This classification covers specialized analytical and measurement instruments other than spectrophotometers, chromatography, and mass spectrometers. It includes physical property measurement instruments such as viscometers, densitometers, melting point apparatus, surface tension meters, particle size distribution analyzers, thermal analysis equipment, electrochemical measuring instruments, and optical measuring devices, as well as equipment used for specialized analytical methods. This group of instruments is used for measuring physical and mechanical properties other than chemical analysis in quality control, research and development, and material evaluation.