It is often necessary to measure points on a part at precise locations. Proximity Triggers is a special utility for this purpose. It places an instrument in a continuous scan mode and triggers a measurement when a probe reaches a specified proximity to a nominal point or vector.
Proximity Triggers asks for a reference point group (or vector group) as an input and then offers a configuration dialog which allows you to define the proximity tolerance settings and output options.
Group to contain measurements. This is the name of the resulting measured point group.
Make Vectors while Measuring. This option allows you to built point to nominal point vectors as part of the measurement process.
With vectors as the nominal target, the analysis is a little different. The vectors that are built are still computed using the point to nominal point (vector origin) distance, but are computed along the vector axis direction only. This gives the appearance of a point to surface analysis, but the vectors are returned at the measured point location. Check the Project results to nominal vector check box to return the vectors at the nominal point position instead. This is not the default because they are often obscured by the nominal guide vectors.
Project result to nominal vector. This option ensures that only differences in vertical displacement are displayed by the vectors, not the displacement of the measured point within the tolerance zone.
Point Distance Threshold. Defines the maximum distance from the nominal point at which a point will be triggered (remember that this is point to point and does not consider point offsets, so surface points may need to be compensated).
Vector axis threshold. This option is only applicable to vector triggers but offers the ability to resolve the distance relative to an axis in addition to the nominal point location. This allows the trigger zone to be defined as a cylinder rather than a simple spherical zone.
Tone ramp start zone.The drive tone is an audible indicator of how close you are to the point. You can adjust the starting location where the noise begins with this control.
Once the mode is initiated, a set of bull’s-eyes are added to the graphics to identify the nominal targets that have not yet been measured. The Proximity Triggers control dialog is broken into two sections:
The top section lists the points to be measured as well as offers measurement controls
Watch Window display offers easy access to a Point to Closest Point Watch Window
Graphical Guide offers a means to display a 2D indicator of position relative the reference points.
The lower half reports the results of the measurement process including the name of each measured point and the error (or distance from the measured to nominal point location).
The points can then be measured in any order and the Measure each point only once check box can be used to determine if only a single measurement is capture or if multiple observations are recorded as the probe gets closer and closer to the nominal within the tolerance zone.
You can use vectors to trigger your measurements rather than the points. Doing so allows you to trigger measurements when you get within a proximity to the vector axis, eliminating any issues with get- ting close enough to the points you want to measure. The proximity trigger zone for vectors is defined as cylindrical zone with a length equal to the point distance threshold and the width equal to the Vector axis threshold. This fine control of both the width and height of the trigger allows the user to precisely trigger points even in tight regions or slots between adjacent CAD surfaces.
Once the routine starts. Run a probe over the part and it will automatically trigger measurements for specific locations every time the probe get within the trigger distance threshold. It will keeping track for you of what points have been measured and which still need to be taken. Once the majority of the points have been measured you can bring up a Graphical Guide or watch window that will help you navigate precisely to the remaining locations, finishing a precise grid measurement of a part.
Proximity Measured Points in progress