Description
Technical Parameters
- Part Number: 8121-DI-DC
- Manufacturer: MTL Instruments (Eaton)
- Series: PAC8000 (8000 Series I/O)
- Input Channels: 16 Channels
- Input Type: Dry contact switches
- Wetting Voltage: 24 VDC (Module-provided on high side)
- Current Levels: * ON Current: >1.2 mA
- OFF Current: <0.3 mA
- Wetting Current: 2.8 mA (typical)
- Isolation: 250 VAC (Any channel to Railbus)
- Response Time: ≤5 ms (Field event to Railbus)
Product Description
The MTL 8121-DI-DC is a high-density, 16-channel discrete input module designed for the PAC8000 (formerly 8000 Series) I/O system. It is specifically engineered to interface with “dry” (voltage-free) contacts, providing its own 24 VDC wetting voltage to the field switches.
The module is non-isolated between channels but features robust galvanic isolation between the field side and the system Railbus. It supports advanced software features such as pulse counting (up to 100 Hz) and input latching, making it suitable for capturing high-speed transitions or brief status changes that might otherwise be missed by a standard controller scan.
Application Areas
- Safe & Hazardous Areas: Certified for use in Class 1, Div 2 and Zone 2 hazardous locations when used with appropriate field terminals.
- Process Monitoring: Tracking the status of limit switches, pressure switches, and level sensors in oil, gas, and chemical plants.
- Pulse Counting: Interfacing with flow meters or utility meters that provide a dry contact pulse output.
- Safety Interlocking: Integrating mechanical interlocks and E-stop status signals into the DCS or PLC environment.
Product Specifications
- Weight: 210 g (0.46 lbs)
- Module Width: 42 mm
- Module Key Code: E1
- Power Requirements: * Railbus (12V): 90 mA (typ.) / 135 mA (max.)
- Bussed Field Power: 60 mA @ 18–30 VDC
- Country of Origin: United Kingdom (England)
Operating Precautions
- Field Wiring: For hazardous area installations, use the 8617-FT-NI field terminal block to maintain non-incendive field wiring parameters (Voc=30 V, Isc=3.5 mA).
- Pulse Mode Debounce: When using pulse counting, configure the selectable input filter (Fast, Slow, or User-defined) to match the mechanical bounce characteristics of the field switch to avoid double-counting.
- Bussed Power: Ensure that the 24 VDC Bussed Field Power is stable; a loss of field power will result in all inputs being reported as “OFF” even if the Railbus communication is healthy.
- Module Seating: Ensure the module is fully latched onto the carrier. The integrated keying (Code E1) prevents the insertion of incorrect module types into the configured slot.
Recommended Similar Products
| Model Number | Product Description | Channels / Type |
|---|---|---|
| 8111-DI-AC | 115 VAC Isolated Input | 8-ch Isolated |
| 8122-DI-DC | 24 VDC Discrete Input | 16-ch (Sink/Source) |
| 8125-DO-DC | Discrete Output Module | 16-ch Output |
| 8215-AM-AS | Analog Input Module | 8-ch 4–20mA |
| 8617-FT-NI | Field Terminal Block | Non-Incendive |
