Ohaus Calibration Weights – OIML-Certified Test Weights for Balance & Scale Verification
Ohaus calibration weights are precision test weights manufactured to OIML (International Organisation of Legal Metrology) standards, used for the routine calibration, verification, and adjustment of laboratory balances, precision scales, and industrial weighing equipment. Available in individual weights and complete sets across OIML accuracy classes E2, F1, F2, M1, and M2, they provide the traceable reference standards needed to verify that weighing instruments are performing within their specified accuracy limits — a requirement for GMP, GLP, ISO 17025, and legal-for-trade compliance.
Regular calibration and verification of weighing instruments is not simply good practice — in regulated environments it is a mandatory requirement. A balance that has drifted out of specification due to temperature change, mechanical shock, or component wear will produce inaccurate results that can compromise product quality, regulatory compliance, and commercial transactions. Ohaus calibration weights provide the traceable reference standard needed to detect this drift and restore confidence in measurement accuracy. Manufactured from stainless steel with polished or matte finishes depending on the accuracy class, they are supplied in protective cases with calibration certificates traceable to national standards.
OIML Accuracy Classes Available
- Class E2 — the highest accuracy class for calibrating Class F1 weights and high-precision analytical balances
- Class F1 — for calibrating Class F2 weights and analytical balances in pharmaceutical and research laboratories
- Class F2 — for calibrating Class M1 weights and precision balances in quality control and industrial applications
- Class M1 — for calibrating Class M2 weights and commercial scales in trade and industrial environments
- Class M2 — for routine verification of industrial and commercial weighing equipment
Key Features
- OIML-certified accuracy across E2, F1, F2, M1, and M2 classes for all calibration requirements
- Stainless steel construction with polished or matte finish depending on accuracy class
- Individual weights and complete sets available to suit single-point and multi-point calibration needs
- Protective storage cases included to prevent damage and contamination between uses
- Calibration certificates traceable to national standards supplied with all weights
- Wide range of denominations from 1 mg to 20 kg to cover all balance and scale capacities
Common Applications
- Laboratory balance calibration — routine verification of analytical, precision, and semi-micro balances
- GMP and GLP compliance — mandatory balance verification in pharmaceutical and regulated laboratory environments
- ISO 17025 accreditation — traceable calibration standards for accredited testing and calibration laboratories
- Industrial scale verification — routine checking of platform, floor, and bench scales in production environments
- Legal-for-trade verification — checking trade-approved scales used in commercial transactions
- Quality management systems — scheduled instrument verification as part of ISO 9001 quality programmes
All Ohaus calibration weights are supplied with calibration certificates traceable to national standards. UKAS-accredited calibration certificates are available on request for applications requiring the highest level of traceability. Contact our team for advice on the correct accuracy class for your balance and application.
Frequently Asked Questions
Which OIML accuracy class do I need for my balance?
As a general rule, the calibration weight should be one accuracy class higher than the balance being calibrated. For example, an analytical balance (Class I) should be calibrated with Class E2 or F1 weights; a precision balance (Class II) with Class F1 or F2 weights; a commercial scale (Class III) with Class M1 or M2 weights. Contact our team with your balance model and application and we’ll confirm the correct weight class.
How often should I calibrate my balance with test weights?
Calibration frequency depends on the balance’s use, environment, and regulatory requirements. In GMP pharmaceutical environments, daily or per-use span checks with calibration weights are typically required. In general laboratory and industrial environments, monthly or quarterly verification is common. Your quality management system or regulatory framework will specify the required frequency — contact our team for guidance.
What is the difference between calibration and verification?
Calibration is the process of adjusting a balance to bring it within its specified accuracy limits using reference weights. Verification (or routine checking) is the process of confirming that a balance is still within its specified limits without making adjustments. Both processes use calibration weights — calibration weights are used to perform the adjustment, and the same or similar weights are used for routine verification checks.
Do Ohaus calibration weights come with certificates?
Yes. All Ohaus calibration weights are supplied with calibration certificates traceable to national standards. UKAS-accredited calibration certificates are available on request for applications requiring the highest level of traceability, such as ISO 17025 accredited laboratories and regulated pharmaceutical environments. Contact our team when ordering to specify your certificate requirements.
How should calibration weights be stored and handled?
Calibration weights should always be handled with tweezers, gloves, or the handling tools provided — never with bare hands, as skin oils and moisture can affect the weight’s mass. Store weights in their protective case when not in use to prevent damage, contamination, and corrosion. Keep weights away from magnetic fields, vibration, and extreme temperature changes. Inspect weights regularly for damage or contamination and return for recalibration if any damage is found.
