Delta CS64A - Manual (Page 15)

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8. Recalibration
The LEDs have a typical operating life of 100,000 hours or about 10 years of continuous
operation.
The intensity of LEDs varies with temperature and aging due to the properties of the
semiconductor materials used. The CS64A sensors use feedback circuitry to maintain
amplitudes over a wide range of temperature and to compensate for LED aging.
The automatic compensation will not eliminate 100% of the variation, so calibration
should be checked regularly. The recalibration period depends on the application. In
many cases, every three to six months or more may suffice, while in very critical
applications, it may be necessary to check every week or every shift.
To check, place the calibration material in the sensing area at the typical sensing distance
and monitor the outputs with a voltmeter or your data acquisition system.
Typically, if any change is needed, you will only need to change one or two gains
slightly. (See Adjustments section for details). If other adjustments seem to be needed,
make certain that you have the proper calibration material and the sensor window and
sensing area are clean before adjusting.
Unless you are using narrow thresholds on the NIR amplitudes, we do not recommend
readjusting all outputs to compensate for small variations in amplitude. Calculate the
ratios, and adjust only to compensate for intensity degradations that affect the ratios.
If practical, we recommend that either a provision be made for adjusting the gains in
software, or that gain adjustment capabilities be built into the analog circuitry to which
the CS64A is connected. The gain adjust pots on the CS64A can be used if no other
adjustment point is available.
9. Maintenance
Cleaning: Under normal conditions, the CS64A requires little or no maintenance other
than keeping the window and sensing area clean. Use only water and cleaning materials
compatible with polycarbonate, such as isopropyl alcohol.
In dusty conditions, an automated air nozzle can be used to help keep the window clean.
The ratio calculations will compensate for signal strength degradation down to about 75%
of normal signal. Beyond that, performance will start to suffer. Once the window and
viewing area are cleaned, the ratio calculations will automatically readjust to the clean
conditions.
If the window becomes scratched or damaged, it should be replaced. Order from Delta:
Part No: CS64A-Window.