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What is the best architecture software to control 40 thermocouples with PWM? Any ideia?



  I am newbie in LabView software. I have a project to control, with PID toolkit, 40 thermocouples with each a PWM (Pulse Width Moddulation ) output. The hardware that i have is a module Daqmx a digital output and Daqmx analogue input. The thermocouples are J-Type.  The frequency of PWM is slow, the minimal frequency ( 1 second ). My big doubt is to choose the best architecture software to control simultaneous all thermocouples to garantee the minimal frequency above. Is it possible?. If it is, i would like if someone with experience could help me.


 Many thanks for your tips.


 Rui Machado.

Rui Machado
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I'm a bit confused by your post. Thermocouples are not devices that you can control, they generate an output voltage based on temperature.

Can you please clarify further.



"It’s the questions that drive us.”
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 Sorry, I am not express very well. It is true, the thermocouples are devices that generate a voltage input ( after convert for temperature) . In my project, i need to control the temperatures of the resistives loads (40)  through PWM output.


I made experience with success to control one resistive load based in this sequential steps:

          thermocouple (read temperature) -> PID toolkit (generate duty cycle) -> PWM output (control the energy to transfer for the resistive load).


 But my problem is:  What is the best architecture software to control for 40 resistives loads simultaneous without the front panel frozen or slow running?



I hope this reply help you a clarify your confusion. 


Rui Machado
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It depends on many parameters such as your hard configuration like the OS, processor, NI hardware... and what you want to do precisely in your VI. In those links you can see that there are many configuration for thermocouple measurements Recommended NI Hardware for Thermocouple Measurements    High-Channel Count Temperature Solutions . Also, depending on your configuration, I invite you to see this links if you want to have an idea of optimizing a multiple acquisition in LV

How to optimize reading multiple temperatures

Why my system slows down with thermocouple module used      

multiple, simultaneous, asynchron acquisition



Message Edité par Steve Mohamed le 01-26-2009 03:24 PM
Steve M.
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I am doing something similar. 32 K-type TC's, PWM driving 16 AC heaters..


Initialy I used the example from the PID toolkit which was a giant while loop. In the end the GUI was horrible to use. (My DMM read took at least 10 seconds to read 32 TC's.)


We are now in the process of re-engineering the system to use a Queued State Machine Producer Consumer Loop. The DMM still takes 10 seconds to read, but the user can queue up front panel events while the system is running.


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