"Richard Clark" wrote in message
...
If that means the lore of paper processing, I was peripherally
involved in trying to characterize Black Liquor
(http://en.wikipedia.org/wiki/Black_liquor). Gladly I was at the
extreme periphery (I am sure my sense of smell was debilitated in
those years).

I once had to check on an instrument I had designed that was used in our
cellulose acetate butyrate esterification area. (Cellulose Acetate
Butyrate is used to make Xelite and Craftsman tool handles.) Acetic
anhydride and butyric acid were used for esterification. For those not
familiar with the odor, think of a mixture of rancid butter, vomit, and
the contents of a cat's week old litter box. Readers who watched the
last season of Whale Wars on TV saw it being used against the Japanese
whaling ship and its cargo.

Since I was unfamiliar with the building, one of my technicians who had
installed the instrument went with me. We stepped off the elevator and
walked into the processing area. What had been an extremely offensive
odor in the elevator suddenly hit me like a ton of bricks. I couldn't
see as my eyes were tearing badly, and it hurt to breathe. My tech told
me to stand still for a moment or two and things would get better.
Within thirty seconds to a minute, my eyes cleared up, my sinuses opened
up, and my breathing became normal again. I could no longer smell the
mixed acids at all. We checked the calibration of the instrument and
talked to the operators about their experiences in using it.

We then left the building and walked the half mile back to the research
labs. Eastman was still using dimethyl-terephthalate in their polyester
production at that time, and as I waked past the DMT distillation area, I
could easily smell the DMT and the Dowtherm heat transfer fluid. My
technician explained that as soon as we returned to the research complex,
we should drop by our group leader's office to let him know where we had
been. We had just opened his door when he said that he could smell where
we had been and to get the heck out of his office! Of course, we
couldn't smell our strong odor at all.

Fortunately my technician had warned me to wear old clothes, old shoes,
and an old belt for when I came home that evening, my wife made me strip
in the foyer and go stright to the shower. She washed the clothes, but
the shoes and belt had to hang outside for a week. It seems that leather
is particularly bad about absorbing the odor.

However, returning to things RF, I also was tasked with calibrating a
wood moisture meter. It used an HF RF source as part of a Z meter
were Z was correlated to moisture content. The probe was a fixed ring
surrounding point probes much like a Kelvin Bridge. It has always
seemed paradoxical that steam is used to dry wood.

We used microwave absorption to measure moisture in cellulose acetate
filter tow (cigarette filters are made from this). Operators would cut
off a length of tow and stuff a weighed amount in a short X-band
waveguide. Attenuation was proportional to moisture.

Now, finding calibrated wood was no easy task. And if we found it, we
would have to first validate it (sort of a circular form of Sysphus'
task). My best guess at that work set to us was that we gun-decked
it.

Calibration of the microwave quipment was checked by weekly sending
samples to be tested by nuclear magnetic resonance. We also used samples
kept in jars over certain salt solutions that maintaned a constant
relative humidity in the jar. See
http://www.conservationphysics.org/satslt/satsalt.php for some typical
solutions. To bring a little electronics into this, the same principle
is used in electrolytic capacitors where glycols, sorbitol, and various
salts are used in the electrolyte to insure that it remains moist.
Electrolytic capacitors are about the only electronic components that are
harmed by an exceptionally dry environment.

It was some years later that that task came around again when I was
measuring K and Kappa as I averred. Here came the requirment for
"Bone Dry" paper. Try as you might to dry paper bone dry (absolutely
no water content), that as soon as it comes out of the oven it is
almost back up to several percent water content (15% to 20% would be
the end point).

You can get close to "bone dry" in a sealed container containing zeolite
molecular sieves baked at 600 C. But as soon as the container is opened,
moisture rushes in from the surround air. We would use glove boxes
pressurized slightly with nitrogen obtained from a liquid nitrogen source
when we needed a really low humidity environment.

Ironies compound in that I now live in a community where 100 years ago
our cedar wood mills produced nearly a Billion shingles in a year.

73's
Richard Clark, KB7QHC

I always enjoyed visiting the University of Washington where Eastman was
on the industrial advisory board of the Center for Process Analytical
Chemistry. I never order salmon from any restaurant in the southeast
after eating the wonderful, fresh-caught salmon you have there!

73, Barry WA4VZQ

P.S. You mentioned black liquor from the Kraft process. I once visited
the Glidden-Durkee plant in Jacksonville, FL. They originally produced
turpentine from pine stumps, but now they start with tall oil extracted
from black liquor. It is hard to believe that essential oils, perfume
stock, and flavorings are all derived from turpentine.

