On 9/30/2013 12:43 AM, DoN. Nichols wrote:
On 2013-09-29, woodchucker wrote:
On 9/29/2013 11:01 AM, axolotl wrote:
On 9/29/2013 9:33 AM, Rob H. wrote:
Oh yes -- and someone mentioned the possibility that it is for
testing moisture content in wood. I don't think that device shown it
would work that way, because there are no provisions for insulating the
two pins from the metal holder. And the black screws coming in from the
sides are to secure the points in the holder, not to connect wires.
(Brass screws would be more likely to be used for electrical
connections, and they would still require the insulation of both the
pins and the screws from the holder.

[ ... ]

You make some good points on this one, the photos were sent in by a
visitor of
the
site so I don't have it in my possession. I think it was marked as
being part of
a
moisture meter when he bought it but I'll pass along your reservations
and see
what he says.


I think the object in question predates high impact plastic; one would
remove the driver and attach connectors to the electrodes.

Here is a modern version:

http://www.gann.de/Zubeh%C3%B6r/ElektrodenHolzfeuchte/EinschlagElektrodeM20/tabid/131/language/en-US/Default.aspx

It shows one which could have the wires directly connected to
the pin holders -- but also the small image expands to show a log with
several pairs of pins standing in it, plus one pair still in the holder.

Kevin Gallimore

What makes you think that the holes for the pins were not insulated?
There were many methods of insulating that did not require plastic,
mica, some form of cardboard (but not really a cardboard) , nylon,
rubber, epoxy , wood...

Or Bakelite as something which predates epoxy and was commonly
used for insulation and structural members. Probably a sleeve and a
disc of the Bakelite would work in the holder.

Enjoy,
DoN.

EXACTLY.. then all you would need are alligator clips

--
Jeff

I mean no disrespect to wood, people who work with it, or people who
measure it's moisture content.
I googled "wood moisture measurement".
As an outsider, I get the impression that measuring wood moisture
content is, as described, a crude, inexact process.
It is likely that, for most uses of wood, accurate and precise
measurements are not needed.
The reference process is: Weigh a piece of wood, dry it, weigh it
again. That is probably reasonably accurate and precise.
The field process seems to be: Make an electrical resistance
measurement between a pair of pins driven an unspecified distance into
the wood, then look in a table to get and idea of the moisture for the
type of wood. Perhaps, use partly insulated pins to measure at some
(incompletely) specified depth.
There was one google hit for someone who simply drilled a couple of
spaced holes in a block, and drove a pair of nails through the holes
into the test piece, using the block as a depth stop. Then he simply
measured the resistance and looked up the moisture content.
As pure water is non-conductive, all the measurements seem to need
calibration for the salts/ion concentration of the specific wood.
If I were still in the invention business, I'd develop and patent an
accurate, precise microwave wood moisture measurement device, but I no
longer care.

So... The thing in the picture (2983) holds a couple of pins. The
robust device is bashed with a hammer to push the pins into a piece of
wood to an unspecified depth. If or when the pins bend or can't be
removed, they are replaced. There is probably some insulation on the
pin shanks so there is a reasonable chance of measuring the resistance,
then pulling the whole thing out and re-using it a few times. It now
all makes sense. I'm happy.

Alexander Thesoso fired this volley in
:

If I were still in the invention business, I'd develop and patent an
accurate, precise microwave wood moisture measurement device, but I no
longer care.



You assume way too much.

First, the pins will be driven a specific distance into the end-grain of
the wood -- into which they will go straight. The operator is trained to
do so. The wood is freshly cut square to the grain for 'official'
measurements.

Second, the relative conductivity of the salts in various woods is well-
known and documented in easy-to-obtain tables. Hell... you can buy very
accurate wood moisture meters with such tables in most high-end
woodworking supplies.

Third, you are permitted to be happy. You may be even happier to know
that microwave ("radar") moisture detectors are already available for
wood analysis. But, then, you'd still need to know the specific "dry"
moisture level of each type of wood (which varies by species). You'd
also have to know the microwave penetration in each species. These are
both issues that are handled nicely by plunging electrodes a known, short
distance into the very core of the freshly-cut lumber.

I think you belittle too much things with which you don't have first-hand
experience.

