Scale/Offset Wizard: Rotary

To access the Scale/Offset wizard:
In Axis Tools, in the Axes Parameters Pane, click the Setup tab. Expand the Tools and Wizards section. Click Launch to open the Scale/Offset Wizard.

The Rotary pages of the Scale/Offset wizard apply only to axes with rotary feedback. The Rotary pages of the wizard describe rotary scale and offset and ask the user to enter information used to calculate the Scale and Offset values.

Page 1 of Rotary Scale/Offset Wizard

1. Desired Position Units

Enter the desired units for the axis. These will be displayed in Axis Tools.

2. Unwind Values

Enter the Position Unwind value and the Count Unwind value. If the axis is configured as Absolute, the Count Unwind must be a power of 2, such as 1024, 2048, 8192, etc.

The Position Unwind value specifies the span of position units for the axis the axis. For example if it is 360, the axis will span 360 position units.

The Count Unwind specifies the number of counts over which the position units will span. For example, if the Position Unwind is 360, and Count Unwind is 2048, the positions will span 360 position units across the 0-2048 counts range. Typically, the Counts Unwind is set the number of counts in one machine (motor, belt, etc.) revolution.

3. Position Unit Range

In step 1, the Position Unwind specified the span of position units. This step asks you to specify the actual range of that span. For example, with a Position Unwind of 360, perhaps you want the range to go from 0 to 360, or -180 to 180. Or, you can specify a custom range. Notice that the range will always span the number of position units specified by the Position Unwind value.

4. Increasing Counts Equal...

This section ensures that the Actual Position changes in the correct direction as you move the axis.

To determine which option to choose:

Move the axis to a location where you want the Actual Position to be small. Note the value of the Counts at this location.
Move the axis to a location where you want the Actual Position to be large. Note the value of the Counts at this location.
If the Counts in step b are larger than the Counts in step a, choose ...increasing position units. If the Counts in step b are less than the Counts in step a, choose ...decreasing position units.

Page 2 of Rotary Scale/Offset Wizard

If the axis is configured as a Rotary Absolute SSI or Resolver, the wizard will contain a second Rotary page for setting the Count Offset.

Count Offset

The Count Offset is important for absolute rotary SSI and Resolver. When the encoder is mounted on the machine, the position at which the encoder gives 0 Counts may not be exactly at the desired position. Instead of having to physically remount the encoder, the Count Offset can be used to adjust the zero counts position.

Example

Consider a rotary axis with a single-turn encoder with a Position Unwind value of 360 and a Position Offset of 0. Therefore, the position range extends from 0 up to, but not including, 360. At zero counts, the position will be 0. The encoder happens to be mounted such that the zero counts is to the right, but the user wants zero counts to be at the top.

To set the Count Offset, the user rotates the encoder so that it is at the top, then on this page of the Sale/Offset wizard, clicks Calculate Count Offset, enters "0" in the position units box and clicks Use Current Value to put the current Counts into the counts box.