06-06-2006 07:12 AM
06-07-2006 06:34 PM
06-15-2006 05:35 AM
Hi Thaison,
Thank you. It has been long since tour post but we were occupied because of a compile server bug (localized Windows) and now we have solved it. We are ready to built our application.
Our application is a power monitor which reads the current and voltage transformer outputs and reads them via ADC (NI9201) and calculates the RMS values, Active and Reactive powers and calculates the harmonics (FFT) if possible. The calculations should be done between two zero crosses of the voltage signals - the utility frequency is 50 Hz and the calculation time is 10 ms). I planned to costruct a FPGA VI that reads the signals and at each zero-cross it updates the RMS and active reactive power values at the system. cRIO is going to work stand alone and there will be no connection to any PC. When I first try the controller I used the zero crossing element under the FPGA Math... >> Control >> Nonlinear... I tried it with a function generator and oscilloscope and worked well except the multiple zero-crosses. When the signal is square then the cRIO senses only one zero-cross but when the signal is sine or triangle then the cRIO shows multiple zero-crosses.
Another handicap is the frequency. The utility frequency is not constant and can vary between 49.5-50.5 Hz (can be 49 - 51 Hz if there is an error at the utility) Since the sampling frequency is constant (500 kHz) then the total number of the samples would change.
I am using LV 8.0, LV FPGA 8.0, NI.RIO 2.0.1. How can I built such a code?
Lastly, there is a Sample&Hold element triggered with time (us to wait for next hold) but I could not find a Sample&Hold element triggered with a logical signal which is time independent.
Thank you again Thaison.
06-19-2006 04:58 PM
06-20-2006 02:54 AM
06-20-2006 02:55 AM
06-21-2006 05:02 PM
06-23-2006 09:21 AM
06-26-2006 12:39 PM
06-27-2006 09:55 AM