K-Type Thermocouple

[abasitparker]

I'm currently using an NI-9214, connected via Ethercat to my cRio, to read values. Currently the values I'm getting are around 24-27.

The connections I have made are as follows

Positive to +

Negative to -

Body to COM

In my VI, along with everything else that's happening, I'm only using a simple indicator to read the value. This gives a value of around 24-27

However, when I put this value into the Example Conversion VI, I get an answer that's in the negative trillions. Any help on this would be appreciated?

The other issue I'm facing is related to this. When I disconnect the Thermocouple and connect it again, the cRio for some reason stops picking up the 24-27 value, even when reconnected. The only solution to this is to switch to configuration mode, then back to Active Mode, which is obviously not the correct solution, and I'm wondering if there's something I'm doing wrong here?

Thanks 🙂

[Blokk]

Can you attach these VIs? I have no idea what is this "Example Conversion VI" for example...

[abasitparker]

It's a VI found under functions, I'll attach it.

[Blokk]

Sorry but what you say does not make sense to me. Could you show the VI which reads the temperature value from the NI-9214? That VI I guess, already gives you a temperature value.

"This gives a value of around 24-27"

It seems to me, these values are already in Celsius degrees, no? So why would you want to convert the already given temperature value?? 

[abasitparker]

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@Blokk wrote:

Sorry but what you say does not make sense to me. Could you show the VI which reads the temperature value from the NI-9214? That VI I guess, already gives you a temperature value.

"This gives a value of around 24-27"

It seems to me, these values are already in Celsius degrees, no? So why would you want to convert the already given temperature value?? 

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I don't have the VI with me right now, and I've attached the conversion VI I'm using.

This is what I don't get, I'm new to Labview and using cRio for the first time, and our company bought it, so I'm going through the documentation while working.

I'll describe how I'm getting 24-27. From the NI-9214 which is connected, I just drag the module on to my block diagram and add an indicator. 

However, I'm unsure whether what I get is actually the temperature or not. For one, when the thermocouple was placed in hot water, this reading went down drastically, as opposed to temperature which you'd expect to go up. My VI was just connecting this indicator value's wire to the VI which I've posted above. Nothing else. 

If I even know what the output I'm getting from my NI-9214 is, I can proceed with decoding what I'm doing wrong, but I'm not sure what the output is. It's too high to be voltage, it can't be current either, and that's not the resistance value either.

[Blokk]

If the temperature value decreases when it should increase, it is a good indication that you wired the thermocouple in the wrong (reversed way).

Besides, I advise you to take some training for LabVIEW, you can find lots of resources. Also, when you have the project what you deploy for the cRIO, zip it and upload it. Including all the VIs, etc.

[OEM_Dev]

My guess is you're making reading in degrees for a J type thermocouple. Try opening up MAX, finding your 9214, and opening the test panels. Set the correct settings there and see if it works. If not, you have a wiring problem. If it does, you probably aren't setting those correctly in your VI.

[abasitparker]

So the block directly gives temperature without conversion? 

The 24-27 is the indicator values pre-conversion

After the conversion from the attached VI above, it gives -100000000 something C

[abasitparker]

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@OEM_Dev wrote:

My guess is you're making reading in degrees for a J type thermocouple. Try opening up MAX, finding your 9214, and opening the test panels. Set the correct settings there and see if it works. If not, you have a wiring problem. If it does, you probably aren't setting those correctly in your VI.

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This is possible, I could find no documentation proving it's a K-Type thermocouple, but the suppliers insisted it was. I'll try this tomorrow and update 

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@Blokk wrote:

If the temperature value decreases when it should increase, it is a good indication that you wired the thermocouple in the wrong (reversed way).

Besides, I advise you to take some training for LabVIEW, you can find lots of resources. Also, when you have the project what you deploy for the cRIO, zip it and upload it. Including all the VIs, etc.

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 I have taken Core 1 and Core 2, along with an ECM (I think, not sure what it was called) course with NI Instructors. What I meant was I've been working on this software for about 2-3 months, and while I know the basics, obviously, when I get stuck, it takes a while. 

On the reversal thing, it's unlikely, since I did flip the two, and what got to me was how similar the values on reversal were as well. Again, with the polarities reversed, the values are still not increasing in hot water 

[OEM_Dev · Accepted solution]

Just to clarify -

I believe the card you are using defaults to degrees Celsius and J-type thermocouples, not that the device you have is J-type vs K-type. But using MAX to verify your wiring is a good first step regardless when things aren't quite working the way you expect