Acquistion avec un thermocouple type K et NI USB 6210

Bonjour,
Dans le cadre de mon stage, je suis amené à utiliser une carte d'acquisition NI USB 6210.
Avec ce matériel, je dois acquérir des températures avec des thermocouples de type K.
J'utilise la tache température comme indiqué dans MAX. Cependant, la valeur varie relativement fortement (+ ou - 5°C) et au bout de quelques minutes dérive complètement vers des valeurs incohérentes (par exemple valeur négative).
J'ai donc plusieurs questions :
La carte NI USB 6210 convient t-elle pour une mesure de température avec un thermocouple?
Pourquoi mon signal dérive de la sorte?
Y a-t-il une autre méthode d'acquisition pour ce type de mesure (thermocouple)
Merci d'avance pour vos réponses.
PS : Une version simple du VI que j'utilise est en pièce jointe.
Pièces jointes :
Temperature.vi ‏28 KB

La carte USB 6210 n'ai pas faite pour faire des mesures sur thermocouples, mais vu la sensibilité et la précision de la carte, vous pouvez quand même le faire.
Par contre attention cette carte ne calcul pas automatiquement la température de soudure froide, donc la valeur de votre thermocouple sera une différence de température uniquement (entre la sonde de votre thermocouple et le raccordement de votre thermocouple).
Pour améliorer la précision, j'ai modifié quelques trucs dans votre vi, vous le trouverez ci-joint :
Chef de Projet
ERM Automatismes Industriels
Certified LabVIEW Associate developer
Pièces jointes :
Temperature 2.vi ‏18 KB

Similar Messages

How do I use AI Temperature with multiple thermocouple types?

Hi,
I am trying to read temperatures from thermocouples. I have the PXI-1112 module. I have 3 thermocouple types. Is there a way to use the AI temperature VI to process all thermocouples with a single wire connection? The VI has an input for thermocouple type, but does not accept arrays. How can I assign a different thermocouple type to each channel?
Thanks

Hello Villalro,
Are you using the DAQmx Create Virtual Channel.vi in your
application? Below is a great example of
how to measure three different types of thermocouples all in the same task. If you are still not able to create the task
correctly, you might try building it in a DAQ Assistant. Once you are able to create the task
correctly in the DAQ Assistant, you can convert it into DAQmx code. Right-click on the DAQ Assistant and then select
Generate NI-DAQmx Code.
Message Edited by Robert F on 08-08-2007 09:40 PM
Respectfully,
Rob F
Test Engineer
Condition Measurements
National Instruments
Attachments:
temp_forums.JPG ‏65 KB

Can I use thermocouple type L with NI4351

Can I use thermocouple type L with high resolution temperature and voltage loggers NI4351
if yes, then where I can find accuracy data

Hello,
I could not find the milliVolt input ranges for that specific type of thermocouple. What I did find was that it has a temperature range between -200 and 900 deg C. Since the temperature ranges seem similar to other types of thermocouples, you can compare these to the ones mentioned in Appendix A of the NI-4351 User's Manual (www.ni.com/manuals, and make a search for "4351") in order to get an idea of the accuracy that you can expect.
Regarding the software, there's two options:
1. To use NI-DAQ: with this, you can create a Temperature Custom Scale and use it with a Virtual Channel so that the Voltage readings will be translated into Temperature readings.
2. You can use the NI-4351 own drivers for reading the voltages, and then you can
add software tables to your program so that those voltages will be translated into temperature values.
Good luck with your application!

Thermocouples with USB-6210 DAQ, readings show big variations from true temp.

I have several type T and type K thermocouples connected to a USB-6210 DAQ. In VI logger, I have set up a thermocouple task, selecting CJC source as constant. Is it correct that software takes care of the CJC, as the connection diagram shows just the thermocouple connected directly into the device? With the CJC value of 18 (room temp), the values start off OK, but over ten minutes they drift to about 40 degrees, and seem to increase and decrease randomly. Do I need additional hardware, and/or what is going wrong? Thank you.

