Subjective color measurement
More complex, but more reliable, are optical devices in which one looks at the test object with one eye and the reference object with the other , similar to a stereo microscope . Such devices have been in use since 1850. Either fixed color normal , changeable reference objects such as B. Color wedges (Pulfrich photometer, according to Carl Pulfrich ) or colored liquids with variable thickness (immersion colorimeter).
Objective color measurement
The objective color measurement is usually done with a spectral analysis . To do this, the incident light is broken down into different spectral ranges and their intensity distribution is examined. Today's devices are not limited to visible light , but can also carry out measurements in infrared or ultraviolet light for special tasks.
Colorimeters are used e.g. B. to
- Determination of star colors (earlier)
- Calibration of color monitors
- Analysis of biological substances (e.g. blood sugar or urine )
- Analysis of chemical substances: With this measuring system, practically all chemical analysis methods in the laboratory that use a colorimetric method are also suitable for quantitative and automated substance analysis. Many different measuring devices have been developed for this purpose and are used with success in practice. Water and wastewater technology are cited as an example . Here, the carbonate hardness , total hardness , silica (SiO 2 ) and the phosphate content in the water are often monitored with such measuring devices.
- The continuous determination and control of values with such measuring devices is particularly necessary in fully automatic chemical plants. For example, constant control of the silica concentration for the fully demineralized water (e.g. feed water , boiler water, condensate and steam / after condensation) in high pressure power plants is important.