User Manual V 1-4.XX User guide

7-8 Setting Up the Input/Output
4. Convert the digital output range to an analog range. For example:
5. Compare the input to the digital-to-analog conversion (C) with
the internal drive units (B).
In Figure 7.5, the values were different so we used Step 6.
6. Calculate the scale. For example, if the input to the digital to
analog conversion is ±1024 and the internal drive units are ±4096,
the scale value should be 4 (4 x 1024 = 4096).
7. Take the inverse of the value you calculated in Step 6. For
example, if the scale value should be 4, you need to actually use
1/4, or 0.25 as your scale value.
8. Enter the offset and scale values into the appropriate parameters.
Setting Up the 4 – 20 mA
Input/Output
When setting up the 4 – 20 mA input/output, you should keep the
following in mind:
• 4 – 20 mA I/O is not bi-directional.
• 4 – 20 mA faults occur when the 4 – 20 mA input is connected to
a current source and then removed. This trip point is -250 drive
units or 0.45 mA.
• The maximum number of drives on the mA output is 3.
• The 4 – 20 mA output can drive a maximum load of 750Ω.
When setting up your 4 – 20 mA input/output, you need to know that
4 mA is equal to 0 internal units and 20 mA is equal to 2048 internal
units.
The scaling and offset parameters for 4 – 20 mA input/output work
similarly to the analog scaling and offset parameters. Figure 7.6
shows an example of the scaling and offset used for the 4 – 20 mA
input.
This digital value: Is converted to this analog value:
+2048 +10
+1024 +5
00
-1024 -5
-2048 -10
If the values are: Then you: Go to:
Identical Do not need to scale the value Step 8
Different Need to scale the value Step 6