On Nov 10, 7:44*pm, "Barry" wrote:
Jim,

I think you need to go back and read Spamhog's original question. *He was
trying to determine whether the center conductor of a piece of coax had
migrated away from center. *He knew where this might have happened - 10
feet from the end, and the migration would have occurred over less than
two inches. *So the question of locating where the problem might be is
moot. *What is needed is a measurement of the cable impedance in this
region.

First, let us get an estimate of what the impedance of the damaged
section might be. *Spamhog was using RG-6 cable with a foamed
polyethylene dielectric. *Its velocity factor is 0.85 making its relative
permittivity 1.384. *The center conductor is 1 mm, and the normal
diameter of the center insulator is 4.7 mm. *The thickness of the
insulator is 1.85 mm. *We need to know the impedance if the center
conductor had migrated 0.925 mm toward the jacket.

For a quick estimate, use the formula for off-center coax
(http://www.microwaves101.com/encyclo...offcenter.cfm). *This
gives an impedance of 69.8 ohms in this section compared to 78.9 ohms in
the non-distorted coax. *A TDR displays the reflection coefficient
from -1 (short) to +1 (open). *Here the reflection coefficient is -0.06..
So the TDR trace will drop from the center line by 6% for 200
picoseconds.

If your 100 MHz scope has a typical Gaussian response, its rise time is
at least 3.5 nanoseconds. *Do you really think that your oscilloscope
trace will clearly show the 200 picosecond dip? *Even with the
wide-screen magnifier that KB7QHC suggested, I think you will have great
difficulty seeing this.

* * 73, Barry *WA4VZQ

It may be that a 100 MHz scope has better than a 3.5 nsec risetime,
given that it is sped'ed for response flatness to that limit and its
response actually extends beyond !00 MHz. In retirement, I no longer
have access to test equipment that would support my point.

On Sun, 14 Nov 2010 18:22:54 -0800 (PST), "Sal M. Onella"
wrote:

It may be that a 100 MHz scope has better than a 3.5 nsec risetime,
given that it is sped'ed for response flatness to that limit and its
response actually extends beyond !00 MHz.

The simple correlation between risetime and bandwidth is roughly:
BW = 1/(3·t)

Unfortunately, peaking bandwidth can degrade risetime, and vice-versa.
O'scopes have a lot of conflicting adjustments within them. The
TEK545 had something like an 8 to 12 hour tune-up procedure for the
average bench tech (a calibration specialist could do it in 3 to 4
hours).

73's
Richard Clark, KB7QHC

"Sal M. Onella" wrote in message
...
It may be that a 100 MHz scope has better than a 3.5 nsec risetime,
given that it is sped'ed for response flatness to that limit and its
response actually extends beyond !00 MHz. In retirement, I no longer
have access to test equipment that would support my point.

See the following article:
http://www.eetimes.com/design/microw...ight-Bandwidth

There are two paragraphs in the article of importance he

"All oscilloscopes exhibit a low-pass frequency response that
rolls-off at higher frequencies, as shown in Figure 1. Most scopes with
bandwidth specifications of 1GHz and below typically have what is called
a Gaussian response, which exhibits a slow roll-off characteristic
beginning at approximately one-third the -3dB frequency. Oscilloscopes
with bandwidth specifications greater than 1GHz typically have a
maximally-flat frequency response, as shown in Figure 2. This type of
response usually exhibits a flatter in-band response with a sharper
roll-off characteristic near the -3dB frequency.

"Closely related to an oscilloscope's bandwidth specification is its
rise time specification. Scopes with a Gaussian-type response will have
an approximate rise time of 0.35/f(sub)BW based on a 10- to 90-percent
criterion. Scopes with a maximally-flat response typically have rise time
specifications in the range of 0.4/f(sub)BW depending on the sharpness of
the frequency roll-off characteristic. But it is important to remember
that a scope's rise time is not the fastest edge speed that the
oscilloscope can accurately measure. It is the fastest edge speed the
scope can possibly produce if the input signal has a theoretical
infinitely fast rise time (0 ps). Although this theoretical specification
is impossible to test (since pulse generators don't have infinitely fast
edges) from a practical perspective, you can test your oscilloscope's
rise time by inputting a pulse that has edge speeds that are 3 to 5 times
faster than the scope's rise time specification."

73, Dr. Barry L. Ornitz WA4VZQ