Janet Harper on wed 2 dec 98
Do any of you have any experience with the MR100 venturi burners? And what
is your opinion on digital vs. analog pyrometers? I'm in the process of
building a kiln again after a clay recess of 17 years to raise kids--it was
worth it, but it sure is nice to have my hands covered in clay again! Glad
you all are here for me! Janet in E. TN
Karen Gringhuis on thu 3 dec 98
Janet - if by analog pyrometer, you meen a needle & a dial,
my reaction is don't even bother. Get a digital pyrometer. I
wouldn't fire w/out one. I have the one in the Bailey Ceramic
Supply catalog by Fluke. It costs around $250 or so but it's
second only to my wheel as the best money I ever spent.
Karen Gringhuis
Bruce Girrell on fri 4 dec 98
Janet Harper wrote...
> Do any of you have any experience with the MR100 venturi
> burners?
> And what is your opinion on digital vs. analog pyrometers?
I have a pair of MR100's that I got from Marc Ward (Ward Burners). I am
presently using a 21 cu. ft. (internal volume) updraft kiln with 9 inch
walls - interior IFB, exterior hard brick. We haven't run to ^10 with it
yet, but I have no fear that it will make it - I have yet to need the second
burner[1]. Most of the time I am throttling back the single burner. Plenty
of heat there.
A friend of ours uses two MR100's for a raku kiln. Great results for her,
too.
My best advice would be to call Marc (don't e-mail him, he'll just mail back
telling you to call him). Be ready to give him the dimensions of you kiln
and he will give you lots of help deciding just what you need.
My second suggestion would be to consider his little pilot burner (I forget
the model, but it's pictured piggybacked on one of the Ransome burners in
the catalog). This burner has worked great for me as my preheat burner[2]. I
don't think that I could throttle the MR100 back enough to keep the
temperature low enough, but the pilot burner is perfect. At about 2 PSI it
will bring a load of ware up to 200F in about 3-4 hours. I usually push up
the pressure on the small burner to start the temperature climb before I
kick in the MR100.
The only thing that I don't like about the MR100's is that they look bad.
You get this hunk of cast iron in the mail, look at it and ask yourself "I
paid how much for this?" The casting is rough and poorly finished. As far as
I can tell, there is no machining done on the casting, other than cleaning
off the flashing, even in the area of the orifice. I don't know how much of
an effect this has on the flame. Nils Lou, in "The Art of Firing" emphasizes
proper flame form as an indication of proper combustion. With the MR100, I
don't see a nicely shaped blue cone as he describes; I see a rather ragged
flame with a small amount of yellow tipping (air fully open). So perhaps my
combustion is not as efficient as it could be, but I certainly get all the
BTUs I need.
Regarding analog vs. digital pyrometers (or anything else) -
Ah, one of my favorite soapbox subjects...
My quick answer is this: I think it would be difficult for someone to
convince me of a significant enough value of a digital readout to warrant
the (typically) increased cost of the readout. Even if the two cost the
same, in the case of a pyrometer, used in the way that we as potters use
them, I would still choose the analog.
In this world there is a place for digital readouts and a place for analog
readouts. Which one is better depends on the application. Digital is not
necessarily better just because it is newer or can display ten decimal
places.
Digital readouts excel where high precision and large dynamic range are
required. Usually analog readouts are limited in the range of precision.
That is, an analog readout might be calibrated to read values between
0.0000001 units and 0.0000005 units, thus providing a very precise readout,
but over a limited range. Conversely, the analog device might read from 0 to
10,000 units, but with a limited precision. Digital units usually offer the
best of both worlds - a large dynamic range plus precision. Because of this
feature, digital readouts are often viewed as being more accurate[3], which
may or may not be true.
Analog readouts have several strengths, the first of which is simplicity. My
analog pyrometer will never need to have its battery changed, nor will its
CPU fail. As an offshoot of simplicity, analog devices are often less
expensive.
