I would like to determine the real CFM in my dust collection system. Mostly for fun, Oneida V3 does a very good job. Does anyone hav a air flow meter that they would recommend. Don’t want or need anything fancy or expensive.
[OP]
Contributor
I would like to determine the real CFM in my dust collection system. Mostly for fun, Oneida V3 does a very good job. Does anyone hav a air flow meter that they would recommend. Don’t want or need anything fancy or expensive.
Contributor
You should be able to make a simple pitot tube with a water manometer for free. The subsequent calculations are left to the reader.
Member
Hey Bernie,
I picked one up off of Amazon a while back. It was probably around 20 bucks... seems to do an ok job, but I haven't really used it much. You can find a ton of them on Amazon.
Contributor
See my post here from a few years ago; https://sawmillcreek.org/showthread....ffer&highlight=
The offer still stands if you are interested.
Member
The cheap "fan in a circle" anemometers on Amazon work well, but FYI you can't run them within a foot or two of your motor or it'll give bad readings due to EMI interference. At least mine did
Hot wire ones should be 100x better.
Contributor
A fan anemometer is not accurate for dust collectors. Lots of people think they are great but.....
I borrowed John's hot wire anemometer a few years ago and did a lot of testing with it. Accurate or even good testing requires a lot of effort setup and knowledge.
The best expert and advice can be found on the Aussie woodworking site by a guy named BobL.
Last edited by Larry Frank; 03-10-2021 at 7:57 PM.
[OP]
Contributor
I'm curious as to your reasoning that a fan anemometer is inaccurate for dust collectors. They measure air velocity and when multiplied by the appropriate area units will result in a quantity of air flowing per time measurement. That said. I'm sure you are correct to say that there are more accurate methods of measuring air speed. Of course air will flow faster in the center than against the edges. But by how much? Significant enough to make a difference? Show me the data. I'll just average it. But now I'm nitpicking. With a good meter I could determine the decrease as a percentage as my pipes narrow down and also loss thru a long run. Might even be able to see if rounded flange edges and abrupt diameter changes make much of a difference. I'm doing this because I'm bored and wanting to have some intelligent fun. Besides then I could lend it out in our woodworking club and watch the anality factor go up.😇Originally Posted by Larry Frank
Contributor
To make the comparisons you mention, you wil need very accurate measurements. Even with excellent instruments, it will be very difficult to measure.
If you want data about the fan anemometer, read BobL's posts on the Aussie forum.
I did a trial with a fan anemometer and got numbers all over the place.
I posted my results of testing on this forum but they are a bit scrambled due to some moderator editing.
Member
Agree, turbulent air can only be measured in several spots then average the numbers. If it works then why waste time chasing a moving target. Lots of things are like that, the theory is generated under laboratory conditions.
Member
How do you read the flow in a duct with a fan anemometer?
I would recommend a Dwyer mini pitot tube and a magnehellic gauge or a digital manometer to use with the pitot tube.
This will also allow you to measure DP across your filters.
You need to read your flows with the tool running to get real numbers.
Last edited by Michael W. Clark; 03-11-2021 at 10:35 AM.
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