Verify certifications, not just logos
Many websites display ISO 9001, CE, and ATEX logos without holding current certificates. Ask for the certificate number, issuing body, and validity date, then verify directly with the issuer. SGS, TÜV Rheinland, DEKRA, and Intertek all provide online or email verification of certificates they issue.
For hazardous-area products, the ATEX or IECEx certificate must name the specific product series. A factory-level ISO 9001 certificate does not make an individual radar transmitter explosion-proof.
- ISO 9001: confirms a working quality management system at the factory.
- CE (EMC + LVD): required for EU import; check the declaration of conformity.
- ATEX / IECEx: must list the exact product model and protection class, e.g. Ex d IIC T6.
- Calibration certificates: every shipped unit should include one with traceable references.
Ask capability questions a trading company cannot answer
Trading companies resell factory stock with a margin but cannot control quality or customize firmware. Five minutes of technical questions usually reveals which one you are talking to: ask about the aging test procedure, calibration equipment models, PCB sourcing, and whether output configuration is done in-house.
A real manufacturer can provide a video factory tour on request, showing the assembly line, calibration bench, and aging-test racks. Video verification costs nothing and filters out most misrepresentation.
- Ask: 'What is your aging test duration and temperature profile?' — a factory answers immediately.
- Ask: 'Can you configure a custom 4-20mA output curve?' — requires in-house firmware capability.
- Ask for a live or recorded video tour before the first order.
Test samples the way your project will use them
Order 1-2 samples at unit price before committing to MOQ. Reputable suppliers refund sample cost against the first bulk order. Test the sample against your actual medium, temperature, and mounting position — not just a bench check.
Record accuracy at 3-5 level points across the range, check output signal stability over 48 hours, and inspect housing sealing. If a supplier resists selling samples or insists on MOQ-only, treat it as a red flag.
Understand the commercial terms that protect you
Standard terms from established instrument factories: T/T with 30% deposit and 70% before shipment, or an L/C at sight for larger orders. Alibaba Trade Assurance adds a layer of dispute protection for platform orders. Typical MOQ for economical level sensors is 50 units; radar transmitters often quote MOQ 10 or lower because of higher unit value.
Lead time of 15-20 days for standard models is normal. Quotes promising 3-5 day production for configured instruments usually mean stock of unknown age or specification.
- Payment: 30/70 T/T, L/C at sight, or platform trade assurance.
- Incoterms: FOB (your forwarder) or CIF (supplier arranges freight) per Incoterms 2020.
- Warranty: 18-24 months is the credible range for industrial sensors.
Red flags that predict quality problems
Price far below the market band usually means reused housings, uncalibrated cores, or skipped burn-in testing. A capacitive level sensor quoted under $20 or an 80GHz radar under $300 should trigger scrutiny rather than excitement.
Other warning signs: no physical address published, refusal of video calls, certificates with mismatched company names, and datasheets copied from other brands with the logo swapped.
Buyer FAQ
What is a typical MOQ for level sensors from a China factory?
Economical capacitive and ultrasonic level sensors commonly have an MOQ of 50 units for bulk pricing. Higher-value instruments such as 80GHz radar transmitters are often available at MOQ 5-10, and most factories sell 1-2 samples at unit price before a bulk order.
How do I verify a Chinese supplier's ISO 9001 certificate?
Ask for the certificate number and issuing body, then verify through the issuer's official channel — SGS, TÜV, DEKRA, and Intertek all support verification requests. Also check that the certificate scope covers design and manufacturing of measurement instruments, not an unrelated activity.
Should I buy from a manufacturer or a trading company?
For configured industrial instruments, a manufacturer is usually safer: it controls calibration, firmware, and quality processes, and can support OEM branding. Trading companies can be acceptable for standard commodity items, but confirm who actually handles warranty claims.
What documents should ship with industrial level sensors?
Each shipment should include a datasheet, wiring diagram, installation guide, and an individual calibration certificate per unit with serial-number traceability. For EU projects, add the CE declaration of conformity; for hazardous areas, the ATEX/IECEx certificate.