J, T, E, K type Thermocouple readings stop reading temperature

[GHAHWT]

I have attached a J, T, E, and K type thermocouple to an NI cDAQ-9184. When I run my VI the readings for all thermocouples match and are correct at freezing, boiling, and room temperature. After a short period of time the readings begin to drop to about -260 C and create a sinusoidal signal. The thermocouples will read correctly again if I interact with them, AKA. apply heat. Then they will read correctly for a short period of time before decreasing into the same incorrect sinusoidal signal. I have attached pictures and my program to this post.

[GHAHWT]

I have attached a J, T, E, and K type thermocouple to an NI cDAQ-9184. When I run my VI the readings for all thermocouples match and are correct at freezing, boiling, and room temperature. After a short period of time the readings begin to drop to about -260 C and create a sinusoidal signal. The thermocouples will read correctly again if I interact with them, AKA. apply heat. Then they will read correctly for a short period of time before decreasing into the same incorrect sinusoidal signal. I have attached pictures and my program to this post.

[GerdW]

Hi GHAHWT,

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@GHAHWT wrote:

I have attached a J, T, E, and K type thermocouple to an NI cDAQ-9184.

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The cDAQ9184 is just a chassis. Which module(s) do you use? How do you connect your thermocouples?

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@GHAHWT wrote:

After a short period of time the readings begin to drop to about -260 C and create a sinusoidal signal. The thermocouples will read correctly again if I interact with them, AKA. apply heat. Then they will read correctly for a short period of time before decreasing into the same incorrect sinusoidal signal.

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Do you get any errors from your DAQmx reading?

Please define "short period of time"…

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@GHAHWT wrote:

I have attached pictures and my program to this post.

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Unfortunately you use the latest LabVIEW version many of us cannot open. Mind to attach a downconverted version of your VI? (File->Save for previous)

Your image is next to worthless as you attached a downscaled version of the image. It's just blurred and unreadable.

But still I can see "bad" code: DAQAssistent ExpressVI, lots of SplitSignal and unneeded indicators!

• Replace the DAQ ExpressVI by plain DAQmx code as is shown in all those DAQmx example VIs…
• Avoid using the DDT wires. It just hides the underlying data…
• When you want to show numeric data next to the chart then you just need to ake the "digital display" visible. No need for additional indicators!

[GerdW]

Hi GHAHWT,

do you really need to read thermocouples at 1kS/s?

(And why did you need to create two threads for the same problem?)