Omron Z3RN-5A N2 Series Optical Serial Link Module for RS-232C Communication

The Omron Z3RN-5A is an optical link module belonging to the N2 series of industrial communication devices. It converts electrical RS-232C signals to optical signals for transmission over fiber optic cable, enabling long-distance, noise-immune serial communication between PLCs, HMIs, and other industrial devices. The module is typically used in pairs: one transmitter and one receiver, connected via plastic optical fiber (POF).

Technical Specifications

Interface: RS-232C (D-sub 9-pin female) on the electrical side. Transmission medium: Plastic optical fiber (POF) with core diameter 1.0mm. Optical connector type: JIS F05 (standard). Wavelength: 660 nm (visible red light). Maximum transmission distance: 200 meters (656 feet) with standard POF. Data rate: from 300 baud to 115,200 baud (automatic detection, no configuration required). The Z3RN-5A is transparent to data format and protocol, supporting all RS-232C signals (TxD, RxD, RTS, CTS, DTR, DSR, GND).

Power and Electrical

Power supply: 24V DC ±10%, 50mA (max). The module is powered from the serial device’s auxiliary power or from an external 24V DC source. The electrical interface is fully isolated from the optical side with 1,500V AC isolation. The RS-232C side uses standard voltage levels: ±5V to ±15V for logic 0/1. The Z3RN-5A does not require handshake signals for basic operation; however, it can pass RTS/CTS for flow control if needed.

Optical Specifications

Optical output power: -12 dBm typical. Receiver sensitivity: -25 dBm. Optical wavelength: 660 nm (visible red). The module features an LED indicator on the front panel that lights when optical signal is being transmitted/received. The fiber connection uses a screw-type lock for secure attachment. Maximum tolerable cable loss: 13 dB. The module can also be used with glass fiber with appropriate adapters, but distance and power will vary.

Indicators and Diagnostics

Front panel LEDs: POWER (green), OPTICAL LINK (green – indicates carrier detect), DATA TX (green – flashes on transmit), DATA RX (green – flashes on receive). A built-in loopback test can be activated by a DIP switch to verify optical path integrity. The module also has a “Signal Quality” indicator (green/yellow/red) to show received light level for troubleshooting fiber attenuation.

Physical Dimensions and Mounting

Dimensions: 64mm (H) x 45mm (W) x 30mm (D). Weight: 90g. Enclosure: Molded plastic, DIN rail mountable (35mm rail) with snap-on clip. The module has side openings for ventilation. The RS-232C port uses a male D-sub 9-pin connector, and the optical connector is on the opposite side. All connections are readily accessible when mounted. Operating temperature: -10°C to 60°C. Humidity: 20-85% non-condensing.

Installation and Fiber Cabling

Use plastic optical fiber with polished ends. Insert the fiber into the connector until it stops, then tighten the sleeve. Maximum bending radius for POF is 25mm. The fiber is rated for industrial environments (oil-resistant, flexible). For distances over 50m, use high-grade POF (e.g., Mitsubishi ESKA). The Z3RN-5A does not require any configuration; simply connect, apply power, and the optical link is established automatically. For full duplex, two modules are required: one at each end.

Compatibility

The Z3RN-5A works with any RS-232C device: Omron PLCs (C, CVM1, CJ, CS series), HMIs (NT, NS), computers, barcode readers, and serial printers. It can also replace point-to-point copper links that suffer from electromagnetic interference (EMI) from motors, VFDs, or welding equipment. The module is compatible with other N2 series optical products such as Z3RN-10 (for longer distance) and Z3RN-2 (for 422/485).

Applications

Typical applications: Connecting a PLC to an HMI located 100 meters away in a noisy factory, linking two PLCs across an area with high voltage cables, or transmitting diagnostic data from a remote sensor. The optical link is also used in explosive environments (with appropriate fiber and mounting) since no electrical signals are present on the fiber itself. Other uses include elevator shaft communication, overhead crane controls, and outdoor installations where lightning protection is needed.

Environmental and Compliance

Operating temperature: -10°C to 60°C. Storage: -20°C to 85°C. Humidity: 20-90% non-condensing. Vibration: 2g at 10-55Hz. The module is CE marked, FCC Part 15 Class A, and RoHS compliant. It has no internal batteries or user-serviceable parts. Mean time between failures (MTBF) exceeds 200,000 hours. The optical output is eye-safe (Class 1 LED product).

Troubleshooting Tips

If optical link LED is off, check fiber connection, cable break, and power. If data LEDs are not flashing, verify baud rate and parity settings of connected devices; the module passes these transparently but both ends must match. For intermittent errors, check fiber bend radius and clean connectors with lens tissue. A red light visible at the fiber end confirms transmitter is working. Use the built-in loopback test to isolate the module or fiber as the fault source.

Conclusion

The Omron Z3RN-5A optical serial link provides robust, long-distance RS-232C communication immune to electrical noise. Its plug-and-play installation and transparent operation make it an excellent choice for extending serial networks in harsh industrial environments.