Delta CS24D - Manual (Page 23)

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With some sorting modes, a second criterion is used to further refine the performance. A limit to the
maximum Error, called the Error Limit, can be used to ensure that the colors match to within a set
tolerance.
The CS24D has the following Sorting Mode choices:
 Closest Color: One sort output would always be turned ON as the best-fit. Does not use the Error
Limit parameter or the No Match output (all outputs off). If needed, one or more “no object”
conditions could be trained as sort outputs so the sensor would not try to fit a background condition
into an object color output.
 Closest Match: The one best-fit sort output would be turned ON providing that Match Error was
lower that the Error Limit parameter, otherwise the sensor would show the No Match output (all
outputs off). More than one Sort output Error lower than the Error Limit parameter is permissible
in this mode, and the output with the lowest error will be considered a match.
 Unique Match: One sort output would be turned ON providing that only that one Sort output
Match Error was lower that the Error Limit parameter, otherwise the sensor would show the No
Match output (all outputs off). In this mode, more than one Sort output Error lower than the Error
Limit parameter would cause a No Match output.
The best choice of sort mode depends on the application. Closest Match is the default setting.
If Closest Match or Unique Match options are selected, the Error Limit parameter is used. This
allows you to specify a maximum permissible error before a color is considered a No Match. The
default value is 5,000 and the maximum value is 65,535. See Analyzing Colors below for information
on how to automatically determine a starting point for this parameter for your Teach data.
8.2 Color Only or Color Plus Intensity
The choice of Color Only or Color Plus Intensity modes depends on the target colors (the colors of
the objects that the CS24D will be working with). Colors such as red versus blue can be easily
distinguished from the color difference from the red, blue and green ratios. However, shades of the
same color (e.g. light red versus dark red) cannot be distinguished by the color information. The
intensity of the received light must be used. The CS24D uses the Intensity value to handle shades of the
same color.
In Color Only mode, differences in the Red/Intensity, Green/Intensity and Blue/Intensity ratios are
used to differentiate between colors and all three are rated equally. Since the CS24D is adjusted such
that the ratios track closely as the distance from the sensor to the target is varied, the ratios compensate
for changes in standoff distance. Ratios also help compensate for environmental effects that reduce
intensity such as dust, dirt, or scratches on the sensor window. Generally, if Color Only can be used to
sort a given set of Teach colors, this is the preferred mode.
In Color Plus Intensity mode, differences in the Intensity values are used along with the ratios to
differentiate between colors. This mode is required if any of the target colors are shades of the same
color. If this mode is used, an attempt should be made to a) minimize the sensor to target distance
variations, and b) prevent dust and dirt from accumulation on the sensor window.
In Color Plus Intensity mode, intensity is rated equally to red, green and blue. In other words, the
weighting factors are all equal to one. In the Color Only, the red, green, and blue weighting factors are
each set to 1.33 and the Intensity weighting factor is set to zero. See the next section for optimizing
weighting factors.