Manometer: Dwyer Mark II Model 40-1 Inquiry

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lsayre
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Post by lsayre » Sat. Jun. 20, 2015 12:31 pm

Have any of you used a Dwyer Model 40-1 instead of the Model 25? Whereas the scale on the 25 spans 3 inches, the model 40-1 spans only 1 inch, so the ease of accurately being able to be read it from a distance should be potentially somewhat superior. ??? (though the span still dwarfs the range that we have interest in)

http://www.amazon.com/Dwyer-40-1-AV-Manometer-0-1 ... ds=Dwyer+M


 
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Post by Lightning » Sat. Jun. 20, 2015 2:56 pm

Actually Larry, it appears to me that the model 25 has a better spread in the range that we need the reading to be in.

On a model 25 at close scrutiny it's possible to make readings at .0025" of water column resolution. I don't see that happening on the model 40
Last edited by Lightning on Sat. Jun. 20, 2015 3:03 pm, edited 1 time in total.

 
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Post by lsayre » Sat. Jun. 20, 2015 3:01 pm

Yes, after looking at this again I believe you are correct. I wonder if they can be forcedly re-scaled in our favor to expand the useful range just by changing the density of the oil?

 
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Post by Lightning » Sat. Jun. 20, 2015 3:06 pm

I've thought about that as well. Another idea I had was to change the angle of inclination slightly to exaggerate the reading.

Since the reading is based on the pull of gravity against the pressure difference.

 
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Post by coaledsweat » Sat. Jun. 20, 2015 4:24 pm

No good, needs to read in hundreths not tenths. Not only that, look at the price! :shock:

 
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Post by Lightning » Sat. Jun. 20, 2015 5:07 pm

coaledsweat wrote:No good, needs to read in hundreths not tenths. Not only that, look at the price! :shock:
Yeah pricey. Each mark between 0 and .1 represent a hundredth :)

 
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Post by coaledsweat » Sat. Jun. 20, 2015 6:13 pm

Lightning wrote:
coaledsweat wrote:No good, needs to read in hundreths not tenths. Not only that, look at the price! :shock:
Yeah pricey. Each mark between 0 and .1 represent a hundredth :)
Yes, but it is nowhere near as accurate as a Mark II. Just compare the scales.

http://www.qualityinstruments-direct.com/product/ ... HwodVqkAKg


 
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Post by Lightning » Sat. Jun. 20, 2015 6:55 pm

Yes sir! I agree :)

 
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Post by lsayre » Sat. Jun. 20, 2015 6:59 pm

I'm still scratching my head over how they can both use the same red oil and yet one scales differently than the other.

 
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Post by Lightning » Sat. Jun. 20, 2015 7:18 pm

I may have an explanation. Notice that the angle of inclination on the model 25 is much shallower than the model 40. Also note that the scale on the model 25 has more length between the same two points than the model 40. Changing the inclination changes the scale length since the same negative pressure will lift the fluid to the same elevation because of the other two constants. Which are gravity and atmospheric pressure.

 
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Post by Lightning » Sat. Jun. 20, 2015 7:26 pm

If the scale were to be tipped vertical, the distance between 0 and .2" of wc would only be a couple millimeters long at best.

 
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Post by Lightning » Sat. Jun. 20, 2015 7:28 pm

Lightning wrote:If the scale were to be tipped vertical, the distance between 0 and .2" of wc would only be a couple millimeters long at best.
Oh, wait for it....

If tipped vertical it would be 2 tenths of an inch long :lol:

 
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Post by lsayre » Sat. Jun. 20, 2015 7:30 pm

It turns out that the lower the density of the oil, the greater the span (and precision) of the manometer. But at a density of 0.827 the Dwyer Red oil is already their least dense oil. No idea if anyone makes a less dense oil. Since 0.827 density is about 6.89 lbs. per gallon, finding something lighter than that (that is both safe to use around fires, and not highly evaporative) is not likely.

 
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Post by warminmn » Sat. Jun. 20, 2015 8:11 pm

After you have your stove set up and running with the right pressure, you don't have to check it very often. I don't think it would matter which manometer you use, once its set, its set, with only minor adjustments after.

Besides all of that, you an use your eyes to set your stove where you think it runs the best and most efficient, regardless of the number on the scale. Then remember the number, or mark the spot, to keep your stove running there. There is no exact number you want to run it at. Every stove and situation is different.

 
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Post by Lightning » Sun. Jun. 21, 2015 11:30 am

A fluid based manometer is a pretty simple device. It wouldn't be very difficult to build one with a shallower inclination for a higher resolution scale. Thing is though, that kind of precision isn't really needed for our application in operating a coal burning unit. .005 (halfway point between markings on the model 25) inches of resolution is plenty. :)


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