Carlo Gavazzi VMU-S String Measurement Unit
| Device Type | Modbus TCP (Ethernet) | RS485 |
|---|---|---|
| Carlo Gavazzi VMU-S | ❌ | ✅ |
System Architecture The VMU-S is a modular system. It requires a VMU-M (Master) unit to handle the RS485 communication. The VMU-S modules plug directly into the side of this master unit.
| VMU-S (String Unit) | VMU-M (Master Unit) |
|---|---|
 |  |
The VMU-S connects to the VMU-M master unit via the local bus connector on the side.
Do not Hot-Swap! Risk of equipment damage: Only join or separate the VMU-S modules from the Master unit when the power supply is OFF. Connecting modules while the system is powered can damage the internal electronics.
Although you are measuring with the VMU-S, the RS485 cable connects to the VMU-M Master unit. The VMU-S sends its data internally to this master unit.
| Device | SmartgridOne Controller model OM1 | SmartgridOne Controller model IG8 | RS485-USB converter | RS485-Ethernet converter |
|---|---|---|---|---|
| Terminal 11 / B- | RS485 A | RS485_POS | RS485 A | TX+ |
| Terminal 12 / A+ | RS485 B | RS485_NEG | RS485 B | TX- |
| Terminal 10 / GND | RS GND | GND | Not available | G |
The VMU-S modules are wired in series with the PV strings:
Polarity Ensure the correct polarity (Top to Bottom). If the polarity is reversed, the Status LED on the VMU-S will blink Violet (Blue -> Violet cycle).
Since the VMU-S has no display, you configure the Modbus settings on the Master unit (VMU-M).
After installing the VMU-S modules, the Master unit must recognize them:
When adding this device to the Controller, you will be asked for the Amount of Strings.
