Siemens ET 200M, Руководство пользователя, Страница: 38 / 284

8-Channel Analog Input MTA
Marshalled Termination Assemblies for ET200M Remote I/O Modules
38 A5E00482820-12
4.3 Operation
Power is supplied via the two removable power connectors which are retained by
screws and marked L+A , MA , and L+B , MB . Each has circuitry to detect the
presence of voltage over 15 VDC and turn on the LED indicator. The LEDs are
marked A POWER and B POWER. There is also a connector ( J3 ) for a Power
Monitor board used to indicate the presence of both A and B power. See Section
19, Power Monitor Board (6ES7650-1BA02-0XX0).
Incoming power from A and B is diode OR’d, in CR106 , to provide the MTA power
from either input source. The output from CR106 is sent to the channel fuses. This
module does not require any power from the I/O power supply and therefore no
module power circuitry is required.
Each channel has an LED to indicate the presence of power and the fuse status. If
there is no power or the fuse is open, then the LED remains dark. If there is power
and the fuse is good then the LED is illuminated.
The MTA has two types of jumpers for customer use:
• I – V jumpers are a header and shunt type that determines the connection to
the input signal.
• Isolation jumpers are wires that can be cut to isolate the input channel from
power return. See Section 4.10, Hardware Configuration.
Field Terminals, C ( Ix+) , Channel – ( Ix - ) , Sensor power ( PWRx ) and
Shield ( SHx ), connect to the field devices. PWRx is the +24 VDC power feed and
is fused (.5A) on a channel-by-channel basis. The field termination connector is
removable for ease of wiring maintenance and is retained by friction.
The channel inputs from the MTA connect to the I/O modules inputs via
J1 and J2 .
Redundant operation uses two modules with one each connected to J1 and J2 ,
while non-redundant systems have one module connected to either J1 or J2 .