NFAF135-S50 Yokogawa Frequency Input Module

Yokogawa NFAF135-S50 Frequency Input Module

The Yokogawa NFAF135-S50, also cataloged as the NFAF135 frequency input module, serves as the primary frequency‑measurement hardware used to execute pulse and frequency acquisition across Yokogawa control platforms. It provides conditioned electrical input handling for turbine, speed, and pulse‑train monitoring circuits.

Hardware Specifications

Channel-to-Channel Isolation and Mixed‑Signal Stability

Yokogawa frequency modules maintain channel‑to‑channel isolation to prevent pulse‑train interference when installed near 4‑20 mA HART loops or Fieldbus PA segments. Internal PCB routing and isolation geometry reduce impedance coupling, ensuring deterministic frequency counting even when analog and digital signals coexist within the same node unit. Cold junction compensation is not applicable to frequency modules, but isolation behavior ensures stable operation in mixed‑signal cabinets.

Frequently Asked Questions

Q: Can the NFAF135-S50 be removed while the node unit is energized? A: Removal under power is not recommended. De‑energize the node or segment to avoid transient faults on connected pulse channels.

Q: Does the module impose additional backplane current load? A: It draws standard power for signal conditioning. No abnormal backplane loading occurs beyond typical Yokogawa frequency modules.

Q: How does the module behave in redundant frequency‑monitoring configurations? A: Redundancy is managed by the controller. The module provides continuous raw frequency input without internal buffering or switchover logic.

Field Installation Guidelines

• Use shielded twisted‑pair or coaxial wiring depending on the pulse‑source characteristics.
• Bond cable shields at the cabinet end only to prevent ground‑loop formation.
• Maintain separation from high‑voltage conductors to reduce induced noise on pulse lines.
• Verify terminal torque to ensure stable contact for high‑frequency pulse signals.
• Avoid sharp bends or mechanical strain on wiring to prevent signal distortion.
• Confirm correct polarity and wiring orientation before energizing the frequency source.