Temperature Measurement

[phywer]

Hi,

I am trying to measure the temperature with pci-6025e and scb-100. I connected 10k NTC to ai0-ai8 and to the current source, 20uA.

I measured the temperature with NI MAX temperature task and with labview script. But I think the measurement is incorrect and noisy.

I would like to know what I am doing wrong and how can I fix it. Is there anything that I can try?

Thanks in advance.

[Tomasz_Kowalczyk]

Hello @phywer!

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Do you have the datasheet of the NTC that you use?

What makes you think that measurements are not correct?

Did you try to perform some control measurements with some other NTC/other metod?

What is the resolution of the given NTC? 

Also, did you try to apply some lowpass filter to your measurement circut?

[phywer]

Hi, thanks!

Yes, please see the attached datasheet

I tried to measure the temperature with same NTC and with another Datalogger, it works. 

But if I do that with daq card, it shows always something between 20.9-21.1°C even the temperature should be more than 25°C 

I tried with some other NTC and lowpass too, still it doesn't work

Which methods can I try?

[Tomasz_Kowalczyk]

Hello again,

Thanks for reply.

Could you please try to measure the voltage instead of configuring temperature measurement task and count the ratio manually/ in LabVIEW?

Let me know, if the measurements of the voltage are good. If not, it is possible that you are not configuring the input properly.

[phywer]

Hello and thanks again. 

I measured the voltage and it shows continuously 0 V.

Then I measured the voltage again but this time without NTC and it starts with -900mV and ends up with 10V. 

Nothing is connected, it is just SCB-100 and DAQ Card. 

[Tomasz_Kowalczyk]

Hi!

Did you compare your results to any reference multimeter?

Also, this is nothing unusual, when you have nothing connected and voltage is changing, because the pins are floating.

Could you please insert some 10k resistor instead of NTC and measure the voltage drop on this resistor both with DAQ and othere reference multimeter?

[phywer]

Hi, Thank you!

I did, they show similar results

I inserted 10k and measured the voltage with DAQ and Multimeter, it is 0V. 

[Tomasz_Kowalczyk · Accepted solution]

Hi again!

My assumption is that your circut (Current supply) is not working properly.

Could you please try to perform a simple voltage divider including your NTC, some 10k resistor and voltage supply, instead of current one?

[phywer]

Hello again! 

You were right. The problem is the current supply. I tried with the voltage supply and still noisy, but it works. Thank you very much for your help.