Ciao Francesco,
ti confermo che la ricerca che hai fatto è corretta.
Il motivo di questa configurazione lo si può ritrovare nel particolare routing dei segnali della scheda.
Per i dettagli ti rimando alla pagina 10-2 del manuale delle serie E:
www.ni.com/pdf/manuals/370503k.pdf
Analog Input Channel
You can select any analog input channel to drive the PGIA. The PGIA
amplifies the signal as determined by the input mode and the input polarity
and range. The output of the PGIA then drives the analog trigger detection
circuit. By using the PGIA, you can trigger on very small voltage changes
in the input signal.
When the DAQ device is waiting for an analog trigger with a AI channel as
the source, the AI muxes should not route different AI channels to the
PGIA. If a different channel is routed to the PGIA, the trigger condition on
the desired channel could be missed. The other channels could also
generate false triggers.
This behavior places some restrictions on using AI channels as trigger
sources. When you use an analog start trigger, the trigger channel must be
the first channel in the channel list. When you use an analog reference or
pause trigger, and the analog channel is the source of the trigger, there can
be only one channel in the channel list.