Lloyd

On 9/30/2013 7:05 PM, Alexander Thesoso wrote:
I mean no disrespect to wood, people who work with it, or people who
measure it's moisture content.
I googled "wood moisture measurement".
As an outsider, I get the impression that measuring wood moisture
content is, as described, a crude, inexact process.
It is likely that, for most uses of wood, accurate and precise
measurements are not needed.
The reference process is: Weigh a piece of wood, dry it, weigh it
again. That is probably reasonably accurate and precise.
The field process seems to be: Make an electrical resistance
measurement between a pair of pins driven an unspecified distance into
the wood, then look in a table to get and idea of the moisture for the
type of wood. Perhaps, use partly insulated pins to measure at some
(incompletely) specified depth.
There was one google hit for someone who simply drilled a couple of
spaced holes in a block, and drove a pair of nails through the holes
into the test piece, using the block as a depth stop. Then he simply
measured the resistance and looked up the moisture content.
As pure water is non-conductive, all the measurements seem to need
calibration for the salts/ion concentration of the specific wood.
If I were still in the invention business, I'd develop and patent an
accurate, precise microwave wood moisture measurement device, but I no
longer care.

So... The thing in the picture (2983) holds a couple of pins. The
robust device is bashed with a hammer to push the pins into a piece of
wood to an unspecified depth. If or when the pins bend or can't be
removed, they are replaced. There is probably some insulation on the
pin shanks so there is a reasonable chance of measuring the resistance,
then pulling the whole thing out and re-using it a few times. It now
all makes sense. I'm happy.
Good I'm glad, I wasn't going to sleep tonight until you were.

There is also a scanning moisture meter these days. What you neglect to
consider is that the moisture in the wood is not just pure water.
Trees have some sugar to them. Some more than others. Resin.


Now don't fret, many of us rely on the moisture content... some don't.
Take care Theo

--
Jeff

On Mon, 30 Sep 2013 22:07:46 -0400, woodchucker wrote:

There is also a scanning moisture meter these days. What you neglect to
consider is that the moisture in the wood is not just pure water.
Trees have some sugar to them. Some more than others. Resin.


Now don't fret, many of us rely on the moisture content... some don't.
Take care Theo

Greetings, all. I was in the "lurking" phase before joining this group
because I am retired now and have vague ideas about finishing my basement.
I intended to wait a few weeks before exposing myself here, to learn the
vocabulary and group norms. (& outspoken personalities, etc.)

But I just could not resist the idea that came into my head about using
magnetic resonance imaging to measure water content in wood. Of course, not
very many people have a few million dollars to spare, a workshop with a few
hundred cubic meters of spare space, and a few kilowatts of spare fusebox
capacity.

Then it struck me like a cartoon "light bulb" balloon. You don't need to do
MRI! You can do molecular microwave resonance measurements using a
microwave oven, which is already tuned for the water molecule.

All you need to do is put a fixed quantity of water at a known temperature
(i.e. exacly 100 ml of water at exactly 0 C) along with your piece of wood.

Then you fire up the oven for a fixed time, (i.e. exacly 100 seconds) and
measure the resultant temperature of the water. If you know the effective
power of your magnetron[1], you should be able to easily calculate the
fraction of the total water content in the oven as it is divided between
your wood piece and the container with the liquid water.

If you are worried about damaging the wood, just use a smaller time period.
The result will be less accurate of course.

[1] You can calculate it just by seeing how long it takes to boil the water
when there is no wood in the oven.

--
http://pages.videotron.com/duffym/index.htm

Mike Duffy wrote:
On Mon, 30 Sep 2013 22:07:46 -0400, woodchucker wrote:

There is also a scanning moisture meter these days. What you neglect
to consider is that the moisture in the wood is not just pure water.
Trees have some sugar to them. Some more than others. Resin.


Now don't fret, many of us rely on the moisture content... some
don't. Take care Theo

Greetings, all. I was in the "lurking" phase before joining this group
because I am retired now and have vague ideas about finishing my
basement. I intended to wait a few weeks before exposing myself here,
to learn the vocabulary and group norms. (& outspoken personalities,
etc.)

But I just could not resist the idea that came into my head about
using magnetic resonance imaging to measure water content in wood. Of
course, not very many people have a few million dollars to spare, a
workshop with a few hundred cubic meters of spare space, and a few
kilowatts of spare fusebox capacity.

Then it struck me like a cartoon "light bulb" balloon. You don't need
to do MRI! You can do molecular microwave resonance measurements
using a microwave oven, which is already tuned for the water molecule.

All you need to do is put a fixed quantity of water at a known
temperature (i.e. exacly 100 ml of water at exactly 0 C) along with
your piece of wood.

Then you fire up the oven for a fixed time, (i.e. exacly 100 seconds)
and measure the resultant temperature of the water. If you know the
effective power of your magnetron[1], you should be able to easily
calculate the fraction of the total water content in the oven as it
is divided between your wood piece and the container with the liquid
water.

If you are worried about damaging the wood, just use a smaller time
period. The result will be less accurate of course.

[1] You can calculate it just by seeing how long it takes to boil the
water when there is no wood in the oven.

Or - you could just go buy dimensional lumber at your local Big Box store,
and simply build the project at hand.

