Ni 6008 acquiring digital inputs from an absolute encoder.

Hi, i'm a student working on my master thesis.
I'm trying to acquire 9 digital channels from a 9bit absolute encoder on the NI-USB 6008 but i'm encountering the following problem.
I'm powering the encoder trough the 0V (GND) and +5V ports on the NI-USB 6008, and if i read the digital outputs directly from the pins
of the encoder with a tester, without connecting them to the NI-USB 6008, i see +5V or 0V with respect to GND.
If then i wire the outputs of the encoder to the NI-USB 6008 digital ports, the readings of the tester, are 5V or 3.6V with respect to GND, so basically
when i try to acquire the signals with Labview, they never switch to logic low.
I'm a doing something wrong or is it a problem with the NI-USB 6008?
Thank you for the help.

Hi,
It seems that NI-USB 6008 works well and that the encoder is not able to force low the digital output signal.
I think that this problem could have different explanations:
- the encoder needs a pull down resistor in order to work properly
- the encoder try to force low the digital port while the 6008 is forcing high the same port
- the encoder is damaged
Try to take a look at the encoder manual in order to see if the encoder needs some additional circuitry to work properly.
Alex

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