Rockwell Automation GV3000/SE AC Gen. Purpose & Vector Bookshelf Drive Start-Up and Reference Manual User Manual
Page 211
Using the Terminal Strip Analog Input
G-3
Figure G.2 illustrates how the analog signal is scaled internally by the drive when it is
used as the speed or trim reference. The solid line indicates the conversion when the
non-inverted state is selected (P.011 is even). The dashed line indicates the
conversion when the inverted state is selected (P.011 is odd).
G.2.1 Adjusting for External Signal Errors Using the Offset and Gain
Parameters
When the analog input is used for speed or trim reference, parameters P.009 (Terminal
Strip Analog Input Offset) and P.010 (Terminal Strip Analog Input Gain) can be used to
compensate for any offset or gain errors in the external circuitry.
The value in P.009 is first added to the converted 10-bit value and then the gain is
applied. If an offset or gain adjustment is needed, the offset should be adjusted first,
with the minimum input applied, and the gain adjusted last, with the maximum input
applied.
To remove a positive external offset, enter a negative value into P.009. In most cases,
the offset is left at the default value of zero and is only adjusted to counteract external
circuitry errors.
The adjustment range for P.009 is -900 to +900. For 0 to 10V (or -10V to +10V input) a
value of +1 equals an offset of approximately 10 mV. For 0 to 20 mA input, a value of
+1 equals an offset of approximately 20
µ
A.
Figure G.2 – Analog Input Conversion Scaling (Speed or Trim Reference)
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+20 ma
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Terminal Strip Analog Input
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