Need Help Regarding Measuring Excitation Current of NI 9219 Module

[npwyckof]

Hi,

I'm having trouble finding the answer to my question.  My question is...  How do you monitor the excitation current of a 9219 module?  It seems that the excitation current that is specified (0.0005 A) is not what is being supplied to the output.  With a 10.5 KOhm load an current of 0.00025 is output.  As the resistance changes both the excitation current and measured voltage seem to change.  I just need to know the resistance... So, if I can monitor both the voltage and current I can calculate the resistace.  BTW, why doesn't the excitation current remain fixed in the first place?

Thanks,

Nate

[GarPar · Accepted solution]

Hi Nate-

     In almost all modes of the 9219, the current and voltage excitation adjusts automatically with the load it experiences.  The resistance is then measured based on the amount of current and voltage sunk by the load.  This is explained in the 9219 User Guide and Specifications.  This guide also specifies the input impedance of the 9219 depending on which mode it is in.

    I hope this helps.  Best of luck with your application!

[coolzlk]

Hi Gary,

Your reply is so helpful that I'm just confusing about why the 9219 has current excitation.

But I found out that the 9219's value of current excitation isn't listed in its spec, does the value of resistance which is measured by 9219 will be automatically displayed in the MAX?

Best regards

Linko