Sourcing optical rotary encoders from China

Duty and classification

Read from the UK Trade Tariff on 17 October 2026, the selected optical instrument, geometrical measurement and parts lines carried 0% duty from China. No anti-dumping or countervailing duty, or suspension, is recorded for these lines. Heading 9031 covers measuring and checking instruments not specified elsewhere, including optical instruments.

The table separates incremental and absolute encoders within the same optical instrument line; these are not separate tariff subdivisions. The supplied facts attach an import control of fluorinated greenhouse gases to the parts line. Confirm its requirement for the actual goods with your customs broker before declaring encoder parts.

Confirm the commodity code using the sensing method, function and whether the shipment contains complete encoders or parts. Do not select a code solely from the supplier's description. See measuring and inspection machines for the wider heading.

Specify the encoder and its interface

Specify incremental or absolute operation, resolution, angular accuracy, repeatability and maximum operating speed. For incremental units, define pulse counting, direction signals and the reference pulse. For absolute units, specify the communication protocol, position format and behaviour after power loss.

Agree supply voltage, output circuit, controller compatibility, connector pin assignments, cable screening and cable exit. Specify solid or hollow shaft, mounting dimensions, coupling, permissible shaft loading and the operating environment. Approve a sample on the intended controller before production.

Electrical and electronic equipment liable to generate electromagnetic disturbance falls within the electromagnetic compatibility regulations, subject to exceptions. Confirm how those rules apply to the supplied encoder and ask for model-specific supporting evidence.

Worked duty example

Illustrative example, not a quote: Illustrative order of optical rotary encoders for a machinery maintenance business under 9031 49 90 00, invoiced at £10,000 free on board, with £900 of freight and insurance to the UK. The customs value is £10,900. Duty at 0% is £0. Import VAT at 20% is charged on the customs value plus duty, £10,900, so it is £2,180. With no duty, the only import tax is the VAT, which a VAT-registered importer can usually reclaim. The import duty and VAT guide explains each step.

Inspection checklist

Identity and fit: compare model labels, shaft dimensions, mounting holes, connector and cable exit with the approved drawing.

Signal and position: rotate in both directions and check counts, reference position or absolute readings against the agreed test method.

Controller operation: test the specified supply and output interface on the intended controller, including restart and the agreed operating speed.

Condition and records: check shaft movement, cable strain relief, connector damage and packaging; retain results against batch identifiers. Use the inspection guide to agree acceptance checks.

What goes wrong

A matching housing can conceal an incompatible output circuit, connector assignment or communication protocol. Different pulse-counting conventions can give an apparent resolution mismatch. An absolute encoder may return position differently after power loss than the controller expects.

Shaft misalignment, coupling loads, damaged cables and contamination of the optical assembly can cause intermittent readings. Compare factory and arrival tests using the same controller settings and fixture. Record failures before fitting the encoders into production machinery.

Cambridge China Bridge sources these products for UK businesses, checking the factory and the documents before shipment. See factory verification. For components and parts, see sourcing for manufacturers.