NI 9223

[dasika]

Hi,

I am developing code in LABVIEW to control matrix converter in open loop for cRIO 9082 chassis.  NI 9223 is used for measuring three phase input voltages to the converter. I am simultaneously reading the channels of the NI 9223 every 100 usec.  When I run the code, I observe that sometimes there is an error in the voltages read from the NI 9223. I am using

typical I/O node operation shown in following link to measure the voltage signals.

http://digital.ni.com/public.nsf/allkb/5250C3AAE0CBAAE68625777F0072438E

Can anyone please let me know if there is an error in the way I am measuring the voltage signals ?

Thanks,

Deepti

[Esteban.R]

Hi dasika, Deepti

What kind of error are you getting? Do you get any error code, problem or it is just an unexpected measurement? Could you add a screen shot or give more information about the error.

In the mean time, the host VI on the RTOS (real time operating system) will probably be running with a 1 KHz rate and refreshing the information approximately around 1ms, even though the FPGA VI acquires data every 100us. This is because in that link they are using interactive front panel communication and you are probably losing data, here is a link with information about the different ways to communicate with the FPGA. I might recommend you to use a DMA FIFO.

Regards

Esteban R.

[dasika]

Hi Esteban R.,

Thanks for responding to my query.

I don't get any error message but I get unexpected measurement.  I would like to run the code on the real time controller of NI cRio 9082 not on RTOS.

Is there an maximum speed at which the real time controller can run ?  Do you suggest to use DMA FIFO to communicate with real time controller ?

Thanks once again for responding. I have changed implementation of couple sub-blocks in my system. I will send the screen shot if I have error even with the new code.

Thanks,

Deepti

[dasika]

Hi Esteban,

Ignore my previous post. I am new to Labview. Do you mean that maximum speed I can run RTOS is 1 KHz ? Is not possible to run it faster ?

Thanks,

Deepti

[Esteban.R]

Hi Deepti

Take a look to this link, where it says “Code that runs faster than necessary reduces the resources available for future expansion and may generate superfluous data.” It can run faster but I will recommend you to use the necessary rate and bet way to keep all the information without losing data is to use a DMA FIFO if you do not care to lose data you can increase the rate of the host VI using a timed loop.

The RTOS (Real time operating system) is the operating system that is installed on the controller of the cRIO

Regards

Esteban R.

[dasika]

Thanks Esteban