KRAL BEM 100 - Modbus Interface; Cable Specification; Pin Assignment; Function Description

5 Function description
4.4 Modbus interface
4.4 Modbus interface
Parameter Value
Interface type RS-485
Baud rate 9600 / 19200 / 38400 / 57600 / 115200
Protocol Modbus RTU
Data format 8N1 (8 data bits, no parity, 1 stop bit)
Refresh time parameter 1/16 [s]
Tab.5: Modbus interface
4.5 Cable specification
Note The manufacturer recommends the observance of the cable specifications at the cables used.
Parameter Unit Value
Conductors
o 2 x power supply (≥1mm²)
o 2 x Modbus communication, twisted-pair and shielded (≥0,25mm²)
Terminating resistor [Ω] 120 (between A and B)
Cable diameter For opening M12
Length max. [m] 300 (at full load)
Tab.6: Cable specification
4.6 Pin assignment
4
3
2
1
5
4
3
2
1
5
MODBUS IN
MODBUS OUT
Fig.3: Pin assignment
Pin Description
1 Shield
2 DC power supply 10–30 V (+)
3 DC power supply 0 V (- or GND)
4 RS-485 A / + / RXTX-P (positive)
5 RS-485 B / – / RXTX-N (negative) / inverted
Tab.7: Pin assignment
5 Function description
5.1 Functional principle
5.1.1 Usage
The processing unit is intended for usage with a KRALflowmeter of the OMECompactseries and is
mounted directly on the flowmeter.
Flowmeters generate a specific number of pulses per flow volume unit –depending on the size and
working point. This device-specific characteristic is called the K-factor (unit:pulses/litre) and is spe-
cified on the calibration certificate.
5.1.2 Communication
The processing unit operates with a Modbus connection (single-bus architecture). Pre-assembled
cables serve to supply electricity and to transfer signals to an external display device, such as a PC or
laptop (Human-Machine Interface / HMI). There the calculated measured results can be displayed.
6
OIE 26en-GB Edition 2021-08
Operating instructions