--

-Mike-

On Mon, 30 Sep 2013 23:55:07 -0400, Mike Marlow wrote:

Or - you could just go buy dimensional lumber at your local Big Box store,
and simply build the project at hand.

I take it then that water content is not something considered important? I
must admit that I am new at this. Perhaps it is only important when you are
working with naturally-procured wood. Is the big-box material usually
pre-conditioned to be at a fairly consistent water content? Should wood be
expected to warp and develop cracks as it ages?

--
http://pages.videotron.com/duffym/index.htm

Mike Duffy wrote:
On Mon, 30 Sep 2013 23:55:07 -0400, Mike Marlow wrote:

Or - you could just go buy dimensional lumber at your local Big Box
store, and simply build the project at hand.

I take it then that water content is not something considered
important? I must admit that I am new at this. Perhaps it is only
important when you are working with naturally-procured wood. Is the
big-box material usually pre-conditioned to be at a fairly consistent
water content? Should wood be expected to warp and develop cracks as
it ages?

You can take it that you are making way more of this than you need to.

--

-Mike-

On 2013-09-30, Alexander Thesoso wrote:
I mean no disrespect to wood, people who work with it, or people who
measure it's moisture content.
I googled "wood moisture measurement".
As an outsider, I get the impression that measuring wood moisture
content is, as described, a crude, inexact process.
It is likely that, for most uses of wood, accurate and precise
measurements are not needed.
The reference process is: Weigh a piece of wood, dry it, weigh it
again. That is probably reasonably accurate and precise.

Probably -- if you can tell when the wood reaches a sufficiently dry
state to re-weigh it. :-) Perhaps bake it at a specified temperature
until another two hours does not produce more than a 1% change in the
weight.

The field process seems to be: Make an electrical resistance
measurement between a pair of pins driven an unspecified distance into
the wood, then look in a table to get and idea of the moisture for the
type of wood. Perhaps, use partly insulated pins to measure at some
(incompletely) specified depth.

There was one google hit for someone who simply drilled a couple of
spaced holes in a block, and drove a pair of nails through the holes
into the test piece, using the block as a depth stop. Then he simply
measured the resistance and looked up the moisture content.

As pure water is non-conductive, all the measurements seem to need
calibration for the salts/ion concentration of the specific wood.

Presumably, the sap constitution is sufficiently standard so it
produces the needed salts when in the just cut state. And thus the
drying would move the resistance along a known curve.

If I were still in the invention business, I'd develop and patent an
accurate, precise microwave wood moisture measurement device, but I no
longer care.

Nor is it clear that anyone needs the measurement to sufficient
precision to provide a market for such a device. :-)

So... The thing in the picture (2983) holds a couple of pins. The
robust device is bashed with a hammer to push the pins into a piece of
wood to an unspecified depth.

Since the exposed part of the pins has two diameters, I would
expect that you drive it in until the shoulder touches the surface of
the wood. (Given that said surface in the raw state is rather
inconsistent even if you strip off the bark first). :-)

If or when the pins bend or can't be
removed, they are replaced. There is probably some insulation on the
pin shanks so there is a reasonable chance of measuring the resistance,
then pulling the whole thing out and re-using it a few times. It now
all makes sense. I'm happy.

I'm not sure that there is insulation in the tool shown, nor on
the shanks of the pins -- but by loosening the screws in the sides, you
could withdraw the body and then measure the resistance between the pins
with no danger of the body shorting them. I think that the primary
function of the body is to be strong enough to drive them in without
problems, and built-in insulation appropriate to the apparent period of
the device may not survive that process with a serious hardwood. What
the tool *does* do is place the two pins at a precise spacing, and if
driven to the shoulders of the pins, at a repeatable depth, too.

Enjoy,
DoN.

--
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Email: | (KV4PH) Voice (all times): (703) 938-4564
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--- Black Holes are where God is dividing by zero ---

On 10/1/13 12:36 AM, DoN. Nichols wrote:

I'm not sure that there is insulation in the tool shown, nor on
the shanks of the pins -- but by loosening the screws in the sides, you
could withdraw the body and then measure the resistance between the pins
with no danger of the body shorting them. I think that the primary
function of the body is to be strong enough to drive them in without
problems, and built-in insulation appropriate to the apparent period of
the device may not survive that process with a serious hardwood. What
the tool *does* do is place the two pins at a precise spacing, and if
driven to the shoulders of the pins, at a repeatable depth, too.

Enjoy,
DoN.

I can imagine two more reasons to remove the body. It would be easier
to connect the meter without shorting, and the pins could best be
extracted one by one.

http://woodgears.ca/lumber/moisture_meter.html

The chart is for 8mm penetration. On the tool, it looks like 15mm to
the shoulders. If 8mm were adequate for a given job, the pins would be
easier to drive and extract. I wonder if the tool was used with a wood
block as a spacer for a chosen depth.