To preface, if you do not have spare time, or you'd rather spend it in your tanks, doing this is not for you. Please just buy the dwyer at price as many have pointed out above. But, if you did like building your own regulator or like the thrill of the ebay hunt for it, read on.
So, this turned into a rabbit hole similar to the ebay regulator thread hunt over there on the plantedtank forum. It took a little while, but I was able to dig up @Bettatail 's flow meter thread, which, all goes back to
@GreggZ anyway. Planted tank link:
Flow meters for our pressurized co2 system. Somehow, I've seen this thread before, but it took me retracing my steps to remember that I did stow it away as an option to look for cheap flow meters. At the time, I probably didn't register it so much because the dwyers were cheaper and thus, going through all this trouble was moot, but now that I didn't want to spend 80, I brushed off the rusty ebay skills, and put myself in patient bargain mode.
As it turns out, because flow meters are still not popular yet, or people are not ebay hunting yet, some can be had for pretty cheap! And really fancy ones too! But much like ebay regulator hunting, you have to know what you're looking for. Thanks to the previous posts, I learned that I'm hunting for something with SCCM (standard cubic centimeters per minute) scale and NOT SCFM (stadard cubic feet per minute) or SCFH (standard cubic feet per hour). Anything larger than cubic centimeters would be hard to show properly on the meter. But would you know, of course, the SCFM/SCFH meters are the cheaper ones that are not applicable to our use.
Equally important for consideration are the connection points! It's no good to get a meter and then have to spend arms/legs to get the right connection adapter for it! I can't say for sure if some of these adapters are a standard size and if they're interchangeable or not, but the ones on my flowmeter were definitely NOT NPT! So don't think you can just solve the issue with an NPT to hose barb or push to fit adapter (which I originally thought).
Keeping in mind those two caveats, onto hunting. Some searches I employed were as follows:
matheson fm-1050
matheson fm-1000
cole palmer flowmeter
gilmont flowmeter
aalborg flowmeter
Like regulators, it seems like some of these are just rebadges. matheson seems to make their own, cole palmer seems to be aalborg rebadges, gilmont seem to be either matheson OR aalborg rebadges. Knowing this and then googling for their spec sheets become critical in the search.
Ebay seems to get an idea of what you want and starts recommending them to you on your home page after a while. From here, it's just continuous exposure and googling that sort of gets you a 'feel' of whats right for our purposes. So for example. This item
COLE PARMER VARIABLE FLOWMETER 65mm Scale N-032-15 | eBay $33
COLE PARMER VARIABLE FLOWMETER 65mm Scale N-032-15
From a bunch of searching over time, I've figured out that cole palmers are aalborg rebadges as I mentioned before. You can search by part number or some tube information. Most interestingly is that you'll probably have to figure out the tube information anyway in order to determine the actual gas flow to see if the meter is right for our purpose. Luckily, this listing actually tells you the tube is N-032-15. Otherwise, u'd have to determine from the pictures.
From the aalborg spec sheets, we can determine that an N-032-15 allows a max flow rate for co2 anywhere from 59 to 279 sML/min (I do believe this converts to sccm, someone correct me if I'm wrong please) depending on the little float ball. The picture LOOKS like a stainless ball, so it'd be 160 sML/min. Then it becomes whether you think you can push that much sccm co2 for you tank for anything to register. The meter goes to 60, so 10 on the meter would probably be ~3x .. roughly 30sccm ?
This one
Cole Parmer PMR1-010265 Flow Meter (Rotameter) with Valve 65mm N042-07 Tube | eBay $50
Cole Parmer PMR1-010265 Flow Meter (Rotameter) with Valve 65mm N042-07 Tube
has a 042-07 tube and from the same tech sheet, you can see it goes anywhere from 6.5 to 40 sML/min. I daresay the black ball might be glass and if so, then 6.5sccm may be a little too low for most tanks unless it's really small.
