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Hoffy
27th May 1999, 02:00 PM
Congratulations on the new Forum. I trust it will work out well. Question. How is moisture measured in timber, and what is used as a reference (0%) to calibrate the "black box" meters. Is the readind a resistive or capacitive measurement. Can anybody point me to a reference to give me the answers?
Thanks in advance
Keith

RETIRED
28th May 1999, 09:14 AM
Keith do a search on moisture meters and you will find a heap of info on them. I found this one about measuring forest material. I think the same principles apply in all meters.

The FUEL MOISTURE METER from Neosystems is designed to measure the moisture content of forest matter. In nearly every case moisture meters are checked by using an oven. A sample is weighed and then put into an oven. After a period of time (when all the moisture has gone from the sample), the sample is removed and the loss in weight is the moisture content. In the case of forest matter this can take up to 16 hours, depending on species type. It usually involves a minimum of 1 full day's wait until the results are know. To get over this long drying period, various methods have sprung up to measure other parameters and infer moisture content from the results. Some of these are electrical conductivity, calcium carbide, RF means, capacitance, etc. Some of the disadvantages of these methods are:
· Because of the wide range of moisture values, the input impedance required is very high when measuring at the lower levels. It requires very little changes on the input to give an incorrect reading.
· Because of the variety of plants and leaves, the electrical conductivity varies between species. This means that you may have to have a calibration curve for each species.
* Profile moisture measurements are not possible because of the wide variations in moisture content.
Neosystems decided to go back to basic principles. The oven is the absolute method but you cannot get enough heat into the samples quickly without burning them and the process takes too long.
The Neosystems meter uses an oven that compresses the sample between two hot plates, thus providing good thermal contact with the sample. A pump is used to remove the moisture-laden air from the oven as well as reducing the vapour pressure within the sample compartment. Sample preparation consists simply of cutting the pieces into sizes of about 1 cm square. With samples of less than about 15%, simply "crunching" them up in the hand is sufficient. The meter takes up to 10 grams of sample. The analyser is portable and operates from a normal car battery. It has simple controls and is easy to operate. Field measurements can be made and the results are known within a few minutes. A patent has been applied for regarding this method of moisture determination.
The switch panel used to control the analyser, indicate oven heating and power and display results, diagnostics, instructions, etc on the display.
OPERATION:
The unit is switched on and initialised. During initialisation, the mechanics are set to the initial state (lift motor down, traverse mechanism to a position over the balance - home) and the operator opens the lid and places the sample on the pan, within the sample holder. The sample holder is placed within a teflon ring which is used as the guide for transport. The operator then closes the lid and the measurement commences. The analyser will then wait until the operating temperature of the oven is reached and then tare the balance by moving the sample away from the balance. The balance then weighs the wet sample and holder and stores the result in memory. The traverse mechanism then moves the sample and holder forward (to the left) until the oven bottom plate is reached. The traverse will then stop and the oven bottom plate is raised. The lift stops when the sample is sandwiched between the top and bottom sprung loaded plates. The sample will stay in this position for approximately 3.5 minutes.
The vacuum pump is switched on when the sample reaches the heating area and switched off after all heating is finished. At this time, the bottom plate will be lowered till the sample holder and sample are level with the traverse path. The lift drive will stop and the traverse will go in reverse(to the right) until the sample is positioned over the balance pan. The sample will be weighed again and the percent moisture reported on the display. If a repeat analysis is required, say for high moisture samples, the operator can re-introduce the sample by pressing the repeat button. (This can be done as many times as required.) If another sample is to be run, the last sample is removed, a new sample is placed on the pan and the lid closed again. This process can continue indefinitely.
SPECIFICATIONS AND FEATURES
MODEL: Fuel Moisture Meter, model FMM1
POWER: 12 volts DC, 120 watts
CLEANING: The meter has easily removable sections to facilitate any cleaning.
PREPARATION: The sample is prepared by cutting it into small (1 cm square) and placing it
between stainless steel gauze mats. This is then placed into the nylon holder,
which is placed on the pan.
RANGE: 1% to 200% (Dry weight)
ACCURACY: 0.2%
ALARMS: Battery low condition (meter is disabled on battery low condition)
Hardware timeout
Oven temperature faults
Mechanical faults
BALANCE: YMC model MK200B, 0-199.00 grams, ruggedly mounted to prevent damage
and ensure stable operation. The balance is further protected by an automatic
locking mechanism that is engaged whenever a reading is not taking place. It
cannot be moved in an unlocked condition.
WIND: The sample area is fully enclosed to prevent errors in readings due to wind.
DISPLAY: The display gives messages indicating progress of measurement, error
messages and results. It is 16 characters by 1 line.
MEMORY: The meter will store 254 readings that can be down loaded through a RS232
interface at a later date. The loaded results can also be viewed at any time.
MODES: Automatic(normal), Manual(service), View memory data, RS232 operation.
SWITCHES: Repeat/select - used for repeat measurements and selection of modes.
Reset - used to reset the meter to the initial conditions in the event of an error.
Up/Down - used to view a function or to view data.
Start - used to start a new measurement.
OVEN: The oven temperature is at 140 degrees Centigrade. This is not adjustable by
the operator but a future option will be available for research purposes. The
user can start operations at 120 degrees when the READY message appears.
From cold it takes about 15 minutes to get to READY.
CYCLE: 3.4 minutes cycle time.
CURRENT USERS:
Department of Conservation & Land Management - Western Australia, Australia
Department of Conservation and Natural Resources - Victoria, Australia
CSIRO - Forest Research - Australian Capital Territory, Australia
US Forest Service - California, USA
Forest ? - Argentina

