On Wed, 30 May 2012 09:52:03 -0400, Spehro Pefhany
wrote:

On Wed, 30 May 2012 06:04:27 -0500, Pete Keillor
wrote:

On 30 May 2012 03:29:08 GMT, "DoN. Nichols"
wrote:

On 2012-05-29, Jon Elson wrote:
Gunner Asch wrote:

Karl..Ive dug out the thermocouples for you.

They are 100 ohm Platinums with leads at least 5' long

Will your controller deal with 100 ohm platinum thermos?

OOps, those are Platinum resistance temp. detectors, NOT
thermocouples.

Most reasonably modern temperature controllers will use those.
Yes, they are not thermocouples, which need a junction of two dissimilar
metal alloys -- such as Chromel and Alumel, or Iron and Constantan. I'm
not sure whether either of those may be what is called Type-K, but I
think that the first may be.

Yes Platinum are variable resistors, not true thermocouples.
But a good controller should be configurable for many types of
temperature detectors. And the Platinum resistance ones are (I believe)
the best for life at high temperatures. (So my just posted question
still stands, even though I missed that you called them thermocouples
instead of thermo-sensors. :-)

Enjoy,
DoN.

I pretty much switched to rtd's in r&d due to their better accuracy
and stability. I had thermocouples drift a few degrees/year in
extruder service with daily temperature cycling to 200+ C. There are
two main rtd calibrations that I am aware of, European or American.
There is a slight difference in temperature coefficient between the
two. You need to know which you have when you set up your controller.

Pete Keillor

Platinum RTDs are best for moderately high temperatures (maybe up to
600°F-800°F), but especially for around room temperature up to a
couple hundred C. They tend to have relatively pokey reponse times and
are more fragile than thermocouples, but for applications such as
plastic extruders, the better stability can be worth it- getting
better than a few degrees with a thermocouple is not so easy/cheap.

Almost everyone uses the Euro standard (alpha = 0.00385) RTD these
days. I have not seen the old US style 0.00392 type in ages).

There's not much platinum in an RTD these days, well under $1, since
just a thin film is generally used (sealed under a glass passivation).

Platinum (actually Platinum/Platinum-Rhodium alloy) THERMOCOUPLES are
such as type R and S are best for very high temperatures (over
2000°F). They are about useless for low temperatures, mostly because
the output is so very low (about 1/10 that of a type K and 1/100 that
of an RTD). Platinum thermocouples are made with platinum (alloy) wire
so they tend to be pricey, even if fine wire is used.

Yeah, seems like I standardized on 385's about 15 years or so before I
retired. However, if Jon's are old stock, it would be important to
know their calibration. Back then, my controllers could handle
either. Don't know if that's still the case or not.

Hi Pete Keillor and/or anyone on RCM

Recently I've sent a couple of messages to RCM to test the waters, so to
speak. If anyone sees this test post of mine, please respond through a a
normal RCM post. Thanks.

Bob Swinney

"Pete Keillor" wrote in message
...

On Wed, 30 May 2012 09:52:03 -0400, Spehro Pefhany
wrote:

On Wed, 30 May 2012 06:04:27 -0500, Pete Keillor
wrote:

On 30 May 2012 03:29:08 GMT, "DoN. Nichols"
wrote:

On 2012-05-29, Jon Elson wrote:
Gunner Asch wrote:

Karl..Ive dug out the thermocouples for you.

They are 100 ohm Platinums with leads at least 5' long

Will your controller deal with 100 ohm platinum thermos?

OOps, those are Platinum resistance temp. detectors, NOT
thermocouples.

Most reasonably modern temperature controllers will use those.
Yes, they are not thermocouples, which need a junction of two dissimilar
metal alloys -- such as Chromel and Alumel, or Iron and Constantan. I'm
not sure whether either of those may be what is called Type-K, but I
think that the first may be.

Yes Platinum are variable resistors, not true thermocouples.
But a good controller should be configurable for many types of
temperature detectors. And the Platinum resistance ones are (I believe)
the best for life at high temperatures. (So my just posted question
still stands, even though I missed that you called them thermocouples
instead of thermo-sensors. :-)

Enjoy,
DoN.

I pretty much switched to rtd's in r&d due to their better accuracy
and stability. I had thermocouples drift a few degrees/year in
extruder service with daily temperature cycling to 200+ C. There are
two main rtd calibrations that I am aware of, European or American.
There is a slight difference in temperature coefficient between the
two. You need to know which you have when you set up your controller.

