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Temperature Measurements with K thermocouple, LabVIEW, compactrio and NI 9214

Hi my name is Manuel Escobar, i am learning how to use compactrio so i dont have much knowledge about this. I was trying to meaasure temperature with a thermocouple K wiring it to the NI 9214 module in the compactrio but i am not sure about both the connections and the program in LabVIEW FPGA because i've made many proofs but at the time of the measurement i get wrong values of voltage.

Mi connections are:
Wires of the thermocouple to the 0 channel of the NI 9214, the yellow wire of the thermocouple to the positive input (TC0+) and the red wire of the thermocouple to the negative input (TC0-).
My program in LabVIEW FPGA:
I just put the mod1/TC0 inside the program and add an indicator.
I hope you can help me please i really want to learn about compactrio and LabVIEW.
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Message 1 of 6
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Hi Manuel,

 

LabVIEW comes with a lot of example VIs. They are also available for cRIO modules, for (more or less) each module you will find an example.

Did you check the example finder?

 

Why don't you use the ScanEngine? It should be fast enough to read some TC measurement values!

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Message 2 of 6
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I also tried the examples but i cant run the program i dont know why, please can you help me with that?

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Message 3 of 6
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Hi Manuel,

 

i cant run the program i dont know why

Well, usually LabVIEW tells you why you can't run a VI!

Mind to show screenshots or tell us the error messages you get?

 

Have you tried any (or all which apply) of these resources? They will help when you want to learn LabVIEW or get familiar with cRIO devices…

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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I've not seen the NI 9214 before, but I've used the NI 9213 quite a lot - you should find some examples for one of the thermocouple modules (e.g. 9211, 9213, 9214) in the example finder.

 

On the FPGA you need to read the TC channel, the CJC channel and the autozero channel and pass these up to the Host (e.g. PC or RT) - you can do this using front panel controls (or using a FIFO - but I suggest starting with front panel controls) on the FPGA which you can then read on the host. You will need to compile your FPGA code before it will run - once compiled, try running it interactively at first to check you see the values.

 

On the host (either PC or RT), you can open a reference to the FPGA VI to run it and then you can use an FPGA Read/Write node to read the values from the FPGA front panel.

 

The conversion from voltage(s) to temperature is done by a VI that's fairly well hidden and it's a fairly complicated lookup so it's not done on the FPGA.


LabVIEW Champion, CLA, CLED, CTD
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Message 5 of 6
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Hi,

 

to add to Sam's comment:

The conversion from voltage(s) to temperature is done by a VI that's fairly well hidden and it's a fairly complicated lookup so it's not done on the FPGA.

But again this conversion VI is shown and explained in the example VIs/projects available for the TC modules!

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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