National Instruments 777878-01 Terminal Block 

National Instruments part number 777878-01 is an identifying part number for the TB-2605 Terminal Block. This is a front-mounting terminal block designed with screw terminals and multiplexing capabilities. It is compatible with NI 2501 and NI 2503 switch cards, connecting directly to their front panel I/O connectors. This terminal block features an analog bus plug for easy expansion of multiplexers. Enclosed to maintain an isothermal environment for the cold-junction sensor and screw terminals, the NI 777878-01 allows connections to each channel except the cold-junction sensor itself. It includes additional connectors on the front panel for linking to the analog bus of adjacent switch cards using a low-voltage AB plug. 

Built with a printed circuit board and screw terminals, the TB-2605 supports thermocouples, voltage signals, thermistors, and RTDs. The isothermal design minimizes temperature gradients across terminals, while an accurate cold-junction temperature sensor ensures precise measurements with thermocouples. The cold-junction sensor offers an accuracy of 0.5°C from 15 to 35°C and 0.9°C from 0°C to 15°C, with readability and output of 0.2°C from 15 to 35°C and 198.54 mV to 19.58 mV from 0 to 55°C respectively. 

To use the TB-2605 terminal block, you need an NI 2501 or 2503 switch card, the corresponding user manual, wire cutters, a 0.10 in. slotted screwdriver, wire insulation stripper, analog bus connectors, and a No. 1 Phillips screwdriver. To ensure accurate cold-junction compensation and maintain the terminal block's isothermal characteristics, position it and the chassis away from significant temperature variations. The connectors on both the switch card and terminal block are polarized, allowing for insertion in only one orientation. Users are advised to avoid forcing the terminal block when inserting or removing it from the NI 2501 or NI 2503 connector to prevent damage.

National Instruments has declared obsolete status for the NI 777878-01, however, it is still available for purchase and repairs at the Apex Waves website.