The DOLD UG 9431.12PM DC Voltage Relay with Modbus RTU Interface (German: DC-Spannungsrelais für Modbus / English: DC Voltage Monitoring Relay for Modbus) is a state-of-the-art measurement, protection, and digitization instrument belonging to the prestigious VARIMETER series, engineered and manufactured by E. DOLD & SÖHNE GmbH & Co. KG in Germany. In the era of industrial digital transformation and rapid green energy expansion (solar photovoltaic utility plants, commercial BESS storage containers, high-power DC fast-charging networks), supervising direct current systems requires more than isolated electromechanical trip contacts. It demands continuous digital telemetry streaming of real-time voltage measurements and predictive fault parameters to central SCADA platforms, master PLCs, and cloud Energy Management Systems (EMS).

The DOLD UG 9431.12PM fulfills these exact requirements within a single compact 22.5 mm DIN-rail enclosure: functioning simultaneously as an autonomous, hardware-reliable voltage safety relay and as a digital transducer featuring an integrated RS-485 Modbus RTU industrial serial communication port. Through the Modbus interface, automation engineers can poll live voltage levels, trip registers, and operating temperature diagnostics in real time, while remotely calibrating tripping thresholds and reaction delays via engineering software without physical panel intervention. Measuring up to DC 1000V directly without external voltage dividers or auxiliary transducers, it simplifies switchboard wiring, lowers installation footprint, and eliminates excess parasitic thermal dissipation inside enclosures.

The instrument is equipped with the ".12" contact architecture featuring two independent changeover contacts (2 C/O - 2 x 1 Wechsler) with high industrial breaking capacity, ensuring dependable hardware-level interlock disconnection alongside serial communication reporting. The "PM" designation indicates a high-tier parameterizable variant complete with pluggable connection terminals, accelerating enclosure assembly while enabling hot-swapping during plant maintenance without disconnecting individual field wires. It supports flexible surveillance modes including Overvoltage, Undervoltage, and Window Monitoring (Fensterüberwachung) with adjustable response delays.

Engineered to operate on a standard industrial DC 24V auxiliary supply, the DOLD UG 9431.12PM interfaces seamlessly with modern PLC systems. Multi-color front diagnostic LEDs provide instantaneous visual status indication for auxiliary power, active Modbus Tx/Rx telegrams, and trip events. Encased in self-extinguishing industrial thermoplastic tailored for 35mm DIN-rail snapping, and compliant with international standards IEC/EN 60255-1 and IEC/EN 60947-1, the DOLD UG 9431.12PM is an indispensable smart monitoring asset for solar PV combiner boxes, BESS container facilities, DC fast EV chargers, and Industry 4.0 automated architectures worldwide.

• Manufacturer: DOLD (E. DOLD & SÖHNE GmbH & Co. KG)
• Country of Origin: Germany
• Product Series: VARIMETER UG 9431
• Full Model Part Code: UG9431.12PM DC20-1000V UH=DC24V
• Technical Classification: DC Voltage Monitoring Relay with Modbus RTU (DC-Spannungsrelais für Modbus)
• Rated Measuring Voltage Range: DC 20 ... 1000 V (Direct high-voltage DC measurement)
• Digital Communication Protocol: Modbus RTU via RS-485 2-wire serial bus (shielded twisted pair)
• Baud Rate Support: 9600, 19200, 38400, 57600, 115200 bps
• Modbus Device Addressing: Configurable via software or coding switches (1 ... 247)
• Auxiliary Supply Voltage (UH): DC 24 V
• Auxiliary Voltage Tolerance: 0.85 ... 1.15 UH
• Monitoring Functions:
  - Overvoltage supervision
  - Undervoltage supervision
  - Voltage Window Monitoring (Umin < U < Umax)
  - Real-time voltage telemetry streaming via Modbus RTU
• Output Contact Arrangement: 2 Independent changeover contacts (2 C/O - 2 x 1 Wechsler)
• Contact Switching Capacity: AC-15: 3A / AC 230V; DC-13: 1A / DC 24V (compliant with IEC/EN 60947-5-1)
• Continuous Thermal Current (Ith): Max. 5A
• Tripping Delay Adjustment: Fully programmable and adjustable via software parameters
• Visual Diagnostic Array: Front LEDs for power supply (PWR), serial bus transmission/reception (Tx/Rx), and relay alarm states
• Module Dimensions (W x H x D): 22.5 x 100 x 121 mm (Compact UG enclosure)
• Mounting Profile: Quick snap-on mounting on standard 35 mm DIN-rail (IEC/EN 60715)
• Terminal Architecture: Pluggable screw or cage clamp terminals for rapid hot-swapping
• Protection Rating: Housing IP40, Terminals IP20 (according to IEC/EN 60529)
• Ambient Operating Temperature: -20°C to +60°C
• Compliant Standards: IEC/EN 60255-1, IEC/EN 60947-5-1, IEC/EN 61000-6-2, IEC/EN 61000-6-4, CE
• Typical Applications: Solar PV string combiner boxes, BESS energy storage containers, EV DC fast chargers, inverter DC-bus links, DC microgrids, and digitized industrial automation