Micromod MOD: 1750N Output holder for MOD 30ML - Manual (Page 8)

Output Holder Instructions
PRODUCT DESCRIPTION
1.6 BASIC HARDWARE
The 1750N, Figure 1-1, is designed for mounting in a panel with a 11.5 inch depth. The
instrument housing contains a 6-point termination facility which accepts all instrument I/O and
power connections.
The 4-20mA output from the MOD 30ML controller is wired in series with the 1750N, and
then to the field. As long as the output from the controller is within the specific limits, the
output holder output is identical to the input (controller output signal). In case of controller
failure resulting in loss of output, the Output Holder retains the last output, thereby enabling
the defective instrument to be replaced without interruption to the process.
A separate output return signal is fed back to the controller, so that when the defective
instrument is replaced the output will automatically match that of the Manual Loader for
bumpless transfer of control. The output holder also provides a discrete output that can be
connected to the controller. This input is the status of the output holder’s presence and can
be used in the controller’s configuration logic.
Use of the Return / Feedback signal (1-5 mA Monitor to controller) and the Output Holder
Sense Discrete signal are optional.
When the 1750N is installed, the output may still be viewed and manipulated when the
controller is removed from the panel for service. Up/Down pushbuttons are provided on the
front panel, allowing direct manipulation of the output by the operator in the event of
controller failure. Output indication is provided by a 10-segment LED bar graph. Screwed
terminal connections are provided for interconnection with the MOD 30ML terminal block.
One Analog Input is required on the MOD 30ML / Modcell for the feedback circuit. Either a
built-in analog input or a plug-in analog input module may be used. A standard configuration
strategy for the MOD 30ML with the feedback circuit is provided in the library of the Visual
Application Designer configuration tool for MOD 30ML / Modcell.
1 -4