User Manual V 1-4.XX User guide

Setting Up the Input/Output 7-5
To get to the desired range of ±4096 (4096 = base motor speed), you
need to scale the internal drive units by 4 (4 x 1024 = 4096).
Figure 7.3 shows an example of the offset and scale values for an
analog input parameter.
Figure 7.3
Example of Offset and Scale for Analog Inputs
To summarize, to determine the offset and scale values for your
analog inputs, you need to:
1. Compare the output range to the internal drive unit range. In the
example shown in Figure 7.3, you would compare the ranges
represented by A and B.
In the example shown in Figure 7.3, the ranges were different, so
we used Step 2.
2. Calculate the offset. For example, if you need a 0 to +10V input
and you have a ±4096 internal range, offset the 0 to +10V range
to get a ± range. In this case, an offset of -5 works because
subtracting 5 from both 0 and 10 gives you a -5 to +5 range.
3. Convert the analog input range to a digital range based on 10V
being equal to 2048. For example:
Analog
Input
Offset Scale
+10
0
+5
–5
+1024
–1024
+4096
–4096
4–50 0 0
Analog to
Digital
Converter
± 5 =
± 1024
Drive Output
Range of the analog
input after the offset
is applied
Range of the analog
input in internal
drive units
0 to +10V pot
A C B
By subtracting 5 from
both 0 and +10, you get
a
± 5 range.
By multiplying
± 1024 by 4,
you get the
± 4096 range
you were looking for.
If the ranges are: Then you: Go to:
The same (that is, both ±,
both 0 to +n, or both 0 to -n)
Do not need an offset Step 3
Different Need an offset Step 2
This analog value: Is converted to this digital value:
+10 +2048
+5 +1024
00
-5 -1024
-10 -2048