Chapter 4 Signal ConnectionsAT-MIO/AI E Series User Manual4-20 National Instruments CorporationDifferential Connection Considerations (DIFF Input Configuration)A differential connection is one in which the AT E Series board analoginput signal has its own reference signal or signal return path. Theseconnections are available when the selected channel is configured inDIFF input mode. The input signal is tied to the positive input of thePGIA, and its reference signal, or return, is tied to the negative input ofthe PGIA.When you configure a channel for differential input, each signal usestwo multiplexer inputs—one for the signal and one for its referencesignal. Therefore, with a differential configuration for every channel,up to eight analog input channels are available (up to 32 channels on theAT-MIO-64E-3).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 AT E Series board aregreater than 10 ft (3 m).• The input signal requires a separate ground-reference point orreturn signal.• The signal leads travel through noisy environments.Differential signal connections reduce picked-up noise and increasecommon-mode noise rejection. Differential signal connections alsoallow input signals to float within the common-mode limits of thePGIA.
