In part 2 of this guide we will focus on selecting right lenses, digital readouts and additional options and accessories for optical comparators.
When selecting proper lens follow the chart below to decide what lens will match the tolerances required. A basic rule of thumb is that
a typical attentive operator can repeatedly discriminate .004″ on the comparator screen. Dividing the “discernible resolution” by the lens magnification determines the minimum resolution attainable for each lens.
| 5X | .0008″ (0.020mm) |
| 10X | .0004″ (0.010mm) |
| 20X | .0002″ (0.005mm) |
| 25X | .00016″ (0.004mm) |
| 31.25X | .0001″ (0.003mm) |
| 50X | .00008″ (0.002mm) |
| 62.5X | .00006″ (0.0016mm) |
| 100X | .00004″ (0.001mm) |
| 200X | .00002″ (0.0005mm) |
| 500X | .000008″ (0.0003mm) |
Another thing to consider when selection optical comparator is digital readout. Select a basic XY digital readout if only positions and distances are required. If measurement of circles, angles, and parametric distance is required, then select a readout with geometric capability. Repetitive part measurement may encourage the selection of a CNC capable readout. Automatic edge sensing should be considered to eliminate operator subjectivity and increase repeatability and accuracy.
Additional options are available when choosing optical comparator. Repeatability and accuracy will suffer if the workpiece is not properly and securely held. Careful consideration should be given to tooling and to the surface on which you place your optical comparator.
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