# Options on the Y-Axis tab of the Trend Object Properties dialog box

The following table shows the options on the Y-Axis tab of the Trend Object Properties dialog box.

Options | Descriptions
--- | ---
Automatic (best fit based on actual data) | Select this option to use the lowest data reading serves as the minimum value and the highest data reading as the maximum value. As the trend acquires new data, the y-axis may re-scale to fit.
Preset (use min/max setting from Pens tab) | Select this option to show the lowest and highest minimum and maximum tag values, configured on the Pens tab, as the y-axis scale. As the chart acquires new data, the y-axis does not re-scale. Which pen's tags are used depends on the Scale options specified on the Y-Axis tab.
Custom | Select this option to specify the minimum and maximum values to use as the y-axis scale.
Minimum value and Maximum value | Actual minimum/maximum value - Select this option to specify an unchanging value as the actual minimum or maximum value on the y-axis scale. Controlled by tag - Select this option to use a tag or expression value as the minimum or maximum value on the y-axis scale. If you assigned Minimum or Maximum tags or expressions on the Connections tab, the name of the tag is shown here.
Isolated graphing | Select this check box to place each pen in a separate band of the chart. Clear this check box to allow pens to overlap. In isolated graphing, major and minor grid lines are not shown for the Y-Axis. Instead, a horizontal line appears above each band. % isolation - Specifies the distance between bands when using isolated graphing. The available range is 0%-10% of the chart height.
Display scale | Select this check box to show y-axis labels on the left side of the chart. To provide accurate data, the Trend object shows the numbers as decimals, even if Octal or Hexadecimal is selected as the Chart Radix on the Display tab. Decimal places - Specifies the number of decimal places included on the y-axis legend. The available values are 0-8. If the number of decimal places is set to anything other than zero, numbers cannot be accurately converted to octal or hexadecimal.
Display grid lines | Select this check box to show horizontal grid lines on the chart. If Isolated graphing is selected, this option is disabled. Grid lines - Specifies how many lines to show. The available values are 0-30. Minor grid lines - Specifies whether to show minor horizontal grid lines on the chart, and how many lines to show. These lines appear between the major grid lines and do not have axis values shown. The available values are 0-10. Grid color - Specifies the color of the horizontal grid lines. If you selected Isolated graphing, this color is used for the horizontal lines between bands.
Scale options | Specifies how multiple pens with different minimum and maximum ranges scale together on a chart.
All pens on same scale | Shows all the pens relative to the same scale. The minimum scale value is the lowest minimum value of all pens. The maximum scale value is the highest maximum value of all pens.
Each pen on independent scale | Scales each pen independently using the pen's minimum and maximum values as the range. Only one pen's range is used in the labels on the vertical axis, which can be misleading of other pens use a different range. To allow the operator to view each pen's vertical axis labels, create a Next Pen button. When the operator presses the button, the vertical axis changes to the new pen's range. The color for the labels changes to the color for the selected pen.
Scale using pen | Uses the same scale for all pens on the chart, based on the minimum and maximum values configured for the specified pen, or based on the best fit for the pen's actual data. Select the pen to use. If you selected the Preset (use min/max setting from Pens tab) option, configure minimum and maximum values on the Pens tab.
Scale as percentage | Shows y-axis values as a percentage of the minimum and maximum range. The y-axis labels show the percentage range from 0 to 100%.

## See also

Set up the vertical axis for the trend