Yokogawa 915U-2-900US Radio Telemetry Module – 915U Series

Yokogawa 915U-2-900US: 900 MHz Wireless Telemetry Module for Industrial Process Automation

The Yokogawa 915U-2-900US is a 900 MHz ISM-band wireless radio telemetry module engineered for deterministic, long-range data acquisition in distributed industrial control architectures. Operating within the 902–928 MHz unlicensed spectrum, this module delivers superior obstacle penetration and extended propagation range compared to 2.4 GHz alternatives — a critical advantage in process plants where structural steel, concrete walls, and dense equipment clusters attenuate higher-frequency signals. The 915U-2-900US functions as a transparent wireless bridge between field instruments and host control systems, enabling engineers to extend SCADA reach, eliminate cable trenching costs, and maintain real-time process visibility across geographically dispersed measurement points.

Within a 915U mesh network, each 915U-2-900US node participates in a self-healing, frequency-hopping spread spectrum (FHSS) topology. FHSS distributes transmission energy across 50+ discrete channels within the 900 MHz band, statistically reducing the probability of sustained co-channel interference to near-zero under typical industrial RF environments. The module’s embedded microcontroller manages channel arbitration, collision avoidance, and acknowledgment retransmission autonomously — offloading protocol overhead from the host PLC or DCS CPU and preserving deterministic scan cycle integrity.

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Technical Parameters

Hardware Logical Analysis

The 915U-2-900US is built around a dual-processor architecture: a dedicated RF baseband processor handles all physical-layer tasks — channel hopping sequence generation, preamble detection, CRC-16 frame validation, and automatic repeat request (ARQ) retransmission — while a separate application processor manages the serial protocol stack, configuration memory, and diagnostic state machine. This separation ensures that RF link degradation events (e.g., a temporary multipath fade) do not introduce jitter into the serial data stream presented to the host controller.

EMC Design: The RF front-end employs a low-noise amplifier (LNA) with a noise figure below 3 dB, paired with a bandpass filter tuned to the 902–928 MHz window. This filter rejects out-of-band interference from adjacent GSM-850 and cellular LTE Band 5 transmitters — a common co-existence challenge in industrial sites with on-site cellular infrastructure. The PCB layout follows a split-ground plane strategy: the RF section ground plane is isolated from the digital logic ground plane and joined at a single star point near the DC input filter, minimizing conducted noise coupling from switching power supplies into the receiver chain.

FHSS Synchronization: The hopping sequence is derived from a pseudo-random number generator (PRNG) seeded with a user-configurable network ID. All nodes sharing the same network ID maintain synchronization via a beacon frame transmitted by the designated master node at each hop interval (typically 20 ms). If a slave node misses three consecutive beacons, it initiates an autonomous re-synchronization scan — scanning all 50 channels in sequence until it re-acquires the master beacon. This mechanism ensures network self-healing without host controller intervention, maintaining data continuity during transient RF obstructions.

Serial Transparency: The module operates in a transparent serial bridge mode by default. Any byte sequence received on the RS-232/RS-485 port is encapsulated in a 915U RF frame, transmitted, and reconstructed byte-for-byte at the remote node’s serial port. This transparency is protocol-agnostic: Modbus RTU, DNP3, PROFIBUS DP (via RS-485 adapter), and proprietary Yokogawa serial protocols all pass through without modification, eliminating the need for protocol conversion middleware.

System Integration Benefits

• Deterministic Latency Budget: End-to-end serial frame latency across a single 915U-2-900US link is ≤ 50 ms at 9,600 bps for a 256-byte payload — predictable enough to satisfy most SCADA polling cycles without impacting PLC scan time budgets.
• Mesh Network Scalability: Up to 48 remote nodes per master gateway in a standard 915U network, expandable via repeater nodes. Each additional hop adds ≤ 50 ms latency, allowing multi-hop architectures across large plant footprints without exceeding typical SCADA timeout thresholds.
• Diagnostic Transparency: Each node continuously logs RSSI (Received Signal Strength Indicator), packet error rate (PER), and retry count per link. These diagnostics are accessible via the 915U configuration software, enabling RF link health trending without interrupting live process data flow.
• Seamless DCS Integration: The 915U-2-900US integrates directly with Yokogawa CENTUM VP via the Vnet/IP gateway, with Yokogawa STARDOM FCN/FCJ via Modbus TCP/RTU, and with ProSafe-RS safety systems via hardwired I/O at the gateway node — preserving SIL-rated signal paths.
• Reduced Infrastructure CAPEX: Eliminating a single 500-meter cable run in a hazardous area (including conduit, cable tray, junction boxes, and installation labor) typically saves USD 15,000–40,000. A 915U-2-900US link covering the same distance costs a fraction of that, with zero ongoing maintenance for buried cable.
• Wide Supply Voltage Tolerance: The 10–30 V DC input range accommodates both 12 V battery-backed field panels and standard 24 V DC instrument bus supplies without additional DC-DC conversion hardware.
• Firmware Field Upgradability: Firmware updates are delivered over the serial configuration port using the 915U PC configuration utility. No module extraction or factory return is required, minimizing maintenance downtime in live plant environments.
• Hazardous Area Compatibility: When installed within a certified Ex e or Ex d enclosure, the 915U-2-900US supports deployment in Zone 2 / Division 2 classified areas, extending wireless telemetry capability into areas where cable installation is cost-prohibitive or structurally impractical.

Quality Assurance & Global Logistics

Every Yokogawa 915U-2-900US unit supplied by siemensplc.com is sourced through verified Yokogawa distribution channels. Each module carries original Yokogawa factory labeling, serial number, and manufacturing date code. Prior to dispatch from our Xiamen, China facility, each unit undergoes a three-stage inspection: visual examination of housing, connector, and label integrity; power-on functional verification of RF link establishment; and serial number cross-reference against Yokogawa’s product traceability database.

Shipping from Xiamen is supported via DHL Express (3–5 business days to most destinations), FedEx International Priority, UPS Worldwide Expedited, and air freight consolidation for volume orders. Export documentation — including commercial invoice, packing list, certificate of origin, and MSDS where applicable — is prepared in compliance with destination country customs requirements. In-stock orders are dispatched within 1–2 business days of payment confirmation. A 12-month warranty covers manufacturing defects; DOA units are replaced or credited within 5 business days of confirmed fault report.

Contact Information

📧 Email: [email protected]
📱 WhatsApp: +86 18359268345
🌐 Web: siemensplc.com
📍 Location: Xiamen, China
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