E2 CLASS CALIBRATION WEIGHTS

1. General Description

E2 Class Calibration Weights are high-precision mass standards used for calibration of analytical balances and for verification/calibration of F1 class weights. These weights provide very low uncertainty and are intended for use in controlled laboratory environments.

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2. Standards & Metrological Compliance

• Accuracy Class: E2

• International Standard: OIML R-111-1

• Calibration Standard: ISO/IEC 17025

• Traceability:

  • Traceable to National Physical Laboratory (NPL), India or equivalent national standard

  • SI unit of mass (kilogram)

• Calibration Requirement: NABL-accredited calibration recommended / mandatory for laboratory use

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3. Nominal Weight Range

• 1 mg to 500 mg (wire / foil type)

• 1 g to 20 kg (solid cylindrical type)

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4. Metrological Characteristics (Typical)

(As per OIML R-111; actual values stated in NABL certificate)

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5. Material Specifications

• Material: High-purity non-magnetic austenitic stainless steel

• Grade: Special metrology-grade SS (vacuum melted)

• Density: (8000 ± 20) kg/m³

• Magnetic Susceptibility: ≤ 0.02

• Residual Magnetism: ≤ 1 µT

• Surface Reactivity: Low adsorption, corrosion resistant

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6. Construction & Surface Finish

• Design:

  • Cylindrical with adjusting cavity (g to kg)

  • Foil / wire type (mg range)

• Manufacturing: Precision CNC machining

• Surface Finish:

  • Mirror polished

  • Surface roughness Ra ≤ 0.2 µm

• Edges: Rounded to minimize air turbulence effects

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7. Dimensional & Thermal Stability

• Coefficient of Thermal Expansion:
  ~16 × 10⁻⁶ /°C

• Long-Term Stability:
  < 1/10 of MPE per year under controlled storage

• Mass Drift: Minimal when stored in protective case

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8. Air Buoyancy & Density Correction

• Air buoyancy correction applied during calibration

• Individual density value stated in calibration certificate

• Suitable for mass comparator-based calibration

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9. Environmental Reference Conditions (Calibration)

• Temperature: 20 °C ± 1 °C

• Relative Humidity: 40 % – 60 % RH

• Atmospheric Pressure: 950 – 1050 hPa

• Vibration: Negligible

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10. Handling & Usage Requirements

• Handle only with gloves or tweezers

• Avoid direct hand contact

• Allow thermal stabilization before use

• Use in draft-free, temperature-controlled lab

• Clean with lint-free cloth or approved cleaning method

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11. Storage & Packaging

• Individual cavities in wooden / aluminium / ABS case

• Dust-free, shock-resistant storage

• Anti-corrosion lining (optional)

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12. NABL Calibration Certificate Includes

• NABL logo & accreditation number

• Nominal & conventional mass values

• Expanded uncertainty (k=2)

• Density of weight

• Environmental conditions

• Traceability statement

• Calibration & due date

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13. Applications

• Calibration of analytical balances

• Calibration of F1 class weights

• NABL / ISO-17025 laboratories

• Pharmaceutical & chemical laboratories

• Research & academic institutions

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14. Compliance Summary

✔ OIML R-111 compliant
✔ NABL / ISO-17025 traceable
✔ High stability & low uncertainty
✔ Suitable for laboratory & audit use