How to calibrate Spectrophotometer s and Colorimeters?

Calibration of Colorimeters and Spectrophotometer s determines the relationship between measured values of color coordinates and the corresponding values of these coordinates under specific conditions and compares them with standards with national and international metrological traceability.

The difference between the value measured by the device and the certified value of the reference standard used is called the calibration. Thus, the result of calibration is the correction and its expanded uncertainty (U). Uncertainty includes all sources or contributions of error affecting the calibration.

What do Lab*, Yxy, ΔE* calibrate?

It is necessary to calibrate those coordinates that are commonly used, as this is one way to understand equipment corrections that affect measurements. Regardless of the coordinates chosen, after calibration, each of them will be corrected for a different color pattern. This correction is what the technician in charge of making measurements with the equipment needs to apply to his measurements.

The table below shows an example of a Spectrophotometer calibration result for a standard:

In the case of Colorimeters, very high color coordinate corrections are sometimes obtained. However, the same device, calibrated in ΔE*, gave very good results.

Next, we show the results of the Colorimeter. Results are displayed as Lab* color coordinates and ΔE* parameters.

Although the color difference results apply only to the Colorimeter, it is important to emphasize that it applies equally to the calibration of the Spectrophotometer . In fact, if the company usually measures the color difference ΔE*, no matter whether the equipment is a color difference meter or a Spectrophotometer , it should be calibrated in this parameter.

The following example shows a color difference measurement between a standard and a sample. The indicated ΔE* corresponds to the value given directly by the device. The correction value is the value supplied by the device plus the correction value obtained during its calibration, which appears on the calibration certificate.