PqPlus UMD97
The PqPlus UMD97 is a three-phase panel-mount power quality analyzer designed for distribution boards in buildings and industrial plants. This Modbus TCP template reads per-phase voltage (L1, L2, L3), per-phase and total current, per-phase and total active power, per-phase and total reactive power, and grid frequency. All registers are 32-bit float, big-endian, read via function code 3. Connecting the UMD97 to the ModbusCloud Gateway gives installers and facility managers continuous visibility into load balance, power factor trends, and grid frequency deviations across a site.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 16, read only
- Brand
- PqPlus
- Last updated
Registers (16)
16 read, 0 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| voltage_l1 | V | Read | |||
| voltage_l2 | V | Read | |||
| voltage_l3 | V | Read | |||
| current_l1 | A | Read | |||
| current_l2 | A | Read | |||
| current_l3 | A | Read | |||
| current | A | Read | |||
| active_power_l1 | W | Read | |||
| active_power_l2 | W | Read | |||
| active_power_l3 | W | Read | |||
| active_power | W | Read | |||
| reactive_power_l1 | W | Read | |||
| reactive_power_l2 | W | Read | |||
| reactive_power_l3 | W | Read | |||
| reactive_power | var | Read | |||
| frequency | Hz | Read |
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Use cases
- Monitor per-phase active power on L1, L2, and L3 to detect load imbalance across distribution circuits.
- Track total reactive power over time to verify whether power factor correction capacitors are performing correctly.
- Alert on voltage deviations per phase to identify supply quality issues before equipment is damaged.
- Compare per-phase current readings against breaker ratings to flag overload risks during peak demand periods.
- Report grid frequency trends at a site to confirm compliance with utility tolerance requirements over time.
Installation
Enable Modbus TCP on the UMD97 by navigating to the communication settings in the device menu or its built-in web interface, then assign a static IP address and confirm the Modbus TCP port is set to 502.
Connect the UMD97 Ethernet port to the same LAN segment as the ModbusCloud Gateway using a standard RJ45 patch cable, ensuring both devices are on the same subnet.
In the ModbusCloud portal, add a new device, select the PqPlus UMD97 template, enter the device IP address, set the Modbus unit ID to match the value configured on the meter, and save.
Verify the connection by checking the live register view in the portal: voltage_l1, voltage_l2, and voltage_l3 should show plausible phase voltages within seconds of saving the configuration.
Things to watch for
All register values show zero or NaN. What is wrong?
The UMD97 stores all Modbus values as 32-bit IEEE 754 float in big-endian byte order across two consecutive 16-bit registers. If your gateway or polling client is configured for little-endian or swapped word order, every reading will be invalid. Confirm the byte order setting in the ModbusCloud Gateway configuration matches big-endian (most significant word first).
The gateway shows the device as unreachable despite a correct IP address.
Verify that Modbus TCP is explicitly enabled in the UMD97 communication settings, not just the web server. The device can respond to HTTP while Modbus TCP port 502 remains closed if the Modbus option was not activated. Also confirm there is no firewall or managed-switch VLAN rule blocking port 502 between the meter and the Gateway.
Phase voltage reads correctly on L1 but L2 and L3 show identical values to L1.
This typically indicates only one Modbus read request is returning data and the portal is duplicating the result. Check that the template addresses 19000, 19002, and 19004 are all being polled as separate 2-register float32 reads. Some Modbus clients batch incorrectly if the stride between addresses is not recognized as contiguous 32-bit pairs.
Reactive power readings appear unexpectedly high. Are the units correct?
Registers reactive_power_l1 through reactive_power_l3 (addresses 19036 to 19040) carry per-phase reactive power with the unit field set to W in the register map, but these represent VAr values. The total reactive_power register at address 19042 is correctly labelled VAr. Trust the physical measurement context: readings above active power on a predominantly resistive load indicate a wiring or CT polarity issue, not a unit error in the template.
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