PID loop in PXI 8106 with FPGA

[ETRND1]

We have PXI 8106 RT with PXI 1044 chassis and three nos. of PXI 7833 FPGA card.

Right one our one continuous machine operates three Cascde PID loops with individual FPGA card. ans we get all PID response time is about 7 micro seconds however we can rely with 800 micro second.

Now our question is can we go for only one FPGA(PXI 7833) for all three Cascade PID loop and can we get response of less than 800 micro seconds with same RT controoler and chassis accept one FPGA card instead of three.

Thanks,

Message Edited by ETRND1 on 03-27-2008 03:47 AM

[Van_L]

Hi ETRND1

Using one board is the way to go to save slots and money.
FPGA is beneficial in a way that it can run parallely (truly)
If you have 3 identical (doesn't need to be) PID you can essentially copy and paste this PID loop into 3 copies and compile it.
You can look at the compile report and see if everything compiled successfully.

FPGA's limitation is its size, which is the number of gates the chip contains. The more gates, the more logic you can fit on it.
As long as your PID X 3 doesn't exceed the maximum size of the chip they will run as if they are on 3 different 7833 FPGA boards.

FPGA is able to run by itself, meaning it doesn't need the RT control to run.
There is one more thing you need to consider, which is the interaction of FPGA with the RT side.
Is there a lot of interaction with it and does it slow it down.

The best thing is to give it a try.
It may save you money and give you extra PXI slots for other cards

Good luck