NABL APPROVED TEST WEIGHT

1. General Description

NABL Approved Test Weights are precision mass standards used for calibration, verification, and performance testing of weighing instruments. These weights are calibrated by NABL-accredited laboratories in accordance with ISO/IEC 17025, ensuring full traceability to national and international mass standards.

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2. Applicable Standards & Accreditation

• Calibration Standard: OIML R-111-1

• Laboratory Accreditation:

  • NABL (ISO/IEC 17025:2017)

• Traceability:

  • Traceable to National Physical Laboratory (NPL), India

  • SI unit of mass (kilogram)

• Certificate Validity: As per NABL / customer requirement (typically 1 year)

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3. Accuracy Classes Available

• E2 – Reference standard weights

• F1 – Precision calibration weights

• F2 – Secondary standard weights

• M1 / M2 – Industrial & legal metrology weights

(Class selected as per application and balance resolution)

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4. Nominal Weight Range

• Milligram weights: 1 mg to 500 mg

• Gram weights: 1 g to 10 kg

• Kilogram weights: 1 kg to 50 kg

• Heavy weights: Up to 1000 kg (CI type)

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5. Metrological Performance (Typical – F1 Class Example)

(Values as per OIML R-111; actual uncertainty stated in NABL certificate)

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6. Material Specifications

Stainless Steel Weights (E2 / F1 / F2)

• Material: Austenitic non-magnetic stainless steel

• Grade: AISI 304 / 316 equivalent

• Density: (8000 ± 30) kg/m³

• Magnetic Susceptibility: ≤ 0.05

• Residual Magnetism: ≤ 2 µT

Cast Iron Weights (M1 / M2)

• Material: High-grade cast iron

• Density: ~7200 kg/m³

• Surface Protection: Anti-rust coating / enamel paint

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7. Construction & Finish

• Design:

  • Cylindrical with knob (SS weights)

  • Hexagonal / block type (CI weights)

• Manufacturing: CNC machined / precision cast

• Surface Finish (SS):

  • Mirror polished

  • Surface roughness Ra ≤ 0.2 µm

• Edges: Rounded to reduce air turbulence

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8. Environmental Reference Conditions (Calibration)

• Temperature: 20 °C ± 1 °C

• Relative Humidity: 40 % – 60 % RH

• Atmospheric Pressure: 950 – 1050 hPa

• Air Density Reference: 1.2 kg/m³

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9. Air Buoyancy & Density Correction

• Air buoyancy correction applied during calibration

• Weight density mentioned in calibration certificate

• Suitable for comparison weighing and mass comparators

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10. Handling & Maintenance

• Handle using gloves or tweezers (mg/g weights)

• Avoid direct hand contact

• Cleaning only with lint-free cloth or soft brush

• Allow thermal stabilization before calibration

• Store in protective case after use

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11. Storage & Packaging

• Individual cavities in wooden / aluminium / ABS box

• Shock-resistant and dust-free storage

• Anti-corrosion lining (optional)

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12. NABL Calibration Certificate Includes

• NABL logo & accreditation number

• Nominal mass value

• Conventional mass

• Expanded uncertainty (k=2)

• Traceability statement

• Environmental conditions

• Date of calibration & due date

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13. Applications

• NABL & ISO-17025 calibration laboratories

• Pharmaceutical & chemical industries

• Research & testing laboratories

• Legal metrology verification

• Precision balance & scale manufacturers

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14. Compliance Summary

✔ OIML R-111 compliant
✔ NABL / ISO-17025 traceable
✔ High accuracy & stability
✔ Suitable for audits & accreditation