Delta CS64A User Manual download pdf (Page 14)

7.2 Edge Effects

The CS64A-00 sees an area of about 0.35 x 0.35 inches. When material is entering or

leaving the sensing area, the color can appear wrong for a variety of static and dynamic

conditions. For best results, read the analog outputs and compute the color only when the

CS64A sees the intended material over the entire viewing area.

7.3 Angle of CS64A to Material

The most consistent readings are obtained if the material is perpendicular to the CS64A

in both planes. If angle differences cannot be avoided, it is preferable to have the angle

the narrow way and the standoff at the longer end of the recommended range (2 inches

for CS64A-00). In some cases when dealing with shiny materials, angling the sensor

slightly with respect to the target may produce more consistent readings. Concave

surfaces should be avoided if possible.

7.4 Distance Performance

The amplitudes of the signals reach the maximum value close to the CS64A (about 1.5"

for CS64A-00) and then decrease with distance. The ratios of Red/NIR, Green/NIR and

Blue/NIR are adjusted to be constant within the specified tolerance over the specified

working range of the sensor. As the sample is moved further from the CS64A, the ratios

will gradually become less consistent. This effect, along with the decrease in signal

amplitude, limits the usable range of the CS64A. In applications where the differences in

samples are large, the CS64A-00 may work well out to 3" or more.

7.5 General Information

The term "color" actually implies visible light--wavelengths from about 400nm (violet) to

about 750nm (deep red), although in this document any wavelength that can be seen by

the CS64A is referred to as a color.

With high intensity blue LEDs (450nm) and several visible wavelengths up to 700nm

available, DELTA's sensors can be made to see practically the entire visible color

spectrum. But the capability does not stop there; the precision photodiode in the sensors

can see into the near infrared up to about 1,000nm, and LEDs are readily available in this

region as well.

NIR LEDs are used in the CS64A-00 and similar general purpose color sensors to

provide a baseline value that is relatively constant for a given type of material regardless

of color. This "divisor color" compensates for distance variations.

The NIR spectrum can be valuable in special applications. For example, the ratio of two

different NIR colors can be used to detect certain types of glue, while ignoring visible

color variations. Contact Delta for more information on these applications.

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Delta CS64A User Manual Page 14