Hi DSharp,
You are correct that the software will account for the CJC value which you set as constant when computing the returned temperature value from the voltage reading. One thing I would suggest trying would be to see if touching the thermocouple or otherwise providing a path to ground for the thermocouple makes the signal return back to a value within the valid range. When measuring a floating source such as a thermocouple in differential mode, it is necessary to provide a path from the instrumentation amplifier inputs to the instrumentation amplifier ground, which can be accomplished through the use of bias resistors being placed between the inputs and AIGND. For more information on bias resistors and properly connecting signals, please refer to the Field Wiring and Noise Considerations for Analog Signals tutorial. There is also more information about the problem you are seeing in "Appendix B: Troubleshooting" of the NI USB-621x User Manual (page B-1). On this page, you will see a topic titled "I am using my device in differential analog input ground-reference mode and I have connected a differential input signal, but my readings are random and drift rapidly. What is wrong?" which also discusses making proper connections. Hope this helps,
Daniel S.
National Instruments

Viewing jpeg type pictures from a usb drive

I am wanting a 20"-22" TV that will allow viewing jpeg type pictures from a usb drive. What TV's will support this?

You'll have to look at specific tvs. We carried a 19inch or a 20 something inch insignia I believe that did it at one time. To be honest, it wasn't anything really fantastic. And make sure you double check on the tv, sometimes it will say "SERVICE ONLY", those you can't use for media.
Former BBY Home Theater Associate 2010 - 2012. Now I work as a graphic designer in the print and prepress industry.

Mesure de fréquence avec NI usb 6210

Bonjour,
Je viens de faire l'acquisition d'une carte NI USB 6210, je cherche à recupérer la fréquence de mon signal alternatif 50hz, mais je n'y arrive pas.
J'ai cabler en entré de l'entrée PFI1 in et DGND mes deux fils conducteur, et ensuite sur Labview signal express j'ai créer un DAQmx fréquence. J'obtiens comme résultat un nombre qui alterne entre 63 et 255. Je ne trouve pas d'expliquation à mon résultat...
Merci d'avance pour votre aide

Bonjour Rj293,
Les caractéristiques de la carte USB 6210 en niveau TTL sont:
- 0/0.8V pour un niveau logic bas
- 2/5.25V pour un niveau logic haut
Avec une amplitude de 2.5V votre mesure de fréquence devrait fonctionner.
Cependant, le signal sinusoidale que vous utilisez à une amplitude de 2.5V en Pkk, et une valeur moyenne nulle? Par ailleurs, pouvez-vous joindre les deux courbes (sinusoidale et carré) avec echelles?
Cordialement,
Rémi D.
National Instruments France
#adMrkt{text-align: center;font-size:11px; font-weight: bold;} #adMrkt a {text-decoration: none;} #adMrkt a:hover{font-size: 9px;} #adMrkt a span{display: none;} #adMrkt a:hover span{display: block;}
>> Les rencontres techniques de NI - Mesures et acquisition de données : de la théorie à la mise en ...

Setting thermocouple type in scan engine

I am using cRIO 9211 to acquire thermocouple data using NI Scan Engine. I don't see any option to specify the type of thermocouple other than by right clicking on the module (in project) and selecting Properties.
Is there a way to programmatically set the type of thermocouple?
If this is not possible, can I can read the cjc and offset channels, so that I can convert the raw voltage to temperature in my RT code?
Will I be able to read the cjc and offset channels if I use NI Scan Engine Advance I/O Access?
"A VI inside a Class is worth hundreds in the bush"
യവന്‍ പുലിയാണു കേട്ടാ!!!

Cross posted here.
"A VI inside a Class is worth hundreds in the bush"
യവന്‍ പുലിയാണു കേട്ടാ!!!

Ranges of thermocouple types

Hi All
Can any one let me know that SCXI 1112 card supports all types of Thermocouples or is it meant for some types.

Hi AUTO TEC,
I have just looked at the manual:
http://digital.ni.com/manuals.nsf/websearch/E16018F7C97EE65C862567C80051C83C
Page A-2 (Appendix) there is a value table. Hope this helps.
Regards,
Jordan Power
Applications Engineer
National Instruments

Mon ipad est bloqué sur une page noire avec le logo itunes et le cordon usb

mon ipad est bloqué sur une page noire avec le logo itunes et le cordon usb

That sign indicates that your iPhone is recovery mode. You need to connect it to your computer and then restore it using the iTunes on your computer.

