Quality Control for Industrial Instruments

METRAVON Engineering Guide · Review date: 2026-08-09

METRAVON quality control: the chain of evidence from manufacturer audit to project acceptance

The quality of industrial instruments cannot be summarized only by "certificate" or "factory qualified". METRAVON splits quality control into six links: manufacturing resource access, technical data freezing, sample verification, production and shipping inspection, delivery traceability and on-site acceptance, and sets different inspection items based on the failure modes of radar level, point switches, process weighing and data acquisition products.

Suppliers’ public information shows that common quality capabilities in the industry include ISO quality system, CE or explosion-proof documents, high and low temperature aging, full inspection, calibration facilities, installation drawings and communication information. METRAVON regards this information as a candidate capability clue rather than a final conclusion; the original certificate, covered model, validity period, issuing agency, sample consistency and current production conditions still need to be checked before procurement and project delivery.

Quality audit focus

Certificates are disconnected from products: A company has a system certificate, which does not mean that each model has CE, explosion-proof, SIL or measurement qualifications.
Parameter sheet does not match the actual product: measuring range, material, process connection, output or firmware version change between sample and batch.
Only functions are tested, not process conditions: the radar works normally in an open environment, but is unstable in heavy dust, false echoes or low dielectric constant materials; the load cell is qualified, but the whole machine is subject to mechanical interference.
Records are not traceable: batches, serial numbers, calibration or functional test records cannot be matched after shipment, making fault analysis and replacement difficult.

Control plan by product category

Level/link	Configure or check focus	target/output
radar level	Echo, blind zone, output, display and parameter consistency; if necessary, perform high and low temperature, dust or simulated false echo verification	Range, antenna, connection, material, firmware and certificate scope
Level Switches	Action point, reset, output contacts, sensitivity and mechanical integrity	Media density, adhesion, insertion length, mounting orientation and protection
process weighing	Zero point, sensitivity, insulation, repeatability, offset load and supporting instrument communication	Range margin, materials, module structure, calibration records and installation accessories
Gateway/RTU	Port, power supply, power-off restart, protocol reading and writing, network recovery and firmware version	Register table, I/O list, platform interface, account permissions and data integrity

Six quality gates

Access review: Verify manufacturing entities, R&D and production sites, quality systems, testing equipment, product line boundaries and after-sales responsibilities.
Data freezing: Freeze models, BOM key items, drawings, data sheets, software or firmware, labels and packaging requirements before ordering.
Sample confirmation: Convert customer process conditions into testable items; when it cannot be reproduced in the laboratory, define the on-site trial period and success criteria.
Process and shipment: First article, patrol inspection, burn-in or full inspection based on risk; not all products require the same test duration.
Document verification: Certificates, calibration and testing documents are checked by model and batch to avoid using expired, wrong model or documents that only cover parts.
On-site feedback: Installation and commissioning problems are classified into product, selection, mechanical, wiring, parameter or communication reasons to formulate corrective measures.

Items recommended for inclusion in procurement or acceptance documents

Models and key configurations cannot be replaced with "equivalent products"; if replaced, a new list of differences must be provided and confirmed.
Clarify the proportion of random inspections, functional test items, judgment limits, recording formats, and rules for the isolation and rework and re-inspection of unqualified products.
For explosion-proof, measurement or safety-related items, record the certificate number, applicable model, mark, temperature group, validity period and installation restrictions.
The acceptance of the entire system must also check the sensors, mechanical installation, instrument parameters, control logic and communication data. It cannot just look at the power on of a single machine.

FAQ

Can ISO9001 prove that the performance of a certain model is qualified?

cannot be proven individually. ISO9001 shows that the company has established a quality management system, and the specific model still needs to be proven by data sheets, test records, and applicable certifications.

What should be checked in the explosion-proof certificate?

At least check the certificate holder, product name and model, certification mark, gas or dust category, temperature group, environmental conditions, special terms of use and validity status, and confirm that the nameplate is consistent with the certificate.

Why can’t weighing systems only look at sensor accuracy?

Systematic errors also come from foundation deformation, eccentric loading, pipe restraints, limit friction, temperature, junction boxes, and calibration methods. Acceptance must verify the entire system after installation is complete.

Can customers request shipping test records?

This can be raised at the inquiry or order stage. The recorded items, sampling ratio, format and whether it is provided one by one should be confirmed in the technical attachment.