NI 9237 connection of external exitation

[karthikj85]

Hi,

I am working with labview 8.6 and using a NI9237 mounted on a Chassis.

I am using 4 strain guauges with an exitation voltage of 10V for which i need to connect a external exitation source.

I am unable to figure out how to do this?There are 2 samll boxes with some connection terminals ,but I am not sure if i am doing it right.

Also, do i need to change my connections in anyway when I use an external exitation source?

[MarkGrot]

The NI 9237 Operating Instructions and Specifications document explains the connections in more detail.  Yes, the smaller connector on the bottom of the module is for external excitation (EX+ is on the top and EX- on the bottom).  When configuring your application, make sure to set the excitation source to be external and 10V.  If you wish to use 4 strain guages at 10V excitation, you are correct in using external excitation since the module can only provide 150mW (see page 15 of the previously linked document).

[karthikj85]

Thanks.

I looked into the  document.

It does not seem to have any info on how to go about connecting those connectors.

I am having a problem with the hardware.

There is a black plug and some metal pieces which look like wire lugs,somewhat. 

I wanted to know how to push them into the slot and connect them.

[karthikj85]

I think i have the external excitation set up now. Thanks for the info 🙂

I seem to have a problem still.

I am using the internal excitation now.

But irrespective of my excitation voltage the voltage  output seems to be constant.

If I measure the output from the load cells directly its varies with excitation voltage.

When i read the ouput via labview its independent.

Seems like black magic to me 

Please help!!!

[ManLongAtNI]

Can you clarifywhat you mean by,

" If I measure the output from the load cells directly its varies with excitation voltage.

When i read the ouput via labview its independent."

What are your settings? What pins are you reading from? Can you provide a screenshot of your code?

Regards,

Glenn

[FightOnSCTrojan · Accepted solution]

Karthik85:

It is not black magic. The constant reading that you get is actually the mv/V value. That needs to be multiplied by the corresponding excitation voltage to get the mV reading. Read this article and hopefully it will clarify any black magic.

 http://digital.ni.com/public.nsf/allkb/21CA039D8F43C5188625729F005AC2F7

Best,

Santiago