Secondly, for many applications, analog readouts are faster and easier to
read. Our brains work especially well as pattern recognizers and the needle
and markers of analog readouts are simple pattern matching devices. Some
examples: 1) When you are driving along and suddenly notice a police car,
you do not need to know whether you are travelling 58 mph or 53 mph; you
simply need to know whether the needle is to the left or right of the little
marker that indicates the 55 mph speed limit. 2) In airplane cockpits, where
there are lots of gauges that have to be scanned frequently, the gauges are
often analog allowing the pilot to quickly glance at the gauges and
determine that everything is working properly simply by recognizing the
pattern of needle positions. If the pilot had to register the numerical
value of a digital readout and determine whether or not that value was
within acceptable limits, the process would take much longer. It's kind of
amusing to look into the cockpit of a modern jet and see that the artificial
horizon is a digital (computer screen) representation of an analog display.
Analog readouts suffer less from noisy inputs. It's far easier to read the
value off a meter that has a little needle jitter than it is to read
incessantly changing numerals. Digital voltmeters drive me nuts because of
this. Some tests are more useful when the value is not stable, such as
looking for a capacitance kick, and digital meters really suck at that sort
of thing. I really detest digital voltmeters.
Finally, when an error in readout occurs, the error is often much less with
an analog readout than with a digital. The amount of error in reading an
analog device is usually a small fraction of the scale, but the error of a
digital readout could be just about anything. Consider if I lose the top
segment of the leading digit in a seven segment readout - Instead of reading
700 degrees, my digital pyrometer reads 100 degrees. If the battery goes
weak, the display can react in very odd ways.
OK. I'll stop. Sorry. I just get carried away sometimes.
I know that there are some things that digital readouts are better for and I
believe that they should be used in those places. I also think that
sometimes we tend to get a little carried away with bells and whistles and
end up putting a digital display where it doesn't belong. A pyrometer is one
of those places where we, as potters, just don't need a digital display.
Maybe a ceramic researcher has a real need for a digital pyrometer, but for
what we use pyrometers for, analog is just fine.
Bruce "Soapboxes-R-Us" Girrell
[1] The current kiln is temporary - I bought the two burners based on a 45
cu. ft. downdraft design.
[2] Let's not start the candling thread again.
[3] I am not going to address the difference between accuracy and precision.
Suffice it to say that I will assume that both the analog and digital
devices have roughly the same accuracy.
Vince Pitelka on fri 4 dec 98
> Do any of you have any experience with the MR100 venturi burners? And what
>is your opinion on digital vs. analog pyrometers?
Janet -
MR-100s are one of the best deals going in venturi burners. They look so
simple and cheap you can hardly believe they will work, but they do. In
fact, they work great, and they hold up very well. A good friend in
Humboldt County, CA has been firing a 35 cubic-foot fiber/brick kiln with
four MR-100s for about fifteen years now. They aren't as pretty as the
ransomes, eclipses, etc., but what counts is that they work well. Be sure
to take the BTU ratings seriously at whatever working pressure you have, and
use enough of them. You can side mount them, but they are also short enough
to mount beneath the kiln.
I guess I'm old fashioned, but for a permanent installation on a single
kiln, I like an analog pyrometer. But for a portable unit that you move
around between a number of kilns, you can't beat the digital pyrometers.
Good luck -
- Vince
Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Don Prey on fri 4 dec 98
In a message dated 12/03/98 7:47:10 AM, you wrote:
<is your opinion on digital vs. analog pyrometers? >>
Janet,
I much prefer the digital display.......easier to read, less likely to
misread, more precise (finer increments) and quicker feedback about changes in
kiln behavior. I currently use both methods by attaching a digital millivolt
meter to a regular analog setup. If the analog meter broke, I would not miss
it at all. (I would have to refer to a temperature-voltage conversion
table....no big deal since I am not all that interested in temperature
anyway.)
Don Prey in Oregon
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