Sourcing turbidity controllers from China

Duty on controllers and associated equipment

Heading 9032 covers automatic regulating or controlling instruments and apparatus. Specify whether the turbidity product compares a measurement with a set point and automatically operates a pump, valve or other output. A display-only instrument needs a separate classification check. The table includes associated equipment imported separately, rather than alternative codes for the same controller. See the wider turbidity meter guide.

Read from the UK Trade Tariff on 1 October 2026, other automatic controllers and parts carried 2% duty from China, while hydraulic or pneumatic regulating instruments carried 0%. The digital valve controller line carries 2% with a conditional 0% autonomous suspension; its footnote excludes mixtures, preparations or products made up of different components containing these products. The controller and parts lines have no suspension. These selected lines show no anti-dumping or countervailing duty.

The UK Trade Tariff attaches an import control of fluorinated greenhouse gases to each selected line. Confirm the applicable requirement with your customs broker using the actual equipment specification. The digital valve controller line also lists supplementary unit import; confirm the declaration quantity with your broker. Confirm the commodity code from the supplied assembly, operating function and separately shipped accessories.

Specify the turbidity control loop

Agree the measuring range, displayed units, accuracy, repeatability, response time and calibration method. Identify the compatible probe, cable length, flow-cell arrangement, wetted materials and cleaning method. Define set points, switching differential, alarm delays and whether rising turbidity starts dosing, diverts flow or stops the process.

Specify supply voltage, output type, relay load, enclosure protection and behaviour after probe failure or a power interruption. Ask for a demonstration using the proposed probe and a representative process sample, with the pump or valve connected. Record the accepted settings and firmware in the purchase specification.

For Great Britain, confirm electrical safety evidence requirements for mains-powered models with the relevant authority. Electromagnetic compatibility rules cover electronic equipment liable to generate electromagnetic disturbance, subject to exceptions. Where hazardous-substance restrictions apply, manufacturers must produce and maintain technical documentation demonstrating compliance. Ask for model-specific reports, a declaration of conformity and applicable CE or UKCA evidence through testing and certification.

Worked duty example

Illustrative example, not a quote: 50 automatic turbidity controllers, illustrative order under 9032 89 00 90, invoiced at £10,000 free on board, with £900 of freight and insurance to the UK. The customs value is £10,900. Duty at 2% is £218. Import VAT at 20% is charged on the customs value plus duty, £11,118, so it is £2,223.60. Import taxes total £2,441.60; a VAT-registered importer can usually reclaim the VAT, so the lasting cost is the £218 of duty. The import duty and VAT guide explains each step.

Inspection checklist

Measurement: compare readings with an agreed reference across the working range, check repeatability and record drift after cleaning and recalibration.

Control action: vary sample turbidity across the set point and confirm output direction, switching differential, alarm delay and operation under the intended load.

Fault response: disconnect the probe, interrupt power and restore it. Check the agreed safe output, alarm indication and retention of settings.

Assembly and documents: check probe identity, terminals, seals, cable entries, labels and English instructions against the approved sample. Match reports to the supplied model and record results during quality inspection.

What goes wrong

Bubbles, deposits on the optical surface and changes in sample colour can distort readings. A controller may appear stable in a clean demonstration sample but switch repeatedly in the buyer's process. Test the sampling arrangement and cleaning procedure alongside the electronics.

A matching connector does not prove probe compatibility. Incorrect output scaling, reversed control action or unsuitable relay loads can cause dosing or diversion errors. Agree the complete probe-and-controller combination and test fault recovery before approving production.

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.