input digital pulses

[abikutn]

Hi guys,

I have AD9643 Digitizer, My clock which is also the sampling rate is at 100 MHz. My input is a Square pulse ( 0 and 1 volt ) with period of 14 us ( pulse period = 400 ns ). 

I dont see any form of the digital pulse on my output but I see it oscilloscope. But with my Digitizer I see negative and postive like capacitor charging and discharging. Is there a way I can go about it to solve this issue. I am not using any trigger as such now.

Best,

Abhi

[TimmTheEnchanter]

Hi Abhi,

Are you using an NI product?  Or just this particular ADC?

If you are using just this ADC, then can you take some better images?  

In particular, the X-axis scale on your oscilloscope image is at 5us/division intervals, and it's very hard to see whether the 400ns pulse is flat on the top.  That is, it's hard to confirm on your oscilloscope that the pulse isn't discharging.

On your LabVIEW program, the image is also unclear, and I'm not sure what the time intervals (us/div) is on the X scale, or what the voltage intervals (V/div) on the Y scale.  

As far as the "discharging" goes, have you compared input impedances (resistance, capacitance) of your oscilloscope with the input impedance of the ADC?  Are you using any other sort of probe with your scope or your ADC which has an additional impedance?

I can't think off the top of my head why the input to the oscilloscope would be consistently positive, and why the input to this ADC would alternate positive/negative.  Try comparing peak values to see what you find.

-Andrew