Thread: Anemometer on special

Originally Posted by Skew ChiDAMN!!

I don't measure flow into the hood; just across & around the work-piece.

OK I understand what you are doing now. It's better than not doing anything but it sounds like you are just measuring air speed (m/s) because this will simply not measure air flow (m^3/s)
Air speed alone is not a reliable indicator of fine dust collection which requires maximum flow or volume collection. it's possible to generate a high air speed - just throttle down or constrain the extraction point, or partially block the entrance with a workpiece. Unfortunately this also ends up throttles down the flow.

Air speed in important in reducing chip scatter but no known DC will produce an air speed that can capture all or even most of the chips from standard turning situations. The speed of the air chips is typically >5x that of the air speed along a lathe spindle line and even less at the tip of the turning tool especially on larger objects. Higher air speeds at the tip of the turning tool can help reduce chip scatter but that's about it. Chip scatter is a lesser order OHS issue in turning, whereas fine dust collection is much more significant.

Out of interest, what constitutes an acceptable air speed? or do you just aim to maximise air speed and live with what you can get?

Elanjacobs, My reply to you was most definitely intended as tongue-in-cheek and as a result of my interpretation of Bobl's reply to your initial Post. It appears my interpretation of Bobl's Post, both content and delivery, is unsupported and erroneous. My apologies to any and all if offended.
I shall return to my burrow and mind my own business.
Geoff

All good. The problem with text is that you can't infer meaning from tone. Smilies can be useful for overcoming that

Originally Posted by TinyTool

Elanjacobs, My reply to you was most definitely intended as tongue-in-cheek and as a result of my interpretation of Bobl's reply to your initial Post. It appears my interpretation of Bobl's Post, both content and delivery, is unsupported and erroneous. My apologies to any and all if offended.
I shall return to my burrow and mind my own business.

Aw Geoff, don't do that.
These fora need more people with wit and a dry sense of humour.

It is so easy to miss-interpret a post. One may have posted something as a joke but you can not tell what they really meant. Sometimes you can add a sentence or something to indicate that what you posted was just in fun and not serious.

TT, you could use one of these but it will be a bit exxy......https://www.testo-direct.ca/product/...ire-anemometer

Originally Posted by Chris Parks

TT, you could use one of these but it will be a bit exxy......https://www.testo-direct.ca/product/...ire-anemometer

Lappa and I have these units and they are indeed pretty useful.
You can get them from China for a bit less although I suspect they will then not include the possibility to purchase a $295 ISO certification.
Mine and Lappa's came with a single point calibration certificate with accuracy of about +/- 8% (only needed when comparing the results from this meter with other meters). Measurement reproducibility is not limited by the ability of the meter (it's read out is to 0.01m/s) but as usual the limitation is the turbulence of DC air flow.

My testing of my Testo against my NIST certified anemometer shows it appears to be generally reading low across the range, and ~10% low at the calibration point speed of 8 m/s.
The Testo does have a thicker telescopic arm than many other hot wire anemometers, probably because it also has a longer arm so it can reach further inside ducting but this may compromise its use in small ducts.

The Testo is vey useful because it connects via Blue tooth to a mobile phone app which shows the readings and stores the data that can then send it in CSV format to anywhere else on the net. This means I use it in my shed and see the results on my laptop located up in the house.

I am guessing here but is it the case that the hot-wire anemometer doesn't need to be inserted into the airflow through a hole in the pipe, like the pressure type sensor?

As our favourite red-head said "please explain!"

Geoff

Unfortunately you have to drill a hole in your pipe. I drilled one about 1.5m down from an elbow on the longest straight run , to measure my flow.
Its a nice little unit as you can capture the info on your PC, phone or iPad and export it as a PDF.
i have a thread somewhere on different measurement techniques using this anemometer. I’ll see if I can find it and post a link.

Heres the link

DE Measurements

Thanks for that Lappa, I thought for a moment there I might have been able to hold the hot-wire sensor head in the airflow at the mouth (or just inside) of the pipe to get a meaningful reading but it seems not. Bugger!
Geoff

TT. I’m thinking of buying one of those cheap vane anemometers, using the information in the USA mining report to measure the flow, then check the results against the Testo anemometer.
I’ll report back here if and when I do.

Update.

Just bought one.

Originally Posted by Lappa

Here’s an interesting article from the Mines Dept in the USA looking at the use of vane anemometers to measure airflow in small diameter pipes. Looks at methods and correction factors etc.

Hi Lappa.

If there is a link in your post it doesn't show for me. Any chance you can post it? I'd like to look at it.

Thanks
Pete

I can't see a link either.

Sorry about that. I’m sure it was there as I always check links in “preview” before posting.

https://www.cdc.gov/niosh/mining/use...dfs/ri9061.pdf