NI TBX-68T Terminal Block for Thermocouples

The NI TBX-68T is an isothermal, 68-pin terminal block designed to interface thermocouple, voltage, thermistor, and RTD signals with National Instruments NI-435x data acquisition systems. This DIN-rail mountable accessory features screw terminals, an integrated cold-junction temperature sensor on Channel 0, and auto-zeroing circuitry on Channel 1. Its isothermal construction minimizes temperature gradients across terminals, delivering the precision required for accurate multi-sensor measurements in laboratory and industrial environments.

– Technical Specifications

• Model: NI TBX-68T
• Pin Configuration: 68-pin with shielded screw terminals
• Form Factor: DIN-rail mountable
• Dimensions: 6.41 × 4.95 × 3.32 inches
• Input Signal Types: Thermocouples, voltage, thermistors, RTDs
• Maximum Input Voltage: ±42 V with respect to ground per channel
• Cold-Junction Sensor (Channel 0): Integrated thermistor with 5,000 Ω nominal resistance at 25 °C; 1,492 to 16,305 Ω over 0–55 °C; 37–408 mV output range over 0–55 °C
• Cold-Junction Accuracy: 0.06 °C (15–35 °C); 0.2 °C (0–15 °C and 35–55 °C)
• Digital Signal Conditioning: 64 mA sink, 15 mA source capability per channel
• Connector Interface: 26-pin latched connectors for signal conditioning accessories

– Key Features

• Isothermal design minimizes measurement errors from temperature gradients
• Excitation source compatibility supports RTD and thermistor measurements via connected NI 435X devices
• Auto-zeroing on Channel 1 eliminates offset drift
• Integrated cold-junction compensation for thermocouple measurements
• Shielded board and transparent protective cover reduce noise and thermal interference
• Enhanced digital signal conditioning with onboard electronics

– Typical Applications

Multi-channel temperature and voltage measurement systems requiring isothermal signal conditioning and DIN-rail installation in laboratory, manufacturing, and process control environments.

– Compatibility & Integration

• Primary Devices: NI USB-4350, NI PCMCIA-4350, NI PXI-4351, NI PCI-4351
• Signal Conditioning Accessories: SC-2060 Series, ER-8, SSR-8
• Compatible Terminal Blocks: NI SCB-68, NI TBX-68, NI TBX-68S
• Recommended Cable: SH6868 shielded or R6868 ribbon cable; PSH32-30F for PCMCIA-4350