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.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 5, read only
- Brand
- Plexlog
- Last updated
Registers (5)
5 read, 0 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| active_power | W | Read | |||
| total_consumption | Wh | Read | |||
| consumption_exponent | Read | ||||
| total_production | Wh | Read | |||
| production_exponent | Read |
Loading registers…
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Use cases
- Monitor instantaneous active power to verify that the PV installation is producing during daylight hours.
- Track total production over weeks to compare actual yield against expected generation targets.
- Track total consumption trends to identify periods of unusually high site load.
- Alert on active power dropping to zero during expected production hours to catch inverter faults early.
- Compare cumulative production and consumption values across multiple sites in the ModbusCloud portal.
Installation
Enable the Modbus TCP Open Gateway on the Plexlog Datalogger by navigating to the communication or direct-marketing section of the device portal and opening port 502 or 503 for Modbus TCP access.
Connect the Plexlog Datalogger and the ModbusCloud Gateway to the same local area network, and note the static IP address assigned to the Plexlog device.
In the ModbusCloud portal, add the ModbusCloud Gateway, import the Plexlog Datalogger template, and set the target IP address and port (502 or 503) along with unit ID 1.
Verify the connection by checking the live value of the active_power register in the portal dashboard and confirming it matches the reading shown on the Plexlog device interface.
Things to watch for
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.
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