Mesure temp%C3%A9rature avec thermocouple

bonjour
je suis une étudiante au 2ème année master, je suis bosoin d'un progarmme de mesure la température dans 14 points dans un joint soudé avec des thermocouple de type k à 14 profondour différents
le but de ce programme c'est mesurer les températures dans différentes zones et déffirentes profondreurs
aide mois
merci
Résolu !
Accéder à la solution.

bonjour
la carte que je doit utiliser c'est PCI NI MIO 16E-4 (PCI NI 6040N) et labview 8.6 et pour les thermocouples LCB-68
je doit les températures dans 7 points donc je doit utiliser 7 thermocouples
merci pour la réponce
JB wrote:
Pourquoi avoir marqué ma réponse (qui n'en est pas une) comme solution ? Du coup, la discussion est considérée comme solutionnée et plus personne ne va s'y intéresser.
A combien d'endroits différents la température doit-elle être mesurée simultanément ? Autrement dit combien de thermocouples doivent pouvoir être connectés à la carte DAQ ? Avez-vous toute liberté pour le choix de cette carte ? Y a-t-il une limite de prix ?
En partant du principe que vous allez utiliser une carte DAQ de NI, cette page consiste un bon départ pour la choisir. Un appel téléphonique auprès de NI pourrait certainement être utile pour des conseils.

Problème d'acquisition de mesures avec un module 6219

Bonjour,
Je possède un module NI 6219 et je souhaite faire des mesures de température avec un thermocouple de type K.
J'arrive à connecter le module au PC mais les mesures que j'obtiens sont désordonnées et complétement incohérentes que ce soit sur LabView ou sur Max. J'ai également fait des mesures de tension et j'obtiens les mêmes résultats.
Pourriez-vous m'aider à résoudre ce problème ?

Hello,
Concernant ton vi, il y aurai pas mal de commentaires...., désolé je ne peux pas rentrer dans détail.
Les réponses précédentes te dirigent vers les exemples, pour être encore plus précis, je te conseil l'exemple "Cont Acq Thermocouple Samples-Int Clk.vi."
dans:
E/S materielles/DAQmx/Mesures analogiques/temperature/Cont Acq Thermocouple Samples-Int Clk.vi.
Tu y verra comment utiliser correctement la fonction de cadencement dont ont parle ci dessus.
Un autre point fondamental : dans ta config de voie, tu n'a pas câblé ni le type de thermocoule, ni la compensation de soudure froide.... C'est vital si tu veux que tes mesures de températures soient justes...
Quel module pour thermocoupe utilises tu dans ton châssis cDaq9181? Selon le hardware, les fréquences d'échantillonnages doivent parfois être contraintes à certaines valeurs (sous multiple de l'horloge, f maxi etc).
Bon courage
antoine

USB 6009 thermocouple noise

I'm using NI-DAQmx 7.5, Labview 7.0, and a USB-6009.
I'm trying to get a more accurate reading from my j-type thermocouple. It is now distorted with noise and jumps rapidly +/- 20 degrees around room temp without any heat being applied. When heat is applied, it climbs as it should but with the same variation. I haven't moved to the labview side of it yet, I'm still trying to get a usable reading in MAX. I have it wired as a differential input with a floating signal source. I've installed 10k ohm resistors for bias current return as instructed. Installing the resistors helped but still leaves me with the readings shown in the attached pic. I've also tried grounding my USB 6009 with no results. Please help. john
Attachments:
thermocouple reading.jpg ‏41 KB

Hi John,
What you are running into is a problem with the actual voltage resolution of your USB-6009. This device has 14-bits of resolution over a minimum range of +/- 1V. That means that the voltage resolution is (1 - (-1))V / (2^14) = 2V / (16384) = 122uV. While this is an excellent resolution for such a low cost USB device, you will still notice problems when trying to make a thermocouple measurement. The reason for that is that Thermocouples make a very small output voltage (see image below).
Common thermocouple types have the following response:
K type: 41 microVolts per degree Celsius
J type: 56 microVolts per degree Celsius
T type: 52 microVolts per degree Celsius
There are a few options for ways to get around this limitation.
Good: You could read the signal in as a voltage and then manually convert that voltage into a temperature. This would be the least accurate method, but it should allow you to average out your signal and then use the Convert Thermocouple Reading.vi to show the voltage as a temperature.
Better: If you want to keep using the USB-6009 to measure thermocouple, what you really need to do is first amplify your signal before you connect it with your device. This should increase your resolution of the thermocouple allowing you to get more accurate temperature specs. This will require some more complex programming to properly scale your measurements, but it will give you more accurate readings for relatively little cost.
Best: Opt for getting a USB device that is designed for taking temperature measurements such as the USB-9211A. This device would give you a voltage resolution of 160mV/2^24 = 9.54 nV! That's over 12500x the resolution of the USB-6009 that you currently have.
Hopefully the above information helps you better understand what is going on and why. If you have any other questions feel free to post them here.
Message Edited by Otis [DE] on 01-13-2006 11:37 AM
Message Edited by Otis [DE] on 01-13-2006 11:38 AM
Otis
Training and Certification
Product Support Engineer
National Instruments
Attachments:
761029-Thermocouple_Voltages.GIF ‏10 KB

