Analog and Digital grounds in cRIO chassis

[Nenad_Mijatovic]

Hi all,

Is a COM  pin in a analog or digital module (C ceries modules) insulated among modules if multiple modules are used in the sam chassy?

Let assume I have 6 modules installed in my cRIO chassy, three NI9205 (AI) and two NI9403 (DIO) module. One of 9205 I want to use as differential input module (not using COM port) and two in single ended (unig COM port). Could you tell me is the COM port isolated between 9205 (each modules) or will it be share? Same question applies for 9403: will the DGNDs (COM) of two modules be coupled or will it ‘float’ with respect to each other?

Kind regards,

Nenad

[crossrulz]

I'm pretty sure all grounds are tied to the chassis inside of the cRIO itself (single point ground).  At least all DAQ boards act this way.  It is simple enough to check with a DMM.

[Izzzzz]

Hello Nenad, 

Most C Series modules are isolated from the chassis and other modules in the chassis. Please check the artwork on each module and/or documentation for each module to see if it is isolated as well as the level of isolation. The isolation is specified as Ch to Earth Ground Isolation. 

The answers to your questions below. 

Is a COM  pin in a analog or digital module (C ceries modules) insulated among modules if multiple modules are used in the sam chassy?

It depends on which module.you are using.

Could you tell me is the COM port isolated between 9205 (each modules) or will it be share?

Yes the com ports are isolated between each NI 9205. 

Same question applies for 9403: will the DGNDs (COM) of two modules be coupled or will it ‘float’ with respect to each other?

Yes the com ports are isolated between each NI 9403. 

Best Regards,

Izzy O.

Product Support Engineer

ni.com/support  

[Nenad_Mijatovic]

Hi Izzy,

Thanks a lot. Very helpfull.

Kind regards,

Nenad