6552 channel input impedance

[Barry Fitz]

Hi,

I am trying to acquire an output from my DUT using the 6552 card, and the input impedance of the 6552 channel is 50 ohms by default. This is pulling down my output so I want to change the input impedance to 10K or 50K but I can't seem to do it.

When I run the Channel Input Impedance.vi example and change the input impedance to 10K or 50K, it remains at 50 ohms. Similarly when I add the relevant property node (to change the input impedance) to my vi, it still stays at 50 ohms. I am using channel 0 as my acquisition channel, and channels 1-7 as my generation channels.

Any ideas?

Regards,

Barry

[Keith.Shapiro · Accepted solution]

Hi, Barry!

Can you post your code?  Also, what version of NI-HSDIO are you using?

Thanks,

Keith Shapiro

National Instruments R&D

[Barry Fitz]

Hi Keith,

I am using NI-HSDIO version 1.5.4.

[Ryan_M]

Barry,

Make sure you have that channel tristated.  If you had previously used it for generation and did not close the task properly it may still be driving an old piece of data.  There is a tristate vi you can call to explicitly set that.

[Barry Fitz]

Hi Keith,

I sent that last reply too soon!

Attached is the example vi I am using.

Regards,

Barry

[Barry Fitz]

Hi Ryan M,

That fixed my problem, I explicitly tristated the channel first and now it's fine.

Thanks a lot,

Barry

[chefcommander]

Hi, i have exact the same problem... i can't set the impedance resistor to 50 ohm...why so?

i use a 6542 i/o card...

thanks

[Rich_Silley_NIUK]

Hi, have you tried using 'niHSDIO Tristate Channels.vi' as Ryan mentioned above?

 

Rich

NI | UK

[DJ_L.]

Hey chefcommander,

The 50 Ohm input impedance is only available with the 6551/2 products, not with the 6541/2. You can find your product's input impedance options in the Specifications, which looks to be 10k Ohm (high impedance). If you need 50 Ohm input impedance you might consider the 655x's.

I hope this helps. Please let us know if you have any further questions or concerns. Thanks, and have a great day.

Regards,

DJ L.