The National Instruments CB-68T is an advanced Isothermal Terminal Block designed to interface seamlessly with the NI PCI-4351, NI PXI-4351, and NI USB-4350 I/O connectors. This terminal block, part number 777926-01, is specifically engineered for use with the CA-1000 enclosure and features a shielded board with easy-to-access screw terminals for various digital signal conditioning accessories. The CB-68T's isothermal design minimizes temperature gradients across the screw terminals, enhancing measurement accuracy for RTDs, thermocouples, thermistors, and voltage signals. It significantly improves the precision of thermistor temperature sensors, effectively integrating cold-junction compensation for thermocouple readings. Constructed for optimal thermal stability, the CB-68T can be housed within a metal enclosure to prevent air currents from disrupting isothermal conditions.

This terminal block provides connections for all digital input/output lines on the NI-435X series products, as well as all analog input channels except CH0 and CH1; CH0 is reserved for the cold-junction sensor, while CH1 is designated for auto-zero circuitry. The recommended connectivity solutions for digital signal conditioning applications include the NB7 or NB8 cable, whereas the SH6868 shielded cable is suggested for general use, with the R6868 ribbon cable also compatible.

The CB-68T features a cold-junction temperature sensor accuracy of 0.06 °C between 15 to 35 °C and 0.2 °C across ranges of 0 to 15 °C and 35 to 55 °C. With an isothermal accuracy of 0.1 °C, it operates effectively on compatible DIN rails (DIN EN 50 022 and DIN EN 50 035) and has a maximum working voltage of ±42 V with respect to ground. Digital I/O capabilities include 8 mA source and sink for non-buffered outputs, with buffered output sources reaching up to 15 mA and sinks of 64 mA. Dimensions for the CB-68T are 6.6 × 6.5 × 1.25 inches, and it comes with a 2-3 year warranty. Detailed user and maintenance manuals are available for download. For pricing information, please contact a sales representative.