Sampling a 12 V AC 50 Hz signal with a NI-9219 card

[MartinAmanouch]

Hello everyone,

As described in the title, I'm trying to visualize a 12 V AC 50Hz signal via a NI-9219 card.

I'm using a cRIO, with the RT scan set to 1 ms.

The NI-9219 board is configured with 3 current inputs and 1 voltage input.

The conversion time is set to "High Speed" to reach 100 Hz.

The signal is connected to the pin 4 and 5.

Unfortunately, when I visualize the signal (either with the HMI or with the distributed system manager) I don't get a sinusoidal signal at all...

 

The signal is indeed 50 Hz, verified by an oscilloscope.

Do you have any recommendations?

Thanks in advance, 

[LVNinja]

Check the connection on the CRio . 

For example use a known signal ( from the scope)  on the input of the CRIo to see if you will see the expected signal. 

IF you cannot see then check the connection with the CRio, confirm that you are reading the proper channel. 

[ZYOng · Accepted solution]

From Figure 2 of Using a Digitizer for Time-Domain Measurements

2x only shows the frequency information of the desired signal, not amplitude or shape. 

[MartinAmanouch]

Hello and thank you for your answers.

@LVNinja thank you for your suggestions, these recommendations had already been made.

I have the option of using 6 or 12 V in both AC 50Hz and DC, by using DC I have the voltage selected.

@ZYOng, thanks for your reply and for the link.Indeed, I was making the mistake that 2 x the sampling frequency would give me the full signal.

I have read the article and I will have another look at the Nyquist-Shannon theorem, I will have learned a lot after these days.

Thanks a lot!