Why does the active_power register return zero or no response?

The Plexlog Open Gateway must be explicitly enabled in the device configuration. By default the port may be closed. Open port 502 (or 503 for the alternate gateway) under the communication or direct-marketing section of the Plexlog portal, then retry the connection from the ModbusCloud Gateway.

Function code 3 returns an illegal-function exception. What is wrong?

The Plexlog Open Gateway exposes data exclusively via function code 4 (input registers), not function code 3 (holding registers). Ensure the template configuration uses FC4. Using FC3 against this device produces exception code 1 and no data will be returned.

The cumulative energy totals look far too large or too small. Why?

The raw values in total_consumption and total_production must be multiplied by 10 raised to the power of the corresponding exponent register. Read both the integer value and the exponent, then apply: actual_value = raw_value x 10^exponent. Ignoring the exponent registers will produce incorrect energy figures.

The gateway connects but reads time out intermittently. What should I check?

Intermittent timeouts on the Plexlog Open Gateway are often caused by network congestion or the device being polled by multiple clients simultaneously. Set a polling interval of at least 5 seconds in the ModbusCloud portal, ensure only one Modbus TCP client polls the device at a time, and verify no firewall rule on the Plexlog is dropping connections after idle periods.

Free Modbus template: Plexlog Datalogger

The Plexlog Datalogger is a PV and energy management device that aggregates real-time and cumulative data from inverters, meters, and sensors across a site. This Modbus TCP template reads active power, total energy consumed, and total energy produced alongside their respective scaling exponents. The exponent registers are required to convert the raw integer totals into correct engineering units. Connecting the Plexlog Datalogger to ModbusCloud via the ModbusCloud Gateway gives installers a single view of site-level generation and consumption without additional hardware.

Name	Address	Function	Type	Unit	Access
active_power Instantaneous net active power, positive values indicate production.	0	FC04	int32	W	R
total_consumption Cumulative energy consumed, scaled by consumption_exponent.	8	FC04	int32	Wh	R
consumption_exponent Power-of-10 scaling exponent for the total_consumption value.	10	FC04	int16		R
total_production Cumulative energy produced, scaled by production_exponent.	11	FC04	int32	Wh	R
production_exponent Power-of-10 scaling exponent for the total_production value.	13	FC04	int16		R

Plexlog Datalogger

Overview

Use cases

Installation

Things to watch for

Registers (5)

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