If you have comments or suggestions, email me at [email protected]



------------------
Ian () Robertson
"We do good turns every day"

Hoffy
28th May 1999, 10:31 AM
Thanks Ian

I appreciate your response. It has given me the answer I need to know. I will search the Web as well. Why didn't I think of that before. thanks again

echnidna
2nd March 2005, 09:32 PM
Keith do a search on moisture meters and you will find a heap of info on them. I found this one about measuring forest material. I think the same principles apply in all meters.

The FUEL MOISTURE METER from Neosystems is designed to measure the moisture content of forest matter. In nearly every case moisture meters are checked by using an oven. A sample is weighed and then put into an oven. After a period of time (when all the moisture has gone from the sample), the sample is removed and the loss in weight is the moisture content. In the case of forest matter this can take up to 16 hours, depending on species type. It usually involves a minimum of 1 full day's wait until the results are know. To get over this long drying period, various methods have sprung up to measure other parameters and infer moisture content from the results. Some of these are electrical conductivity, calcium carbide, RF means, capacitance, etc. Some of the disadvantages of these methods are:
· Because of the wide range of moisture values, the input impedance required is very high when measuring at the lower levels. It requires very little changes on the input to give an incorrect reading.
· Because of the variety of plants and leaves, the electrical conductivity varies between species. This means that you may have to have a calibration curve for each species.
* Profile moisture measurements are not possible because of the wide variations in moisture content.
Neosystems decided to go back to basic principles. The oven is the absolute method but you cannot get enough heat into the samples quickly without burning them and the process takes too long.
The Neosystems meter uses an oven that compresses the sample between two hot plates, thus providing good thermal contact with the sample. A pump is used to remove the moisture-laden air from the oven as well as reducing the vapour pressure within the sample compartment. Sample preparation consists simply of cutting the pieces into sizes of about 1 cm square. With samples of less than about 15%, simply "crunching" them up in the hand is sufficient. The meter takes up to 10 grams of sample. The analyser is portable and operates from a normal car battery. It has simple controls and is easy to operate. Field measurements can be made and the results are known within a few minutes. A patent has been applied for regarding this method of moisture determination.
The switch panel used to control the analyser, indicate oven heating and power and display results, diagnostics, instructions, etc on the display.
OPERATION:
The unit is switched on and initialised. During initialisation, the mechanics are set to the initial state (lift motor down, traverse mechanism to a position over the balance - home) and the operator opens the lid and places the sample on the pan, within the sample holder. The sample holder is placed within a teflon ring which is used as the guide for transport. The operator then closes the lid and the measurement commences. The analyser will then wait until the operating temperature of the oven is reached and then tare the balance by moving the sample away from the balance. The balance then weighs the wet sample and holder and stores the result in memory. The traverse mechanism then moves the sample and holder forward (to the left) until the oven bottom plate is reached. The traverse will then stop and the oven bottom plate is raised. The lift stops when the sample is sandwiched between the top and bottom sprung loaded plates. The sample will stay in this position for approximately 3.5 minutes.
The vacuum pump is switched on when the sample reaches the heating area and switched off after all heating is finished. At this time, the bottom plate will be lowered till the sample holder and sample are level with the traverse path. The lift drive will stop and the traverse will go in reverse(to the right) until the sample is positioned over the balance pan. The sample will be weighed again and the percent moisture reported on the display. If a repeat analysis is required, say for high moisture samples, the operator can re-introduce the sample by pressing the repeat button. (This can be done as many times as required.) If another sample is to be run, the last sample is removed, a new sample is placed on the pan and the lid closed again. This process can continue indefinitely.
SPECIFICATIONS AND FEATURES
MODEL: Fuel Moisture Meter, model FMM1
POWER: 12 volts DC, 120 watts
CLEANING: The meter has easily removable sections to facilitate any cleaning.
PREPARATION: The sample is prepared by cutting it into small (1 cm square) and placing it
between stainless steel gauze mats. This is then placed into the nylon holder,
which is placed on the pan.
RANGE: 1% to 200% (Dry weight)
ACCURACY: 0.2%
ALARMS: Battery low condition (meter is disabled on battery low condition)
Hardware timeout
Oven temperature faults
Mechanical faults
BALANCE: YMC model MK200B, 0-199.00 grams, ruggedly mounted to prevent damage
and ensure stable operation. The balance is further protected by an automatic
locking mechanism that is engaged whenever a reading is not taking place. It
cannot be moved in an unlocked condition.
WIND: The sample area is fully enclosed to prevent errors in readings due to wind.
DISPLAY: The display gives messages indicating progress of measurement, error
messages and results. It is 16 characters by 1 line.
MEMORY: The meter will store 254 readings that can be down loaded through a RS232
interface at a later date. The loaded results can also be viewed at any time.
MODES: Automatic(normal), Manual(service), View memory data, RS232 operation.
SWITCHES: Repeat/select - used for repeat measurements and selection of modes.
Reset - used to reset the meter to the initial conditions in the event of an error.
Up/Down - used to view a function or to view data.
Start - used to start a new measurement.
OVEN: The oven temperature is at 140 degrees Centigrade. This is not adjustable by
the operator but a future option will be available for research purposes. The
user can start operations at 120 degrees when the READY message appears.
From cold it takes about 15 minutes to get to READY.
CYCLE: 3.4 minutes cycle time.
CURRENT USERS:
Department of Conservation & Land Management - Western Australia, Australia
Department of Conservation and Natural Resources - Victoria, Australia
CSIRO - Forest Research - Australian Capital Territory, Australia
US Forest Service - California, USA
Forest ? - Argentina

