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Member
panoskak
Posts: 8
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Could PXIe 6124 be used for control?

Hi,

I need for second time your help. I have an NI pxie 6124, combined with the 8133 controller,
the 1082 chassis and the BNC 2090A. We bought this equipment for data acquisition, but I
am wondering if I could use this to control an IGBT switch. The control technique is extremely
demanding, but I was trying to find which is the highest switching frequency that I could
achieve.

The results, for the simplest model (a pulse generator and a digital output) in matlab (because
I am more familiar with) was a diassapointing Ts of about 1 ms. The strangest thing was that

the period was not constant but variable, even if I had a fixed step model.

 

I am quite novice with NI - Labview. My goal is to achieve a sampling time of 20e-6s and to

decide for the switch state after some calculations.


Thanks in advance.

Member
Jeff.St
Posts: 73
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Re: Could PXIe 6124 be used for control?

Hi Panoskak,

 

The PXIe-6124 has 2 analog output channels and 24 bi-directional digital channels, so it is capable of being used for control.  Here is a link that gives the specifications of the card.

 

http://www.ni.com/pdf/manuals/372526b.pdf

 

Best,

Jeff S.
National Instruments
Member
panoskak
Posts: 8
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Re: Could PXIe 6124 be used for control?

Thanks for your reply.

 

I have seen the specifications because I already used the one digital output. The reason for this post is to find

if someone else has checked the digital outputs capability as for the switching frequency.

 

I need for my control strategy to read three analog inputs, evaluate some equations, and to decide for the switch

state, and all these in 50 μs. My test, with only a pulse generator and one digital output has shown that the

switching pulses were not constant even if I had a fixed step model, and the maximum switching period was sth

about ms. Do you know if there is a constraint? Maybe my thought is completely wrong. I used matlab with only

the pulse generator in a fixed step model, nothing else.

 

The digital outputs are only for some on-off applications or are capable of controlling sth in kHz? Why under a

constant period pulse generator the period differentiates when in μs, or ms? Could you give me a simple vi to test

a pulse generator at 20 kHz in Labview (I am quite novice to be sure for my results).

 

I need your help if sb knows.

 

Thanks again.

Member
panoskak
Posts: 8
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Re: Could PXIe 6124 be used for control?

I would like to add that maybe matlab communication with the 6124 deteriorates speed, resulting in a not

constant switching frequency. PXIe 6124 is not supported by the real time target library in simulink.

 

Is it possible to find an IV to generate pulses directly in Labview. The express library only gives me the

capability to determine on/off, not switching...

Member
Jeff.St
Posts: 73
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Re: Could PXIe 6124 be used for control?

Hi Panoskak,

 

I don't think you're going to be able to do all of those things in 50 micro seconds.  I agree that MATLAB might be slowing down your output, but I am not very familiar with interfacing through MATLAB.

 

You can find examples for how to output a 20 kHz signal in the NI Example Finder.  On the browse tab, follow this path...

 

Hardware Input and Output>>DAQmx>>Digital Generation>>(VI)

 

Best,

Jeff S.
National Instruments
Member
panoskak
Posts: 8
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Re: Could PXIe 6124 be used for control?

Thanks, I will try and post again my findings. It is about the time interval to read data, to do some calculations, and then to output the pulse. I do not know where to find this information. I use a Texas microprocessor but the speed is not so high as I would like.

 

Could I ask sth not related to my post?

(I have installed Labview 2009 but under license manager I see Labview (...) (...) but it does not say sth about mathscript.

In the received mail from Labview said: Labview 2009, professional (...) , full (...) , Labview 8.6.1 deployment (...) with mathscript for 32 and 64 bit and the activation codes. I can not find anywhere in the license manager this to activate. Am I supposed to install Labview 8.6 and then activate mathscript, Where could I find this to download?)

 

Thanks again.

Member
JtotheB
Posts: 195
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Re: Could PXIe 6124 be used for control?

Hey panoskak,

 

Licensing has changed for Mathscript since LabVIEW 8.6. After the 8.6 release, Mathscript functionality was removed from core LabVIEW and was moved into the separate Mathscript module. For LabVIEW 2009, you will need to install and activate the Mathscript module separately.

 

mslm.PNG

 

You can download the module here. If you need the older version of LabVIEW, you can download that here. Have a great weekend!

John B.
Embedded Networks R&D
National Instruments
Certified LabVIEW Developer