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Installation of K & R type TC on same location but produce different output temperature

Hi Everyone,


I installed two different (K & R) type Thermocouple on the same location but getting the huge difference in output values. please refer to the attached images for my written code.


 Looking forward for result oriented reply.


Best Regards

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Message 1 of 9

Please attach the VI instead of picture. Thanks.


(Are you sure the termocouples are OK? Which one shows the correct temperature. What is a "huge difference"? fractions of a degree? hundreds of degrees?)

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Message 2 of 9



Please find the attachment, Vi for K & R TC. The R type TC output does not appear properly, fractions of degree difference but the output produces the notches such as a sinusoidal signal. It should be smooth, please review it and give the suggestion as per your knowledge.

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Message 3 of 9

What do you mean by "notches"?  Perhaps you can attach a picture of the signal that looks bad.


Is it all the type R thermocouples or just one?  What if you only had a task of a single type R thermocouple and no type K's, does that look any better?

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Message 4 of 9



In the first eight-channel, only one K type TC is connected and in the last eight channels only one R type TC is connected,


Notches mean a sudden distortion or you can take it as noise. 

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Message 5 of 9

Maybe you are picking up noise from the open channels.  Ones you are reading, but don't have thermocouples attached to.

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Message 6 of 9

I don't think so empty slot produces the noise.

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Message 7 of 9

Granted I do not have any experience with NI-DAQ devices but I do use thermocouples and other devices for reading them. 


When I see someone using a DAQ for thermocouples my first question is:


How are you handling Cold Junction Compensation?


Most devices designed for reading thermocouples have an internal cold junction reference, most DAQ device do not.


Also remember that when reading thermocouples you are measuring millivolts/degree, that puts the DAQ in a very low voltage range and will be very sensitive to any noise. Possibly some measurement integration could help with this but most time noise needs to be dealt with on the hardware level. Like grounding all unused inputs of the DAQ to start with...

=== Engineer Ambiguously ===
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Message 8 of 9

@TaufeeyTonello wrote:

I don't think so empty slot produces the noise.

I don't know what you are trying to say here.

If an empty slot picks up noise, perhaps that is being passed along into the non-empty sensors as well. 



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Message 9 of 9