Minimum sample rate for 10KHz square wave with MIO

Need to display a 10KHz square wave input to a 16E MIO. Presently sampling 1 channel at 400KS/s. Gives me 2.5uS/sample. Even at 800KS/s-same thing. How come I can't get a decent picture of the waveform. Presently I see a ramp up-down akin to an RC time constant. At 1KHz I get a decent waveform. I'm wondering if I have something set wrong in my program. Did I miss something in determining the proper sample rate?

Hi Steve,
Are you sure you are sampling at 400 and 800 KS/s?
I thought those boards only go up to about 100KS/s.
(show your point on your plot. Are you getting 40 samples per period?)
If you really are sampling that fast, then you have partially answered your own question. There is a small capacitance at teh input to the board. A high impeadance source will combine the input capacitance of the board to give you the charge ramp you mentioned. Only solution to this situation is ussing a low impeadance output buffer between your signal source and the AI.
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

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