M-Bus master terminal KL6781
Receive LED
Error LED
Send LED 
Run LED 
Power contact
+24 V
Power contact 0 V
Top view 
Contact assembly 
extended shock and vibration range

KL6781 | M-Bus master terminal

The KL6781 M-Bus master terminal enables the direct connection of M-Bus devices. The M-Bus (Meter Bus) is a fieldbus for the acquisition of consumption data from electricity, water, gas or energy meters. The KL6781 does not contain the M-Bus protocol; instead, it converts the data present on the terminal bus into M-Bus compliant physics. 24 byte data are available on the K-bus for this. In conjunction with the TwinCAT M-Bus library, it is possible to work without an external M-Bus gateway, i.e. the M-Bus devices can be connected directly to the KL6781. With a total cable length of 300 m, up to 40 M-Bus devices (each with a current consumption of 1.5 mA) can be connected.

Technical data KL6781
Technology M-Bus
Data transfer standard M-Bus physics
Data transfer channels 1
M-Bus devices max. 40 each with a current consumption of 1.5 mA
Data transfer rates 300…9,600 baud (default 2,400 baud)
Bus access master-slave mode (polling)
Cable length max. 300 m
Current consumpt. K-bus typ. 65 mA
Current consumption power contacts max. 250 mA
Short-circuit-proof yes
Electrical isolation 500 V (K-bus/M-Bus)
Bit width in the process image input/output: 24 bytes
Configuration TwinCAT (M-Bus function blocks)
Nominal voltage 24 V DC (-15 %/+20 %)
Input voltage 24 V DC (-15 %/+20 %)
Special features connection of up to 40 M-Bus devices; TwinCAT library: TwinCAT PLC M-Bus
Weight approx. 60 g
Operating/storage temperature 0…+55 °C/-25…+85 °C
Relative humidity 95 %, no condensation
Vibration/shock resistance conforms to EN 60068-2-6/EN 60068-2-27
EMC immunity/emission conforms to EN 61000-6-2/EN 61000-6-4
Protect. class/installation pos. IP 20/variable
Approvals CE, UL
TwinCAT PLC M-Bus The library is installed free of charge together with TwinCAT from V2.11 Build 2229 (R3 and x64 engineering).
subsystem For further subsystem products please see the system overview.