How about this...http://www.mccdaq.com/usb-data-acquisition/usb-2001-
How about this...http://www.mccdaq.com/usb-data-acquisition/usb-2001-
CSensor::HidTEMPer) you can use to poll it.)http://www.mccdaq.com/usb-data-acquisition/usb-2001-tc.aspx
How about this...
http://www.mccdaq.com/daq-software/Linux-Support.aspx
I can't help with the Linux part, but maybe you can use some
Thermocouples are really really horrible temperature sensors--almost as
"Thermocouples generate a voltage related to the temperature difference
Thermocouples are very linear and can messure upto 2320 degrees celsius.
Do you really have to use thermocouples? They are the hardest way to
Yes, that is a good one, and I can't argue with Phil's assessment of TC
.Not to mention that they involve a reference junction for
"Nice and linear" is in the eye of the beholder. They're a lot better
You can solder RTDs down, which is about the same thing. And theOn Tue, 30 Nov 2010 14:15:28 -0500, Rich Webb wrote:
On Tue, 30 Nov 2010 13:11:18 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:
Glen Walpert wrote:
On Mon, 29 Nov 2010 16:36:56 +0000, ratullloch_delthis wrote:
Greetings All
I'm looking for a recommendation for a low cost thermocouple DAQ that
works with ubuntu linux. Can someone recommend one. I'm trying to
record temperture measurements over time. tia sal22
http://www.mccdaq.com/daq-software/Linux-Support.aspx
Single channel thermocouple to USB with linux support $99, multiple
channels more $.
Thermocouples are really really horrible temperature sensors--almost as
bad as ICs. Their advantages are small size, relatively low cost, and
(potentially) high speed, but their disadvantage is that it's really
hard to get good measurements.
One reason for this is thermal conduction down the leads (which is a big
problem for most temperature sensors). There's a worse one, though: due
to their very low sensitivity, thermocouples are extremely vulnerable to
errors caused by offset drift in the circuitry. See Figure 20.3 on P.
803 at http://electrooptical.net/www/book/draftthermal.pdf
"Thermocouples generate a voltage related to the temperature difference
between two junctions of dissimilar metal wires, and are a pain in the
neck. ... For less specialized applications, avoid thermocouples like
fleas."
Okay, now I'm going to *have* to buy that book!
Yes, that is a good one, and I can't argue with Phil's assessment of TC
accuracy, but "You can learn all you ever wanted to know about them from
the Omega Engineering catalogue." is true only if you have no interest in
how they actually work (as opposed to how to use them) or how to make a
really good low drift TC measurement system with accurate CJC and high
immunity to EMI, for instance.
There are many trade-offs in sensor selection, and thermocouples excel in
temperature range and durability as well as (sometimes) speed. A TC can
be smashed flat with a hammer and suffer no loss in accuracy until the
wires break, or welded to metal parts for excellent thermal contact with
the part being measured, for instance. Try that with a thermistor
If all you need is a degree or two's accuracy near room temperature,
From the perspective of your book - temperature stabilization of electro-Glen Walpert wrote:
On Tue, 30 Nov 2010 14:15:28 -0500, Rich Webb wrote:
Thermocouples are really really horrible temperature sensors--almost
as bad as ICs. Their advantages are small size, relatively low cost,
and (potentially) high speed, but their disadvantage is that it's
really hard to get good measurements.
One reason for this is thermal conduction down the leads (which is a
big problem for most temperature sensors). There's a worse one,
though: due to their very low sensitivity, thermocouples are
extremely vulnerable to errors caused by offset drift in the
circuitry. See Figure 20.3 on P. 803 at
http://electrooptical.net/www/book/draftthermal.pdf
"Thermocouples generate a voltage related to the temperature
difference between two junctions of dissimilar metal wires, and are a
pain in the neck. ... For less specialized applications, avoid
thermocouples like fleas."
Okay, now I'm going to *have* to buy that book!
Yes, that is a good one, and I can't argue with Phil's assessment of TC
accuracy, but "You can learn all you ever wanted to know about them
from the Omega Engineering catalogue." is true only if you have no
interest in how they actually work (as opposed to how to use them) or
how to make a really good low drift TC measurement system with accurate
CJC and high immunity to EMI, for instance.
There are many trade-offs in sensor selection, and thermocouples excel
in temperature range and durability as well as (sometimes) speed. A TC
can be smashed flat with a hammer and suffer no loss in accuracy until
the wires break, or welded to metal parts for excellent thermal contact
with the part being measured, for instance. Try that with a thermistor
You can solder RTDs down, which is about the same thing. And the
circuit details aren't really information about the _sensor_--any
sufficiently poor sensor will have those problems.
I've used thermocouples reasonably often, generally running inside an
evaporator or someplace like that, and attached to a Fluke thermocouple
thermometer with built-in cold junction compensation. That was probably
good to a couple of degrees, which was all I really needed, especially
since I didn't have to replace the TCs, so the measurements correlated
pretty well over time.
I'm not too impressed with the Electronics Cooling article. TheOn Wed, 01 Dec 2010 20:21:21 -0500, Phil Hobbs wrote:
Glen Walpert wrote:
On Tue, 30 Nov 2010 14:15:28 -0500, Rich Webb wrote:
Thermocouples are really really horrible temperature sensors--almost
as bad as ICs. Their advantages are small size, relatively low cost,
and (potentially) high speed, but their disadvantage is that it's
really hard to get good measurements.
One reason for this is thermal conduction down the leads (which is a
big problem for most temperature sensors). There's a worse one,
though: due to their very low sensitivity, thermocouples are
extremely vulnerable to errors caused by offset drift in the
circuitry. See Figure 20.3 on P. 803 at
http://electrooptical.net/www/book/draftthermal.pdf
"Thermocouples generate a voltage related to the temperature
difference between two junctions of dissimilar metal wires, and are a
pain in the neck. ... For less specialized applications, avoid
thermocouples like fleas."
Okay, now I'm going to *have* to buy that book!
Yes, that is a good one, and I can't argue with Phil's assessment of TC
accuracy, but "You can learn all you ever wanted to know about them
from the Omega Engineering catalogue." is true only if you have no
interest in how they actually work (as opposed to how to use them) or
how to make a really good low drift TC measurement system with accurate
CJC and high immunity to EMI, for instance.
There are many trade-offs in sensor selection, and thermocouples excel
in temperature range and durability as well as (sometimes) speed. A TC
can be smashed flat with a hammer and suffer no loss in accuracy until
the wires break, or welded to metal parts for excellent thermal contact
with the part being measured, for instance. Try that with a thermistor
You can solder RTDs down, which is about the same thing. And the
circuit details aren't really information about the _sensor_--any
sufficiently poor sensor will have those problems.
I've used thermocouples reasonably often, generally running inside an
evaporator or someplace like that, and attached to a Fluke thermocouple
thermometer with built-in cold junction compensation. That was probably
good to a couple of degrees, which was all I really needed, especially
since I didn't have to replace the TCs, so the measurements correlated
pretty well over time.
From the perspective of your book - temperature stabilization of electro-
optical components - I agree completely that thermocouples should
generally be avoided like fleas. From my perspective, with a background
in power plant control, thermocouples and RTD's are the rule and
thermistors the rare exception.
What really irks me about Omega is that their "Thermocouple Introduction
and Theory" section is actually a "thermocouple introduction and
completely bogus theory". Correct theory can be found at:
http://www.electronics-cooling.com/Resources/EC_Articles/JAN97/
jan97_01.htm
And better yet is another article which I can no longer find on the web,
which I will post on ABSE with thread title "thermocouple theory article"
in case anyone is interested.
Glen