Pete Keillor

Platinum RTDs are best for moderately high temperatures (maybe up to
600°F-800°F), but especially for around room temperature up to a
couple hundred C. They tend to have relatively pokey reponse times and
are more fragile than thermocouples, but for applications such as
plastic extruders, the better stability can be worth it- getting
better than a few degrees with a thermocouple is not so easy/cheap.

Almost everyone uses the Euro standard (alpha = 0.00385) RTD these
days. I have not seen the old US style 0.00392 type in ages).

There's not much platinum in an RTD these days, well under $1, since
just a thin film is generally used (sealed under a glass passivation).

Platinum (actually Platinum/Platinum-Rhodium alloy) THERMOCOUPLES are
such as type R and S are best for very high temperatures (over
2000°F). They are about useless for low temperatures, mostly because
the output is so very low (about 1/10 that of a type K and 1/100 that
of an RTD). Platinum thermocouples are made with platinum (alloy) wire
so they tend to be pricey, even if fine wire is used.

Yeah, seems like I standardized on 385's about 15 years or so before I
retired. However, if Jon's are old stock, it would be important to
know their calibration. Back then, my controllers could handle
either. Don't know if that's still the case or not.

On Sun, 3 Jun 2012 09:28:58 -0500, wrote:

Hi Pete Keillor and/or anyone on RCM

Recently I've sent a couple of messages to RCM to test the waters, so to
speak. If anyone sees this test post of mine, please respond through a a
normal RCM post. Thanks.

Bob Swinney

Hi, Bob.

Pete Keillor
"Pete Keillor" wrote in message
.. .

On Wed, 30 May 2012 09:52:03 -0400, Spehro Pefhany
wrote:

On Wed, 30 May 2012 06:04:27 -0500, Pete Keillor
wrote:

On 30 May 2012 03:29:08 GMT, "DoN. Nichols"
wrote:

On 2012-05-29, Jon Elson wrote:
Gunner Asch wrote:

Karl..Ive dug out the thermocouples for you.

They are 100 ohm Platinums with leads at least 5' long

Will your controller deal with 100 ohm platinum thermos?

OOps, those are Platinum resistance temp. detectors, NOT
thermocouples.

Most reasonably modern temperature controllers will use those.
Yes, they are not thermocouples, which need a junction of two dissimilar
metal alloys -- such as Chromel and Alumel, or Iron and Constantan. I'm
not sure whether either of those may be what is called Type-K, but I
think that the first may be.

Yes Platinum are variable resistors, not true thermocouples.
But a good controller should be configurable for many types of
temperature detectors. And the Platinum resistance ones are (I believe)
the best for life at high temperatures. (So my just posted question
still stands, even though I missed that you called them thermocouples
instead of thermo-sensors. :-)

Enjoy,
DoN.

I pretty much switched to rtd's in r&d due to their better accuracy
and stability. I had thermocouples drift a few degrees/year in
extruder service with daily temperature cycling to 200+ C. There are
two main rtd calibrations that I am aware of, European or American.
There is a slight difference in temperature coefficient between the
two. You need to know which you have when you set up your controller.

Pete Keillor

Platinum RTDs are best for moderately high temperatures (maybe up to
600°F-800°F), but especially for around room temperature up to a
couple hundred C. They tend to have relatively pokey reponse times and
are more fragile than thermocouples, but for applications such as
plastic extruders, the better stability can be worth it- getting
better than a few degrees with a thermocouple is not so easy/cheap.

Almost everyone uses the Euro standard (alpha = 0.00385) RTD these
days. I have not seen the old US style 0.00392 type in ages).

There's not much platinum in an RTD these days, well under $1, since
just a thin film is generally used (sealed under a glass passivation).

Platinum (actually Platinum/Platinum-Rhodium alloy) THERMOCOUPLES are
such as type R and S are best for very high temperatures (over
2000°F). They are about useless for low temperatures, mostly because
the output is so very low (about 1/10 that of a type K and 1/100 that
of an RTD). Platinum thermocouples are made with platinum (alloy) wire
so they tend to be pricey, even if fine wire is used.

Yeah, seems like I standardized on 385's about 15 years or so before I
retired. However, if Jon's are old stock, it would be important to
know their calibration. Back then, my controllers could handle
either. Don't know if that's still the case or not.

On 2012-06-03, wrote:
Hi Pete Keillor and/or anyone on RCM

Recently I've sent a couple of messages to RCM to test the waters, so to
speak. If anyone sees this test post of mine, please respond through a a
normal RCM post. Thanks.

Bob Swinney

I see it. I trimmed all the unrelated quoted material in this
followup.

Enjoy,
DoN.

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