7
INM9120 Rev 8
3 SETUP AND TESTING
3 .1 SWITCHES
Two switches are provided on the front face of the power supply, located in the top right-hand corner.
Operation of these switches requires the use of a small screwdriver, or similar
3 .1 .1 “Host Pwr” switch
Some host fieldbus I/O cards need to draw 10–20mA of current from the fieldbus in order to operate.
If this is required, the “Host Pwr” switch on the 912X–IS unit should be set to the ON position. The
voltage provided on the fieldbus is in the range 14–32 V dc, at a maximumcurrent of 30 mA
IMPORTANT
- If more than one 912X–IS power supply is connected to the same host segment,
only
one
of them should have its “Host Pwr” switched to the ON position. All the others on this same host
segment must have their “Host Pwr” switch set to OFF.
WARNING !
If the equipment is mounted in Zone 2, the Host Power and Terminator switches
shall only be operated if the equipment is de-energised or the area is known to be
gas free.
3 .1 .2
Terminator switch
A terminator is required at each end of a fieldbus segment .
If a single 912X–IS power supply is
connected to the remote end of a host segment, a terminating impedance must be applied by setting
its “T (Host)” switch to ON. A fieldbus terminator must also be applied, or connected, at the host end
of the segment
IMPORTANT -
If more than one 912X–IS power supply is connected to the same host segment,
only
one
of them should have its “T (Host)” terminator switch set to ON. All the others on this same host
segment must have their “T (Host)” switch set to OFF.
,
.
WARNING !
If the equipment is mounted in Zone 2, the Host Power and Terminator switches
shall only be operated if the equipment is de-energised or the area is known to be
gas free.
3 .2 TESTING
The following checks refer to the LED indicators (see Figure 9)
Power LED (green)
This should normally be ON. If not, check the power connections.
Fault LED (red)
This should normally be OFF. If it is ON, it indicates:
(a) a short circuit on the IS fieldbus or,
(b) excessive transmitter load, i.e too many field devices.
Host or IS LED (yellow)
Both of these should normally be ON.
OFF indicates a permanent comms error and flashing indicates an occasional communications error.
Figure 8 - Host power supply and host trunk terminator
