Chapter 4 Signal ConnectionsVXI-MIO Series User Manual4-14 National Instruments CorporationDifferential Connection Considerations (DIFF Input Configuration)A differential connection is one in which the VXI-MIO Series moduleanalog input signal has its own reference signal or signal return path.These connections are available when the selected channel isconfigured in DIFF input mode. The input signal is tied to the positiveinput of the PGIA, and its reference signal, or return, is tied to thenegative input of the PGIA.When you configure a channel for differential input, each signal usestwo multiplexer input lines—one for the signal and one for its referencesignal. Therefore, with a differential configuration for every channel,up to 32 analog input channels are available.You should use differential input connections for any channel thatmeets any of the following conditions:• The input signal is low level (less than 1 V).• The leads connecting the signal to the VXI-MIO Series module aregreater than 10 ft (3 m).• The input signal requires a separate ground-reference point orreturn signal.• The signal leads travel through noisy environments.DIFF input connections reduce pick-up noise and increasecommon-mode noise rejection. Differential signal connections alsoallow input signals to float within the common-mode limits of thePGIA.
