IEC 62056-21 converter to Modbus, type ELM-07S

IEC 62056-21 decoder to modbus RTU/TCP systems

ELM-07S is specially designed to allow easy accomodation of electricity meters to global remote reading system. IEC 62056-21 (former 61107) is serial protocol for transmitting data, designed specially for electricity meters. Since it is ASCII-based, information in basic case is too heavy to be read and takes a lot of time (and cost). Here comes ELM-07S converter. Converter acts as a master that reads regulary all connected electricity meters through RS-485 interface. Readed information is saved in modbus register map. For each meter is available memoey space, where information from up to 63 registers from IEC 62056-21 can be transffered to modbus. Modbus is both RTU and TCP, which means that one can use ELM-07S as direct remote gateway to read electricity meters.

Normally RS-485 drivers in most of electricity meters allow up to 32 devices in the network, that is why our ELM-07S is designed exactly for 32 slaves. Nevertheless, ELM-07S comes with RS-485 driver for 250 devices, so if electricity meters allow it - we can increase number of supported electricity meters in one network.

Devices comes in aluminium enclosure and is mounted on a standard DIN-rail, usually in industrial enclosures. Modbus RTU is on terminal blocks, Modbus TCP on standard RJ-45 plug.

user manual

Technical characteristics of ELM-07S

max. number of IEC62056-21 devices 32
converted registers/values up to 63
power supply 165-235 VAC (210-270 VDC)
power consumption < 5 W
IEC interface bps 300/1200/2400/4800/9600/19200/38400/115200 bps, 7 data bits, Even
Modbus RTU bps 300/1200/2400/4800/9600/19200/38400/115200 bps, 8 data bits, None
work temperature from -20° C to +50° C
storage temperature from -50° C to +90° C
humidity 40 ÷ 90 %
dimensions (HxWxD), mm 105/107/74 mm
protection class IP20
display 3 LEDs (on, IEC activity, Modbus activity)
own weight 475 g

Operation of ELM-07S

ELM-07S begins operation immediately after power-up. The sequence is the following:

Initialization mode:

  • In the first 0.2-0.3s the device initializes its internal data structures. LED “on” is lit
  • After 10s ELM-07 starts reading the network of IEC62056-21 devices. All devices to be read should have their addresses preprogrammed in ELM-07S memory

Normal operation

In normal mode ELM-07 waits predefined period of time and then reads all pre-programmed IEC62056-21 devices. For each device (32 meters at most) there are 128 16-bit Modbus registers (4096 registers total). These registers are updated on each device readout. The value of each IEC62056-21 register is split in two Modbus registers, which means that for every electricity meter can be saved up to 63 values. Before reading the IEC62056-21 devices user should activate each meter ID (since in IEC 62056 meters are read through their unique 8-digit ID) in ELM-07S internal memory. Then user should also program which registers/values he needs from every meter and on which modbus address he wants data to be written. Each activated meter has a memory space for up to 64 values (32-bit each) and this area is predefined (look at modbus map).

IEC62056-21 devices can be added, deleted, their registers changed any time when device is operational. The Modbus registers can be accessed any time either on Modbus RTU or TCP, as well as simultaneously via both RTU and TCP.

For easy setup and administration we provide free software, which can read and set configuration to ELM-07S both through modbus RTU and TCP.

All the connections of ELM-07S are on industrial terminal blocks except LAN connector, which is standard RJ-45 plug. Mounting should be made by qualified technicians and is on standard M-36 DIN-rail.

Mounting and electrical wiring