What Is an Inter-Instrument Agreement?

Inter-instrument agreement refers to how similar two or more spectrophotometers’ measurements are when reading the same color. A close inter-instrument agreement (IIA) signals your instruments are reliable and produce replicable results, while a poor IIA indicates your instruments are not uniform across your supply chain. 

IIA has limited useability if you’re only operating one spectrophotometer, but it’s vital if you have many instruments operating in your supply chain. Keep your color measurement instruments consistent by ensuring proper inter-instrument agreement across your chain of equipment.

Why Is Inter-Instrument Agreement Important?

Inter-instrument agreement is essential for ensuring the uniformity of products, test samples and scientific readings across your facilities and supply chain. Without IIA, there is no way to ensure color quality across test samples. Significant inter-instrument agreement also reduces the need for new batches due to color errors and helps you save money in the long run. 

Inter-instrument agreement helps you achieve the necessary numerical tolerances for acceptable color differences, known as Delta E tolerances. Delta E tolerances minimize color inconsistencies across a global supply chain by referring to colors using standardized numerical values. 

Every spectrophotometer comes with specs that tell you the Delta E tolerance of your equipment. The smaller your equipment’s Delta E tolerance, the higher your rate of inter-instrument agreement. This factor allows you to streamline your global color operation by ensuring color quality at a universal scale. 

How to Determine Inter-Instrument Agreement

Instrument manufacturers usually determine inter-instrument agreements during the quality assurance process. In this procedure, the manufacturer compares the instrument for analysis against the average spectrophotometer. This step is achieved in a test that uses 12 BRCA tiles as a control standard, including an additional white and black tile. 

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After the color difference for each tile is calculated, the instrument’s DEs are averaged across all tiles to achieve the inter-instrument agreement number. Your spectrophotometer should include a manufacturer-published specification outlining your device’s DE and inter-instrument agreement. 

You can also compare your spectrophotometry instruments to your supply chain or another supplier by holding a controlled test for stable color standards. The BRCA tileset or another form of diagnostic tilesets is the best way to do this, as they are the most stable and durable materials for testing color. Always ensure your tilesets are tested under controlled conditions for humidity, temperature, ultraviolet (UV) components, aperture size and lenses. Your instrument will produce two DE readings for your target and master instrument.

Purchase Spectrophotometers From HunterLab

At HunterLab, we assure your product quality so you can have confidence in everything you do and uphold your reputation. Each of our spectrophotometers comes with accurate color measurement instrument agreement analysis — you can rest assured our products are calibrated to the highest degree of quality. Whether you work in food processing, health research, construction, fashion or another sector, we can help you ensure your products’ appearance with precision and consistency. 

Contact us online today to learn more about our spectrophotometry solutions and what we can do for your business.