9030.90 - Parts and accessories:

This HTS category, 9030.90, specifically covers **parts and accessories** for the instruments and apparatus described in heading 9030. This includes components, attachments, and replacement parts that are essential for the operation or maintenance of oscilloscopes, spectrum analyzers, and other instruments used for measuring or checking electrical quantities, as well as those for measuring or detecting ionizing radiations. The classification as "parts and accessories" is determined by whether the item is designed for use with a specific instrument or apparatus of heading 9030 and is not a standalone functional device itself.

Distinguishing 9030.90 from its sibling categories is crucial. While siblings like 9030.10.00.00 cover instruments for detecting ionizing radiations and other subheadings address specific types of measuring instruments (e.g., oscilloscopes, telecommunications equipment), this category is solely for the components and add-ons that facilitate their function. Therefore, a probe for an oscilloscope, a display screen for a spectrum analyzer, or a radiation detector head designed to be used with an ionizing radiation measuring instrument would fall under 9030.90, rather than being classified as a complete instrument.

The subcategories within 9030.90 further refine the classification based on the parent instrument they are intended for. For instance, "For articles of subheading 9030.10" indicates parts and accessories specifically designed for instruments that measure or detect ionizing radiations. Conversely, "Other" would encompass parts and accessories for the remaining instruments under heading 9030, such as oscilloscopes and electrical quantity measuring devices not covered by specific subheadings. This granular approach ensures accurate tariff assignment based on the ultimate application of the part or accessory.