Overview
Configured for field signal termination and ModuleBus distribution in the ABB S800 I/O system, the ABB TBU838 (TU838 Extended Module Termination Unit) provides direct physical and electrical connections between installed I/O modules, field wiring, process power, and the downstream ModuleBus. The unit supports up to 16 I/O channels and uses mechanical coding to restrict incorrect module insertion.
Hardware Specifications
| Parameter | Specification |
|---|---|
| Model | TBU838 / TU838 |
| Brand | ABB |
| Product Type | Extended Module Termination Unit |
| System | ABB S800 I/O |
| I/O Channels | Up to 16 channels |
| Maximum Rated Voltage | 50 V |
| Maximum Rated Current per Channel | 3 A |
| Maximum Process Connection Current | 10 A |
| Process Connections | 40 total connections |
| Sensor Power Connections | 8 fused sensor power outlets |
| Process Power Connections | 4 process power connections |
| Process Power 0 V Connections | 12 process power 0 V connections |
| Solid Wire Size | 0.2 – 4 mm2 |
| Stranded Wire Size | 0.2 – 2.5 mm2 |
| AWG Range | 24 – 12 AWG |
| ModuleBus Function | Distributes ModuleBus communication to the installed module and downstream MTUs |
| Mounting | Standard DIN rail mounting with mechanical locking latch |
| Mechanical Keying | 2 keys, 6 positions per key, 36 possible configurations |
| Protection Class | IP20 according to IEC 60529 |
| Operating Temp | 0 deg C to +55 deg C |
| Storage Temp | -40 deg C to +70 deg C |
| Relative Humidity | 5% to 95%, non-condensing |
| Dimensions | Approx. 126 mm W x 110 mm H x 64 mm D |
| Weight | Approx. 0.26 kg |
| Compliance Information | CE, EN 61010-1, UL 61010-1, ATEX Zone 2, and selected marine approvals as specified for the applicable configuration |
ABB S800 I/O Bus and I/O Density Integration
The TBU838 provides the physical infrastructure required for modular I/O density scaling within an ABB S800 I/O station. It routes ModuleBus communication through the installed module position and continues the bus path to downstream termination units.
In addition, the unit distributes field and sensor power through dedicated process connections. This arrangement separates module mounting and field wiring functions, allowing maintenance personnel to handle the I/O module independently from the installed field conductors where the applicable system procedure permits.
The mechanical coding system also supports controlled module replacement. Two coding keys provide six positions each, creating 36 possible configurations and reducing the possibility of inserting an incompatible I/O module into the termination position.
Frequently Asked Questions (FAQ)
Q: Does the ABB TBU838 perform signal processing or I/O conversion?
A: No. The TBU838 functions as an Extended Module Termination Unit. The installed S800 I/O module performs the applicable input, output, and signal processing functions.
Q: How does the TBU838 support ModuleBus communication?
A: The unit provides the physical ModuleBus connection to the installed I/O module and passes the ModuleBus connection onward to the next MTU in the configured station.
Q: Can an incorrect I/O module be inserted into the TBU838?
A: The MTU uses two mechanical coding keys with six positions each. Correct keying must match the intended I/O module and system configuration.
Field Installation Guidelines
- Mount the TBU838 on a correctly installed standard DIN rail and verify that the mechanical locking latch engages fully.
- Disconnect or isolate applicable field and process power sources before installing or removing field wiring.
- Use conductor sizes within the specified terminal acceptance range.
- Keep field wiring organized to prevent mechanical stress on the terminal connections.
- Apply the required grounding and shielding practices according to the ABB S800 I/O installation documentation and the connected field device requirements.
- Verify the mechanical key positions before installing the corresponding I/O module.
- Check process power polarity and 0 V connections before energizing the I/O station.
- Maintain enclosure conditions within the specified IP20 installation environment.
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Contact: Manski Wong +86 18030205725 manski@cambia.cn
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