Pattern Generator Output Impedance

[CharlieO21]

Hello, I'm using the pattern generator with the output type set to open drain when the output is Z, measuring the output impedance I read almost 5K Ohm, What could be the problem?

[JColvin]

Hi @CharlieO21,

Could you attach a picture of your physical set up on how you measuring the impedance? When I measured the output impedance of a pin on the pattern generator set to constant with an output Z, I measured. Here is a picture of my setup.

Thanks,
JColvin

[attila]

Hi @CharlieO21

The digital IOs have series PTCs and protection diodes to ground and internal 3.3V. 
https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual#digital_io

Having the DMM COM connected to AD DIO and DMM Ohm to AD ground, the DMM will measure the "forward resistance" of the PTC+diode.

[CharlieO21]

20 hours ago, JColvin said:

Hi @CharlieO21,

Could you attach a picture of your physical set up on how you measuring the impedance? When I measured the output impedance of a pin on the pattern generator set to constant with an output Z, I measured. Here is a picture of my setup.

Thanks,
JColvin

I'm using the same measurement. 

9 hours ago, attila said:

Hi @CharlieO21

The digital IOs have series PTCs and protection diodes to ground and internal 3.3V. 
https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual#digital_io

Having the DMM COM connected to AD DIO and DMM Ohm to AD ground, the DMM will measure the "forward resistance" of the PTC+diode.

I think you are right, that "forward resistance" make a voltage divider on my setup and my signal never go up