Delta MMC120 - Manual (Page 130)

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NULL DRIVE
This field displays the amount of drive in millivolts that it takes to hold the ACTUAL
POSITION at the TARGET POSITION while at rest. Ideally this number should be zero
if the valve is perfectly nulled. This field is automatically updated toward the Integral
Drive when the ACTUAL POSITION is exactly equal to the COMMAND POSITION
and the speed is zero.
This field is only used in open loop mode. NULL DRIVE gets added to the drive output.
Why Bother?
The NULL DRIVE field can be used to null valves and drives. Usually there is a null or
offset adjustment on the valve or amplifier that can be adjusted so the NULL DRIVE is 0.
STEP
This field shows the current step the axis is executing of the 256 steps in the Event Step
Table. This is valid only when Event Control is being used. Use this field in conjunction
with the Link Value status word to monitor the progress of an axis through the step table.
LINK VALUE
This field is used only when the axis is using the Event Step Table. It represents the
current event step link value of the current step for the axis. The current step is displayed
in the STEP status word.
For delay link types (types ‘D’ and ‘d’), this field displays the number of delay units left
(in either counter ticks or milliseconds).
Appendix E: Event Step Link Reference
Link Types and Link Values
Link Type and Link Value specify the condition that causes the motion controller to
execute the next step in a sequence. These fields may be edited manually; however in
most cases it is easier to use the Popup Editor. Start the popup editor by pressing Enter
in, or double-clicking on, either the Link Type or Link Value field.
The Link Type and Link Value dialog box divides the link types into three categories:
• System-wide (Basic, non-axis dependent)
These link types allow the axis to wait on a global condition such as a time delay.
These link types are listed below; select a link type for further details: