# Multifunction DAQ

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## How do you obtain high impedence on digital output line?

I would like to switch between logic zero and high impedence on the digital output lines of a 6115. However, there are pullup resistors that prevent the output from floating.  Is there a way around this? Ideally, negligible current will flow through devices connected to the digital output lines when the output is tristate, high impedence.
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## Re: How do you obtain high impedence on digital output line?

Hi Dekay,

I pulled this from the S Series Help

Each line has a weak pull-up resistor connected to it, as described in the specifications document for your device.

It sounds like you want to simply switch your lines from an output with logic 0 to an input which will have a high-impedance state.

Maybe if you tell us more about what it is you are trying to do we could give you some better details.

Regards,

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## Re: How do you obtain high impedence on digital output line?

Hi!
You should be able to do it in max, in device configuration.

If you're programming in CVI, have a look at this function:

DAQmxSetChanAttribute (, "", DAQmx_DI_Tristate, );

(see help for further details....)

Hope it helps!

graziano
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## Re: How do you obtain high impedence on digital output line?

Otis -

I would like to use the digital lines to selectively create or eliminate a ground path. I have a resistor with one end connected to DIO0 and the other to a circuit in which I would like to change the resistance. Switching between DO0=0 and DI0=high impedance was expected to put the resistor in the circuit or take it out, but it still puts 5V out on DI0 when in hi-z.  A program sample is attached.

Thanks

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## Re: How do you obtain high impedence on digital output line?

Hi Dekay,

Instead of creating a Digital Input Channel on the same line as the Digital Output Channel, just use a single Digital Output Channel and use the DO.Tristate property to tristate the line. Your code has two tasks sharing the same line. Let us know if this helps.
--
Michael P
National Instruments
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