Product Insight
The Yokogawa ALR121-S51 is a half-duplex serial communication module with start-stop synchronization. It supports RS-422/RS-485 interfaces for point-to-point or multipoint connections. This module transmits up to 1200 meters with speeds from 1200 to 38400 bps. It is designed for standard environments with ISA G3 option and no explosion protection.
Oiltech Controls’s Insight
- Reliable communication for distributed control systems.
- Perfect for upgrading legacy serial networks.
- Tested for industrial noise immunity and signal integrity.
Technical Specifications
- Manufacturer: Yokogawa
- Model: ALR121-S51
- Type: Serial Communication Module
- Interface: RS-422 / RS-485 (4-wire)
- Connection: Point-to-point (RS-422) or Multipoint (RS-485)
- Transmission Speed: 1200, 2400, 4800, 9600, 19200, 38400 bps
- Synchronization: Start-stop
- Communication: Half-duplex
- Transmission Code: ASCII / Binary
- Character Length: 7 / 8 bits
- Stop Bit: 1 / 2 bits
- Parity: None / Even / Odd
- Lag Time: 1 ms (wait before receive)
- Distance: Max 1200 m (total extended)
- Wiring: 3-pair shielded cable, AKB161/AKB162
- Terminal: M4 screw clamp (5 poles x 2)
- Current: 0.5 A
- Weight: 0.34 kg
- Mounting: Fits ANB10, ANB11, ANR10, AFF50, AFV10, AFV30, AFV40
Suitable Equipment
- Yokogawa CENTUM VP, ProSafe-RS, and STARDOM controllers.
- Legacy DCS and PLC systems requiring serial connectivity.
- Retrofit projects for Modicon Quantum and other hybrid networks.
Environmental & Certifications
- Standard type with no explosion protection.
- Includes ISA Standard G3 option for harsh environments.
- Temperature range: -10 to 60 °C (ambient).
- Humidity: 5 to 95 % RH (non-condensing).
Installation & Wiring
- Clamp wiring with M4 screws – secure and simple.
- Use 3-pair shielded cable for noise reduction.
- Ensure total extended length ≤1200 m.
Shipping & Logistics
- Warranty: 12 months from shipment.
- Dispatch: 24–28 hours after order.
- Carriers: FedEx, UPS, DHL – worldwide.
Professional FAQ
- Q: What is the maximum baud rate for reliable long-distance communication?
A: For 1200 m, we recommend 9600 bps or lower to avoid signal degradation. We have tested this module in field installations at 38400 bps only for short runs under 200 m. - Q: Can I use this module with Modbus RTU devices?
A: Yes, the ALR121-S51 supports ASCII/Binary and 7/8 bit data, making it compatible with Modbus RTU. Ensure parity and stop bits match your slave devices. - Q: Which mounting base is most common for this module?
A: The ANB10 is widely used. However, check your rack type; we often see it in ANR10 for redundant configurations. Contact us if unsure. - Q: Is the ISA G3 option necessary for non-harsh environments?
A: Not mandatory, but we recommend it for plants with intermittent chemical exposure or high humidity – it adds a safety margin. - Q: How do I select between RS-422 and RS-485?
A: Use RS-422 for a single device (point-to-point) and RS-485 for multiple devices (multipoint). The module supports both, but wiring differs.
Why Buy From Oiltech Controls?
- Decades of expertise in industrial automation spares.
- Global delivery network – we ship to your site anywhere.
- Quality-checked surplus and refurbished stock.
- Full 12-month coverage on every unit.
- Pre-shipment technical verification ensures functionality.
- Specialist support for obsolete systems like Modicon Quantum.
Contact Information:
Email: info@oiltechcontrols.com
WhatsApp: +86 158 8020 0923
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