Thien Cyclone done! Pics coming...

[dbhost]

Cool...

Is the tank in the vac supposed to get LESS in it when tossing a clean filter at it? I am actually surprised by how I just have a thin dusting on the tank.

[LCHIEN]

Cool...

Is the tank in the vac supposed to get LESS in it when tossing a clean filter at it? I am actually surprised by how I just have a thin dusting on the tank.

could be static charge on the dust particles from being whipped around at speed. They then cling to the plastic tenaciously.

[cgallery]

it would be intersting if you measured the amps of the vac running without the sep to the amps of the vac running with the sep and the amps with the hose blocked completely off. The amps is an indication of the air flow, to some extent. If it remains the same then the sep has not affected the air flow, if it changes by 20% then you have a considerable impact on the air flow.

I wanted to follow-up on Loring's brilliant idea.

Shop vac w/ only 1-1/2' hose connected: 11.85 amps.

Now connect hose to separator, with nothing connected to separator's inlet: 11.4 amps.

Now block separator's inlet with block of wood: 8.1 amps.

This experiment was performed with a cheap Radio Shack clamp-on (analog). The vac was a Ridgid WD1450.

One question I have is, how accurate is the RS ammeter? The specs for the Ridgid claim it is 11 amps. But I started at 11.85 amps with a short hose. So maybe the Radio Shack meter isn't that accurate? Is it customary for devices to exceed the amperage of what a manufacturer claims on their web site?

I will do more testing with a larger unit and a conventional blower. I think the higher initial SP of the shop vac handles the loss of the separator w/o much problem.

[LCHIEN]

I wanted to follow-up on Loring's brilliant idea.

Shop vac w/ only 1-1/2' hose connected: 11.85 amps.

Now connect hose to separator, with nothing connected to separator's inlet: 11.4 amps.

Now block separator's inlet with block of wood: 8.1 amps.

This experiment was performed with a cheap Radio Shack clamp-on (analog). The vac was a Ridgid WD1450.

One question I have is, how accurate is the RS ammeter? The specs for the Ridgid claim it is 11 amps. But I started at 11.85 amps with a short hose. So maybe the Radio Shack meter isn't that accurate? Is it customary for devices to exceed the amperage of what a manufacturer claims on their web site?

I will do more testing with a larger unit and a conventional blower. I think the higher initial SP of the shop vac handles the loss of the separator w/o much problem.

I'm not too sure about that RS meter... the website shows a clamp on analog meter but this the first ever meter which des not give specs in the Tech specs section so it must be pretty bad and accuracy a low priority to the marketing dept.

one of the problems with measuring AC is that its a much more complex measurement than DC. And Current is always more inaccurate than measuring voltage. Because AC is converted to equivalennt DC and Current is converted to Voltage. For example I have 2 very good handheld meters, a Fluke 83 and a Fluke 87.

DCV spec is +/-.1%
ACV spec is +/-.5 to .7%
DCA spec is .4%
and ACA spec is 1.2%
the resolution is 1/4000 counts or .025%

this reflects that DC volts is the native measurement and there are conversion errors going from either current to voltage and from AC to DC and is worst going from AC Amps to DCV.

I also have a AC current clamp from HF - cost me about $12 on sale I think. And I have a Kill-a-Watt meter, they go for about $20-30.

With my Fluke meters I can measure current directly (I have a special cord that plugs into the wall, has an outlet for the appliance and a pair of plugs to go in the COM and Amp jacks on the meter - this puts the full curret through you meter so you have to take care, but you can measure AC or DC this way. I can also measure the AC current with a current clamp probe, this one was from fluke and cost about $60 IIRC, it has equivalent of 1000: 1 so a wire in the jaws passing 1 amp will cause a milliamp to flow, you plug this into the mA jack on your meter and 1 mA indicated 1000 mA or 1A of current.

I measured pretty ACVolts pretty close on all the devices- F83=123.4, F87=123.4, HF=123, KaW=122.7 So most all devices will measure pretty closely on the ACVolts scale.

MY shop vac is a 7.3A rated Ridgid W06250
With no hose i measured KaW=7.8A, F83direct=6.55, F87Direct=7.70, HF=6.7 to 8.3 (see note), F83clamp=6.73 and F87clamp=7.70

With the hose on giving some restriction a tiny bit.

