National Instruments 777687-08 Current Input Terminal Block 

National Instruments part number 777687-08 is an identifying part number for the SCXI-1308, a Current Input Terminal Block. The NI 777687-08 is a 32-channel terminal block featuring 78 screw terminals. It can connect to SCXI-1102/B/C and SCXI-1100 modules. The terminal block includes 32 precision 249 Ω resistors that convert current to voltage for 0 to 20 mA and 4 to 20 mA measurements. The connected SCXI module then measures the voltage, allowing the data acquisition board to obtain the voltage. There are 32 pairs of screw terminals for the 32 differential inputs of the SCXI modules. One pair of terminals connects to the module’s chassis ground pins. Three terminals connect to the SCXI module OUTPUT and AOREF pins, along with the SCXIbus guard. The remaining terminals are reserved for future use. 

This Current Input Terminal Block converts current to voltage, allowing the data acquisition board to measure the voltage. For a 4 to 20 mA current source, the voltage measured ranges from 0.996 to 4.98 VDC. The NI 777687-08 can measure both current and voltage sources. When measuring voltage signals, the current-loop resistor for the specific input channel should be removed. To set up and use the NI 777687-08 Terminal Block, you will need the Installation Guide, an SCXI chassis, the SCXI-1102/B/C or SCXI-1100 module, No. 1 and No. 2 Philips-head screwdrivers, and 1/10 inch and ¼ inch flathead screwdrivers. Start by connecting the Terminal Block to the SCXI module’s front connector, then secure it by tightening the top and bottom thumbscrews on the rear of the Block. 

The device supports channel-to-channel and channel-to-earth voltages up to 30 Vrms, 42.4 Vpeak, or 60 VDC. It operates in temperatures from 0° to 50° C, can be stored in temperatures ranging from –20° to 70° C, and functions in a non-condensing relative humidity range of 5% to 90%. To clean the terminal block, use a soft, nonmetallic brush to remove light dust. For other contaminants, use deionized water and a stiff nonmetallic brush. Ensure the unit is completely dry and free from contaminants before returning it to service.