Current Help System: PC-DMIS CMM (View Core Help)

#### Gage Scan Filter

To enable the gage scan filter, access the Circle Analog Scan Strategy available in the Measurement Strategy tab of the Auto Circle's Probe Toolbox and mark the Use Gage Scan Filter check box.

This filter corrects measured scan data by comparing it to similar scan data from a gage. This comparison reduces the amplitude of frequencies found in the measured scan data by gage amplitudes of the same frequency. This adjustment eliminates noise characteristics intrinsic to the measuring machine and probe, thereby providing more accurate measurements of the part.

Configuring the Filter

The gage scan filter is associated with the sensor tip data. You can use the single tip calibration command to associate scan data with the active tip. This filter applies to ring gages for inner circle scans; it also applies to ring gages and calibration spheres for outer circle scans.

1. Measure the gage at the desired point density using a Circle Basic Scan. If using a calibration sphere, be sure to carefully position the probe so that the circle scan takes place right on the equator.

2. Choose Insert | Calibrate | Single Tip to insert a single calibrate active tip command.

3. Reference the scan in the single tip command, by typing the scan ID into the calibrate active tip command, similar to this example:

SCN2 =BASICSCAN/CIRCLE,NUMBER OF HITS=2986,SHOW HITS=NO,SHOWALLPARAMS=YES

<-3.8456,-33.4523,0>,CutVec=0,0,1,IN

InitVec=1,0,0,DIAM=100,ANG=0,ANG=360,DEPTH=10,THICKNESS=0,PROBECOMP=YES,AVOIDANCE MOVE=NO,DISTANCE=0

FILTER/NULLFILTER,

EXEC MODE=FEATURE,USEHSSDAT=YES,USEDELAYPNTS=NO

BOUNDARY/

HITTYPE/VECTOR

NOMS MODE=MASTER

ENDSCAN

CALIBRATE ACTIVE TIP WITH FEAT_ID=SCN2

3. If desired, you can also reference both the inner and outer circle scans by adding another calibrate active tip command, like this:

CALIBRATE ACTIVE TIP WITH FEAT_ID=SCN2 (SCN2 is the inner circle scan)

CALIBRATE ACTIVE TIP WITH FEAT_ID=SCN3 (SCN3 is the outer circle scan)

Your tip data stores the gage scan inside the probe file (.PRB file). This means, once the tip has been associated with the gage scan data, the saved program and the probe file can be included in part programs that need to use the gage scan filter as well.

Improving Accuracy

- When scanning the gage artifact, the theoretical gage location should match the actual gage location. Any deviation between the two will introduce a frequency proportional to the positional offset. This will negatively impact the results.

- The point density (sample frequency) used to measure the feature should be as close as possible to the point density used to measure the gage. Since the gage scan filter is applied in the frequency domain, achieving greater similarity between the gage's point density compared to the feature scan's point density, will result in more effective correction.

- Your filter results will also improve the closer feature's size is to the ring gage's size.