I would like to control temperature.

[wrossi]

I would like to control temperature using a type K thermocouple and a NI-6220 board. The outputs will be SSRs. What is the easiest way to configure this. I'm new to Lab_view

[Matt_A]

Hello wrossi,

There is a KnowledgeBase on our website here that discusses using SSR Modules with an M Series Multifunction DAQ device (like the NI 6220). The document itself is not that detailed, but there are some good links at the bottom, including one for a tutorial on SSR Modules and device specific How-To's. This should get you started.

[wrossi2]

Thanks for the reply.
I have the thermocouples and the SSRs connected to a CB68L PR. I have configured the NI measurement & Automation Explorer to receive a Mv signal and to output a 5v on or off to the SSRs. How should I proceide in writing a VI to control the temp. to a certain set point that I can Very?

[Matt_A]

Hello wrossi,

I would recommend that you examine a few shipping examples to see good demonstrations of how to architect this application. You can find example programs in the NI Example finder; to open the example finder from LabVIEW click on the Help menu and select Help>>Find Examples... Once you have opened the NI Example Finder you can navigate to DAQ examples by clicking the Browse tab and selecting Hardware Input and Output>>DAQmx. The examples are then categorized by the type of operation which they perform.

There are a few examples which I think are particularly applicable to your operation. Acq Thermocouple Sample.vi (Hardware Input and Output>>DAQmx>>Analog Measurement>>Temperature) demonstrates how to make temperature measurements using a thermocouple. Write Dig Chan.vi (Hardware Input and Output>>DAQmx>>Digital Generation) demonstrates how to write values to a digital output channel. Finally, PID Control-Single Channel.vi (Hardware Input and Output>>DAQmx>>Control>>General) demonstrates how to do a control loop using Analog Input and Analog Output. You should be able to combine the first two examples based on the structure in PID Control-Single Channel.vi to perform the temperature control you described. You would read the thermocouple as your input and compare it to the user defined set point. Then, you would determine what value to write to your digital channel based on the value of the thermocouple. An example of this operation is shown in the image below.

In this code, the thermocouple data is compared with the user-defined Set Point control. If the temperature is less than or equal to the set point, the digital line is set to True or 5V (close SSR, turn oven on, etc). If the signal is greater than the set point, the digital line is set to False or 0V (open SSR, turn off oven, etc.)

Message Edited by Matt A on 04-25-2007 02:14 PM