measuring multiple grounds

[MrBear]

Hi.

I am new to this Labview so please bear with me. 

I have 2 questions that I am having trouble finding simple answers to.

1) I would like to measure 2 independent systems (not connected via ground) at the same time with one daq 6009. Is that possible? 

2) I have made a very simple program that lets me sense voltage on one of my inputs. If I try to reduce the sampling-frequency to a low value (less than 10) I get an error, if I reduce the "timeout" to -1 the program will run, but no data is being displayed or saved to the file......... Why is that? 

The first is the voltage measurement that only works with "high" sampling rate and the second is the alternative program I made to measure voltage on a battery over long periods

Thank you 

// Bjorn

[johnsold]

Bjorn,

1) No. Both systems must be connected to the same reference potential (commonly called ground). Depending on the nature of the systems and how much voltage exists between the individual reference potentials, it might be easy to adapt to make the measurements or very complicated and expensive.

Think of the inputs of the 6009 as requiring a (very small) amount of current to flow from the signal being measured to ground. If the two systems are not connected to the same ground, that current cannot flow correctly.

2) I do not have the DAQ Assistant code so I cannot comment on that issue.

Lynn