Analog Input Terminal Configuration

S Series devices support only differential (DIFF) input mode. The channels on S Series devices are true differential inputs, meaning both positive and negative inputs can carry signals of interest. For more information about DIFF input, refer to Connecting Analog Input Signals, which contains diagrams showing the signal paths for DIFF input mode.

NI 6110/6111 and NI 6115/6120 only

The channels on these S Series devices are pseudodifferential inputs. The input signal of each channel, AI <0..3> +, is connected to the positive input of the instrumentation amplifier, and each reference signal AI <0..3> –, is connected to the negative input of the instrumentation amplifier. The inputs are differential only in the sense that ground loops are broken. The reference signal, AI <0..3> –, is not intended to carry signals of interest but only to provide a DC reference point for AI <0..3> + that may be different from ground.

Pseudodifferential signal connections reduce noise pickup and increase common-mode noise rejection. This connection type also allows input signals to float within the common-mode limits of the PGIA.

Caution Exceeding the differential and common-mode input ranges distorts the input signals. Exceeding the maximum input voltage rating can damage the device and the computer. NI is not liable for any damage resulting from such signal connections. The maximum input voltage ratings are listed in the Protection column of the I/O Terminal Summary table in the specifications document for each S Series device.