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do it yourself pyrometer using a palm pilot or computer?



 
 
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  #1  
Old September 2nd 03, 10:08 PM
Bri
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Posts: n/a
Default do it yourself pyrometer using a palm pilot or computer?

Hello All:
I discovered the lookup sheets for voltage output of a type K T/C wire
and I would like to use that data on my palm pilot or computer so I
could have a digital pyrometer with tracking and print capabilities.
Unfortunately I am too ignorant to program so I was wondering if anyone
has come up with a program to do these tasks or knew of some public
domain stuff like that?
Thanks, Bri.
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  #2  
Old September 4th 03, 09:56 AM
Jake Loddington
external usenet poster
 
Posts: n/a
Default

In article , Bri "Share,D,Computer"@boein
g.com writes
Hello All:
I discovered the lookup sheets for voltage output of a type K T/C wire
and I would like to use that data on my palm pilot or computer so I
could have a digital pyrometer with tracking and print capabilities.
Unfortunately I am too ignorant to program so I was wondering if anyone
has come up with a program to do these tasks or knew of some public
domain stuff like that?
Thanks, Bri.


Unless your computer has an analogue port (bring back the BBC Model B!),
you might need an A-D converter. Many such chips are available, but may
require a higher input than the thermocouple will produce, in which case
an op-amp pre-amplifier would also be needed.

I recently made a similar non-computerised device for raku, using a Type
N thermocouple, an OP177 op-amp, and a 7107 digital display driver. This
was cheating, because the output of the couple is of course not linear
with temperature. However, I couldn't be bothered to use a look-up table
to give an accurate reading; the Type N isn't *too* non-linear, and who
cares with raku anyway?

Sorry I can't help with a computer program; I've forgotten all the Turbo
Pascal I ever knew.

Regards

Jake Loddington, POULTON-LE-FYLDE, Lancs. UK

  #3  
Old September 4th 03, 02:38 PM
Bob Masta
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Posts: n/a
Default

On Thu, 4 Sep 2003 09:56:13 +0100, Jake Loddington
wrote:

In article , Bri "Share,D,Computer"@boein
g.com writes
Hello All:
I discovered the lookup sheets for voltage output of a type K T/C wire
and I would like to use that data on my palm pilot or computer so I
could have a digital pyrometer with tracking and print capabilities.
Unfortunately I am too ignorant to program so I was wondering if anyone
has come up with a program to do these tasks or knew of some public
domain stuff like that?
Thanks, Bri.


Unless your computer has an analogue port (bring back the BBC Model B!),
you might need an A-D converter. Many such chips are available, but may
require a higher input than the thermocouple will produce, in which case
an op-amp pre-amplifier would also be needed.

I recently made a similar non-computerised device for raku, using a Type
N thermocouple, an OP177 op-amp, and a 7107 digital display driver. This
was cheating, because the output of the couple is of course not linear
with temperature. However, I couldn't be bothered to use a look-up table
to give an accurate reading; the Type N isn't *too* non-linear, and who
cares with raku anyway?

Sorry I can't help with a computer program; I've forgotten all the Turbo
Pascal I ever knew.


Another approach is to just buy a cheap digital voltmeter
for $10 or less (Harbor Freight, etc) , and commit it to pyrometer
use. You read mV directly, not temperature, but this in itself
isn't much of a problem.. Usually you will be shooting for
some particular temperature, which you look up ahead of time
to find its mV. Then during your run you can see how close
you are to the target mV... no need to know the actual
temperature most of the time.

One caveat, which applies to this and all pyrometers, is
that the junction of the thermocouple wires at the meter
(the "cold junction" makes another thermocouple which
subtracts from the main one (the "Hot junction"). So you
really need "cold junction compensation", or you need
another temperature measurement device to read the
cold junction so you can correct your results. I think
many pyrometers ignore this error, but it's definitely not
negligible; just look at how close the different cone maturity
temperatures are on an Orton chart.

Cold junction compensation can be done with a separate
circuit that reads a thermistor, a diode junction, or a
special temperature sensor chip. Or you can do it the
old-fashioned way, which is to put the cold junction in an
ice-water bath. That's the standard for those thermocouple
charts anyway.


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
Shareware from Interstellar Research
www.daqarta.com
  #4  
Old September 4th 03, 05:18 PM
Bri
external usenet poster
 
Posts: n/a
Default

I had not thought of the second connection being a problem however I
tried the T/C on my rat shack digital that reads mv but got a non
accurate reading fluctuations of -0.3mv to 0.3mv while it was sitting at
room temp. I clamped the meter leads right to the T/C block.
Do the cheapo harbor freight meters go to .xxx mv ?
Thanks, Bri

Bob Masta wrote:

On Thu, 4 Sep 2003 09:56:13 +0100, Jake Loddington
wrote:

In article , Bri "Share,D,Computer"@boein
g.com writes
Hello All:
I discovered the lookup sheets for voltage output of a type K T/C wire
and I would like to use that data on my palm pilot or computer so I
could have a digital pyrometer with tracking and print capabilities.
Unfortunately I am too ignorant to program so I was wondering if anyone
has come up with a program to do these tasks or knew of some public
domain stuff like that?
Thanks, Bri.


Unless your computer has an analogue port (bring back the BBC Model B!),
you might need an A-D converter. Many such chips are available, but may
require a higher input than the thermocouple will produce, in which case
an op-amp pre-amplifier would also be needed.

I recently made a similar non-computerised device for raku, using a Type
N thermocouple, an OP177 op-amp, and a 7107 digital display driver. This
was cheating, because the output of the couple is of course not linear
with temperature. However, I couldn't be bothered to use a look-up table
to give an accurate reading; the Type N isn't *too* non-linear, and who
cares with raku anyway?

Sorry I can't help with a computer program; I've forgotten all the Turbo
Pascal I ever knew.


Another approach is to just buy a cheap digital voltmeter
for $10 or less (Harbor Freight, etc) , and commit it to pyrometer
use. You read mV directly, not temperature, but this in itself
isn't much of a problem.. Usually you will be shooting for
some particular temperature, which you look up ahead of time
to find its mV. Then during your run you can see how close
you are to the target mV... no need to know the actual
temperature most of the time.

One caveat, which applies to this and all pyrometers, is
that the junction of the thermocouple wires at the meter
(the "cold junction" makes another thermocouple which
subtracts from the main one (the "Hot junction"). So you
really need "cold junction compensation", or you need
another temperature measurement device to read the
cold junction so you can correct your results. I think
many pyrometers ignore this error, but it's definitely not
negligible; just look at how close the different cone maturity
temperatures are on an Orton chart.

Cold junction compensation can be done with a separate
circuit that reads a thermistor, a diode junction, or a
special temperature sensor chip. Or you can do it the
old-fashioned way, which is to put the cold junction in an
ice-water bath. That's the standard for those thermocouple
charts anyway.

Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
Shareware from Interstellar Research
www.daqarta.com

  #5  
Old September 5th 03, 03:42 AM
No Body
external usenet poster
 
Posts: n/a
Default

Oh.. this is doing it the "hard way"....

try:

http://embeddeddatasystems.com/Merchant2/merchant.mvc?
Screen=CTGY&Category_Code=HA

(join the two lines above to get the full URL)

Coupled with:

http://www.aagelectronica.com/aag/index.html (look at the 1-wire sensors
and the thermocouple adaptor.)

You will have to do some software work to get the cold junction stuff
to work on your palm.. but they give you working examples.

Steve
 




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