Delta CS64A - Manual (Page 18)

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1602 Ultra-flat black. Some materials and finishes may provide acceptable performance
without painting. They may not be obvious, however black anodized aluminum reflects
in the near-infrared spectrum, for example, and should not be used without painting. The
CS64A can be used to test materials—look for very low readings on all four outputs. A
slot is a good way to eliminate ambient light, and soft weather-stripping or brush can be
used to seal the bottom if required.
Q. What is the minimum size that I can make the slot that the CS64A looks through?
A. If space is tight, you can reduce the slot to about 5/8 x 3 inches providing the sensor
is centered well. A better solution might be to angle the sides of the hole so the dimension
closest to the sensor is 3/4 by 3 1/2 inches and tapers down to about 1/2 x 2 inches.
Q. Can I use the CS64A pointing up?
A. The CS64A can be mounted in any orientation. With the sensor pointing up, it is
important to watch dust build-up on the sensing window. Using ratios dramatically
reduces the sensitivity to dust and other environmental factors.
Q. How often should the calibration be checked?
A. As with all similar instruments, the calibration of the CS64A should be checked
periodically. The CS64A uses special compensation circuitry to greatly reduce the time
and temperature drift inherent with the LEDs. The required frequency of recalibration
depends on the required precision, and could be as often as once a week, or as infrequent
as once a quarter or more. It is generally most convenient to do the calibration in
software in the host system, in which case it can be highly automated if desired.
Q. Is it necessary to use a special material to verify calibration of the CS64A?
A. No. As explained in the CS64A manual, the user can use virtually any stable material
as a calibration standard. The CS64A is factory calibrated to read Spectralon (>99%
diffuse reflective over the visible and NIR range) as 9.50V volts at 1.75" standoff
distance. If you wish to maintain the factory calibration, Spectralon is available from
Labsphere (www.labshpere.com). They sell this material in a convenient 2" diameter
disk: SRS-99-020 99% 2.38D x 0.60H. If you place this disk 1.75" from the bottom of
the sensor, block out all ambient light, and adjust all four outputs to 9.5V, you will
duplicate factory calibration. (You can adjust either at the sensor or through software).
Q. If a color sensor is disconnected and not used for a several months and then
reconnected and powered will it require calibration?
A. It should not change significantly over time just sitting on the shelf if it is protected
from dirt, etc. However, we would recommend recalibrating until it can be verified that it
is not necessary in your application. Thanks to the feedback compensation, the CS64A
stabilizes within a few minutes of powering on.
Q. I left a demo unit running overnight and am getting slightly different readings. Why
is this?
A. Our demo units probably do not meet the specifications for temperature and time
drift. On demo units, we verify basic functionality and recalibrate before shipping, but we
do not check drift. Production units have low temperature and time drift. Although all
LEDs experience intensity changes with both temperature and time, the CS64A uses
special circuitry to dramatically reduce this variation. If all readings are going down, this
could also be due to dust on the sensing window or an increase in distance from sensor to
target material. Using ratios automatically compensate for these changes. Although any