CONTREX MLP-Drive - Manual (Page 76)

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Offset Mode
Offset mode is a variation of Follower mode. In Offset mode, an additional quantity
(offset term) is added to or subtracted from the standard calculated follower scaled
reference. The quantity of the offset term is determined by the analog input level and
three additional scaling parameters; offset null, offset authority and offset polarity.
A common use for Offset mode is dancer pot control on a web follower operation. In this
application, the dancer pot is brought into the analog input of the MLP-Drive to provide
an offset to the web follower operation.
The following Control Parameters give the MLP-Drive the necessary information for
Offset mode:
Analog Input Allocation (CP-84)
Setting CP-84, Analog Input Allocation, to a value of "3" establishes the
Offset mode of operation.
Follower Engineering Units (CP-21)
The actual value of the Follower Engineering Units when the lead and
feedback are operating at their maximum speeds; i.e. Max RPM Lead
(CP-33) and Max RPM Feedback (CP-34). This entry is typically the
ratio of the maximum feedback RPM to the maximum lead RPM.
Max RPM Feedback (CP-34)
This is the maximum RPM of the feedback sensor shaft during system
operation.
PPR Feedback (CP-31)
The number of gear teeth or encoder lines on the feedback sensor per
revolution.
Max RPM Lead (CP-33)
This is the maximum RPM of the lead sensor shaft during system
operation.
PPR Lead (CP-30)
The number of gear teeth or encoder lines on the lead sensor per
revolution.
Offset Null (CP-75)
Offset Null is used to determine the analog input level where the offset
term is zero (has no influence).