The Interface Module XCModbus is designed for use with the EMH LZQJ-XC and DMTZ-XC
meters. The module is equipped with a RS485 (2 wires) interface. The module can be plugged
easily into the module compartment of the meter. It can be mounted or exchanged during
operation (without breaking approval seal). An integrated Modbus interface provides a simple
means of connecting multi-energy meters. This makes multi-energy applications an affordable
proposition for domestic use. Due to the communication, the modules are suitable for a lot of
control centres.
Compatible meters
LZQJ-XC (special meter for industrial applications):
- Standard meter for direct connection
- Transformer connection version Cl. B (Cl. 1)
- Precision meter Cl. C (Cl. 0.5S)
- Precision meter Cl. 0,2S
DMTZ-XC (industry meter)
Functions
RS-485 (2 wires) interface for bi-directional
communications
Protocol converter for meter data (max. 125 values)
into Modbus-Format (non transparent data readout)
Transmission protocol: Modbus RTU (8N1)
Internal communication interface for the transfer
service data (TS) between the meter and the
interface module
Internal power supply from meter
Exchangeable during the meter operation
The owner of the interface modules is responsible that all persons engaged on
work with the modules:
• Are competent and qualified in accordance with national regulations (see ISSA
"Guideline for Assessing the Competence of Electrically Skilled Persons").
• Have read and understood the relevant sections of the user manual.
• Strictly observe the safety regulations (according to the following section) and
the instructions in the individual chapters.
Safety Notes
The owner of the modules is also responsible for:
• The protection of persons.
• The prevention of material damage.
• The training of personnel.
The following safety regulations must be observed at all times:
• Devices which have fallen down should not be installed, even if no damage is apparent, and should
be returned for testing to an authorised service centre (internal damage possible).
•Modules must never be cleaned with running water or high pressure devices. Water can cause
4. Insert the interface module [3] carefully at the
place provided in the meter [2].
5. Push the module in to the internal contacts.
6. Connect the cable.
7. Close the transparent module cover [1].
8. Close the terminal cover [5].
Removing of the interface module:
9. Remove the terminal cover [5].
10. Open the transparent module cover [1].
11. Disconnect the cable.
12. Remove the interface module.
13. Close the transparent module cover [1].
14. Close the terminal cover [5].
Power/Tx
green
Status and communication via Modbus interface:
LED signals, that the module is supplied with power
LED goes off during transmit data via Modbus (RS485) interface
Rx
yellow
Communication via Modbus (RS485) interface: receive data
Error
red
Communication error (internal meter interface), LED flashes in 3 sec.
cycle
Installation Hints
The installation must be done in a way, that even in the case of cable break no dangerous voltages
are applied to touchable parts of the module. Generally, meters are delivered with the communication
modules installed. The fitting of a meter with a communication module is, therefore, an exception and
can be necessary e.g. when a module needs to be replaced.
The interface module is exchangeable during the meter operation. Fit the interface module in the meter
as follows:
LED Displays
Three LED’s display the current operating status of the module and give information about the data
transfer.
The interface port RS485 is conforming to “Modbus Application Protocol V1.1b”: Modbus RTU
(Remote Terminal Unit).
Fixed baud rate from the 2nd electrical interface (see EMH COMBI-TOOL-Software: communication
interfaces, set please the data transmission at a fixed baud rate without baud rate changeover), data
format: 8N1;
The following rules define the protocol for information transfer between a Modbus MASTER and the
Interface Module XC Modbus:
The module supports only the “Modbus RTU Mode of Transmission”: Read Holding Registers.
Transmission settings: 8N1 (1 start bit, 8 data bits, no parity, 1 stop bit).
All communications on the RS485 bus conform to a MASTER/SLAVE scheme. In this scheme,
information and data is transferred between a Modbus MASTER device (e.g. AMR Software) and
up to 32 SLAVE devices (Modbus Interface Module XC).
The MASTER initiates and controls all information transfer on the communications loop.
A SLAVE device never initiates a communications sequence.
All communications activity on the loop occurs in the form of “PACKETS”. A packet is a serial
string of 8 bit / byte. The maximum number of bytes contained within one packet is 255.
All packets transmitted by a MASTER are REQUESTS. All packets transmitted by a SLAVE are
RESPONSES.
At most one SLAVE can respond to a single request from a MASTER.
The Modbus module supports the Function Code 3 (Read Holding Registers) with signed 32 bit
values (Signed Int32, Type D). All values includes 2 words (registers) with 16 bits each: first register
(even register addresses: 0,2,4,6...) for high-word and second register (odd register addresses:
1,3,5,7...) for low-word.
Example:
Value = 12345678
(32 bit := 4 Byte) start at register address 20:
Hex
The Modbus module uses for ID-Address the first data value in the service data list (TS): register
addresses 0 and 1. For setting the value use please the EMH COMBI-TOOL-Software.
Possible value range: 1 to F7
:= 1 to 247
Hex
/ Value outside of this range: ID-Address := 1 (default)
→ Modbus register address (start register) := address in the device – 40001
Data Field:
Request: four bytes (start register: 2 bytes, # of registers: 2 bytes) Response: (1 + 2 n) bytes (counter: 1 byte, n registers: 2 n bytes)
Error Check Field (Checksum): two bytes, a 16-bit Cyclic Redundancy Check (CRC16: Cyclic
Redundancy Check)
Example:
ID-Address: 123
Dec
(:= 7B
) / start register: 14
Hex
(00 0E
Dec
) / # of registers: 2 (:= one 32 bit value)
Hex
Request:
Response:
Value = 59
(00 00 00 3B
Dec
Hex
)
Accepting the meter data
The Modbus module reads the service data list (TS) from the meter periodically (interval between two
readings: ca. 0.5 seconds) and creates an internal table with 16 bit registers (words): first data value
from meter is saved at register 0 and 1 (ID-Address). Via Modbus is it possible to read all this
registers.
Values at empty registers := FFFF
(:= 65535
Hex
Dec
).
All meter values between curved brackets (OBIS coded) will be transformed to 32 bit values. Possible
range of the values: -231 to 231-1 (-2147483648
Parameterisation of the meter (EMH COMBI-TOOL-Software)
At the first read the read all data from the meter (via optical IR interface):
Baud rate
The Interface Module XCModbus uses the same baud rate like the communication interface at the
meter. For setting use please the EMH COMBI-TOOL-Software:
menu Meter Interfaces Electrical supplement / aditional interface:
For correct working set please a fixed bad rate (e.g. 9600 baud). If you use the baud rate changeover
according to mode C: the communication is possible with 300 baud only. For the addressing set the
value “optionally” or “ignore”.
Reset
Note: The EMH LZQJ-XC meter performs automatically a daily reset at 00:00 in the interface module.
Service Data / (Service Table TS) and Modbus ID-Address
For setting the meter data list use menu
Lists Reading lists Service Table TS:
Note 1: The Modbus module uses for ID-Address the first data value in the service data list
(TS): register addresses 0 and 1.
In this example we use the identification number 1 (OBIS 0.0.1) for ID-Address:
menu Meter Meter ID OBIS Register 0.0.1, e.g. value 123 (:= 00000123):
Note 2: Only the first 125 values from the service data list (TS) will be used.