If you have comments or suggestions, email me at [email protected]



------------------
Ian () Robertson
"We do good turns every day"

Beejay said something today about people responding to dead threads.
So I thought I'd have a look at the very first woodwork thread and 's first answer is almost the size of a page of a newspaper. So I really don't feel like the effort in reading it but maybe someone else would like to comment.
:cool: :p ;) :D :D :confused: :o :eek: :( :mad: :) :rolleyes:

Sturdee
2nd March 2005, 11:00 PM
is no longer so longwinded in his posts. :D :D :D


Peter.

beejay1
2nd March 2005, 11:14 PM
is no longer so longwinded in his posts. :D :D :D
And hoffy seems to have disappered 3 years ago, did he read himself into oblivion or electrocute himself changing a light bulb? Come back hoffy.
beejay1

http://community.webshots.com/user/eunos9

Sturdee
2nd March 2005, 11:26 PM
And hoffy seems to have disappeared 3 years ago, did he read himself into oblivion or electrocute himself changing a light bulb?

I think he is still there diligently searching the web for a more concise answer. :D :D :D Hope he is keeping up his strenght by eating lots of pancakes. :D :D :D


Peter.

Cliff Rogers
3rd March 2005, 12:37 AM
And hoffy seems to have disappered 3 years ago, ....
It's funny how some people that were active posters just suddenly stop one day & are never heard of again & others go out like a blazing comet. :D

RETIRED
3rd March 2005, 01:11 AM
is no longer so longwinded in his posts. :D :D :D


Peter.
I love cut and paste. :D

echnidna
3rd March 2005, 01:38 PM
Is interesting (for lack of a better word) that there was only 1 reply years ago but half a dozen in the last few days. And pancakes and foileies haven't been mentioned yet. :p :p :p :p :p :p :p :p :p :p :p :p :p :p :p :p :p :p

DanP
3rd March 2005, 04:11 PM
... eating lots of pancakes. :D :D :D


Look again.

Dan

HappyHammer
3rd March 2005, 04:23 PM
http://images.google.com.au/images?q=tbn:UGqTylqMZSgJ:http://www.jeremyflint.com/baby/images/asleep-in-car.jpg

Pretty close to my reaction after 1st two sentences.

HH.

JackoH
3rd March 2005, 04:36 PM
Did you actually read all that ?

Sturdee
3rd March 2005, 04:40 PM
I love cut and paste. :D


So do my three year old nieces. They love cutting out shapes like little squares and hearts with their little scissors and pasting them down with clagg.

Fun isn't it . :D :D :D


Peter.

outback
3rd March 2005, 04:55 PM
Problem is, when tries it, the hearts end up blocking the monitor so he can't keep an eye on us. :D
Thats' how we got three or four pages of seppo bashing, was cleaning his monitor. :D