Ultrafast temperature logging using thermocouple

[johnkl]

Has anybody tried to measure temperature(10-50 degree C) at 2K samples/s?
Which thermocouple has the fastest response time in the market?

[JenK]

Here is a link to Omega's thermocouple selection guide:
http://www.omega.com/toc_asp/subsectionSC.asp?subsection=A01&book=Temperature
This should be able to assist you in selecting the fastest thermocouple.

Have a great day!

Jennifer

[LYu]

Hi,

The following link will provide you withe the different hardware options from NI available and the associated sampling rates:

http://digital.ni.com/public.nsf/websearch/F0196F5B6CD8F60286256D4B00728B78?OpenDocument

Hope this helps,
Lesley Y.

[johnkl]

according to the knowledgebase you provided

http://digital.ni.com/public.nsf/websearch/F0196F5B6CD8F60286256D4B00728B78?OpenDocument

Max rate = 100 kHz / (number of CJCs + number of channels).

my question is: is there any thermocouple that has a response time less than 10 microseconds?

if the thermocouple can not respond fast enough, the max rate will be reduced to 1/(thermocouple response time)

the fastest thermocouple i can find is 3 millisecond. so the max sampling rate is 333Hz.

any suggestions?

thanks

[JenK]

John,

I think you might be interested in the SCXI 1102 or 1112 module. They have scan rates up to 333kS/s. Here is some more information on them:
http://sine.ni.com/apps/we/nioc.vp?cid=10316〈=US
http://sine.ni.com/apps/we/nioc.vp?lang=US&pc=mn&cid=1654
http://sine.ni.com/apps/we/nioc.vp?lang=US&pc=mn&cid=3649

Hope this is what you were looking for.

Jennifer

[Nepu]

Jennifer,



JohnKL is not looking for a fast DAQ solution but asks for a fast sensor.
Your links point to the detection part, he needs info about the sensor part.
In particular is asking for some temperature sensor on the market (not neccesarily from NI) that has a fast time constant.


cheers

Markus

[JenK]

John,

It looks like you just want to know what the fastest thermocouples are out there. National Instruments does not manufacture thermocouples, so I would suggest contacting a thermocouple manufacturer such as Omega (www.omega.com). I think they might be more helpful to you.

Sincerely,

JenK
Applications Engineer
National Instruments

[johnkl]

thanks to all the replies first

below is the email i got from NI applications engineer

Thank you for contacting National Instruments! The response time of a thermocouple is really zero because it's a voltage source, it's sampling
rate is limited by the use of hardware. National Instruments doesn't sell thermocouples, but any thermocouple in the market will provide you a
zero response time voltage (in other words, it will provide you a voltage value at every single point in time, not just every 20 microseconds.) What you should be looking for then is a hardware that can sample the maximum possible number of samples per seconds for more accurate readings of
your temperatures. Depending on the number of channel that you will have, an M-Series DAQ board with SCXI-1102 and SCXI-1303 terminal block or an
M-Series DAQ board with SCXI-1112 is the best option.

does the t/c response time matter in the temperature measurement?

thanks

[Nepu]

Hi John, dear NI support:


a NI application engineer wrote:
"The response time of a thermocouple is really zero because it's a voltage source"

oopsy

John, take care. This is not correct. Certainly every T/C has a response time. Not an electrical one, but a thermal one. Imagine you have your T/C connected to a heat plate. When the heat plate changes the temperature, the T/C will need some time to reach the same temperature. The time constant for that process is proportional to the mass m of the T/C and the specific heat capacity C, but inverse proportional to the heat conductivity K.

The time constant is usually larger for gas measurements than for liquid or solid contact measurements. The time constant also critically depends on the thermal contact between the T/C and the object of interest.


Once more: Each thermocouple has a certain response time. which depends on a lot of parameters. Certainly, the smaller the T/C the faster the response time. You want to measure temperatures of your object with 2kS/s (500 us). You are looking for a real tiny T/C.


Of course, the T/C voltage can be sampled even with 333kS/s and the reading will reflect the actual (average) temperature of the T/C junction - but this is not the temperature of the object of interest. You are looking for a tiny, fast T/C (demanding). On the DAQ side you evenmight use your PC's microphone input to sample 16 bit, 2kS/s (not so demanding).


Nepu.

[Nepu]

Hi John,

can you describe your setup in more detail? What is the device under test you want to sample (material, size, environment, ...)?
Maybe thermo-couples are not the right choice for 2 kS/s.

Have you ever though about optical or magnetical detection?

Nepu.