Testing Janitza UMG 103-CBM Meter
The customer assumed the necessity of purchasing a WE 1800 USB/RS485 converter and GridVis software for setting the transformer ratio. For one-time testing, this would mean an unnecessary investment in accessories they would not use further.
Key question: Is there an alternative such as custom setup or short-term rental?
Technical Analysis
KBH conducted a detailed analysis of the device capabilities. The UMG 103-CBM communicates via standardized Modbus RTU protocol as a slave device through RS485 interface. Key parameters:
- Modbus ID is set mechanically with switches on the panel (cannot be overwritten via software)
- Default communication: speed auto-detection, no parity, one stop bit
- Registers can be read and written from any PLC or PC using Modbus Client (for example Modpoll or qModmaster)
Data Formats and Flexibility
The device offers data in two formats:
Float values: Include the conversion ratio of current and voltage measuring transformers - ready for direct use
Integer values: Raw data without conversion, calculated from actually measured values at inputs
All Modbus values are available in Little Endian byte ordering, which increases compatibility with various systems.
Key Finding: USB Converter Is Not the Only Way
The WE 1800 USB converter and GridVis software are not mandatory components. Their primary purpose is for service technicians in the field - quick reading and setup at the installation site. For development tests in the laboratory, more efficient solutions exist via Modbus protocol using standard tools like Modpoll or qModmaster.
Offered Solution
KBH presented a comprehensive view of UMG 103-CBM capabilities and offered two practical alternatives:
Option 1 - Pre-configuration Before Shipment If the customer knows the required settings, KBH will configure the UMG 103-CBM free of charge before sending. Just add the requirements to the order.
Option 2 - Additional Setup When the need for setup arises later:
- Send the device to KBH
- Next day shipment back via Toptrans
- Total costs up to 1000 CZK (unpacking, setup, packing, shipping)
Result
The customer received:
- Ability to test the device without investment in accessories
- Flexible solution through standard Modbus protocol
- Cost savings - instead of several thousand for converter and software only up to 1000 CZK for service
- Fast processing with next-day turnaround
Lessons from the Case
The case shows three key principles:
- Standardized protocols increase flexibility - thanks to Modbus RTU, the device can be controlled in various ways without proprietary tools
- Service approach saves costs - for one-time or test use, it is often more efficient to use a service than to buy equipment
- Technical knowledge brings alternatives - understanding that the UMG 103-CBM works as a Modbus slave and allows different data formats opens the way to various integration solutions
In solar applications, the UMG 103-CBM is typically used as a Modbus value generator and electrical quantity converter - protocol flexibility enables deployment without the need for connection to a SCADA system.
Technical parameters UMG 103-CBM: Measurement up to 40th harmonic, accuracy class 0.5S (for ../5 A currents), redundant data memory, DIN rail mounting 71.5 mm.