6602 speed : intox ?

[Eric.Arnould]

Hi,
I'm trying to use a 6602 card as a pulse train generator.
Main counter clock is 80Mhz, so that it enables to reach 20Mhz for a pulse train for example (http://digital.ni.com/public.nsf/websearch/145AF8BCC51C925386256874005EC9C7).

My probleme is that if i set frequency to 2Mhz, square pulse train is functionnal but not very beautiful, at 5Mhz, square pulse train is a triangle ! At 20 Mhz, there is nothing except noise 🙂
So, have i a probleme with my card or is it normal ?

I add a file as exemple of the 20Mhz square pulse train generation (queekly done, extremly easy).

[AnalogKid2DigitalMan]

I presume you are using an oscilloscope to view the waveform.

Almost sounds like a probe/cabling issue- too much capacitance is degrading the signal.

Do you have another high frequency square wave source you can look at?

[Eric.Arnould]

Yes i'm using an oscilloscope with probe.
I can see a 80Mhz generated signal from a generator and it'is perfect !

[ElRambo]

Hi,

Can you tell me what are your generator output impedance and oscilloscope input impedance, and what kind of cable / probe are you using (give the impedance too, and the equivalent capacitance) ?

Best regards,

Message Edité par Maxime MULLER le 02-07-2008 09:35 AM