8.5 Verifying Calibration
Calibration should be verified periodically depending on user requirements and system use. At a minimum, calibration should be verified monthly. Calibration should also be verified after the system has been serviced or moved. NIST-traceable calibration standards are available from Starrett including a line standard and a calibration grid. Refer to “ Spare Parts and Accessories” later in this document for ordering information. The following is a brief description of the steps recommended for the verification of your system.
Figure 30. X and Y Calibration Axes
8.5.1 Calibration Validation Procedure
To validate calibration, perform the following steps:
1. Place the calibrated standard along the X axis. Secure the standard to the stage with a holder (available from Starrett, part number 7430).
2. Skew the center of the two end circles of the calibration standard. Refer to the MetLogix M3 Video and FOV Inspection Software User’s Guide for proper alignment procedure.
3. Using the HDV system, measure the position of fiducials spaced every 25 millimeters. For each fiducial, take the average of multiple readings for improved accuracy.
4. Calculate the absolute measurement error for each fiducial by subtracting the calibrated position of the fiducial from the above average readings.
5. Verify that the calculated absolute X measurement errors are within the HDV system accuracy specification, which is E2 = 3.0 µm + L/33 mm.
6. Repeat for the Y axis.
7. Enter the absolute X and Y errors on an X-Y Axes Accuracy Validation Results Plot, as shown below.
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