Square wave DC/AC coupling on AD2

[daanwielens]

Hi, 

For an experiment I need to send a 20 Hz triangle wave and measure the response of a DUT. I plan to generate and measure the signals both with the AD2. I noticed that the measured signal was not purely triangular, but a bit curved, which reminds me of AC/DC coupling issues on a classical scope.

Hence, I switched to a 20 Hz 2Vpp square wave. Here, the measured signal shows even more features resembling DC rejection. Nevertheless, the scope settings are configured to DC coupling. Why is my square wave not 'really square'?

[JColvin]

Hi @daanwielens,

How do you have the Analog Discovery 2 connected? With direct MTE loopback connected on mine, I can some of the noise band indicating a nonstraight edge (not quite as aggressive as yours)

but as I zoom in to get a better look with a more narrow timebase and use the better accuracy range setting (500 mV/div or less), I only end up actually seeing the non-square shape once I start seeing the rise time Wavegen itself.

Thanks,
JColvin

[daanwielens]

Hi @JColvin,

Thanks for your quick reply. I didn't know what MTE meant, so I googled the BNC adapter PCB to see if it'd be related to that one. There, I came across the AC/DC coupling text which indicated that there are jumpers on the PCB. I completely missed this, and unfortunately my PCB's jumper was set to AC. After changing this one, the signal is as expected. 

Best,

Daan