The Allen-Bradley 1794-TB3TS, also cataloged as the 1794-TB3TS FLEX I/O Terminal Base Unit, operates as a dedicated hardware component for field signal termination and backplane bus routing within FLEX I/O control systems.
Hardware Specifications
Parameter
Specification
Model
1794-TB3TS
Brand
Allen-Bradley
Origin
USA
Weight
1.44 lbs (0.65 kg)
Dimensions
Standard FLEX I/O base footprint
Operating Temp
-20 to 70 deg C
Power Consumption
Passive backplane load
Voltage Rating
125 VAC/DC max
Current Rating
10 A max
Wire Size
22 to 12 AWG (0.35 to 2.5 mm sq)
Terminal Type
Spring Clamp
Sensor Support
Cold Junction Compensation (CJC)
I/O Capacity
16 I/O Terminals
Power Terminals
10 Common Terminals, 4 +Voltage Terminals
Protection Rating
IP20
Mounting Format
DIN-rail / Panel Mount
Cold Junction Compensation and Channel-to-Channel Isolation
The 1794-TB3TS terminal base integrates built-in Cold Junction Compensation (CJC) sensors designed for high-accuracy thermocouple and temperature I/O module processing. Internal trace layout ensures stable channel-to-channel isolation while routing 16 field signals directly into the FLEX I/O backplane bus. Designed to maintain signal fidelity in high-density analog node layouts, the base unit preserves high backplane bus communication velocity and eliminates thermal gradient errors across field terminal contacts.
Frequently Asked Questions
Q: Does removing the active temperature module installed on the 1794-TB3TS disrupt backplane communications to adjacent nodes?
A: No. The internal backplane communication logic and pass-through bus reside permanently within the 1794-TB3TS base assembly, enabling Removal and Insertion Under Power (RIUP) of the module without interrupting system operation.
Q: What are the advantages of the spring-clamp termination design on the 1794-TB3TS?
A: Spring-clamp connections provide continuous gas-tight holding force on 22 to 12 AWG wiring, eliminating terminal loosening caused by thermal expansion or high-vibration field environments.
Field Installation Guidelines
Latch the terminal base securely onto a standard 35 mm DIN rail, verifying that the mechanical locking mechanism engages completely.
Slide the unit firmly against adjacent FLEX I/O adapter or terminal base modules to fully seat the backplane expansion connectors.
Insert strip conductors into the spring-clamp terminals using a flat-head screwdriver to actuate the spring mechanism, accommodating 22 to 12 AWG field wiring.
Route temperature and analog signal cables away from high-voltage AC power lines to maintain thermocouple CJC measurement precision.
Verify that the DIN-rail grounding foot makes clean, unpainted metallic contact with an earth-grounded steel DIN rail.
