On the toolbar on the left, click the Sensors tab.
On the Sensors pane, click the Surface Area Sensor button.
In the graphics window, select the surface you want to monitor with a sensor.
On the Surface Area Sensor command bar, click the Accept (checkmark) button.
In the Surface Area Sensor Parameters dialog box, define the sensor parameters, then click OK.
The sensor is displayed on the Sensors pane.
Tip:
You can use the options on the command bar to specify whether you want to create a positive area sensor or a negative area sensor. A negative area sensor monitors the holes or internal boundaries in a surface.