Here's an example where they claim it's an n042-07 but if you look closer at the pics,
Cole Parmer N042-07 Flow Meter Flow Tube 0-65 Used | eBay $20
It actually shows to be a 014-96 tube which goes from 5379 all the way to 15000 sccm, so that's way too much for most tanks and the scale will be useless for our use. As always on ebay, buyer beware. Seller takes return becomes important here.
Mathesons need to be researched against their own site.
MATHESON Online Store for Gas Pressure Regulators, Gas Detection Equipment, Welding Equipment, and Welding Supplies
store.mathesongas.com
store.mathesongas.com
Matheson FM-1050-NV High Accuracy Flowmeter with Holder | eBay $28
But this may not be a good choice because the scaling doesn't seem right and I can't seem to determine what the model numbers mean. However, I did consider this because it has the right tube adapters for .. wait, I wonder if they just couldn't find the right fit and teflon'ed it all the way.. wow. maybe. bullet dodged. buyer beware! I mean .. mayybe, it's the right solution if you really want to be cheap.
Matheson FM-1050 Series High Accuracy Flowmeter ME13D601E800. Brand New. | eBay $50
finally, a 'new' enough part number to mean something. From matheson's site, you can tell that the E800 at the tail end of the partnumber ME13D601E800, it'll do SLPM instead of SCCM. So this item is NOT what we need, BUT, those proper factory matheson connection adapters to air tubing are very attractive. more on this later.
And sometimes you actually encounter the actual dwyer you want!
Dwyer RMA-150-SSV Adjustable Flowmeter 1/8 FNPT (10-100 cc/min air) | eBay $35
Close? I heard we reaaaly want the 151 version with a lower scale of 0-50 sccm -- unless you have a very big tank!
Anyway, you get the picture.
As for me, I lucked out on this guy
MATHESON 1301-1166 FLOWMETER NSNP | eBay $47
MATHESON 1301-1166 FLOWMETER NSNP
Got a great deal on it... because the seller was taking offers. So don't be afraid to make an offer if you see that button. These things don't sell so sometimes they'll be glad to take an offer just to get it off their hands. I got it for $35.
I took a gamble because even though I was not able to pull up specs for the tube, the pictures actually show sccm air on it. And the meter goes from 0-60. In my research, co2 and air is slightly different so my readings may not reflect accurately for co2 --meaning 12 sccm air is not 12 sccm co2, but whatever. At this point, all I needed was a relative reading to gauge what I'm injecting. Some of these older things don't follow tech sheets or if they had tech sheets, they probably don't exist on the internet anymore, or my googling is weak. The seller took returns, so I based it on whether they'd take my offer or not.
Like fancy regulators, the quality on these things are no joke. They're rock solid and built for a much higher purpose. I doubly lucked out and the valve on this guy is labeled HA, this means its a high accuracy valve that requires over 15 turns to manage their range from 0 to max flow. The valve alone lists for over $100 on matheson's site. It's pretty much a very fancy needle valve. As I have a bit finicky, cheaper SMC needle valve on my regulator, I was able to just open that up and let this HA valve control the injection rate instead. Also, like regulators, you'll notice that you can replace almost everything on this flowmeter. From the valve to the tube to the connection adapters -- which brings me to my next obstacle.
The connections that came with my meter were compression fittings.
MATHESON Online Store for Gas Pressure Regulators, Gas Detection Equipment, Welding Equipment, and Welding Supplies
store.mathesongas.com
I need ones to work with co2 hose. Remember the fancy matheson factory air tubing connection adapters I mentioned before? so ONE of these retails close to $50 and you have to buy TWO! if the meter you got doesn't come with it. Well, being fully daunted by such an issue, I went back to ebay -- and found another opportunity.
Gilmont Instruments 65 MM Flowmeter | eBay $17
On this item someone had seemingly worked out connectors and adapters for push to fit air tubing. I recognized the tube cube print on the back that indicates that this is a matheson and thereforce, figured that the connections would work on my matheson.
I made an offer and got this for $12
In the same matheson connection page above, there was a helpful video that shows how to swap these out. They are NOT the same on both ends! There's a valve end one and a seal end one! So beware of this if you do the same.
