Varec Mark Space (M/S) Output - Endress+Hauser Proservo NMS 5 series Technical Information

Varec Mark Space
(M/S) Output
18
Vb = voltage drop across transmitter
Vc = voltage drop across receiver
Bus Address
Each transmitter on a signal loop has an individual bus address. This is defined within the transmitter by
mechanical dip switch on com board.
Bus Cabling
The bus cabling is galvanically isolated from the transmitter and the PC plug-in board or the interface adapter.
BS5308 or equivalent 1.5sq.mm screened twisted pairs are recommended for bus cabling.
Bus Topology
The suitable topologies for the WM550 current output are depending on number of transmitter & cable quality
on the loop. Recommended number of transmitter on single loop shall be less than 15 units to achieve the
maximum performance.
The bus is normally connected to Interface Unit (IFU), Data acquisition Processor (DAP), RTU 8 or other upper
host system via 4 wire M/S serial bus link.
Termination Resistors
Admissible termination resistance should be calculated as follow.
R = (48 - 33) / {60mA + N (2.0mA)}
R = terminal resistance in the system
N = number of transmitter in the system
48 = supply voltage to receiver
33 = minimum M/S board operation voltage
60mA = required current for system operation
2.0mA = required current per transmitter
Bus Address
Each transmitter on a signal loop has an individual bus address. This is defined within the transmitter by
mechanical dip switch on com board.
Bus Cabling
The bus cabling is galvanically isolated from the transmitter and the PC plug-in board or the interface adapter.
The total length of field wiring shall be determined by calculation of maximum resistance within the system &
required operation current. Once the total length is determined, distance has to be reduced by half because
of current flow in both B+ & B- leads.
Bus Topology
The suitable topologies for the M/S serial pulse output are depending on number of transmitter & cable quality
on the loop.
Proservo
Endress+Hauser