National Instruments 777687-60 Current Input Terminal Block 

National Instruments part number 777687-60 is an identifying part number for the USB-1308 a Current Input Terminal Block. The NI 777687-60 is a 32-channel terminal block with 78 screw terminals, designed for use with SCXI-1102/B/C and SCXI-1100 modules. It includes 32 precision resistors of 249 Ω, which convert current to voltage for measuring 0 to 20 mA and 4 to 20 mA process current sources. The SCXI module then measures this voltage, enabling the data acquisition board to obtain the voltage readings. The terminal block connects 32 pairs of screw terminals to the 32 differential inputs of the SCXI modules. 

One pair of terminals links to the module’s chassis ground pins, while three terminals connect to the SCXI module's OUTPUT and AOREF pins, and the SCXIbus guard. The remaining terminals are reserved for future use. This Terminal Block converts current to voltage, measures the voltage, and allows the data acquisition board to obtain the voltage. For a 4 to 20 mA current source, the measured voltage ranges from 0.996 to 4.98 VDC. Additionally, the 777687-60 can measure both current and voltage sources. When measuring voltage signals, the user should remove the current-loop resistor for the specific input channel. 

The device supports channel-to-channel and channel-to-earth voltages up to 30 Vrms, 42.4 Vpeak, or 60 VDC. To set up and operate this 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. The installation process involves connecting the Terminal Block to the front connector of the SCXI module and then securing it by tightening the bottom and top thumbscrews on the rear of this block. National Instruments has declared obsolete status for the 777687-60, however, it is still available for purchase and repairs at the Apex Waves website.