The power register returns zero even when the PV inverter is running. What is wrong?

Check the CT orientation on the AC cable. The ET112 reports a signed value, so a reversed current transformer will return a negative or near-zero reading. Flip the CT clip 180 degrees and verify that the power value becomes positive and matches the inverter's own display.

No response from the meter at all. The Gateway shows a timeout error.

Confirm the Modbus unit ID in the portal matches the address programmed in the ET112 via the UCS Configurator. The factory default is address 1, but meters on a shared bus must have unique addresses. Also verify RS485 polarity (A+ and B-) and that bus termination is applied at the last device by bridging terminals A- and T.

The energy register value seems to reset or jump unexpectedly over time.

The energy register is a signed int32. At high accumulated totals the raw integer value can wrap. Confirm your polling application handles the int32 range correctly and applies any necessary scaling based on the meter variant. Do not compare raw register values between different EM/ET100 firmware revisions without checking the protocol document for that revision.

Multiple ET112 meters on one RS485 bus conflict with each other. How do I resolve this?

Each ET112 ships with Modbus address 1 by default. When daisy-chaining meters on a single RS485 cable, use the Carlo Gavazzi UCS Desktop Configurator to assign a distinct address to each unit before connecting them to the shared bus. Connect one meter at a time during re-addressing to avoid ID conflicts.

Free Modbus template: Carlo Gavazzi ET112 (pv)

The Carlo Gavazzi ET112 is a single-phase, DIN-rail energy transducer used to monitor AC power and energy in PV installations, ESS systems, and sub-metering applications. This template connects via Modbus RTU over RS485 and reads two core registers: instantaneous active power and cumulative active energy. Deployed in the PV role, the ET112 measures the AC output of a grid-tied solar inverter, giving the ModbusCloud portal live generation data without requiring inverter integration. The register set is minimal but sufficient for yield tracking and threshold alerting.

Name	Address	Function	Type	Unit	Access
power Instantaneous active power, signed int32, positive = import.	4	FC04	int32	W	R
energy Cumulative active energy counter, signed int32.	32	FC04	int32	Wh	R

Carlo Gavazzi ET112 (pv)

Overview

Use cases

Installation

Things to watch for

Registers (2)

Working with Modbus in your projects?

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