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Home › Products › Protocol Converters › WT50C
Protocol Converters
Most smart energy meters in India speak only DLMS/COSEM (IS 15959), while PLCs, SCADA, building management systems and data loggers speak Modbus. The WT50C sits next to the meter: it holds the DLMS session on RS-232 and answers Modbus RTU polls on RS-485 — voltage, current, power and energy arrive as plain input registers, with no DLMS software on the master.
Animation: the WT50C reads one value at a time from a DLMS energy meter over RS-232, and a Modbus master polling it over RS-485 receives the same value as an input register.
Two conversations run at once. On RS-232 the WT50C keeps a DLMS session with the meter and reads its OBIS objects one by one; on RS-485 it answers every Modbus poll from the values it holds. The master asks slave ID 1 with function 04 and gets plain numbers back — it never speaks DLMS.
| Voltage L1 | 231.4 | V |
|---|---|---|
| Voltage L2 | 229.8 | V |
| Voltage L3 | 232.6 | V |
| Current L1 | 5.42 | A |
| Current L2 | 4.87 | A |
| Current L3 | 6.03 | A |
| Power factor L1 | 0.982 | |
| Power factor L2 | 0.976 | |
| Power factor L3 | 0.969 |
| Power factor, total | 0.975 | |
|---|---|---|
| Frequency | 50.01 | Hz |
| Active power | 3.683 | kW |
| Reactive power | 0.832 | kvar |
| Apparent power | 3.776 | kVA |
| Active energy, import | 18452.317 | kWh |
| Apparent energy, import | 18901.552 | kVAh |
| Reactive energy, lag | 3487.208 | kvarh |
| Reactive energy, lead | 12.406 | kvarh |
Sample values from a simulated three-phase load; OBIS codes as in IS 15959. On site, these are your meter’s readings.
One 8-pin terminal carries everything: the 12–24 V DC supply, the RS-485 pair to the Modbus master, a 5 V feed for the meter’s communication port, and the RS-232 link to the meter. Nothing else is needed at the meter.
Supply12–24 V DC
ModbusRS-485 · RTU slave
Meter supply5 V DC out
Meter linkRS-232 · DLMS
Modbus input registers, read with function code 04 — no DLMS software on the master.
| PWR | SolidPowered. If it is dark, check the 12–24 V DC supply first. |
|---|---|
| CON | Even blink, 500 msMeter not connected: check the meter cable and that the baud rate matches. |
| CON | 2 pulses every 3 sMeter connected; the WT50C is polling it. |
| STAT | One flash per readA meter value was read. Steady flashing means data is flowing. |
| STAT | Slow, 1 s on / 1 s offThe meter does not answer: check the meter password, meter address and meter profile. |
| RXD + TXD | RXD, then TXDModbus healthy: a request came in and the WT50C answered. |
| RXD only | TXD stays darkThe master polls a slave ID or register range this WT50C does not serve. |
| RXD + TXD | Both darkNo Modbus master is polling, or D+ and D- are swapped. |
| Function | DLMS/COSEM energy meter → Modbus RTU slave |
|---|---|
| Meter Interface | RS-232 (RXD · TXD) |
| Modbus Interface | RS-485 (D+/T+ · D-/T-) · Modbus RTU slave · input registers (function 04) |
| Meter Port Supply | 5 V DC output |
| Readings | V, I and PF per phase · total PF · frequency · kW · kvar · kVA · kWh · kVAh · kvarh lag / lead · meter serial number |
| Supported Meters | Secure (Premier 300, Premier 350, Saral 305) · L&T ER300P · HPL · Capital |
| Configuration | Windows configuration tool · from the Client Portal |
|---|---|
| Power | 12–24 V DC |
| LED Indicators | PWR · CON · TXD · RXD · STAT |
| Front Panel | USB port · reset button |
| Terminal | 8-pin |
The billing meter usually belongs to the utility and speaks only DLMS, so it cannot simply be swapped for a Modbus meter. The WT50C reads it through its communication port and hands every reading to the Modbus system already on site.
Read the utility’s DLMS meter at a rooftop or ground-mounted plant into the same data logger or SCADA that reads the inverters, so metered energy sits beside inverter generation in one report.
Utility meter→WT50C→Plant data logger
ReadskWhkVAhkWV · I · PF
Bring the incoming utility meter into the EMS or BMS next to the Modbus sub-meters, so internal consumption adds up against the bill and losses show.
