E91-DTU series is an industrial-grade LoRa RS485 wireless data transmitter featuring up to 37dBm output, IP67 waterproof protection, and Modbus protocol support for high-reliability, long-range communication in harsh environments.
| Parameter | Specifications |
|---|---|
| Product Models | E91-DTU(400SL30) / E91-DTU(900SL30) / E91-DTU(400SL37) |
| Frequency Range | 410.125-493.125 MHz / 850.125-930.125 MHz |
| Transmit Power | 30dBm (1W) / 37dBm (5W) Adjustable |
| Communication Interface | RS485 (5-pin M12 Waterproof Connector) |
| Ingress Protection | IP67 (Sealed with Silicone O-ring and Resin Potting) |
| Operating Voltage | 8V - 28V DC (Standard 12V/24V Industrial Power) |
| Logic Support | Modbus RTU, LBT, RSSI, AT/HEX Commands |
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Application
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Offshore Oil & Gas Extraction: Utilizing the 37dBm (5W) high-power output, the E91-DTU overcomes signal attenuation caused by dense steel structures and multi-path interference on drilling platforms, ensuring stable telemetry data transmission over several kilometers without additional repeaters.
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Precision Agriculture & Smart Irrigation: With an IP67-rated flame-retardant housing and M12 waterproof connectors, the device is deployed in open fields to manage solenoid valves. The 30dBm LoRa modulation ensures reliable control signals penetrate through dense foliage and uneven terrain across large-scale plantations.
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Distributed Photovoltaic (PV) Monitoring: Integrated into solar farm inverters via the RS485 interface, the E91-DTU uses Modbus RTU transparency to transmit real-time voltage and current data to a central gateway. The built-in LBT (Listen Before Talk) functionality prevents data collisions in high-density sensor environments.
FAQ
Q: How does the power supply ripple affect the RF performance of the E91-DTU(400SL37)?
A: For a 5W (37dBm) high-power transmitter, the instantaneous current can peak significantly during transmission. We recommend a power supply capable of delivering at least 2A with a ripple voltage below 100mV. Excessive ripple can lead to phase noise in the frequency synthesizer and potentially cause the LoRa spread spectrum signal to deviate from the center frequency, reducing the effective receiver sensitivity at the remote end.
Q: What is the significance of the 50-ohm impedance matching for the external antenna?
A: The RF output stage of the E91-DTU is optimized for a 50-ohm characteristic impedance. If the connected antenna or coaxial cable has a high Voltage Standing Wave Ratio (VSWR > 1.5), a portion of the 30-37dBm power will be reflected back to the module as heat. This not only reduces the radiated power and communication range but also increases the thermal stress on the power amplifier (PA) transistor, potentially shortening the hardware lifespan.
Q: How does the Listen Before Talk (LBT) feature improve channel efficiency in industrial Modbus networks?
A: LBT is a carrier sense mechanism where the E91-DTU monitors the RSSI level of the current channel before initiating a transmission. If the detected noise floor exceeds a predefined threshold (typically -80dBm), the module backsoff to avoid a packet collision. This is critical in Modbus networks where multiple nodes share the same frequency, as it significantly reduces the packet error rate (PER) caused by overlapping RF emissions.
Q: What are the logic level requirements for the RS485 interface on the E91-DTU?
A: The device utilizes a standard RS485 differential signaling transceiver. It interprets a differential voltage (VA - VB) greater than +200mV as a logic high and less than -200mV as a logic low. The interface includes built-in ESD protection and high-level isolation, allowing it to interface directly with industrial PLC ports or SCADA systems without the need for external pull-up or pull-down resistors in most standard bus lengths.