With the hose blocked off giving essentially no air flow KaW=5.60 F83direct=4.83 F87Direct=5.40

What I observed was that the HF clamp depended a great deal upon where the wire was in the loop - moving it closer to the seam got like 6.9A and farthest from the gap got 8.3A I suspect the theres some magnetic leakage where the clamp closes and it affects the reading, The more tight Fluke clamp (remember this clamp cost $60 and did not include the meter) had a small loop and was not affected by position and gave very consistent readings even compared to the direct method. I'm thus finding it hard to recommend any cheap clamp device (this may eplain your reading).

I am very partial to the best equipment and the Fluke 87 will read AC better than other meters because it uses a True RMS calculation which accurately measures distorted waveforms which is what you sometimes get with inductive motors under load.

I'm not sure if the Kill-a-Watt meter uses true RMS calculation but it appears it does. I am very impressed with it and it appears to give readings that follow very closely +/- 2% to my true RMS FLuke 87 which means the KaW meter is much better than my Fluke 83 which does not have True RMS calculations.

So to answer your original question I can see how your meter could be way off, inexpensive current clamp and analog meter (always good for 1-2% reading error), possible inaccurate current conversion and low cost meter make for questionable values. I think the variability I find in the clamp position are the worst source of error.

The Kill-A-Watt meter in my estimation is a very good device. It has AC outlet built in which makes all these suicide cords (Thats Electrical engineer speak for dangerous power cords with open clips and plugs for making measurements or powering devices with no cord) unneeded. At the push of a button it deliveres ACV, AC Amps, and watts very accurately. Its great for measuring power to devices, not good for troubleshooting because you can't probe anywhere else. I got mine for $20 off eBay, a great value, HF has them for $30.

As for the other question, can a vac take more power than the nameplate says, mine did 7.7A with a plate raing of 7.3. Of course my nominal AC power was 5% higher than 115V so that would make the current go up by about 5% as it measures compared to a nameplate rating at 115VAC.

11.85 is about 3-4% higher than 11.4; Between questions about your meter and probe accuracy and the actual line voltage, you don't really know that its too high.

[cgallery]

EXCELLENT information, thank you.

I'll order a Kill-A-Watt from eBay. HF only seems to have KAW strips for $99 .

[cgallery]

Okay, got the Kill-A-Watt (HF DID have them in the store).

Measured the vac w/ the short hose: 10.43 amps.

Measured the vac w/ the short hose blocked: 6.71 amps.

Measured the vac w/ the hose connected to the cyclone with nothing connected to inlet: 10.31 amps.

I'm not sure what this means.

If I had to approximate the hit to CFM based on current draw, I'd say:

(10.43-10.31) / (10.43-6.71) = .0322 or roughly 3-4%.

I think that is way off. From my other experiments I'd predict a larger hit to CFM. Need to do more experimenting, or rethink how I'm looking at this.

-----
I also tried with my larger (30-something gallon can w/ HF blower that uses universal motor).

Blower all by itself: 5.0 amps.

Blower attached to separator lid, with nothing on inlet: 4.92 amps.

-----

I also found that my table saw (BT3K) free-spinning a 10" blade (not cutting anything) draws 6.5 amps, and my DW-618 spinning a bit but not routing material draws 4.12 amps. Just kinda interesting.

[LCHIEN]

...
If I had to approximate the hit to CFM based on current draw, I'd say:

(10.43-10.31) / (10.43-6.71) = .0322 or roughly 3-4%.

...

that kinda assumes a linear relationship which its probably not and measuring air flow is very difficult.

And by the way what was the voltage? Strictly speaking the voltage can vary over time due to loads in your house an loads on the grid.
If its 112 one day and 118 another then your results will also vary. So if you measure 10.4 on your 11A vac, I'd ask what the voltage was (right after asking you what meter you used, but now that you got a KaW that's fixed).

I was thinking something like a calibration.. flare the hose into a larger cross section area. Close off the end with a piece of 1x4. Using a drill press, drill precision 1/4" holes in the end piece.
You can incrementally decrease the restriction by drilling more holes. or increase the restriction by plugging holes off (or covering them).
If you drill the holes on a grid like 5 x N then you can close off 5 at a time by sliding a plate over them and get finer resolution by plugging single holes.
Then you can plot current vs number of holes or current vs. orifice size which is the number of open holes times the area of each hole which is of course 3.14159 x (1/8") x (1/8") square inches.


Just an incomplete idea....

[cgallery]

that kinda assumes a linear relationship which its probably not and measuring air flow is very difficult.

Yeah, absolutely not linear.

And by the way what was the voltage? Strictly speaking the voltage can vary over time due to loads in your house an loads on the grid.

