Principle overview
Luo Weipeng colorimeter and iron cobalt colorimeter are two types of visual color measurement instruments widely used in the industrial field, and their design principles are based on the standard color scale comparison method, but there are significant differences in the specific implementation method and application standards. The Luo Weipeng colorimeter usually uses a set of calibrated red, yellow, and blue primary color filters with specific hues and saturations, and matches the sample color by superimposing different numbers of filters, and its numerical results are expressed in the number or length unit of each color sheet. Its theoretical basis is related to the principle of additive color mixing, and formulas are available Lobs = k · Σ (Ci · li) Approximate description of the observed color in relation to the filter combination, where: Ci represents the filter concentration coefficient,li for the use of length.
Iron-cobalt colorimeters rely on a pre-prepared standard color scale of inorganic salt solutions with gradually darkening colors, usually formulated with ferric chloride, cobalt chloride and hydrochloric acid in specific proportions. The user visually compares the liquid sample with these standard solutions under the same conditions to determine the closest color code. The method is based on the Lambert-Beale law, where the color depth of the solution is proportional to its concentration within a certain range, and the relationship can be simplified to: A = ε · c · l, among them A is absorbance,ε absorbance coefficient for molarity,c is the concentration,l It is the optical process.
Comparison
In terms of instrument structure, the Luo Weipeng colorimeter mainly includes a light source, an observation eyepiece, a sample cell and a set of sliding three-color primary filter sets. To do this, place the sample in the optical path and read the filter scale by increasing or decreasing the number of filters until the color on both sides of the field of view is the same. The whole process emphasizes the visual matching of the operator.
The structure of the iron-cobalt colorimeter is relatively simple, with a series of sealed glass tubes (colorimetric tubes) containing a standard color scale solution and a dedicated colorimetric frame. The operation process is to inject the sample into a colorimetric tube consistent with the specifications of the standard tube, place it side by side on the colorimetric rack, and perform vertical visual comparison under a standard light source or diffused sunlight to find the standard color number closest to the color depth of the sample.
| Compare items | Luo Wei Peng is a color scheme | Iron and cobalt color scheme |
| Core components | Filter sets, eyepieces, sample cells | Standard color scale solution tube, color cuvette |
| Output results | Red, yellow, and blue values | Single shade (e.g. 1-18) |
| Sample morphology | Transparent or translucent liquid, partial grease | Clarify clear liquid |
| Main operation | Adjust the filter to match the color | Sample compared to static standard tube |
| Standard dependence | Filter calibration values | Standard solution formulation specifications |
Applications:
Luo Wei Peng colorimeters are widely used in the color rating of vegetable oils, rosin, chemicals and beverages. Its methodology is often cited in many international and national standards to evaluate the color quality of products. The instrument has a strong ability to distinguish between yellow and red tones.
Iron-cobalt colorimeters have traditionally been used primarily for color determination of clear liquids such as varnishes, clear oils, solvents, and certain petroleum products. Its color scale standard is specified by many standard methods in the chemical field and is suitable for a series of evaluations of colors from light yellow to brownish-red, and the results are expressed as a single linear color number.
| Feature dimensions | Luo Wei Peng is a color scheme | Iron and cobalt color scheme |
| Color Scale System | 3D (Red, Yellow, Blue) | 1D (color depth) |
| Examples of applicable standards | Determination of oil and resin color | Coating and solvent colorimetric measurement method |
| requirements for operators | Color matching training required | Color level interpretation training is required |
| Long-term stability | The filter may be aging | Standard solutions may deteriorate |
Measurement characteristics and influencing factors are discussed
Both instruments belong to the visual colorimetric method, and the measurement results are significantly affected by the visual characteristics of the human eye, the observer's experience and the lighting conditions. The Luo Weipeng colorimeter controls the optical path through a mechanical structure, which reduces the error caused by sample cell differences, but the long-term optical stability of the filter needs to be checked regularly. The error of the iron-cobalt colorimeter mainly comes from the preparation accuracy of the standard solution, the storage stability and the optical consistency of the colorimetric tube. Ambient temperature can also have a perceptible effect on the color of the liquid sample and the hue of the standard solution.
In terms of reproducibility and reproducibility, both methods may exhibit a certain degree of discreteness in comparison between different laboratories. This highlights the need for strict adherence to standard operating procedures, uniform lighting conditions, and standardized training for operators.
Conclusion
Luo Weipeng colorimeter and iron cobalt colorimeter are classic visual colorimetric tools based on different physical standards and operating logic. The Luo Weipeng method can provide multi-dimensional color information, which is suitable for quality control scenarios that need to distinguish hues. The Iron Cobalt Rule provides intuitive linear color numbers with a long tradition in industry-specific product specification conformity inspections. The choice of instrument depends fundamentally on the nature of the sample to be tested, the dimension of the required color information, and the specific product standard to be followed. In practical applications, understanding the principle differences and limitations of the two is of clear significance to ensure the reliability and comparability of color evaluation results.