5604 Input/Output (I/O) Module - Hardware Manual
October 19, 2007
outputs for which 24V-drive capability is required. Otherwise, the DC/DC converter can be turned
off to conserve power.
Turn on Digital Output 32 to turn ON the 12V to 24V DC/DC converter. When the converter is
turned on 24Vdc is provided to the VLoop power and to the Analog Output module.
Turn off Digital Output 32 to turn OFF the 12V to 24V DC/DC converter. When the converter
is turned off VLoop power and the Analog Output module use is the applied input power.
Internal Digital Input 32 indicates the status of the 12V to 24V DC/DC converter. Digital Input 11
is set when the 12V to 24V DC/DC converter is on and is cleared when the 12V to 24V DC/DC
converter is off.
The 12V to 24V DC/DC converter is turned on when the LED power is enabled. This feature is
provided for service and diagnostics. Refer to the LED Power Control section in the hardware
manual of your respective controller board for further information on this feature
4.4.2 VLoop Power Control
The DC/DC converter output can be used to power analog input current loops or other
instrumentation. This output, VLoop, is controlled for intermittent or continuous operation. Turning
the VLoop output off when it is not required can save considerable electrical power.
The switched VLoop power source is the output of the DC-DC 12/24V converter if it is turned on.
See the DC/DC Converter Control section for converter information. The VLoop power source is
the applied input power if the DC-DC converter is turned off.
Turn on Digital Output 33 to turn ON the VLoop output.
Turn off Digital Output 33 to turn OFF the VLoop output.
Note: When VLoop is first turned on, the user application program must wait at least one second
for input readings to stabilize. This time may be increased depending on field sensors and
transmitters. Documentation for these devices should be consulted.
The VLoop output is turned on when the LED power is enabled. This feature is provided for service
and diagnostics. Refer to the LED Power Control section in the hardware manual of your respective
controller board for further information.
4.4.3 VLoop Over-Current Protection
When VLoop output is turned on, it is monitored for excessive current consumption caused by field
wiring or instrumentation problems. If sustained over-current is detected (100 ms), VLoop is turned
off even though internal Digital Output 33 is turned on. This protection prevents unnecessary fuse
blowing, circuitry damage and rapid battery depletion.
When VLoop output is turned on, using internal Digital Output 33, and a short circuit is detected
VLoop will turn off. VLoop will turn on to try again 5 seconds after turning off. If the fault
condition still exits VLoop will again turn off and retry after a 5 second delay. While the fault
condition exists internal Digital Input 34 will be ON.
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