GST classification of analytical and measuring instruments determines taxable treatment under the Schedule three goods listing. Instruments and apparatus for physical or chemical analysis and devices for measuring or checking viscosity, porosity, expansion, surface tension, quantities of heat, sound or light, including polarimeters, refractometers, spectrometers, gas or smoke analysis apparatus, exposure meters and microtomes, are classified as Schedule 3 goods and attract the specified GST rate for the stated period.