Thermcouple Calibration using an NI CDAQ-9174.Ni 9214, NI 9417, and NI 9481

[CPME]

I am currently working on a project involving calibration of multiple thermocouples simulationously up to 300 deg. C. The goal is to collect the voltage signals from the Type K thermocouples and compare them to the temperatures received from the RTD probe. I only want the system to collect data at user defined temperatures so that they can later be graphed and a calibration curve created. This is what I have attempted to do with the first part of the code. When the specified temperature is reached I then want to pass each of the individual thermocouple voltages into different subarrays which are paired with the temperature readings from the thermocouple. This is what I am attempting on the later half of the code.

As for the control loop, I am going to use the RTD temperatures as feedback to the PID temperature controller and output a signal to a solid state relay connected to a 120V source. I have a cartridge heater placed in a copper block that I can attach each of the thermcouples to. The copper block is thermally isolated using 2 in of cellular glass insulation.

I am very inexperienced with LabView so any insight into solving my problem would be great. I may not even be taking the right approach, but based on what I have read so far I think I am going in the right direction. Once I get all the data properly placed in the arrays I am going to pass all of the information into a MS report generator so that the user can print out the result.

Any input would be greatly appreciated 🙂

P.S. This is a really rough draft, all the formating will be fixed when I have working code!

[Mike.F]

Hi,

It seems like you are in the right direction in your code implementation. I'd like to ask you which part of your code will be in charge

of the PID loop control. If you want an excellent responce you need to remove the DAQ Assistans because that will add delay to your

application. If you use low level VIs to improve your code responce then you will have a better responce in the loop control.

If you open LabVIEW/Help/Find Examples. you will be able to find some good examples of how you can use low level VIs to acquire data from thermocaouples. 

You can also find a lot of examples in our website: www.ni.com/code

Regards,

Miguel Fonseca

Applications Engineer

National Instruments