Siemens BETA Low-Voltage Circuit Protection

BETA Measuring

Three-Phase Measuring Devices

KT1 31, 7KT1 34, 7KT1 35 multicounters

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Siemens ET B1 · 10/2008

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More information

Communication interfaces

Multicounters with PROFIBUS interface

Multicounters are also available with PROFIBUS interface. In a

PROFIBUS network, the multicounters act as PROFIBUS DP

slave according to the usual standard V0 (cyclic communication

only).

In a PROFIBUS network, several PROFIBUS slaves are always

assigned to a single master. A PC with a PROFIBUS communication

module or PLC, such as the PLCs of the SIMATIC range from

Siemens, can be used as the master. The master communicates

with the connected slaves cyclically at extremely brief intervals.

The master sends the slaves a request message to which the

slave replies with a response message. The communication

frame of the message (e.g. number of send and receive bytes)

is slave-specific and is defined in a standardized text file; the

device data base file (DDBF). This DDBF file is read in by the

software configuration tools of the various PROFIBUS masters,

whereby the master knows which communication frame the

respective slave requires.

In normal cyclic mode, the multicounter sends a response

message in the specified communication frame in reply to the

request message from the master. This communication frame

contains all 35 measured quantities in encoded form as user

data. The master receives the message, decodes it and then

uses the measurement data for a range of tasks.

As well as the DDBF file, a detailed description of the communication

and the configuration of the user data are also required for the

configuration and implementation of a PROFIBUS network with

multicounters. For more information please visit us on the

Internet at:

http://www.siemens.com/beta

Multicounters with Modbus interface

The Modbus RTU is a very common communications solution. It

is a serial, asynchronous form of communication, which requires

RS 485 networks as the hardware platform. RS 485 networks can

be set up with 2-wire copper or optical fiber cables and, compared

to the RS 232 serial interface, offer fast transmission rates.

In a Modbus network, each bus station has a bus address within

the range from 1 to 255. All stations within a network must be set

to the same transmission rate. We recommend transmission

speeds of 9600 or 19200 bit/s. The address and transmission

speed can be set in the user menu of the multicounters.

In order to customize a Modbus installation, it is necessary to

implement the appropriate software application for the master.

This requires specific information about communication with

multicounters. For more information please visit us on the

Internet at:

http://www.siemens.com/beta

Multicounters with LAN coupler on LAN

The 7KT1 390 LAN couplers support connection of up to

ten 7KT1 34 multicounters to a LAN network. The LAN couplers

and multicounters are interlinked over an RS 485 network.

Setting the bus address in the 7KT1 34 multicounters to "0"

specifies that it is operating in "LAN" mode. It is not necessary to

set the transmission speed, as a fixed transmission rate is always

used in this mode. It is also not necessary to set the address of

the bus stations, as the LAN coupler automatically detects and

identifies the multicounter connected.

The server components run on the PC in the background and

handle the data transmission and storage of the most recent

measured values from all the multicounters connected over one

or more LAN couplers.

For more information on LAN operation and the MS E

xcel

operator

interface, see 7KT1 390 LAN couplers

on page 11/16 ff.

Voltage measurement

Depending on the selected connection type, the multicounter

measures the delta voltages L1 against L2; L2 against L3 and L3

against L1 or the star voltages L1, L2, L3 against N.

L symbol for the 3-phase system

This indicates that all physical units shown under this symbol are

always 3-phase.

Temperature

The temperature indication of the multicounter is not suitable for

an exact measurement of the ambient temperature. The device

does not have a temperature sensor. It is also not possible to

connect an external temperature sensor.

The temperature information merely enables a rough estimate of

the temperature conditions in the device interior and immediate

surroundings.

L1-N

L1-L2

L3-L1

L3-N

L2-N

L2-L3

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