Digital Master

Signal processor driven M-Bus Master / Level- Converter for 120 or 250 slaves

  • modular design:

  • as Master with plug-in CPU-Board and integrated Master-Software

  • as Repeater for bus system extension (more than 250 slaves, more cable length)

  • as Level-Converter for RS232, RS485 or 20mA Current-Loop

  • Baudrates: 300 to 9600 Baud

  • Version for 38400 Baud with limited specifications

  • Bit-Recovery (recovery of bit times)

  • Overcurrent and short-circuit protection on the M-Bus

  • external voltage and lightning protection on the M-Bus

  • Echo cancellation and collision detection with break signalling

  • Displays for power, data transmission, max. bus current and short-circuit

  • 2 serial lines (modem and service)

Function of the M-Bus Central Unit

The M-Bus Central Unit scans the data from up to 250 meters in selectable intervals. All meters with M-Bus protocol according to EN1434-3 are automatically detected and read. This means that the user is saved the laborious task of configuring the measuring points in the software.

It is possible to operate the M-Bus Central Unit on-site by the keypad and the LCD, without any auxiliary devices. A PC can be used to read the stored meter data on-site or by a modem connection ( for example with a standard terminal software). The operating system is available in different languages and can easily be updated by software.

Technical Data

Operating Voltage

42 DC

Power Consumption

max. 25W

Temperature Range

0 .. 55 °C

M-Bus Voltage (without load)


Bus Impedance

approx. 10 Ω

M-Bus Standby Current

max. 375mA bei DR001 (250 standard load)
max. 180 mA bei DR002 (120 standard load)

Overcurrent Threshold

500mA (DR001), 250mA (DR002)

M-Bus Baud Rate

300 .. 38400 Baud

Galvanic Isolation



Grey ABS plastic,
protection class IP52
H x W x D: 85 x 200 x 240 mm


NEC V25 (8MHz)


512 kB FLASH (optional 4MB)
512 kB static RAM


battery-backed real-time clock

Watchdog module

Operating Controls

Membrane keypad with 20 keys

LCD with 4 lines and 16 columns


M-Bus, RS232C, Modem intern, Modem extern

Order Information

Order Number



Master with CPU/Soft (250 Slaves)


Master with CPU/Soft (120 Slaves)


Level-Converter RS232 (250 Slaves)


Level-Converter RS232 (120 Slaves)


Level-Converter RS485 (250 Slaves)


Level-Converter RS485 (120 Slaves)


Repeater for system extension


Level-Converter TTY (250 Slaves)

Copyright© 2018  Relay GmbH

Designed By T.McDowell