Incomer meter→WT50C→EMS / BMS
ReadskWhkVAhkvarh
Give the PLC or energy manager the billing meter’s live kVA, so it can warn or shed non-critical loads before demand crosses the contracted limit.
Billing meter→WT50C→PLC / EMS
ReadskVAkWPF
Track power factor and lag / lead kvarh at the meter the bill is raised from, and check the APFC panel against it. Under kVAh billing, a poor power factor is paid for directly.
Billing meter→WT50C→SCADA
ReadsPFkvarh lag / leadkVAh
Poll the WT50C from a Wiman 4G gateway such as the WT400M or the WT460M, and the meter’s readings reach your server or cloud dashboard from rooftops, pump houses and unmanned sites.
Meter→WT50C→4G gateway→Cloud
Readsevery reading
Feeder and distribution-transformer meters that speak only DLMS join an RTU or SCADA system that polls Modbus, with no DLMS driver on the master.
Feeder / DT meter→WT50C→RTU / SCADA
ReadsV · I · PFkW · kVAkWh
Anywhere a DLMS / IS 15959 meter has to report to a PLC, SCADA, BMS, EMS or data logger:
New to smart meters? Here is what DLMS is, how a meter names its readings, and who is allowed to read them.
DLMS/COSEM (IEC 62056) is the common language of electricity meters. India’s smart meter standard, IS 15959, is built on it, so meters from different makers can be read the same way.
Each value comes with its unit and scale, and the meter answers only inside a session it has agreed to.
PLCs, SCADA and building systems speak Modbus, not DLMS. The WT50C speaks DLMS to the meter for them.
Every reading in a DLMS meter has a fixed six-part name, its OBIS code. The same code means the same reading on every make.
1.0.32.7.0.255Voltage, phase L11.0.31.7.0.255Current, phase L11.0.14.7.0.255Frequency1.0.1.8.0.255Active energy, import (kWh)0.0.96.1.0.255Meter serial numberThe WT50C reads the meter by OBIS code and puts each value in a Modbus register. The master never needs to know OBIS.
A meter opens a session, called an association, before it answers. Each session has an access level:
No securitypublic
Anyone may read a few basics, such as the meter’s serial number and clock.Low-level (LLS)password
A password opens the session. The usual level for reading values.High-level (HLS)key
A secret-key challenge instead of a plain password, kept for higher access such as settings.On the WT50C, the meter password, address and profile are set once in the configuration tool.
| DLMS | Modbus | |
|---|---|---|
| Made for | Energy meters | PLCs and industrial devices |
| A value is found by | Its OBIS code | A register number |
| Unit and scale | Sent with the value | Written in the register map |
| Session and password | Yes, every time | No, the master just asks |
| On the WT50C | RS-232, to the meter | RS-485, to the master |
Smart energy meters talk DLMS/COSEM (IS 15959), while most PLCs, SCADA systems, building management systems and data loggers talk Modbus. The WT50C reads the meter in DLMS on RS-232 and answers Modbus RTU requests on RS-485, so the master sees the meter as an ordinary Modbus slave.
The WT50C carries meter profiles for Secure (Premier 300, Premier 350, Saral 305), L&T ER300P, HPL and Capital meters. The meter profile, meter address and meter password are set with the configuration tool.
Wherever a utility's DLMS billing meter has to report to a Modbus system: commercial buildings, IT parks, hospitals, hotels and malls on a BMS; factories and data centres on an energy management system; solar, wind and DG plants beside the inverters; water pumping stations and STPs; telecom towers; EV charging hubs; cold storage and warehouses; railway and metro stations; and utility substations, feeders and distribution transformers on SCADA.
No. Pins 5 and 6 of the WT50C give 5 V DC to the meter's communication port, so nothing else is needed at the meter.
The meter serial number; voltage, current and power factor on each phase; total power factor and frequency; active, reactive and apparent power; active and apparent energy (kWh, kVAh); and reactive energy, lag and lead (kvarh). All are Modbus input registers, read with function code 04.
Poll the WT50C on RS-485 from a Wiman IoT gateway such as the WT460M (4G + LAN) or the WT400M (4G LTE). The gateway sends the readings on to your server or cloud platform.
Through the Client Portal. The Windows configuration tool is not a public download; it is shared with customers in the portal.