly round shape), to measure the increase of diameter(volume) against time for actual flow rate.

 

[Sulla]

conversion factor is 0.74, from air to co2, for most of the thermal mass flow meters with co2 flow range below 5L/m.

for calibration, use another proven Mass flow meter with four times higher precision(four times lower error margin, or 4+ other flowmeters with the same error margin). Or use a weather balloon(perfectly round shape), to measure the increase of diameter(volume) against time for actual flow rate.

Thanks mate. Have made successful contact with the company as well. Pretty sure they'll confirm the 0.74.

As for a machine 4 times more sensitive...jeez luize. Not sure where I'm going to find that at a remotely affordable price. May use the balloon method.

In the end for my use case..it's mainly about consistency more than the actual measurement to be honest, as well as comparative changes. But of course the more accurate the better. Will investigate the balloon. Thanks!

 

[renesis]

I haven't tried to calibrate yet, waiting on more flow data between the sensor and my load cell first as I've only had 2 full days of data without me flashing, and resetting the controllers or messing with it... But the early data suggests the afs01 is over reading by a little bit.

I'm seeing about 1.22 - 1.35 g/L usage between the load cell and the flow sensor. With pure co2 weighing ~1.83 - 1.98 g/L depending on temperature. So based on just the last 2 days, the cylinder lost 0.63-0.74 of what the flow meter reported. So I believe my meter is over reporting slightly. I'll update in a few days once I have more data.