National Instruments USB-7845R Multifunction Reconfigurable I/O Device

The USB-7845R (part numbers: 783200-02 and 783200-01) is a Multifunction Reconfigurable I/O Device from National Instruments. The USB-7845R provides connectivity for 8 AI (analog input) channels, 8 AO (analog output) channels, and 48 DIO (digital input/output) channels. The difference between the two part numbers for the USB-7845R Reconfigurable I/O Device is that part number 783200-01 is an enclosed device, while part number 783200-02 is the standard version of the device that is not enclosed. There are three pins for every analog input channel of the National Instruments USB-7845R—AI+, AI-, and AIGND. Using these pins, the end-user can connect both differential voltage signals and single-ended signals. This device also features a pin referred to as AISENSE. This pin can be used to connect single-ended signals that are non-referenced or have a remote ground connection.

While connecting single-ended, referenced voltage signals to the NI USB-7845R, the end-user should connect the voltage GND signal to the AI GND. This is necessary to retain the common mode voltage in the defined range. The end-user can connect the sources of the grounded or floating differential signals with the Multifunction Reconfigurable I/O Device. The negative signal will be connected to AI- and the positive signal will be connected to AI+. To connect a grounded differential signal to the NI USB-7845R, the end-user must connect the reference signal to the AI Ground.

While connecting floating differential signals to the National Instruments USB-7845R, the end-user must connect the negative signal line to the AI- pin, the positive line to AI+, and add a 1 MΩ resistor between AI- and AIGND to maintain a reference. This module can sample data at a maximum rate of 500 kS/s aggregate across all AI channels, not per channel.