Measuring temperature and acceleration simultaneously

[Bnzi]

Hi,

I am having problems getting a correct and stable temperature measurement, I think the acceleration measurements are correct. I am using a daq PCI 61110 and the temp sensor is a type-k thermocouple I tried switching the thermocouple with a probe but the result did not change and I have checked the examples to see if I have gotten something wrong in my code but I can't seem to find it. Please could somebody help me and the vi is attached below.

[JohnMc19 · Accepted solution]

Hi Bnzi,

I've looked at your code and it seems fine to me, so I would suggest try out the simple tests to see if it's working.

Try ensuring you can see your card in Measurement&Automation (MAX).

• Open LabVIEW, got to 'Help' tab > Find Examples
• Look in the middle field and open 'Hardware Input & Output >> DAQmx >>> Analog Measurements >>>> Temperature'
• Then choose a suitable example (e.g Acq Thermocouple Sample) and try it with your hardware

If this works then it should narrow down whether the problem is the code, drivers, or your hardware.

Hope this helped!

Regards,

[Henrik_Volkers]

I don't know your DAQ card, but I assume you are measuring in the voltage range for the accelerometer and them try to measure in the µV  from the TC.

If you have channel crosstalk, your weak signal from the TC gets buried in noise. 

Try to have some input channels connected to GND inbetween, maybe that helps.

Wait, I took a look into the spec (BTW 6111 or 6110??) your minimum resolution is 98µV, that would equal around 2K resolution, accuracy is 353µV (around 8K with type K TC ... not quite the right card for a thermocouple reading!!)  Well and you don't have a CJ compensation....in other words: You don't have the right DAQ for thermocouple readings.

NI has a USB thermocouple device that woul fit your needs and is not too costly... or use a B5 module or other thermocouple signal conditioner with a 10V output.

Depending on your needs maybe a small NTC with a resistor as an voltage divider can be used to measure temperatur ...

[Bnzi]

Hi John

thank you for the advice I will take a look at the example and see what's wrong.

Bnzi

[Bnzi]

Hi Henrik

Thank you for your input and you have brought interesting info to my attention I appreciate your help

Bnzi

[Bnzi]

Hi Henrik

Since the daq card I am using does not have cold junction compensation would using a AD8495 thermocouple amplifier help?

Bnzi

[Henrik_Volkers]

Yes, looks like a possible solution. You get the signal amplified and CJ compensated. 

I would try to buy a ready converter like this one

(Because it is cheaper for my boss to buy it than having me to DIY)

Are you forced to use a TC as a temperature sensor? 

BTW You should correct your solution marking 😉

[Bnzi]

Lol, yes I'm sort of forced to because the expense for my project should  be kept to a minimum. I got to make it work with what I got.