122.5. I took a reading before and after my testing. But I think I may have noticed the voltage dropping slightly when I was running the vac. However, wouldn't the Kill-A-Watt take that into account?

If its 112 one day and 118 another then your results will also vary. So if you measure 10.4 on your 11A vac, I'd ask what the voltage was (right after asking you what meter you used, but now that you got a KaW that's fixed).

I didn't check it the other day when testing w/ the RS meter. When I have more time I'll try to make some direct comparisons.

I was thinking something like a calibration.. flare the hose into a larger cross section area. Close off the end with a piece of 1x4. Using a drill press, drill precision 1/4" holes in the end piece.
You can incrementally decrease the restriction by drilling more holes. or increase the restriction by plugging holes off (or covering them).
If you drill the holes on a grid like 5 x N then you can close off 5 at a time by sliding a plate over them and get finer resolution by plugging single holes.

Then you can plot current vs number of holes or current vs. orifice size which is the number of open holes times the area of each hole which is of course 3.14159 x (1/8") x (1/8") square inches.

Just an incomplete idea....

I was thinking something similar, but I don't know if I'd come up with anything any more accurate than my weather-vane type anemometer for relative measurements. Still, it is worth more experimenting.

Next, I think I'll try inflating a balloon with the exhaust from the vac (or blower) with, and without the separator on the inlet of the vac (or blower). I can time how long it takes for the balloon to inflate, and compute the internal area of the balloon.

I just need a giant balloon that has no elasticity.

[LCHIEN]

Yeah, absolutely not linear.



122.5. I took a reading before and after my testing. But I think I may have noticed the voltage dropping slightly when I was running the vac. However, wouldn't the Kill-A-Watt take that into account?



I didn't check it the other day when testing w/ the RS meter. When I have more time I'll try to make some direct comparisons.



I was thinking something similar, but I don't know if I'd come up with anything any more accurate than my weather-vane type anemometer for relative measurements. Still, it is worth more experimenting.

Next, I think I'll try inflating a balloon with the exhaust from the vac (or blower) with, and without the separator on the inlet of the vac (or blower). I can time how long it takes for the balloon to inflate, and compute the internal area of the balloon.

I just need a giant balloon that has no elasticity.

Yeah, the balloon will offer increased resistance as it fills so it will be nonlinear.

If you have an annemometer and you make the variable restriction like I suggest, you can then plot airflow vs. motor current for many combinations of restriction. That way, you won't have to use the anemometer in normal use, you just measure the current with your KaW and then look up on the chart what the Airflow in CFM is that corresponds to the current... That'll be much easier next time you want to check airflow, the KaW is much cleaner than a bunch of wires and a probe being inserted.

[cgallery]

Yeah, the balloon will offer increased resistance as it fills so it will be nonlinear.

I know, that is why I need a giant balloon (1200F^3) with zero elasticity.

I wonder how they do this in a lab. I've used everything from low-end weather-type anemometers to extravagant gear used by the folks at Johnson Controls (they're headquartered here and I have a friend that works there).

I mean, if NIST wanted to super-accurately measure CFM, how would they do it?

Everything seems like just an approximation.

[Tom Slick]

Just tossing out an idea but I wonder if measuring differential pressure would be an indication of flow restriction. It is easy enough to measure, I have no idea what scale on the guage you'd need though. I've used it for monitoring filter condition on large dust collection equipment.

[cgallery]

Just tossing out an idea but I wonder if measuring differential pressure would be an indication of flow restriction. It is easy enough to measure, I have no idea what scale on the guage you'd need though. I've used it for monitoring filter condition on large dust collection equipment.

Well, I've been most interested in maintaining readings in CFM, as that is the money number in dust collection.

I had supposed that I could actually measure the left of a column of water with and without my separator lid in line, but would converting the drop in water lift to drop in CFM be straight forward?

I'm probably going to have to read some books on fluid dynamics.

[jking]

This thread is further proof why I hated my electrical engineering classes.

[LCHIEN]

Well, I've been most interested in maintaining readings in CFM, as that is the money number in dust collection.

I had supposed that I could actually measure the left of a column of water with and without my separator lid in line, but would converting the drop in water lift to drop in CFM be straight forward?

I'm probably going to have to read some books on fluid dynamics.

I don't think so. As the restriction changes, and the CFM changes so does the head. They are all interrelated and you can't keep one constant.

[Tom Slick]

why the focus on measuring absolute flow? relative numbers, such as measuring restriction, would give you an indication of efficiency.