How to measure thermocouple in lab view and save the data..

hi.. i am using my DAQ with 2 analog channels.. i need to acquire signal from thermo couple i have T type thermo couple with brown jacket.. i have connected the thermocoupe in ai0.. and i selected the thermocouple type... when i select the built in option.. it shows some error.. then if i use cjc value as constant 25 its working.. but the signal acquired is not matching well.. it show huge variation.. some times it goes for -20 and maximum of 60 which is not possible at all...just in air medium i checked it... when i used infrared thermometer it shows around 24 C... kindly help me.. i have attached the screen shot of the block diagram panel... and acquired signal..
Attachments:
Doc1.docx ‏425 KB

Hi,
You hooked up to the analog inputs on your device correctly. Thermocouples measure the difference in temperature between the DAQ and the location where the wires are welded together. They need to be insulated thermally and electrically in-between. Thermocouples have very low response compared to the normal 10 volt DAQ range. Type T is only 43 uV/C (thats 0.000043V compared to 10 volts). To see if the thermocouple is working, you need to heat up the welded end. They measure 0 V when the welded end is at room temperature. Type T only goes up to a few hundred C, so be careful, but you can probably wave a lighter under it to see if it's working. You might try the audio in on your device. You don't need a high sampling rate and it may have a better amplifier and dynamic range.
To get absolute temperature you need to offset the thermocouple reading from the DAQ temperature (room temp usually). You could do this by measuring it with your IR thermometer. Check into the NI 9211 and simliar which are much better suited to thermocouple measurements.
Good luck!

Multiple tc types on one scxi 1102

Does anybody know if you can use two different thermocouple types on one SCXI-1102 module?
I need to measure both Type K and Type T thermocouples. I am using a SCXI 1303 connector block and plan to use the internal CJC.
Thanks in advance
doloop

Hello doloop,
You can indeed configure a task to have to two different types of
thermocouples, and acquire from multiple thermocouple types in one
DAQmx Task. For each channel, the NI-DAQmx driver will apply
different conversion coefficients to convert voltage measurements from
different thermocouple types into temperature measurements. You
can configure this easily in Measurement & Automation Explorer
(MAX), by creating a DAQmx Task of the thermocouple type, and adding
multiple physical channels from the SCXI 1102 module to the channel
list. For each channel in the scan list, under the settings tab,
you will have the option to select what type of thermocouple to
associate with each channel, along with CJC settings. You can
also do this programmatically in LabVIEW using the DAQmx Create Channel
VI. I've attached a shot of a block diagram that shows how to
program this.
I hope this helps!
Travis G.
Applications Engineering
Message Edited by Travis G. on 04-18-2006 05:09 PM
Attachments:
MultipleThermocoupleTask.Jpg ‏68 KB

Can the USB-9211 Thermocouple Input device measure voltages ?

Can the USB-9211 be used to measure voltages ? It is designed for thermocouple measurements and its operating manual states there is a current source between its TC+ and TC- input terminals.
What amount of current is flowing ? Does it depend on the selected thermocouple type ? Can the current level be controlled by sotware ?
One application for me is to measure resistances of 1 ohm or less by measuring the voltage drop across the resistance induced by flowing a current through it. Might the 92111's current source be somehow used for this ?
What is its peak to peak input noise ? Its specs say 1 uV rms.
This is a delta-sigma converter. Is each successive measurement accurate or does some digital filtering have to be account for and thus it takes several readings for a signal change to become accurate ?

The 9211 measures voltages between 0 and 80 mV only. The current source is only use to force a full scale input if an open thermocouple is connected and cannot be controlled by software. The input impedance of each channel between TC- and TC+ is 20M Ohm. However, the current that flows in the amplifier is very small, 50 nA.
The main problem here is the fact that the current source is not controlled by the user. This means that connecting a resistor of 1 Ohm between TC- and TC+ would not just produce a voltage that maybe due to external exitation, but the internal source should also be taken into account. Since the user has control over it, it would be a guess work to try to make sense of any voltage value read in.
its peak to peak input noise is 1 uV rms as indicated in the specs.
So as long as the measurements allow for enough settling time (12S/s), each one is accurate.

Acquistion avec un thermocouple type K et NI USB 6210

Similar Messages

Maybe you are looking for