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temperature monitor and control

Hi,
my goal is to monitor and control the temperature of the sample during the etching process. The temperature is determined by the thermocouple. My current system is LabView 7.0. Right now I am thinking of:
1. getting a SCXI-1112 (Thermocouple Inpur module)
2. upgrading LabView to 8.2 and getting a PID Control Toolset
3. writing a code that would help to control the temperature of the sample using PID
4. getting a power source with serial connection to output the signal (and thus adjust the temperature)
If anybody knows an easier way to do monitoring/control, please help me. I am really new to this whole LabView world.
ThanksSmiley Happy
Message 1 of 5
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Hello,
 
From Hardware point of view, it looks like you are missing an output signal from you list. How are you planning to do that? PWM or analog output? You have to find a way to control your system.
 
After that, you can look at the lastest examples DAQmx >> Control, where they show how to create a control system with DAQ. They even cover the PWM example (if that is the case).
 
After that, you could use the PID Toolkit and look at the examples to understand how to use the PID Toolkit for your application. In special, the latest PID 8.2 cover most of the different configurations (fixed gains, autoscheduling, alarming, autotune from a controlled PI).
 
Adding those two together, you should be able to get started. After that, you should be able to control the plant manually from the computer, start with P controller (just add Proportional Gain, leaving the rest in zero) to see if the plant responds and, in the end, add the integral part and use the autotune to better tunning the controller in a specific gain.
 
Remember that you should also add code (in general comparisons) to handle abnormal conditions as sensor is open and you have INF or NaN, alarming if set point is going to high, shutdown procedure if it has problems (as ramp down if condition happen).
 
Well, thats enough for you to get started...
Alex Barp
Barp - Control, Simulation, RTT and HIL - National Instruments
Message 2 of 5
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I don't really know your application, but I have developed a large scale SCXI temperature monitoring system for a customer a few years ago. Before you go out looking at things too much just be aware of the speeds you are interested in turning around based on temperature changes. It is real easy to use a scxi system to monitor even hundreds of channels of thermocouples. As long as you are not having expectations of instant temperature change detection you can easily write your own system with relays to click things on and off. It is fairly easy with the scxi chassis, relays for it, and the thermocouples. You might think about not worrying too much about control theory models if you simply have a range of ok temperatures, are not too worried about over-temp for small periods, etc. I would go from a simple setup of scxi, relays and thermocouples with your own labview monitoring system to using a more complex model later on. It all depends on your application at hand of course.

Mark

Message 3 of 5
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hello
i need to control the temperature using atmega8 controller and labview 8.2. i need help with the labview interface. i need the .vi program or something like this.
the data acquisition are made via serial port.
i need some exemples of how to realise the .vi
thank you
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Message 4 of 5
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dandana,

I would first look at the LabVIEW serial examples in the example finder and become familiar with the functions you will need to be using.  After you have looked at these, please feel free to ask more specific questions.  You will probably yield the best results asking your questions in the Instrument Control section of the forum.
Regards,

Jared Boothe
Staff Hardware Engineer
National Instruments
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