# Dot Spacing

In addition to specifying the origin, orientation, and handedness of the coordinate space, you can also use a set of specially-located extra dots on a grid-of-dots plate to specify the dot spacing. The tool defines four special locations, one in each quadrant of the plate, that define the plate's dot spacing. Each location may either be blank or have a dot. The four locations together are used to compose a 4-bit value.

The four bit positions are defined as follows:

- Bit 0: In the +X/+Y quadrant located with an X-position between the first and second grid dot in the +X direction and a Y-position between the first and second grid dot in the +Y direction.
- Bit 1: In the -X/+Y quadrant located with an X-position between the first and second grid dot in the -X direction and a Y-position between the first and second grid dot in the +Y direction.
- Bit 2: In the -X/-Y quadrant located with an X-position between the first and second grid dot in the -X direction and a Y-position between the first and second grid dot in the -Y direction.
- Bit 3: In the +X/-Y quadrant located with an X-position between the first and second grid dot in the +X direction and a Y-position between the first and second grid dot in the -Y direction.

For a plate with a right-handed coordinate system (the default for Cognex-supplied grid-of-dots plates), the bits are arranged in the counter-clockwise direction, as shown in the following figure:

The possible grid spacing values that can be expressed using this scheme are listed below:

Table 1. Grid spacing values

Value | Description
--- | ---
0 | No dots: grid pitch specified by user
1 | 20 millimeters
2 | 10 millimeters
3 | 5 millimeters
4 | 2 millimeters
5 | 1 millimeter
6 | 50 millimeters
7 | 100 millimeters
8 | 1.0 inch
9 | 0.5 inches
10 | 0.25 inches
11 | 0.125 inches
12 | 0.1 inches
13 | 2.0 inches
14 | 4.0 inches
15 | 12.0 inches

The spacing defined in the example shown above is 2.0 inches (1101 =13).

Note: If the tool detects these marks, it will overwrite any grid spacing value that you have entered or specified manually.