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.

Free Modbus template: 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.

Name	Address	Function	Type	Unit	Access
voltage_l1 Phase-to-neutral RMS voltage on phase L1, volts.	19000	FC03	float32	V	R
voltage_l2 Phase-to-neutral RMS voltage on phase L2, volts.	19002	FC03	float32	V	R
voltage_l3 Phase-to-neutral RMS voltage on phase L3, volts.	19004	FC03	float32	V	R
current_l1 RMS current on phase L1, amperes.	19012	FC03	float32	A	R
current_l2 RMS current on phase L2, amperes.	19014	FC03	float32	A	R
current_l3 RMS current on phase L3, amperes.	19016	FC03	float32	A	R
current Total three-phase RMS current sum, amperes.	19018	FC03	float32	A	R
active_power_l1 Active real power on phase L1, watts.	19020	FC03	float32	W	R
active_power_l2 Active real power on phase L2, watts.	19022	FC03	float32	W	R
active_power_l3 Active real power on phase L3, watts.	19024	FC03	float32	W	R
active_power Total three-phase active real power, watts.	19026	FC03	float32	W	R
reactive_power_l1 Reactive power on phase L1, VAr equivalent.	19036	FC03	float32	W	R
reactive_power_l2 Reactive power on phase L2, VAr equivalent.	19038	FC03	float32	W	R
reactive_power_l3 Reactive power on phase L3, VAr equivalent.	19040	FC03	float32	W	R
reactive_power Total three-phase reactive power, VAr.	19042	FC03	float32	var	R
frequency AC grid frequency, hertz, typically 50 or 60.	19050	FC03	float32	Hz	R

PqPlus UMD97

Overview

Use cases

Installation

Things to watch for

Registers (16)

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