Instrument Selection | Procurement Guide: 5 Signs to Spot Low-Quality Instruments

In industrial instrument procurement, a low price may conceal high maintenance costs or even safety risks. This article outlines five typical signs of inferior instruments to help you develop a sharp eye for quality and avoid potential pitfalls!

1. Compromised Materials ❌
   Issue: Substituting standard plastic for engineering-grade plastic in housings, or using 304 stainless steel instead of Hastelloy for diaphragms.

✅ How to Identify:

1. Request material inspection reports (e.g., spectral analysis) from the supplier.
2. Use a magnet to test stainless steel materials (high-quality 316 stainless is typically non-magnetic).

二、 Inflated Accuracy and Poor Stability ❌
Issue: Advertised accuracy of 0.5%, but actual errors exceed 2% with significant drift during use.

✅ How to Identify:

1. Request third-party calibration reports (e.g., CNAS-accredited verification).

1. On-site sampling test: Verify repeatability at 10%, 50%, and 90% of the measuring range.

3、 Incomplete or Forged Certifications ❌
Issue: Claiming suitability for hazardous areas without essential explosion-proof certifications (e.g., ATEX, IECEx).

✅ How to Identify:

1. Verify the authenticity of the certificate number on the certification body’s official website (e.g., UL, TÜV).
2. Check the completeness of explosion-proof markings: Each code in “Ex d IIB T6 Gb” must correspond to the actual working conditions.

4、 Crippled Software Features ❌
Issue: Smart transmitters cannot output diagnostic information, and the HART protocol supports only partial commands.

✅ How to Identify:

1. Test full functional access using a universal configuration tool (e.g., PACTware).
2. Verify communication protocol compatibility: Ensure seamless integration with the existing DCS system.

Six Golden Rules for Instrument Procurement
✅ Avoid Blind Price Comparison: Comprehensively evaluate the total lifecycle cost (purchase price + maintenance expenses + production downtime losses).
✅ Start with Small Trial Orders: Purchase 1–2 units for a 3-month on-site performance test.
✅ Lock in Accountability: Specify “liability for accidents caused by instrument quality issues” in the contract.