adc_bridge in ngspice
You should have posted the error message as well:


  Unknown model type adc_bridge - ignored


That's the reason you don't see any output for node cmd.



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Check the manual, chapter 12 of the manual  

You will find that adc_bridge is a XSPICE extension.

And at the beginning at chapter 12, it reads:


  To make use of the XSPICE extensions, you need to compile them in. 


I've no experience with that, but hope you can continue from here.